Articles de revues : « Sensory afferences »

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Aflalo, Joanna, Flavien Quijoux, Charles Truong, François Bertin-Hugault et Damien Ricard. « Impact of Sensory Afferences in Postural Control Quantified by Force Platform : A Protocol for Systematic Review ». Journal of Personalized Medicine 12, n^o 8 (16 août 2022) : 1319. http://dx.doi.org/10.3390/jpm12081319.

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Older adults’ postural balance is a critical domain of research as balance deficit is an important risk factor for falls that can lead to severe injuries and death. Considering the effects of ageing on sensory systems, we propose that posturographic evaluation with a force platform exploring the effect of sensory deprivation or perturbation on balance could help understand postural control alterations in the elderly. The aim of the future systematic review and meta-analysis described in this protocol is to explore the capacity of older adults to maintain their balance during sensory perturbations, and compare the effect of perturbation between the sensory channels contributing to balance. Seven databases will be searched for studies evaluating older adults’ balance under various sensory conditions. After evaluating the studies’ risk of bias, results from similar studies (i.e., similar experimental conditions and posturographic markers) will be aggregated. This protocol describes a future review that is expected to provide a better understanding of changes in sensory systems of balance due to ageing, and therefore perspectives on fall assessment, prevention, and rehabilitation.

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Piovesan, EJ, PA Kowacs, CE Tatsui, MC Lange, LC Ribas et LC Werneck. « Referred Pain After Painful Stimulation of the Greater Occipital Nerve in Humans : Evidence of Convergence of Cervical Afferences on Trigeminal Nuclei ». Cephalalgia 21, n^o 2 (mars 2001) : 107–9. http://dx.doi.org/10.1046/j.1468-2982.2001.00166.x.

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Cranial sensory innervation is supplied mainly by the trigeminal nerves and by the first cervical nerves. Excitatory and inhibitory interactions among those nerve roots may occur in a mechanism called nociceptive convergence, leading to loss of somato-sensory spatial specificity. Three volunteers in an experimental trial had sterile water injected over their greater occipital nerve on one side of the neck. Pain intensity was evaluated 10, 30 and 120 s after the injection. Two of the patients reported intense pain. Trigeminal autonomic features, suggestive of parasympathetic activation, were seen associated with trigeminally distributed pain. These data add to and reinforce previous evidence of convergence of cervical afferents on the trigeminal sensory circuit.

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Alegre, M., A. Labarga, I. G. Gurtubay, J. Iriarte, A. Malanda et J. Artieda. « Beta electroencephalograph changes during passive movements : sensory afferences contribute to beta event-related desynchronization in humans ». Neuroscience Letters 331, n^o 1 (octobre 2002) : 29–32. http://dx.doi.org/10.1016/s0304-3940(02)00825-x.

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Clarke, Andrew H., K. Just, W. Krzok et U. Schönfeld. « Listing's plane and the 3D-VOR in microgravity – The role of the otolith afferences ». Journal of Vestibular Research 23, n^o 2 (2013) : 61–70. http://dx.doi.org/10.3233/ves-130476.

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Guilherme Augusto Moreira Silva, Ruan Kaique de Oliveira, Ana Maria de Castro, Nathália Fernandes da Silva, Bruna Almeida Pires Franco de Oliveira, Maria Eduarda Moreira Lino et Rodrigo Franco de Oliveira. « Effectiveness of proprioceptive training in athletes with and without ankle instability : systematic review ». Manual Therapy, Posturology & ; Rehabilitation Journal 20 (27 décembre 2022) : 1–7. http://dx.doi.org/10.17784/mtprehabjournal.2022.20.1277.

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Background: The proprioceptive program is directly related to neuromuscular control, which uses proprioceptive afferences to provide dynamic stabilization of the joint. Some variables can be considered risk factors for injuries, such as sprains, sudden and unexpected movement activities, simple quick changes of direction, soil type or footwear, among others. The balance training program contributes to lower injury rates and increases sports performance rate. Thus works the perception and maintenance of postural balance from information coming from sensory afferences. Objective: To perform a systematic review and verify the effect of proprioceptive training on ankle joint in athletes. Methods: A search for clinical trials was performed in the PUBMED, WEB OF SCIENCE, PEdro and SCIELO databases, the terms used for the search were “Proprioception”, “Athletic” and “Rehabilitation”, with the filters: articles published between the years of 2015 to 2020 and research in humans. Only studies published in the English language that addressed the proposed theme were included. The PEDro scale was used to evaluate the quality of studies with clinical trials, where studies with a score lower than 6/10 on the scale were excluded. Results: With the search 69 articles were found, removing the duplicates we obtained 67 eligible articles, of these, 15 studies met the inclusion and exclusion criteria. After complete analysis, 9 studies were included. Conclusion: Proprioceptive training in athletes, lasting at least three weeks with weekly protocols composed of dynamic exercises directed at individuals with ankle instability is totally effective for both joint injury prevention and rehabilitation. In addition to the increase of variables such as postural balance, coordination, postural control and functional performance.

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Ruggieri, Vezio, et Gian Piero Sera. « Bodily Perception in the Organization of Postural Attitude and Movement ». Perceptual and Motor Skills 82, n^o 1 (février 1996) : 307–12. http://dx.doi.org/10.2466/pms.1996.82.1.307.

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In the present research we hypothesized that some particular areas or points of the body play a role in the modulation of muscular (tonic and phasic) activity. In particular, we hypothesized that subjects utilize some bodily points as constant perceptual afferences in organizing the motoric responses of the whole body. The bodily points (called perceptual focal points) could have the same role as the bow of a boat for the sailor in orienting the spatial position of the boat and its movement. We have observed the presence of these perceptual focal points in 85% of a group of undergraduate students of psychology, 21 women and 19 men, during a real and an imagined movement of the whole body. Results indicated also that, if subjects were told to modify their habitual focal points, important modifications in subjective feelings of instability, pleasure, and tension appeared.

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Fetter, Michael, Hans-Christoph Diener et Johannes Dichgans. « Recovery of Postural Control After an Acute Unilateral Vestibular Lesion in Humans ». Journal of Vestibular Research 1, n^o 4 (1 octobre 1991) : 373–83. http://dx.doi.org/10.3233/ves-1991-1405.

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Postural control during stance was investigated using the EQUITEST® system in 10 patients during recovery after an acute unilateral vestibular lesion and was compared to the time course of recovery of the static and dynamic vestibulo-ocular imbalance. During the acute phase the patients showed a characteristic pattern with normal upright stance as long as at least one accurate sensory input (visual or somatosensory) was provided and severe postural disturbances when they had to rely primarily on vestibular afferences. Both static vestibulo-ocular and vestibulo-spinal balance recovered very fast, showing basically normal results on postural testing within about 2 weeks after the lesion. Thereafter, no pathological pattern was detectable during postural testing even in patients with persistent complete unilateral vestibular lesions. Reflexive postural responses to unexpected rapid displacements of the support surface seemed not to be influenced by vestibular imbalance even in the acute phase of the lesion.

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Eric, Matheron. « Management of Non-contact Injuries, Nonspecific Chronic Pain, and Prevention via Sensory Conflicts Detection : Vertical Heterophoria as a Landmark Indicator ». Journal of Novel Physiotherapy and Rehabilitation 8, n^o 1 (25 mars 2024) : 005–13. http://dx.doi.org/10.29328/journal.jnpr.1001057.

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Sensory and sensorimotor conflicts can lead to sensory and motor efficiency disturbances, such as pain and less efficient motor control. Vertical heterophoria (VH) and vertical orthophoria (VO) are respectively the latent vertical misalignment of the eyes when the retinal images are dissociated, or not. Mild VH (< 0.57°) could indicate the presence of a conflict resulting from eye refraction problems and/or a disruption of the somaesthetic cues. Canceling the conflict(s) can immediately restore VO, making it possible to observe an improvement in the mobility of spinal and peripheral joints, the performance in the motor and balance tests after initial alternation, and a decrease in pain. The Maddox Rod Test was used to detect mild VH but doesn’t determine the sensory conflict origin. The aim of this retrospective study is to show its use as a landmark in which sensory afferent conflict could induce symptoms (i.e. pain; decreased range of motion; nonoptimal postural and motor control) and how to manage it, analyzing data from 525 subjects. The clinical process is intended to inhibit or neutralize afferent signals involved in the sensorimotor loops required by the central nervous system in motor control in order to spot the locus of conflict (stomatognathic system, pelvis, plantar afferences, piercings (body art) or/and eye refraction problems). This investigation protocol based on VH detection provides trackers for the therapeutic intervention in the management of nonspecific chronic pain, non-contact injuries, and prevention, and a key role for practitioners in the multidisciplinary management required for patients/athletes, in the world of work/health.

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Mirino, Pierandrea, Anna Pecchinenda, Maddalena Boccia, Adriano Capirchio, Fabrizia D’Antonio et Cecilia Guariglia. « Cerebellum-Cortical Interaction in Spatial Navigation and Its Alteration in Dementias ». Brain Sciences 12, n^o 5 (20 avril 2022) : 523. http://dx.doi.org/10.3390/brainsci12050523.

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The cerebellum has a homogeneous structure and performs different computational functions such as modulation/coordination of the communication between cerebral regions, and regulation/integration of sensory information. Albeit cerebellar activity is generally associated with motor functions, several recent studies link it to various cognitive functions, including spatial navigation. In addition, cerebellar activity plays a modulatory role in different cognitive domains and brain processes. Depending on the network involved, cerebellar damage results in specific functional alterations, even when no function loss might be detected. In the present review, we discuss evidence of brainstem degeneration and of a substantial reduction of neurons in nuclei connected to the inferior olivary nucleus in the early stages of Alzheimer’s disease. Based on the rich patterns of afferences from the inferior olive nucleus to the cerebellum, we argue that the subtle alterations in spatial navigation described in the early stages of dementia stem from alterations of the neuromodulatory functions of the cerebellum.

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Yu, Jerry. « Spectrum of myelinated pulmonary afferents (III) cracking intermediate adapting receptors ». American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 319, n^o 6 (1 décembre 2020) : R724—R732. http://dx.doi.org/10.1152/ajpregu.00136.2020.

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Conventional one-sensor theory (one afferent fiber connects to a single sensor) categorizes the bronchopulmonary mechanosensors into the rapidly adapting receptors (RARs), slowly adapting receptors (SARs), or intermediate adapting receptors (IARs). RARs and SARs are known to sense the rate and magnitude of mechanical change, respectively; however, there is no agreement on what IARs sense. Some investigators believe that the three types of sensors are actually one group with similar but different properties and IARs operate within that group. Other investigators (majority) believe IARs overlap with the RARs and SARs and can be classified within them according to their characteristics. Clearly, there is no consensus on IARs function. Recently, a multiple-sensor theory has been advanced in which a sensory unit may contain many heterogeneous sensors, such as both RARs and SARs. There are no IARs. Intermediate adapting unit behavior results from coexistence of RARs and SARs. Therefore, the unit can sense both rate and magnitude of changes. The purpose of this review is to provide evidence that the multiple-sensor theory better explains sensory unit behavior.

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Barios, Juan A., Santiago Ezquerro, Arturo Bertomeu-Motos, Marius Nann, Fco Javier Badesa, Eduardo Fernandez, Surjo R. Soekadar et Nicolas Garcia-Aracil. « Synchronization of Slow Cortical Rhythms During Motor Imagery-Based Brain–Machine Interface Control ». International Journal of Neural Systems 29, n^o 05 (29 mai 2019) : 1850045. http://dx.doi.org/10.1142/s0129065718500454.

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Modulation of sensorimotor rhythm (SMR) power, a rhythmic brain oscillation physiologically linked to motor imagery, is a popular Brain–Machine Interface (BMI) paradigm, but its interplay with slower cortical rhythms, also involved in movement preparation and cognitive processing, is not entirely understood. In this study, we evaluated the changes in phase and power of slow cortical activity in delta and theta bands, during a motor imagery task controlled by an SMR-based BMI system. In Experiment I, EEG of 20 right-handed healthy volunteers was recorded performing a motor-imagery task using an SMR-based BMI controlling a visual animation, and during task-free intervals. In Experiment II, 10 subjects were evaluated along five daily sessions, while BMI-controlling same visual animation, a buzzer, and a robotic hand exoskeleton. In both experiments, feedback received from the controlled device was proportional to SMR power (11–14[Formula: see text]Hz) detected by a real-time EEG-based system. Synchronization of slow EEG frequencies along the trials was evaluated using inter-trial-phase coherence (ITPC). Results: cortical oscillations of EEG in delta and theta frequencies synchronized at the onset and at the end of both active and task-free trials; ITPC was significantly modulated by feedback sensory modality received during the tasks; and ITPC synchronization progressively increased along the training. These findings suggest that phase-locking of slow rhythms and resetting by sensory afferences might be a functionally relevant mechanism in cortical control of motor function. We propose that analysis of phase synchronization of slow cortical rhythms might also improve identification of temporal edges in BMI tasks and might help to develop physiological markers for identification of context task switching and practice-related changes in brain function, with potentially important implications for design and monitoring of motor imagery-based BMI systems, an emerging tool in neurorehabilitation of stroke.

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Cabrera-Álvarez, Jesús, Nina Doorn, Fernando Maestú et Gianluca Susi. « Modeling the role of the thalamus in resting-state functional connectivity : Nature or structure ». PLOS Computational Biology 19, n^o 8 (3 août 2023) : e1011007. http://dx.doi.org/10.1371/journal.pcbi.1011007.

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The thalamus is a central brain structure that serves as a relay station for sensory inputs from the periphery to the cortex and regulates cortical arousal. Traditionally, it has been regarded as a passive relay that transmits information between brain regions. However, recent studies have suggested that the thalamus may also play a role in shaping functional connectivity (FC) in a task-based context. Based on this idea, we hypothesized that due to its centrality in the network and its involvement in cortical activation, the thalamus may also contribute to resting-state FC, a key neurological biomarker widely used to characterize brain function in health and disease. To investigate this hypothesis, we constructed ten in-silico brain network models based on neuroimaging data (MEG, MRI, and dwMRI), and simulated them including and excluding the thalamus. and raising the noise into thalamus to represent the afferences related to the reticular activating system (RAS) and the relay of peripheral sensory inputs. We simulated brain activity and compared the resulting FC to their empirical MEG counterparts to evaluate model’s performance. Results showed that a parceled version of the thalamus with higher noise, able to drive damped cortical oscillators, enhanced the match to empirical FC. However, with an already active self-oscillatory cortex, no impact on the dynamics was observed when introducing the thalamus. We also demonstrated that the enhanced performance was not related to the structural connectivity of the thalamus, but to its higher noisy inputs. Additionally, we highlighted the relevance of a balanced signal-to-noise ratio in thalamus to allow it to propagate its own dynamics. In conclusion, our study sheds light on the role of the thalamus in shaping brain dynamics and FC in resting-state and allowed us to discuss the general role of criticality in the brain at the mesoscale level.

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Roy, Martin, Elsa Gilbert, Michel Maziade et Pierre Marquet. « T26. VISUO-TACTILE TRANSFER AND AUDIO-VISUAL INTEGRATION IMPAIRMENT AS A NEW VULNERABILITY MARKER IN CHILDREN-AT-RISK OF SCHIZOPHRENIA, BIPOLAR DISORDER OR RECURRENT DEPRESSIVE DISORDER ». Schizophrenia Bulletin 46, Supplement_1 (avril 2020) : S241. http://dx.doi.org/10.1093/schbul/sbaa029.586.

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Abstract Background Major psychiatric disorders (MPD) such as schizophrenia, bipolar disorder and recurrent major depression have shared neurodevelopmental vulnerability due to early neuronal and sensory defect as revealed by sensory and cognitive endophenotypes observed in our cohorts (e.g. Gagné et al., Schizophr. Res., 2019). There is considerable evidence that a harmonious self-development - known to be disrupted in MPDs - requires a synchronized multisensory perception and an adequate integration of sensory afferences (e.g. tactile, visual, auditory and proprio / interoception) with cognition. Early impairment in intermodal transfer (IMT) and multisensory integration (MSI) may jeopardize a stable and unified self’s and world’s representation and then would undermine self-development and represent a risk factor for MPD. IMT is the capability to transfer a percept coming exclusively from a sensory modality (e.g. tactile) to another modality (e.g. visual). MSI is the ability to integrate sensory inputs from different modalities (e.g. visual and auditory) to have a better information processing. This study shows that impairment in IMT/MSI may be a vulnerability marker in children genetically at-risk. Methods Sample: Forty-four offspring (21 girls) of patients suffering from a MPD and thus genetically at-risk for MPD (GatR) aged from 9–15 years old (mean age = 12.06) were recruited from the cohort study INTERCEPT through the HoPE program of the CIUSSS de la Capitale-Nationale. Twenty-five controls (19 girls) with no family history of MPD and no DSM-V disorder aged from 9–15 years old (mean age = 12.87) were recruited using advertisements or control bank. IMT Task: Each condition has 12 trials and the shapes are hidden from sight during palpation. MSI Task: - Simple reaction time (RT) task comprising 80 trials with unimodal stimuli (Auditory OR Visual) and 40 trials with AV (Auditory and Visual simultaneously) multimodal stimuli presented randomly. Results IMT task: When compared to controls, GatR were impaired in the three conditions (T-T: 9.77 vs. 10.32, T-V: 9.89 vs. 9.96, V-T: 9,11 vs. 9.92) with significant impairments both for T-T (t(60.53) = 2.18, p = 0.017) and V-T (t (57.28) = 2.33, p = 0.012) conditions. MSI task: GatR showed a deficit in MSI for almost all RT ranges (except for a peak at 185 ms), while control participants showed MSI facilitation for ranges from 150 to 200 ms. Discussion Developmentally genetically high-risk children would show significant impairments both in IMT and MSI that might enter into the group of indicators of brain dysfunctions, or risk endophenotypes, that both children at risk and adult patients carry (Paccalet et al., Schizophr. Res., 2016; Maziade, New Eng J Medicine, 2017). In addition, the two tasks would be valid and sensitive to the early sensory alterations in self-development. Finally, the battery is brief, user-friendly and playful for children.

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Cadoni, Gabriella, Pasqualina Maria Picciotti, Rolando Rolesi, Marco Sulfaro, Margherita Guidobaldi, Filippo Amore, Guido Conti, Gaetano Paludetti et Simona Turco. « Posturographic Analysis in Patients Affected by Central and Peripheral Visual Impairment ». Journal of Personalized Medicine 12, n^o 10 (13 octobre 2022) : 1709. http://dx.doi.org/10.3390/jpm12101709.

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Although vision loss is known to affect equilibrium maintenance, postural control in patients affected by low vision has been poorly investigated. We evaluated postural stability and the ability to use visual, proprioceptive and vestibular information in different low vision patterns. Ten adults with normal vision (NC), fourteen adults affected by central visual impairment (CLV) and eight adults affected by peripheral visual impairment (PLV) were enrolled in our study. Patients underwent visual, vestibular and postural evaluation (bedside examination, Computed Dynamic Posturograophy). Motor Control Tests were performed to analyze automatic postural adaptive responses elicited by unexpected postural disturbances. Clinical evaluations did not show abnormality in all patients. In the Sensory Organization Test, CLV and PLV patients performed more poorly in conditions 3–6 and 3–4, as compared to NC subjects. The condition 5 score was significantly lower in the CLV group with respect to the PLV patients. Composite equilibrium scores demonstrated significant differences between low-vision subjects vs. NC subjects. No differences were found for somatosensorial contribution. Visual afferences showed lower values in all visually impaired subjects, while vestibular contribution was lower in the CLV patients as compared to the NC and PLV patients. MCT latencies were significantly worse in the CLV subjects. In the low-vision patients, postural control was modified with a specific pattern of strategy adaptation. Different modulations of postural control and different adaptive responses seemed to characterize CLV patients as compared to PLV subjects.

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Clarke, Andrew H., et Ludmila Kornilova. « Ocular torsion response to active head-roll movement under one-g and zero-g conditions ». Journal of Vestibular Research 17, n^o 2-3 (1 mars 2008) : 99–111. http://dx.doi.org/10.3233/ves-2007-172-305.

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Transitions to and from microgravity, as experienced during a spaceflight mission, radically alter the demands on sensorimotor coordination. In this contribution, attention is directed to the vestibulo-oculomotor response to active head roll-tilt, generally referred to as ocular counterroll (OCR). Results are presented from a single-case longitudinal study over a 435-day spaceflight and from three further subjects over a 30-day period in microgravity. 1. Under one-g test conditions, with the head initially in the comfortable-upright position, active head-to-trunk roll tilt elicits a combined canal- and otolith-mediated oculomotor response, which manifests as a volley of torsional nystagmus beats combined with a tonic OCR. In microgravity it appears that only the transitory canal-mediated torsional nystagmus response remains. In both conditions the initial nystagmus response commences with an anticompensatory torsional fast phase. 2. Under zero-g conditions the head movements were comparable to those under one-g conditions but a consistent reduction in head velocity was observed. Despite this, eye velocity and eye-head velocity gain for the torsional component were found to be enhanced by up to 50% over the first thirty days in prolonged microgravity. 3. The results obtained from the 435-day mission indicate that the initially enhanced response decreases – over the course of several months – to preflight baseline level. The findings indicate that otolith- and canal-ocular responses are not simply added linearly, but rather that the afferent otolith signal also plays an inhibitory, or stabilising role on the canal-mediated response. Further, presuming a re-weighting of otolithic afferent information during prolonged microgravity, it is proposed that a corollary inverse re-weighting of corollary neck-proprioceptive afferences provides an effective substitute. In contrast to the idea that the torsional VOR is an evolutionary relic, it is postulated from the above findings that the anticompensatory saccade and the inherent low gain of OCR result as a compromise between intended reorientation to a tilted visual field and VOR compensation.

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Jammes, Y. « Tonic sensory pathways of the respiratory system ». European Respiratory Journal 1, n^o 2 (1 février 1988) : 176–83. http://dx.doi.org/10.1183/09031936.93.01020176.

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Both respiratory centres and the preganglionic vagal motoneurones, which control respiratory (striated) and airway (smooth) muscles respectively, receive information on the lungs, the circulation and the skeletal and respiratory muscles. Each of these nervous pathways has two components: one is phasic, i.e. in phase with biological rhythms, and comes from mechanoreceptors connected to large myelinated fibres; the second has a tonic low frequency firing rate and corresponds to the spontaneous activity of polymodal receptors connected to thin sensory fibres, which act mostly as sensors of changes in extracellular fluid composition (O2 and/or CO2 partial pressure, pH, release of algesic agents etc...). Some of them also detect large mechanical disturbances or local temperature changes. The influence of tonic background sensory activity is well known in animals concerning the role played by arterial chemoreceptors in the control of ventilation and of thin vagal afferents from the lungs (bronchopulmonary C-fibres and irritant receptors) in reflex facilitation of the bronchoconstrictor vagal tone. Moreover, the stimulation of thin sensory fibres in particular circumstances is responsible for hyperventilation (arterial chemoreceptors and muscle afferents), increased airway tone (arterial chemoreceptors and mostly thin vagal afferent fibres) or bronchodilation (muscle afferents). These peripheral inputs project centrally on different structures and also on brain stem neurones, which integrate simultaneously chemosensory, vagal and muscle information. This results in complex interactions between the different sensory pathways.

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Büyükşahin, Utku, et Ahmet Kırlı. « A low-cost, human-like, high-resolution, tactile sensor based on optical fibers and an image sensor ». International Journal of Advanced Robotic Systems 15, n^o 4 (1 juillet 2018) : 172988141878363. http://dx.doi.org/10.1177/1729881418783631.

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Tactile sensors are commonly a coordinated group of receptors forming a matrix array meant to measure force or pressure similar to the human skin. Optic-based tactile sensors are flexible, sensitive, and fast; however, the human fingertip’s spatial resolution, which can be regarded as the desired spatial resolution, still could not be reached because of their bulky nature. This article proposes a novel and patented optic-based tactile sensor design, in which fiber optic cables are used to increase the number of sensory receptors per square centimeter. The proposed human-like high-resolution tactile sensor design is based on simple optics and image processing techniques, and it enables high spatial resolution and easy data acquisition at low cost. This design proposes using the change in the intesity of the light occured due to the deformation on contact/measurement surface. The main idea is using fiber optic cables as the afferents of the human physiology which can have 9 µm diameters for both delivering and receiving light beams. The variation of the light intensity enters sequent mathematical models as the input, then, the displacement, the force, and the pressure data are evaluated as the outputs. A prototype tactile sensor is manufactured with 1-mm spatial and 0.61-kPa pressure measurement resolution with 0–15.6 N/cm2 at 30 Hz sampling frequency. Experimental studies with different scenarios are conducted to demonstrate how this state-of-the-art design worked and to evaluate its performance. The overall accuracy of the first prototype, based on different scenarios, is calculated as 93%. This performance is regarded as promising for further developments and applications such as grasp control or haptics.

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Feng, Bin, Sonali C. Joyce et G. F. Gebhart. « Optogenetic activation of mechanically insensitive afferents in mouse colorectum reveals chemosensitivity ». American Journal of Physiology-Gastrointestinal and Liver Physiology 310, n^o 10 (15 mai 2016) : G790—G798. http://dx.doi.org/10.1152/ajpgi.00430.2015.

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The sensory innervation of the distal colorectum includes mechanically insensitive afferents (MIAs; ∼25%), which acquire mechanosensitivity in persistent visceral hypersensitivity and thus generate de novo input to the central nervous system. We utilized an optogenetic approach to bypass the process of transduction (generator potential) and focus on transformation (spike initiation) at colorectal MIA sensory terminals, which is otherwise not possible in typical functional studies. From channelrhodopsin2-expressing mice (driven by Advillin-Cre), the distal colorectum with attached pelvic nerve was harvested for ex vivo single-fiber recordings. Afferent receptive fields (RFs) were identified by electrical stimulation and tested for response to mechanical stimuli (probing, stroking, and stretch), and afferents were classified as either MIAs or mechanosensitive afferents (MSAs). All MIA and MSA RFs were subsequently stimulated optically and MIAs were also tested for activation/sensitization with inflammatory soup (IS), acidic hypertonic solution (AHS), and/or bile salts (BS). Responses to pulsed optical stimuli (1–10 Hz) were comparable between MSAs and MIAs whereas 43% of MIAs compared with 86% of MSAs responded tonically to stepped optical stimuli. Tonic-spiking MIAs responded preferentially to AHS (an osmotic stimulus) whereas non-tonic-spiking MIAs responded to IS (an inflammatory stimulus). A significant proportion of MIAs were also sensitized by BS. These results reveal transformation as a critical factor underlying the differences between MIAs (osmosensors vs. inflammatory sensors), revealing a previously unappreciated heterogeneity of MIA endings. The current study draws attention to the sensory encoding of MIA nerve endings that likely contribute to afferent sensitization and thus have important roles in visceral pain.

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el Manira, A., D. Cattaert, P. Wallen, R. A. DiCaprio et F. Clarac. « Electrical coupling of mechanoreceptor afferents in the crayfish : a possible mechanism for enhancement of sensory signal transmission ». Journal of Neurophysiology 69, n^o 6 (1 juin 1993) : 2248–51. http://dx.doi.org/10.1152/jn.1993.69.6.2248.

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1. Central electrical coupling between primary afferent axons was investigated in an in vitro preparation of the crayfish thoracic locomotor system by using intracellular recordings. 2. Intracellular injection of the dye Lucifer yellow in single afferents resulted in staining of one to three additional afferents through dye-coupling. Three-dimensional confocal imaging of dye-coupled axons revealed a large zone of close apposition that may correspond to the gap junction site. 3. A depolarization preceding the spike in one sensory terminal was shown to facilitate the excitatory postsynaptic potential occurring in postsynaptic motoneurons. Further, a spike in one afferent axon can depolarize other, electrically coupled, axons above spike threshold, resulting in an increased number of active afferents. 4. The electrical coupling occurred between sensory afferents of similar function. It may therefore serve to facilitate sensory signal transmission from functionally homologous afferents onto postsynaptic target neurons.

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Mendelson, B., et E. Frank. « Role of competition among sensory neurons in regulation of pattern of innervation at their central and peripheral targets ». Journal of Neurophysiology 62, n^o 5 (1 novembre 1989) : 1189–200. http://dx.doi.org/10.1152/jn.1989.62.5.1189.

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1. The importance of competitive interactions among muscle sensory afferents on their projections to central and peripheral targets was studied by producing large reductions in the number of afferents during development. Removal of the brachial dorsal root ganglion (DRG2), which normally supplies the entire sensory innervation of the forelimb, in bullfrog (Rana catesbeiana) tadpoles caused a smaller number of neurons in the adjacent thoracic ganglion (DRG3) to sprout into the forelimb and into the brachial spinal cord. 2. Horseradish peroxidase labeling in postmetamorphic animals showed that DRG3 neurons innervating the triceps muscle arborize in a novel but now appropriate area of the spinal cord, the region containing motoneuronal dendrites. These foreign afferents do not arborize in inappropriate regions of the spinal gray matter, and their collaterals have the same rostrocaudal distribution as those of normal DRG2 muscle afferents. 3. After metamorphosis, the number of DRG3 sensory axons in individual triceps muscle nerves was determined. Normally, two-thirds of all triceps afferents project to the medial head alone, even though each of the three heads is of similar size and is contacted by similar numbers of motoneurons. After DRG2 removal, although the total number of DRG3 afferents projecting to the triceps muscle was smaller than normal, the medial head still received approximately two-thirds of the axons, just as in normal frogs. These results suggest that the proportional sensory innervation of the triceps muscle-heads is not dependent on competitive interactions among afferents. 4. DRG3 afferents projecting to the forelimb also sprouted to innervate appropriate brachial motoneurons. The average strength of connection between individual sensory and motor neurons was found to be the same as in normal animals, even though there was presumably more central target space available for each afferent axon. This suggests that the number and/or strength of central connections made by individual fibers may be an intrinsic property of muscle sensory neurons.

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Anderson, Edmund G. « Serotonergic Modulation of Sensory Afferents ». Japanese Journal of Pharmacology 43 (1987) : 1. http://dx.doi.org/10.1016/s0021-5198(19)43484-7.

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Connor, Mark, Ligia A. Naves et Edwin W. McCleskey. « Contrasting Phenotypes of Putative Proprioceptive and Nociceptive Trigeminal Neurons Innervating Jaw Muscle in Rat ». Molecular Pain 1 (1 janvier 2005) : 1744–8069. http://dx.doi.org/10.1186/1744-8069-1-31.

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Background: Despite the clinical significance of muscle pain, and the extensive investigation of the properties of muscle afferent fibers, there has been little study of the ion channels on sensory neurons that innervate muscle. In this study, we have fluorescently tagged sensory neurons that innervate the masseter muscle, which is unique because cell bodies for its muscle spindles are in a brainstem nucleus (mesencephalic nucleus of the 5th cranial nerve, MeV) while all its other sensory afferents are in the trigeminal ganglion (TG). We examine the hypothesis that certain molecules proposed to be used selectively by nociceptors fail to express on muscle spindles afferents but appear on other afferents from the same muscle. Results: MeV muscle afferents perfectly fit expectations of cells with a non-nociceptive sensory modality: Opiates failed to inhibit calcium channel currents ( ICa) in 90% of MeV neurons, although ICa were inhibited by GABAB receptor activation. All MeV afferents had brief (1 msec) action potentials driven solely by tetrodotoxin (TTX)-sensitive Na channels and no MeV afferent expressed either of three ion channels (TRPV1, P2X3, and ASIC3) thought to be transducers for nociceptive stimuli, although they did express other ATP and acid-sensing channels. Trigeminal masseter afferents were much more diverse. Virtually all of them expressed at least one, and often several, of the three putative nociceptive transducer channels, but the mix varied from cell to cell. Calcium currents in 80% of the neurons were measurably inhibited by μ-opioids, but the extent of inhibition varied greatly. Almost all TG masseter afferents expressed some TTX-insensitive sodium currents, but the amount compared to TTX sensitive sodium current varied, as did the duration of action potentials. Conclusion: Most masseter muscle afferents that are not muscle spindle afferents express molecules that are considered characteristic of nociceptors, but these putative muscle nociceptors are molecularly diverse. This heterogeneity may reflect the mixture of metabosensitive afferents which can also signal noxious stimuli and purely nociceptive afferents characteristic of muscle.

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Merfeld, Daniel M., Laurence R. Young, Charles M. Oman et Mark J. Shelhamert. « A Multidimensional Model of the Effect of Gravity on the Spatial Orientation of the Monkey ». Journal of Vestibular Research 3, n^o 2 (1 février 1993) : 141–61. http://dx.doi.org/10.3233/ves-1993-3204.

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A “sensory conflict” model of spatial orientation was developed. This mathematical model was based on concepts derived from observer theory, optimal observer theory, and the mathematical properties of coordinate rotations. The primary hypothesis is that the central nervous system of the squirrel monkey incorporates information about body dynamics and sensory dynamics to develop an internal model. The output of this central model (expected sensory afference) is compared to the actual sensory afference, with the difference defined as “sensory conflict”. The sensory conflict information is, in turn, used to drive central estimates of angular velocity (“velocity storage”), gravity (“gravity storage”), and linear acceleration (“acceleration storage”) toward more accurate values. The model successfully predicts “velocity storage” during rotation about an earth-vertical axis. The model also successfully predicts that the time constant of the horizontal vestibulo-ocular reflex is reduced and that the axis of eye rotation shifts toward alignment with gravity following postrotatory tilt. Finally, the model predicts the bias modulation, and decay components that have been observed during off-vertical axis rotations (OVAR).

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Shepherd, I. T., Y. Luo, F. Lefcort, L. F. Reichardt et J. A. Raper. « A sensory axon repellent secreted from ventral spinal cord explants is neutralized by antibodies raised against collapsin-1 ». Development 124, n^o 7 (1 avril 1997) : 1377–85. http://dx.doi.org/10.1242/dev.124.7.1377.

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During embryogenesis, different subclasses of sensory neurons extend central projections to specific locations in the spinal cord. Muscle and cutaneous afferents initially project to the same location in the dorsal cord. Later, specific muscle afferents leave other afferents behind and project into the ventral cord. Previous studies have shown that ventral spinal cord explants secrete a repellent for sensory neurites. We now find that antibodies to collapsin-1 neutralize this repellent activity. Additional data suggest that all afferents respond to collapsin-1 when they are first confined to the dorsal cord, but that ventrally projecting muscle afferents become collapsin-1 insensitive as they project into the ventral cord. Our results suggest that the transient dorsal expression of collapsin-1 prevents all efferents from entering the cord early and sustained ventral expression prevents dorsally terminating afferents from entering the ventral cord later.

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Cattaert, Daniel, et Michelle Bévengut. « Effects of Antidromic Discharges in Crayfish Primary Afferents ». Journal of Neurophysiology 88, n^o 4 (1 octobre 2002) : 1753–65. http://dx.doi.org/10.1152/jn.2002.88.4.1753.

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Contrary to orthodromic spikes that are generated in sensory organs and conveyed to CNS, antidromic spikes are generated in the axon terminals of the sensory neurons within the CNS and are conveyed to the peripheral sensory organ. Antidromic discharges are observed in primary afferent neurons of both vertebrates and invertebrates and seem to be related to the rhythmic activity of central neural networks. In this study, we analyzed the effect of antidromic discharges on the sensory activity of a leg proprioceptor in in vitro preparations of the crayfish CNS. Intracellular microelectrodes were used both to record the orthodromic spikes and to elicit antidromic spikes by injecting squares pulses of depolarizing current at various frequencies. Experiments were performed on the three types of identified sensory afferents (tonic, phasotonic, and phasic). The main results showed a reduction of the firing frequency of the orthodromic activity in 82% of the tested afferents. In tonic afferents, during their occurrences and according to their frequency, antidromic spikes or bursts reduced or suppressed the orthodromic activity. Following their terminations, they also induced a silent period and a gradual recovery of the orthodromic activity, both of which increased as the duration and the frequency of the antidromic bursts increased. In phasotonic and phasic afferents, antidromic bursts reduced or suppressed the phasic responses as their frequency and durations increased. In phasotonic afferents, if elicited prior to the movements, long-duration bursts with increasing frequency reduced more rapidly the tonic background activity than the phasic one whereas short-duration bursts at high frequency produced strong decreases of both. The effect of antidromic bursts accumulated when they are repetitively elicited. Antidromic bursts induced a much larger decrease of the sensory activity than adaptation alone. The occurrences of antidromic spikes or bursts may have a functional role in modulating the incoming sensory messages during locomotion. The mechanisms by which antidromic spikes modulate the firing sensitivity of the primary afferents may well lie in modifications of the properties of either mecanotransduction and/or spike initiation.

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Arabzadeh, Ehsan, Colin W. G. Clifford, Justin A. Harris, David A. Mahns, Vaughan G. Macefield et Ingvars Birznieks. « Single tactile afferents outperform human subjects in a vibrotactile intensity discrimination task ». Journal of Neurophysiology 112, n^o 10 (15 novembre 2014) : 2382–87. http://dx.doi.org/10.1152/jn.00482.2014.

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We simultaneously compared the sensitivity of single primary afferent neurons supplying the glabrous skin of the hand and the psychophysical amplitude discrimination thresholds in human subjects for a set of vibrotactile stimuli delivered to the receptive field. All recorded afferents had a dynamic range narrower than the range of amplitudes across which the subjects could discriminate. However, when the vibration amplitude was chosen to be within the steepest part of the afferent's stimulus-response function the response of single afferents, defined as the spike count over the vibration duration (500 ms), was often more sensitive in discriminating vibration amplitude than the perceptual judgment of the participants. We quantified how the neuronal performance depended on the integration window: for short windows the neuronal performance was inferior to the performance of the subject. The neuronal performance progressively improved with increasing spike count duration and reached a level significantly above that of the subjects when the integration window was 250 ms or longer. The superiority in performance of individual neurons over observers could reflect a nonoptimal integration window or be due to the presence of noise between the sensory periphery and the cortical decision stage. Additionally, it could indicate that the range of perceptual sensitivity comes at the cost of discrimination through pooling across neurons with different response functions.

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Oakley, R. A., A. S. Garner, T. H. Large et E. Frank. « Muscle sensory neurons require neurotrophin-3 from peripheral tissues during the period of normal cell death ». Development 121, n^o 5 (1 mai 1995) : 1341–50. http://dx.doi.org/10.1242/dev.121.5.1341.

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To determine if muscle sensory neurons require neurotrophin-3 (NT3) during the period of normal cell death, we used an NT3-specific antiserum to deplete NT3 from peripheral tissues during this period in chick embryos. DiI staining of dorsal roots indicated that limb injections of anti-NT3 reduced the spinal projection of muscle spindle afferents. In contrast, injection of the antiserum into the spinal cord had no demonstrable effect, indicating that the reduced projection following limb injection was due to peripheral blockade of NT3 signaling. Counts of neurons retrogradely labeled from muscle and cutaneous nerves showed that peripheral blockade of NT3 selectively reduced the survival of muscle sensory neurons without affecting the survival of cutaneous sensory neurons or motoneurons. In situ hybridization with trkC probes indicated that, during the period of cell death, most large diameter muscle sensory neurons express trkC transcripts, whereas few cutaneous neurons express this receptor for NT3. We conclude that large diameter muscle afferents, including spindle afferents, require NT3 from peripheral tissues to survive the normal period of sensory neuron death in vivo.

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McCoy, Daniel D., Ligang Zhou, Anh-Khoi Nguyen, Alan G. Watts, Casey M. Donovan et David D. McKemy. « Enhanced insulin clearance in mice lacking TRPM8 channels ». American Journal of Physiology-Endocrinology and Metabolism 305, n^o 1 (1 juillet 2013) : E78—E88. http://dx.doi.org/10.1152/ajpendo.00542.2012.

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Blood glucose concentration is tightly regulated by the rate of insulin secretion and clearance, a process partially controlled by sensory neurons serving as metabolic sensors in relevant tissues. The activity of these neurons is regulated by the products of metabolism which regulate transmitter release, and recent evidence suggests that neuronally expressed ion channels of the transient receptor potential (TRP) family function in this critical process. Here, we report the novel finding that the cold and menthol-gated channel TRPM8 is necessary for proper insulin homeostasis. Mice lacking TRPM8 respond normally to a glucose challenge while exhibiting prolonged hypoglycemia in response to insulin. Additionally, Trpm8 -/- mice have increased rates of insulin clearance compared with wild-type animals and increased expression of insulin-degrading enzyme in the liver. TRPM8 channels are not expressed in the liver, but TRPM8-expressing sensory afferents innervate the hepatic portal vein, suggesting a TRPM8-mediated neuronal control of liver insulin clearance. These results demonstrate that TRPM8 is a novel regulator of serum insulin and support the role of sensory innervation in metabolic homeostasis.

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Desai, Sapan S., Catherine Zeh et Anna Lysakowski. « Comparative Morphology of Rodent Vestibular Periphery. I. Saccular and Utricular Maculae ». Journal of Neurophysiology 93, n^o 1 (janvier 2005) : 251–66. http://dx.doi.org/10.1152/jn.00746.2003.

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Calyx afferents, a group of morphologically and physiologically distinct afferent fibers innervating the striolar region of vestibular sensory epithelia, are selectively labeled by antibodies to the calcium-binding protein calretinin. In this study, the population of calretinin-stained calyx afferents was used to delineate and quantify the striolar region in six rodent species: mouse, rat, gerbil, guinea pig, chinchilla, and tree squirrel. Morphometric studies and hair cell and calyx afferent counts were done. Numbers of hair cells, area, length, and width of the sensory epithelium increase from mouse to tree squirrel. In the mouse and rat, calretinin is found in 5–9% of all type I hair cells, 20–40% of striolar type II hair cells, and 70–80% of extrastriolar type II hair cells. Numbers of calyx afferents increase from mouse to squirrel, with more complex calyx afferents in larger species. About 10% of calyx afferents are branched. Based on our counts of total numbers of calyx afferents in chinchilla maculae and in comparison to fiber counts in the literature, the proportion of calyx afferents is greater than previously described, constituting nearly 20% of the total. Because morphometric measures increase with body weight, we obtained additional data on vestibular end organ surface areas from the literature and used this to construct a power law function describing this relationship. The function holds for species with body weights less than ∼4 kg. Greater than 4 kg, the surface area of the sensory epithelia remains constant even with increasing body weight.

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Montalbetti, Nicolas, James G. Rooney, Allison L. Marciszyn et Marcelo D. Carattino. « ASIC3 fine-tunes bladder sensory signaling ». American Journal of Physiology-Renal Physiology 315, n^o 4 (1 octobre 2018) : F870—F879. http://dx.doi.org/10.1152/ajprenal.00630.2017.

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Acid-sensing ion channels (ASICs) are trimeric proton-activated, cation-selective neuronal channels that are considered to play important roles in mechanosensation and nociception. Here we investigated the role of ASIC3, a subunit primarily expressed in sensory neurons, in bladder sensory signaling and function. We found that extracellular acidification evokes a transient increase in current, consistent with the kinetics of activation and desensitization of ASICs, in ~25% of the bladder sensory neurons harvested from both wild-type (WT) and ASIC3 knockout (KO) mice. The absence of ASIC3 increased the magnitude of the peak evoked by extracellular acidification and reduced the rate of decay of the ASIC-like currents. These findings suggest that ASICs are assembled as heteromers and that the absence of ASIC3 alters the composition of these channels in bladder sensory neurons. Consistent with the notion that ASIC3 serves as a proton sensor, 59% of the bladder sensory neurons harvested from WT, but none from ASIC3 KO mice, fired action potentials in response to extracellular acidification. Studies of bladder function revealed that ASIC3 deletion reduces voiding volume and the pressure required to trigger micturition. In summary, our findings indicate that ASIC3 plays a role in the control of bladder function by modulating the response of afferents to filling.

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Sharma, K., Z. Korade et E. Frank. « Development of specific muscle and cutaneous sensory projections in cultured segments of spinal cord ». Development 120, n^o 5 (1 mai 1994) : 1315–23. http://dx.doi.org/10.1242/dev.120.5.1315.

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Development of sensory projections was studied in cultured spinal segments with attached dorsal root ganglia. In spinal segments from stage 30 (E6.5) and older chicken embryos, prelabeled muscle and cutaneous afferents established appropriate projections. Cutaneous afferents terminated solely within the dorsolateral laminae, whereas some muscle afferents (presumably Ia afferents) projected ventrally towards motoneurons. Development of appropriate projections suggests that sufficient cues are preserved in spinal segments to support the formation of modality-specific sensory projections. Further, because these projections developed in the absence of muscle or skin, these results show that the continued presence of peripheral targets is not required for the formation of specific central projections after stage 29 (E6.0). Development of the dorsal horn in cultured spinal segments was assessed using the dorsal midline as a marker. In ovo, this midline structure appears at stage 29. Lack of midline formation in stage 28 and 29 cultured spinal segments suggests that the development of the dorsal horn is arrested in this preparation. This is consistent with earlier reports suggesting that dorsal horn development may be dependent on factors outside the spinal cord. Because dorsal horn development is blocked in cultured spinal segments, this preparation makes it possible to study the consequences of premature ingrowth of sensory axons into the spinal cord. In chicken embryos sensory afferents reach the spinal cord at stage 25 (E4.5) but do not arborize within the gray matter until stage 30. During this period dorsal horn cells are still being generated. In spinal segments, only those segments that have developed a midline at the time of culture support the formation of midline at the time of culture support the formation of specific sensory projections.(ABSTRACT TRUNCATED AT 250 WORDS)

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Bielefeldt, Klaus, Fang Zhong, H. Richard Koerber et Brian M. Davis. « Phenotypic characterization of gastric sensory neurons in mice ». American Journal of Physiology-Gastrointestinal and Liver Physiology 291, n^o 5 (novembre 2006) : G987—G997. http://dx.doi.org/10.1152/ajpgi.00080.2006.

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Recent studies suggest that the capsaicin receptor [transient receptor potential vanilloid (TRPV)1] may play a role in visceral mechanosensation. To address the potential role of TRPV1 in vagal sensory neurons, we developed a new in vitro technique allowing us to determine TRPV1 expression directly in physiologically characterized gastric sensory neurons. Stomach, esophagus, and intact vagus nerve up to the central terminations were carefully dissected and placed in a perfusion chamber. Intracellular recordings were made from the soma of nodose neurons during mechanical stimulation of the stomach. Physiologically characterized neurons were labeled iontophoretically with neurobiotin and processed for immunohistochemical experiments. As shown by action potential responses triggered by stimulation of the upper thoracic vagus with a suction electrode, essentially all abdominal vagal afferents in mice conduct in the C-fiber range. Mechanosensitive gastric afferents encode stimulus intensities over a wide range without apparent saturation when punctate stimuli are used. Nine of 37 mechanosensitive vagal afferents expressed TRPV1 immunoreactivity, with 8 of the TRPV1-positive cells responding to stretch. A small number of mechanosensitive gastric vagal afferents express neurofilament heavy chains and did not respond to stretch. By maintaining the structural and functional integrity of vagal afferents up to the nodose ganglion, physiological and immunohistochemical properties of mechanosensory gastric sensory neurons can be studied in vitro. Using this novel technique, we identified TRPV1 immunoreactivity in only one-fourth of gastric mechanosensitive neurons, arguing against a major role of this ion channel in sensation of mechanical stimuli under physiological conditions.

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Zhang, J. W., J. F. Walker, J. Guardiola et J. Yu. « Pulmonary sensory and reflex responses in the mouse ». Journal of Applied Physiology 101, n^o 3 (septembre 2006) : 986–92. http://dx.doi.org/10.1152/japplphysiol.00161.2006.

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Mouse model research is proliferating because of its readiness for genetic manipulation. Little is known about pulmonary vagal afferents in mice, however. The purpose of this study was to determine whether their pulmonary afferents are similar to those in large animals. Single-unit activity was recorded in the cervical vagus nerve of anesthetized, open-chest, and mechanically ventilated mice. We evaluated airway sensory activity in 153 single units; 141 were mechanosensitive, with 134 inflation receptors and 7 deflation receptors. The remaining 12 receptors were chemosensitive and mechanically insensitive, showing low basal firing frequency and behaving like C-fiber or high-threshold Aδ-receptors. In separate studies, phrenic activity was recorded as an index of respiratory drive to assess pulmonary reflexes. Lung inflation produced a typical Hering-Breuer reflex, and intravenous injection of phenylbiguanide produced the typical chemoreflex resulting in apnea, bradycardia, and hypotension. These reflexes were blocked by bilateral vagotomy. We conclude that mice possess a similar set of airway sensors and pulmonary reflexes as typically found in larger animals.

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Boada, M. Danilo. « Relationship between electrophysiological signature and defined sensory modality of trigeminal ganglion neurons in vivo ». Journal of Neurophysiology 109, n^o 3 (1 février 2013) : 749–57. http://dx.doi.org/10.1152/jn.00693.2012.

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The trigeminal ganglia (TG) innervate a heterogeneous set of highly sensitive and exposed tissues. Weak, innocuous stimuli can evoke pain as a normal response in some areas such as the cornea. This observation implies, however, the capability of low-threshold mechanoreceptors, inducing pain in the normal condition. To clarify this matter, the present study correlates the electrical signature (both fiber conduction velocity and somatic electrical properties) with receptor field, mechanical threshold, and temperature responsiveness of sensory afferents innervating tissues with dissimilar sensitivity (skin vs. cornea) in the trigeminal domain. Intracellular recordings were obtained in vivo from 148 neurons of the left TG of 62 mice. In 111 of these neurons, the peripheral receptor field was successfully localized: 96 of them innervated the hairy skin, while the remaining 15 innervated the cornea. The electrical signature was defined and peripheral responses correlated with tissue target. No high threshold neurons were found in the cornea. Moreover, the electrical signature of corneal afferents resembles nociceptive neurons in the skin. TG skin afferents showed similar membrane electrical signature and sensory modality as skin afferents from dorsal root ganglion, although TG afferents exhibited a shorter duration of afterhyperpolarization then those previously described in dorsal root ganglion. These data suggest than new or different ways to classify and study TG sensory neurons may be required.

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Stemme, Torben, et Sarah E. Pfeffer. « Anatomy of the Nervous System in Chelifer cancroides (Arachnida : Pseudoscorpiones) with a Distinct Sensory Pathway Associated with the Pedipalps ». Insects 13, n^o 1 (24 décembre 2021) : 25. http://dx.doi.org/10.3390/insects13010025.

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Many arachnid taxa have evolved unique, highly specialized sensory structures such as antenniform legs in Amblypygi (whip spiders), for instance, or mesosomal pectines in scorpions. Knowledge of the neuroanatomy as well as functional aspects of these sensory organs is rather scarce, especially in comparison to other arthropod clades. In pseudoscorpions, no special sensory structures have been discovered so far. Nevertheless, these animals possess dominant, multifunctional pedipalps, which are good candidates for being the primary sensory appendages. However, only little is known about the anatomy of the nervous system and the projection pattern of pedipalpal afferents in this taxon. By using immunofluorescent labeling of neuronal structures as well as lipophilic dye labeling of pedipalpal pathways, we identified the arcuate body, as well as a comparatively small mushroom body, the latter showing some similarities to that of Solifugae (sun spiders and camel spiders). Furthermore, afferents from the pedipalps terminate in a glomerular and a layered neuropil. Due to the innervation pattern and structural appearance, we conclude that these neuropils are the first integration centers of the chemosensory and mechanosensory afferents. Within Arthropoda, but also other invertebrates or even vertebrates, sensory structures show rather similar neuronal arrangement. Thus, these similarities in the sensory systems of different evolutionary origin have to be interpreted as functional prerequisites of the respective modality.

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Hay, M., et D. L. Kunze. « Glutamate metabotropic receptor inhibition of voltage-gated calcium currents in visceral sensory neurons ». Journal of Neurophysiology 72, n^o 1 (1 juillet 1994) : 421–30. http://dx.doi.org/10.1152/jn.1994.72.1.421.

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1. Metabotropic glutamate receptors (mGluRs) have been suggested to modulate neurotransmission of glutamatergic pathways via autoreceptive action. Visceral sensory afferents and baroreceptor afferents in particular are thought to utilize L-glutamate (L-glu) as a primary neurotransmitter. The purpose of this study was to investigate whether visceral sensory afferents possess a mGluR and determine the effect of mGluR activation on voltage-gated calcium currents in these neurons. 2. Activation of mGluRs by the selective agonist trans-(+/-)-1-amino-1,3-cyclopentanedicarboxylic acid (t-ACPD) reversibly suppressed the voltage-gated calcium currents in visceral sensory afferents of the nodose ganglion. Concentrations of t-ACPD ranging from 50 to 1,000 microM consistently decreased the evoked calcium current with a maximum suppression of the peak current of 25–30%. This response was repeatable and reversible within a given cell. 3. Metabotropic GluR activation selectively decreased the high-threshold calcium current evoked from step potentials greater than -30 mV and had no effect on the low-threshold calcium current. The inhibitory effects of t-ACPD on the high-threshold channel was partially blocked by omega-conotoxin (omega-CTx-GVIA) suggesting that at least part of the effects of mGluR inhibition of the voltage-gated calcium current is because of a modulation of the omega-CTx-GVIA sensitive high-threshold current. 4. Finally, the inhibitory effects of quisqualate (quis) on the high-threshold calcium current were blocked by pretreatment of the neurons with pertussis toxin (PTX). These results suggest that visceral sensory afferents do possess a PTX-sensitive mGluR and activation of this receptor results in the inhibition of a omega-CTx-GVIA sensitive high-threshold calcium channel.

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Hinckley, Christopher A., Eric P. Wiesner, George Z. Mentis, David J. Titus et Lea Ziskind-Conhaim. « Sensory Modulation of Locomotor-Like Membrane Oscillations in Hb9-Expressing Interneurons ». Journal of Neurophysiology 103, n^o 6 (juin 2010) : 3407–23. http://dx.doi.org/10.1152/jn.00996.2009.

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The central pattern generator can generate locomotor-like rhythmic activity in the spinal cord in the absence of descending and peripheral inputs, but the motor pattern is regulated by feedback from peripheral sensory inputs that adjust motor outputs to external stimuli. To elucidate the possible role of Hb9-expressing interneurons (Hb9 INs) in the locomotor circuitry, we investigated whether their induced oscillatory activity is modulated by low-threshold afferents in the isolated spinal cords of neonatal Hb9:eGFP transgenic mice. Low-intensity stimulation of segmental afferents generated short-latency, monosynaptic excitatory responses in 62% of Hb9 INs. These were associated with longer-latency (∼13 ms) excitatory postsynaptic currents that were evoked in all Hb9 INs, probably by slow conducting afferents that synapse directly onto them. Concomitant morphological analysis confirmed that afferent axons with immunoreactive expression of vesicular glutamate transporter-1 and parvalbumin, presumably from primary afferents, contacted somata and dendrites of all Hb9 INs. Most of the putative synaptic contacts were on distal dendrites that extended to an area with profuse afferent projections. We next examined whether low-threshold afferents in upper (flexor-related) and lower (extensor-related) lumbar segments altered the timing of neurochemically induced locomotor-like rhythms in Hb9 INs and motoneurons. Excitation of flexor-related afferents during the flexor phase delayed the onset of subsequent cycles in both Hb9 INs and segmental motoneurons while maintaining the phase relationship between them. The in-phase correlation between voltage oscillations in Hb9 INs and motor bursts also persisted during the two- to threefold increase in cycle period triggered by extensor-related afferents. Our findings that low-threshold, presumably muscle afferents, synapse directly onto these interneurons and perturb their induced locomotor-like membrane oscillations in a pattern that remains phase-locked with motor bursts support the hypothesis that Hb9 INs are part of the sensorimotor circuitry that regulates the pattern of locomotor rhythms in the isolated cord.

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Fu, Liang-Wu, et John C. Longhurst. « A new function for ATP : activating cardiac sympathetic afferents during myocardial ischemia ». American Journal of Physiology-Heart and Circulatory Physiology 299, n^o 6 (décembre 2010) : H1762—H1771. http://dx.doi.org/10.1152/ajpheart.00822.2010.

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Myocardial ischemia activates cardiac sympathetic afferents leading to chest pain and reflex cardiovascular responses. Brief myocardial ischemia leads to ATP release in the interstitial space. Furthermore, exogenous ATP and α,β-methylene ATP (α,β-meATP), a P2X receptor agonist, stimulate cutaneous group III and IV sensory nerve fibers. The present study tested the hypothesis that endogenous ATP excites cardiac afferents during ischemia through activation of P2 receptors. Nerve activity of single unit cardiac sympathetic afferents was recorded from the left sympathetic chain or rami communicates (T2-T5) in anesthetized cats. Single fields of 45 afferents (conduction velocities = 0.25–4.92 m/s) were identified in the left ventricle with a stimulating electrode. Five minutes of myocardial ischemia stimulated 39 of 45 cardiac afferents (8 Aδ, 37 C fibers). Epicardial application of ATP (1–4 μmol) stimulated six ischemically sensitive cardiac afferents in a dose-dependent manner. Additionally, epicardial ATP (2 μmol), ADP (2 μmol), a P2Y agonist, and α,β-meATP (0.5 μmol) significantly activated eight other ischemically sensitive afferents. Third, pyridoxal phosphate-6-azophenyl-2′,4′-disulfonic acid, a P2 receptor antagonist, abolished the responses of six afferents to epicardial ATP (2 μmol) and attenuated the ischemia-related increase in activity of seven other afferents by 37%. In the absence of P2 receptor blockade, cardiac afferents responded consistently to repeated application of ATP ( n = 6) and to recurrent myocardial ischemia ( n = 6). Finally, six ischemia-insensitive cardiac spinal afferents did not respond to epicardial ATP (2–4 μmol), although these afferents did respond to epicardial bradykinin. Taken together, these data indicate that, during ischemia, endogenously released ATP activates ischemia-sensitive, but not ischemia-insensitive, cardiac spinal afferents through stimulation of P2 receptors likely located on the cardiac sensory neurites.

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DiCaprio, Ralph A., Harald Wolf et Ansgar Büschges. « Activity-Dependent Sensitivity of Proprioceptive Sensory Neurons in the Stick Insect Femoral Chordotonal Organ ». Journal of Neurophysiology 88, n^o 5 (1 novembre 2002) : 2387–98. http://dx.doi.org/10.1152/jn.00339.2002.

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Mechanosensory neurons exhibit a wide range of dynamic changes in response, including rapid and slow adaptation. In addition to mechanical factors, electrical processes may also contribute to sensory adaptation. We have investigated adaptation of afferent neurons in the stick insect femoral chordotonal organ (fCO). The fCO contains sensory neurons that respond to position, velocity, and acceleration of the tibia. We describe the influence of random mechanical stimulation of the fCO on the response of fCO afferent neurons. The activity of individual sensory neurons was recorded intracellularly from their axons in the main leg nerve. Most fCO afferents (93%) exhibited a marked decrease in response to trapezoidal stimuli following sustained white noise stimulation (bandwidth = 60 Hz, amplitudes from ±5 to ±30°). Concurrent decreases in the synaptic drive to leg motoneurons and interneurons were also observed. Electrical stimulation of spike activity in individual fCO afferents in the absence of mechanical stimulation also led to a dramatic decrease in response in 15 of 19 afferents tested. This indicated that electrical processes are involved in the regulation of the generator potential or encoding of action potentials and partially responsible for the decreased response of the afferents. Replacing Ca2+ with Ba2+ in the saline surrounding the fCO greatly reduced or blocked the decrease in response elicited by electrically induced activity or mechanical stimulation when compared with control responses. Our results indicate that activity of fCO sensory neurons strongly affects their sensitivity, most likely via Ca2+-dependent processes.

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Bui, Tuan V., et Robert M. Brownstone. « Sensory-evoked perturbations of locomotor activity by sparse sensory input : a computational study ». Journal of Neurophysiology 113, n^o 7 (avril 2015) : 2824–39. http://dx.doi.org/10.1152/jn.00866.2014.

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Sensory inputs from muscle, cutaneous, and joint afferents project to the spinal cord, where they are able to affect ongoing locomotor activity. Activation of sensory input can initiate or prolong bouts of locomotor activity depending on the identity of the sensory afferent activated and the timing of the activation within the locomotor cycle. However, the mechanisms by which afferent activity modifies locomotor rhythm and the distribution of sensory afferents to the spinal locomotor networks have not been determined. Considering the many sources of sensory inputs to the spinal cord, determining this distribution would provide insights into how sensory inputs are integrated to adjust ongoing locomotor activity. We asked whether a sparsely distributed set of sensory inputs could modify ongoing locomotor activity. To address this question, several computational models of locomotor central pattern generators (CPGs) that were mechanistically diverse and generated locomotor-like rhythmic activity were developed. We show that sensory inputs restricted to a small subset of the network neurons can perturb locomotor activity in the same manner as seen experimentally. Furthermore, we show that an architecture with sparse sensory input improves the capacity to gate sensory information by selectively modulating sensory channels. These data demonstrate that sensory input to rhythm-generating networks need not be extensively distributed.

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Sailer, Uta, Marlene Hausmann et Ilona Croy. « Pleasantness Only ? » Experimental Psychology 67, n^o 4 (juillet 2020) : 224–36. http://dx.doi.org/10.1027/1618-3169/a000492.

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Abstract. When gently stroked with velocities between 0.1 and 30 cm/s, participants typically rate velocities around 3 cm/s as most pleasant, and the ratings follow an inverted u-shape. This pleasantness curve correlates often, but not always, with the firing rate of unmyelinated C-tactile (CT) afferents, leading to the notion that CT afferents code for the hedonic or emotional aspect of gentle touch. However, there is also evidence that CT firing does not necessarily equal pleasantness, and the range of attributes that CT afferents code for is not known. Here, participants were stroked with different velocities assumed to activate CT afferents to a different extent while they rated the touch on several sensory and emotional attributes. We expected an inverted u-shaped rating curve for pleasantness and other emotional attributes, but not for sensory attributes. Inverted u-shaped rating patterns were found for the emotional attributes “pleasant” and “not burdensome,” but also for the sensory attribute “rough.” CT-directed stimulation is thus not only experienced as hedonic. The sensations arising from CTs together with all other types of mechanoreceptors might be centrally integrated into a percept that represents those aspects which are most salient for the stimulation at hand.

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Ménard, Ariane, Hugues Leblond et Jean-Pierre Gossard. « Sensory Integration in Presynaptic Inhibitory Pathways During Fictive Locomotion in the Cat ». Journal of Neurophysiology 88, n^o 1 (1 juillet 2002) : 163–71. http://dx.doi.org/10.1152/jn.2002.88.1.163.

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The aim of this study is to understand how sensory inputs of different modalities are integrated into spinal cord pathways controlling presynaptic inhibition during locomotion. Primary afferent depolarization (PAD), an estimate of presynaptic inhibition, was recorded intra-axonally in group I afferents ( n = 31) from seven hindlimb muscles in L6–S1 segments during fictive locomotion in the decerebrate cat. PADs were evoked by stimulating alternatively low-threshold afferents from a flexor nerve, a cutaneous nerve and a combination of both. The fictive step cycle was divided in five bins and PADs were averaged in each bin and their amplitude compared. PADs evoked by muscle stimuli alone showed a significant phase-dependent modulation in 20/31 group I afferents. In 12/20 afferents, the cutaneous stimuli alone evoked a phase-dependent modulation of primary afferent hyperpolarization (PAH, n = 9) or of PADs ( n = 3). Combining the two sensory modalities showed that cutaneous volleys could significantly modify the amplitude of PADs evoked by muscle stimuli in at least one part (bin) of the step cycle in 17/31 (55%) of group I afferents. The most common effect (13/17) was a decrease in the PAD amplitude by 35% on average, whereas it was increased by 17% on average in the others (4/17). Moreover, in 8/13 afferents, the PAD reduction was obtained in 4/5 bins i.e., for most of the duration of the step cycle. These effects were seen in group I afferents from all seven muscles. On the other hand, we found that different cutaneous nerves had quite different efficacy; the superficial peroneal (SP) being the most efficient (85% of trials) followed by Saphenous (60%) and caudal sural (44%) nerves. The results indicate that cutaneous interneurons may act, in part, by modulating the transmission in PAD pathways activated by group I muscle afferents. We conclude that cutaneous input, especially from the skin area on the dorsum of the paw (SP), could subtract presynaptic inhibition in some group I afferents during perturbations of stepping (e.g., hitting an obstacle) and could thus adjust the influence of proprioceptive feedback onto motoneuronal excitability.

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Ray, Didier Le, François Clarac et Daniel Cattaert. « Functional Analysis of the Sensory Motor Pathway of Resistance Reflex in Crayfish. II. Integration of Sensory Inputs in Motor Neurons ». Journal of Neurophysiology 78, n^o 6 (1 décembre 1997) : 3144–53. http://dx.doi.org/10.1152/jn.1997.78.6.3144.

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Le Ray, Didier, François Clarac, and Daniel Cattaert. Functional analysis of the sensory motor pathway of resistance reflex in crayfish. II. Integration of sensory inputs in motor neurons. J. Neurophysiol. 78: 3144–3153, 1997. The in vitro preparation of the fifth thoracic ganglion of the crayfish was used to analyze the connections supporting the monosynaptic reflex responses recorded from the depressor motor neurons (Dep MNs). Dep MNs are directly connected by the release-sensitive afferents from a proprioceptor, the coxo-basipodite chordotonal organ (CBCO), which is released by upward movements of the leg. Sine-wave movements, applied to the CBCO strand from the most released position, allowed us to stimulate the greatest part of release-sensitive CBCO fibers. Systematic intracellular recordings from all Dep MNs performed in high divalent cation saline allowed us to determine the connections between CBCO afferents and their postsynaptic Dep MNs: it highlighted the sequential activation of the different Dep MNs involved in the monosynaptic reflex. The convergence of different sensory afferents onto a given Dep MN, and the divergence of a given sensory afferent onto several Dep MNs illustrates the complexity of the sensory-motor reflex loops involved in the control of locomotion and posture. Electrophysiological experiments and simulations were performed to analyze the mechanisms by which Dep MNs integrate the large amount of sensory input that they receive. Paired intracellular recording experiments demonstrated that postsynaptic response shapes characteristic of both phasic and phaso-tonic afferents could be induced by varying the presynaptic firing frequency, whatever the postsynaptic Dep MN. Compartment model simulations were used to analyze the role of the sensory-motor synapse characteristics in the summation properties of postsynaptic MN. They demonstrated the importance of the postsynaptic compartment geometry, because large postsynaptic compartments allowed to generate greater excitatory postsynaptic potential (EPSP) summations than small ones. The results presented show that velocity information is the most effective to elicit large compound EPSPs in MNs. We therefore suggest that the negative feedback reflex is mainly based on the detection of leg movements.

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Gu, Qihai, et Ruei-Lung Lin. « Heavy metals zinc, cadmium, and copper stimulate pulmonary sensory neurons via direct activation of TRPA1 ». Journal of Applied Physiology 108, n^o 4 (avril 2010) : 891–97. http://dx.doi.org/10.1152/japplphysiol.01371.2009.

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Airway exposure to zinc dust and zinc-containing ambient particulates can cause symptoms of airway irritation and inflammation, but the underlying molecular and cellular mechanisms are largely unknown. Transient receptor potential A1 (TRPA1) is selectively expressed in a subpopulation of pulmonary C-fiber afferents and has been considered as a major irritant sensor in the lung and airways. Using whole cell patch-clamp recording and Ca2+ imaging, we have demonstrated that application of ZnCl2 concentration dependently evoked inward current and Ca2+ transient in isolated vagal pulmonary sensory neurons; both responses were almost completely inhibited after pretreatment with AP18, a specific TRPA1 antagonist. In anesthetized spontaneously breathing animals, intratracheal instillation of ZnCl2 (2 mM, 25 μl) induced pronounced respiratory depression in wild-type mice, and the effect was essentially absent in TRPA1-deficient mice. In addition, our study showed that two other heavy metals, cadmium and copper, also stimulated pulmonary sensory neurons via a direct activation of TRPA1. In summary, our results suggest that activation of TRPA1 in pulmonary C-fiber sensory nerves may contribute to the respiratory toxicity induced by airway exposure to these three heavy metals.

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Ito, Takayuki, et David J. Ostry. « Somatosensory Contribution to Motor Learning Due to Facial Skin Deformation ». Journal of Neurophysiology 104, n^o 3 (septembre 2010) : 1230–38. http://dx.doi.org/10.1152/jn.00199.2010.

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Motor learning is dependent on kinesthetic information that is obtained both from cutaneous afferents and from muscle receptors. In human arm movement, information from these two kinds of afferents is largely correlated. The facial skin offers a unique situation in which there are plentiful cutaneous afferents and essentially no muscle receptors and, accordingly, experimental manipulations involving the facial skin may be used to assess the possible role of cutaneous afferents in motor learning. We focus here on the information for motor learning provided by the deformation of the facial skin and the motion of the lips in the context of speech. We used a robotic device to slightly stretch the facial skin lateral to the side of the mouth in the period immediately preceding movement. We found that facial skin stretch increased lip protrusion in a progressive manner over the course of a series of training trials. The learning was manifest in a changed pattern of lip movement, when measured after learning in the absence of load. The newly acquired motor plan generalized partially to another speech task that involved a lip movement of different amplitude. Control tests indicated that the primary source of the observed adaptation was sensory input from cutaneous afferents. The progressive increase in lip protrusion over the course of training fits with the basic idea that change in sensory input is attributed to motor performance error. Sensory input, which in the present study precedes the target movement, is credited to the target-related motion, even though the skin stretch is released prior to movement initiation. This supports the idea that the nervous system generates motor commands on the assumption that sensory input and kinematic error are in register.

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Kirkup, Anthony J., Alan M. Brunsden et David Grundy. « I. Receptors on visceral afferents ». American Journal of Physiology-Gastrointestinal and Liver Physiology 280, n^o 5 (1 mai 2001) : G787—G794. http://dx.doi.org/10.1152/ajpgi.2001.280.5.g787.

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Visceral afferents are the information superhighway from the gut to the central nervous system. These sensory nerves express a wide range of membrane receptors that can modulate their sensitivity. In this themes article, we concentrate on those receptors that enhance the excitability of visceral afferent neurons. Some receptors are part of a modality-specific transduction pathway involved in sensory signaling. Others, which are activated by substances derived from multiple cellular sources during ischemia, injury, or inflammation, act in a synergistic fashion to cause acute or chronic sensitization of the afferent nerves to mechanical and chemical stimuli. Such hypersensitivity is the hallmark of conditions such as irritable bowel syndrome. Accordingly, these receptors represent a rational target for drug treatments aimed at attenuating both the inappropriate visceral sensation and the aberrant reflex activity that are the foundation for alterations in bowel function.

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Rousselot, P., D. A. Poulain et D. T. Theodosis. « Ultrastructural visualization and neurochemical characterization of spinal projections of primary sensory afferents from the nipple : combined use of transganglionic transport of HRP-WGA and glutamate immunocytochemistry. » Journal of Histochemistry & ; Cytochemistry 42, n^o 1 (janvier 1994) : 115–23. http://dx.doi.org/10.1177/42.1.8263323.

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We used transganglionic transport of the neuronal tracer horseradish peroxidase coupled to wheat germ agglutinin (HRP-WGA) and post-embedding immunogold staining to determine the spinal projections and neurochemical identity of sensory afferents originating from a discrete cutaneous area. After SC injection of tracer into the nipple of lactating rats and reaction with tetramethylbenzidine stabilized with diaminobenzidene (TMB-DAB) or DAB and cobalt (TMB-DAB-Co), we found labeled terminals in the internal part of the first two layers of the dorsal horn where they formed axodendritic synapses and, at times, central elements of glomeruli, synaptic complexes believed to be involved in the integration of sensory messages. Immunogold staining of ultra-thin sections of tissue reacted with TMB-DAB-Co revealed that many mammary afferents contained glutamate as putative neurotransmitter. This combined approach thus offers the possibility of marking a limited set of primary afferents, after capture of tracer by sensory receptors of restricted peripheral areas, to visualize their projections at the spinal level and to determine their neurochemical nature with electron microscopy.

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Lüdtke, Niklas, et Mark E. Nelson. « Short-Term Synaptic Plasticity Can Enhance Weak Signal Detectability in Nonrenewal Spike Trains ». Neural Computation 18, n^o 12 (décembre 2006) : 2879–916. http://dx.doi.org/10.1162/neco.2006.18.12.2879.

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We study the encoding of weak signals in spike trains with interspike interval (ISI) correlations and the signals' subsequent detection in sensory neurons. Motivated by the observation of negative ISI correlations in auditory and electrosensory afferents, we assess the theoretical performance limits of an individual detector neuron receiving a weak signal distributed across multiple afferent inputs. We assess the functional role of ISI correlations in the detection process using statistical detection theory and derive two sequential likelihood ratio detector models: one for afferents with renewal statistics; the other for afferents with negatively correlated ISIs. We suggest a mechanism that might enable sensory neurons to implicitly compute conditional probabilities of presynaptic spikes by means of short-term synaptic plasticity. We demonstrate how this mechanism can enhance a postsynaptic neuron's sensitivity to weak signals by exploiting the correlation structure of the input spike trains. Our model not only captures fundamental aspects of early electrosensory signal processing in weakly electric fish, but may also bear relevance to the mammalian auditory system and other sensory modalities.

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Umeda, Tatsuya, Tadashi Isa et Yukio Nishimura. « Proprioceptive information coded by populational sensory afferents ». Journal of Physical Fitness and Sports Medicine 3, n^o 5 (2014) : 477–82. http://dx.doi.org/10.7600/jpfsm.3.477.

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Runold, M., N. R. Prabhakar et N. S. Cherniack. « Effect of adenosine on vagal sensory afferents ». Biological Psychology 29, n^o 1 (août 1989) : 78–79. http://dx.doi.org/10.1016/0301-0511(89)90071-9.

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