Journal articles: 'Primary Visual Cortex (PVC)'

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Dai, Peishan, Jinlong Zhang, Jing Wu, Zailiang Chen, Beiji Zou, Ying Wu, Xin Wei, and Manyi Xiao. "Altered Spontaneous Brain Activity of Children with Unilateral Amblyopia: A Resting State fMRI Study." Neural Plasticity 2019 (July 25, 2019): 1–10. http://dx.doi.org/10.1155/2019/3681430.

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Objective. This study is aimed at investigating differences in local brain activity and functional connectivity (FC) between children with unilateral amblyopia and healthy controls (HCs) by using resting state functional magnetic resonance imaging (rs-fMRI). Methods. Local activity and FC analysis methods were used to explore the altered spontaneous brain activity of children with unilateral amblyopia. Local brain function analysis methods included the amplitude of low-frequency fluctuation (ALFF). FC analysis methods consisted of the FC between the primary visual cortex (PVC-FC) and other brain regions and the FC network between regions of interest (ROIs-FC) selected by independent component analysis. Results. The ALFF in the bilateral frontal, temporal, and occipital lobes in the amblyopia group was lower than that in the HCs. The weakened PVC-FC was mainly concentrated in the frontal lobe and the angular gyrus. The ROIs-FC between the default mode network, salience network, and primary visual cortex network (PVCN) were significantly reduced, whereas the ROIs-FC between the PVCN and the high-level visual cortex network were significantly increased in amblyopia. Conclusions. Unilateral amblyopia may reduce local brain activity and FC in the dorsal and ventral visual pathways and affect the top-down attentional control. Amblyopia may also alter FC between brain functional networks. These findings may help understand the pathological mechanisms of children with amblyopia.

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Padnick, Lissa B., Robert A. Linsenmeier, and Thomas K. Goldstick. "Perfluorocarbon emulsion improves oxygenation of the cat primary visual cortex." Journal of Applied Physiology 86, no. 5 (May 1, 1999): 1497–504. http://dx.doi.org/10.1152/jappl.1999.86.5.1497.

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Tissue[Formula: see text] was measured in the primary visual cortex of anesthetized, artificially ventilated, normovolemic cats to evaluate the effect of small doses [1 g perfluorocarbon (PFC)/kg] of a PFC emulsion (1 g PFC/1.1 ml emulsion; Alliance Pharmaceutical, San Diego, CA) on brain oxygenation. The change in tissue [Formula: see text]([Formula: see text]), resulting from briefly changing the respiratory gas from room air to 100% oxygen, was measured before and after intravenous infusion of the emulsion. Before emulsion, [Formula: see text] was 51.1 ± 45.6 Torr ( n = 8 cats). Increases in [Formula: see text] of 34.0 ± 26.1 (SD) % ( n = 8) and 16.3 ± 8.4% ( n = 6) were observed after the first and second emulsion infusions, respectively. The further increase in [Formula: see text] after the third dose (7.9 ± 10.5%; n = 7) was not statistically significant. The observed increases in tissue oxygenation as a result of the PFC infusions appear to be the result of enhanced oxygen transport to the tissue.

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Reed, Catherine L. "Divisions within the posterior parietal cortex help touch meet vision." Behavioral and Brain Sciences 30, no. 2 (April 2007): 218. http://dx.doi.org/10.1017/s0140525x07001574.

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AbstractThe parietal cortex is divided into two major functional regions: the anterior parietal cortex that includes primary somatosensory cortex, and the posterior parietal cortex (PPC) that includes the rest of the parietal lobe. The PPC contains multiple representations of space. In Dijkerman & de Haan's (D&dH's) model, higher spatial representations are separate from PPC functions. This model should be developed further so that the functions of the somatosensory system are integrated with specific functions within the PPC and higher spatial representations. Through this further specification of the model, one can make better predictions regarding functional interactions between somatosensory and visual systems.

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Karabanov, Anke, Seung-Hyun Jin, Atte Joutsen, Brach Poston, Joshua Aizen, Aviva Ellenstein, and Mark Hallett. "Timing-dependent modulation of the posterior parietal cortex–primary motor cortex pathway by sensorimotor training." Journal of Neurophysiology 107, no. 11 (June 1, 2012): 3190–99. http://dx.doi.org/10.1152/jn.01049.2011.

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Interplay between posterior parietal cortex (PPC) and ipsilateral primary motor cortex (M1) is crucial during execution of movements. The purpose of the study was to determine whether functional PPC–M1 connectivity in humans can be modulated by sensorimotor training. Seventeen participants performed a sensorimotor training task that involved tapping the index finger in synchrony to a rhythmic sequence. To explore differences in training modality, one group ( n = 8) learned by visual and the other ( n = 9) by auditory stimuli. Transcranial magnetic stimulation (TMS) was used to assess PPC–M1 connectivity before and after training, whereas electroencephalography (EEG) was used to assess PPC–M1 connectivity during training. Facilitation from PPC to M1 was quantified using paired-pulse TMS at conditioning-test intervals of 2, 4, 6, and 8 ms by measuring motor-evoked potentials (MEPs). TMS was applied at baseline and at four time points (0, 30, 60, and 180 min) after training. For EEG, task-related power and coherence were calculated for early and late training phases. The conditioned MEP was facilitated at a 2-ms conditioning-test interval before training. However, facilitation was abolished immediately following training, but returned to baseline at subsequent time points. Regional EEG activity and interregional connectivity between PPC and M1 showed an initial increase during early training followed by a significant decrease in the late phases. The findings indicate that parietal–motor interactions are activated during early sensorimotor training when sensory information has to be integrated into a coherent movement plan. Once the sequence is encoded and movements become automatized, PPC–M1 connectivity returns to baseline.

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Yan, Xiaodan. "Dissociated Emergent-Response System and Fine-Processing System in Human Neural Network and a Heuristic Neural Architecture for Autonomous Humanoid Robots." Computational Intelligence and Neuroscience 2010 (2010): 1–8. http://dx.doi.org/10.1155/2010/314932.

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The current study investigated the functional connectivity of the primary sensory system with resting state fMRI and applied such knowledge into the design of the neural architecture of autonomous humanoid robots. Correlation and Granger causality analyses were utilized to reveal the functional connectivity patterns. Dissociation was within the primary sensory system, in that the olfactory cortex and the somatosensory cortex were strongly connected to the amygdala whereas the visual cortex and the auditory cortex were strongly connected with the frontal cortex. The posterior cingulate cortex (PCC) and the anterior cingulate cortex (ACC) were found to maintain constant communication with the primary sensory system, the frontal cortex, and the amygdala. Such neural architecture inspired the design of dissociated emergent-response system and fine-processing system in autonomous humanoid robots, with separate processing units and another consolidation center to coordinate the two systems. Such design can help autonomous robots to detect and respond quickly to danger, so as to maintain their sustainability and independence.

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Liu, Qin, Antonio Ulloa, and Barry Horwitz. "Using a Large-scale Neural Model of Cortical Object Processing to Investigate the Neural Substrate for Managing Multiple Items in Short-term Memory." Journal of Cognitive Neuroscience 29, no. 11 (November 2017): 1860–76. http://dx.doi.org/10.1162/jocn_a_01163.

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Many cognitive and computational models have been proposed to help understand working memory. In this article, we present a simulation study of cortical processing of visual objects during several working memory tasks using an extended version of a previously constructed large-scale neural model [Tagamets, M. A., & Horwitz, B. Integrating electrophysiological and anatomical experimental data to create a large-scale model that simulates a delayed match-to-sample human brain imaging study. Cerebral Cortex, 8, 310–320, 1998]. The original model consisted of arrays of Wilson–Cowan type of neuronal populations representing primary and secondary visual cortices, inferotemporal (IT) cortex, and pFC. We added a module representing entorhinal cortex, which functions as a gating module. We successfully implemented multiple working memory tasks using the same model and produced neuronal patterns in visual cortex, IT cortex, and pFC that match experimental findings. These working memory tasks can include distractor stimuli or can require that multiple items be retained in mind during a delay period (Sternberg's task). Besides electrophysiology data and behavioral data, we also generated fMRI BOLD time series from our simulation. Our results support the involvement of IT cortex in working memory maintenance and suggest the cortical architecture underlying the neural mechanisms mediating particular working memory tasks. Furthermore, we noticed that, during simulations of memorizing a list of objects, the first and last items in the sequence were recalled best, which may implicate the neural mechanism behind this important psychological effect (i.e., the primacy and recency effect).

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Everling, Stefan, and Kevin Johnston. "Control of the superior colliculus by the lateral prefrontal cortex." Philosophical Transactions of the Royal Society B: Biological Sciences 368, no. 1628 (October 19, 2013): 20130068. http://dx.doi.org/10.1098/rstb.2013.0068.

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Several decades of patient, functional imaging and neurophysiological studies have supported a model in which the lateral prefrontal cortex (PFC) acts to suppress unwanted saccades by inhibiting activity in the oculomotor system. However, recent results from combined PFC deactivation and neural recordings of the superior colliculus in monkeys demonstrate that the primary influence of the PFC on the oculomotor system is excitatory, and stands in direct contradiction to the inhibitory model of PFC function. Although erroneous saccades towards a visual stimulus are commonly labelled reflexive in patients with PFC damage or dysfunction, the latencies of most of these saccades are outside of the range of express saccades, which are triggered directly by the visual stimulus. Deactivation and pharmacological manipulation studies in monkeys suggest that response errors following PFC damage or dysfunction are not the result of a failure in response suppression but can best be understood in the context of a failure to maintain and implement the proper task set.

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Oh, Jihoon, Jae Hyung Kwon, Po Song Yang, and Jaeseung Jeong. "Auditory Imagery Modulates Frequency-specific Areas in the Human Auditory Cortex." Journal of Cognitive Neuroscience 25, no. 2 (February 2013): 175–87. http://dx.doi.org/10.1162/jocn_a_00280.

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Neural responses in early sensory areas are influenced by top–down processing. In the visual system, early visual areas have been shown to actively participate in top–down processing based on their topographical properties. Although it has been suggested that the auditory cortex is involved in top–down control, functional evidence of topographic modulation is still lacking. Here, we show that mental auditory imagery for familiar melodies induces significant activation in the frequency-responsive areas of the primary auditory cortex (PAC). This activation is related to the characteristics of the imagery: when subjects were asked to imagine high-frequency melodies, we observed increased activation in the high- versus low-frequency response area; when the subjects were asked to imagine low-frequency melodies, the opposite was observed. Furthermore, we found that A1 is more closely related to the observed frequency-related modulation than R in tonotopic subfields of the PAC. Our findings suggest that top–down processing in the auditory cortex relies on a mechanism similar to that used in the perception of external auditory stimuli, which is comparable to early visual systems.

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Sellers, Kristin K., Davis V. Bennett, Axel Hutt, James H. Williams, and Flavio Fröhlich. "Awake vs. anesthetized: layer-specific sensory processing in visual cortex and functional connectivity between cortical areas." Journal of Neurophysiology 113, no. 10 (June 2015): 3798–815. http://dx.doi.org/10.1152/jn.00923.2014.

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During general anesthesia, global brain activity and behavioral state are profoundly altered. Yet it remains mostly unknown how anesthetics alter sensory processing across cortical layers and modulate functional cortico-cortical connectivity. To address this gap in knowledge of the micro- and mesoscale effects of anesthetics on sensory processing in the cortical microcircuit, we recorded multiunit activity and local field potential in awake and anesthetized ferrets ( Mustela putoris furo) during sensory stimulation. To understand how anesthetics alter sensory processing in a primary sensory area and the representation of sensory input in higher-order association areas, we studied the local sensory responses and long-range functional connectivity of primary visual cortex (V1) and prefrontal cortex (PFC). Isoflurane combined with xylazine provided general anesthesia for all anesthetized recordings. We found that anesthetics altered the duration of sensory-evoked responses, disrupted the response dynamics across cortical layers, suppressed both multimodal interactions in V1 and sensory responses in PFC, and reduced functional cortico-cortical connectivity between V1 and PFC. Together, the present findings demonstrate altered sensory responses and impaired functional network connectivity during anesthesia at the level of multiunit activity and local field potential across cortical layers.

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Hedrick, Tristan, and Jack Waters. "Acetylcholine excites neocortical pyramidal neurons via nicotinic receptors." Journal of Neurophysiology 113, no. 7 (April 2015): 2195–209. http://dx.doi.org/10.1152/jn.00716.2014.

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The neuromodulator acetylcholine (ACh) shapes neocortical function during sensory perception, motor control, arousal, attention, learning, and memory. Here we investigate the mechanisms by which ACh affects neocortical pyramidal neurons in adult mice. Stimulation of cholinergic axons activated muscarinic and nicotinic ACh receptors on pyramidal neurons in all cortical layers and in multiple cortical areas. Nicotinic receptor activation evoked short-latency, depolarizing postsynaptic potentials (PSPs) in many pyramidal neurons. Nicotinic receptor-mediated PSPs promoted spiking of pyramidal neurons. The duration of the increase in spiking was membrane potential dependent, with nicotinic receptor activation triggering persistent spiking lasting many seconds in neurons close to threshold. Persistent spiking was blocked by intracellular BAPTA, indicating that nicotinic ACh receptor activation evoked persistent spiking via a long-lasting calcium-activated depolarizing current. We compared nicotinic PSPs in primary motor cortex (M1), prefrontal cortex (PFC), and visual cortex. The laminar pattern of nicotinic excitation was not uniform but was broadly similar across areas, with stronger modulation in deep than superficial layers. Superimposed on this broad pattern were local differences, with nicotinic PSPs being particularly large and common in layer 5 of M1 but not layer 5 of PFC or primary visual cortex (V1). Hence, in addition to modulating the excitability of pyramidal neurons in all layers via muscarinic receptors, synaptically released ACh preferentially increases the activity of deep-layer neocortical pyramidal neurons via nicotinic receptors, thereby adding laminar selectivity to the widespread enhancement of excitability mediated by muscarinic ACh receptors.

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Zuo, Yanfang, Yanwang Huang, Dingcheng Wu, Qingxiu Wang, and Zuoren Wang. "Spike Phase Shift Relative to Beta Oscillations Mediates Modality Selection." Cerebral Cortex 30, no. 10 (June 4, 2020): 5431–48. http://dx.doi.org/10.1093/cercor/bhaa125.

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Abstract How does the brain selectively process signals from stimuli of different modalities? Coherent oscillations may function in coordinating communication between neuronal populations simultaneously involved in such cognitive behavior. Beta power (12–30 Hz) is implicated in top-down cognitive processes. Here we test the hypothesis that the brain increases encoding and behavioral influence of a target modality by shifting the relationship of neuronal spike phases relative to beta oscillations between primary sensory cortices and higher cortices. We simultaneously recorded neuronal spike and local field potentials in the posterior parietal cortex (PPC) and the primary auditory cortex (A1) when male rats made choices to either auditory or visual stimuli. Neuronal spikes exhibited modality-related phase locking to beta oscillations during stimulus sampling, and the phase shift between neuronal subpopulations demonstrated faster top-down signaling from PPC to A1 neurons when animals attended to auditory rather than visual stimuli. Importantly, complementary to spike timing, spike phase predicted rats’ attended-to target in single trials, which was related to the animals’ performance. Our findings support a candidate mechanism that cortices encode targets from different modalities by shifting neuronal spike phase. This work may extend our understanding of the importance of spike phase as a coding and readout mechanism.

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Parra, Andres, Christopher A. Baker, and M. McLean Bolton. "Regional Specialization of Pyramidal Neuron Morphology and Physiology in the Tree Shrew Neocortex." Cerebral Cortex 29, no. 11 (January 31, 2019): 4488–505. http://dx.doi.org/10.1093/cercor/bhy326.

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Abstract The mammalian cerebral cortex is divided into different areas according to their function and pattern of connections. Studies comparing primary visual (V1) and prefrontal cortex (PFC) of primates have demonstrated striking pyramidal neuron (PN) specialization not present in comparable areas of the mouse neocortex. To better understand PFC evolution and regional PN specialization, we studied the tree shrew, a species with a close phylogenetic relationship to primates. We defined the tree shrew PFC based on cytoarchitectonic borders, thalamic connectivity and characterized the morphology and electrophysiology of layer II/III PNs in V1 and PFC. Similar to primates, the PFC PNs in the tree shrew fire with a regular spiking pattern and have larger dendritic tree and spines than those in V1. However, V1 PNs showed strikingly large basal dendritic arbors with high spine density, firing at higher rates and in a more varied pattern than PFC PNs. Yet, unlike in the mouse and unreported in the primate, medial prefrontal PN are more easily recruited than either the dorsolateral or V1 neurons. This specialization of PN morphology and physiology is likely to be a significant factor in the evolution of cortex, contributing to differences in the computational capacities of individual cortical areas.

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Isayama, Reina, Michael Vesia, Gaayathiri Jegatheeswaran, Behzad Elahi, Carolyn A. Gunraj, Lucilla Cardinali, Alessandro Farnè, and Robert Chen. "Rubber hand illusion modulates the influences of somatosensory and parietal inputs to the motor cortex." Journal of Neurophysiology 121, no. 2 (February 1, 2019): 563–73. http://dx.doi.org/10.1152/jn.00345.2018.

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The rubber hand illusion (RHI) paradigm experimentally produces an illusion of rubber hand ownership and arm shift by simultaneously stroking a rubber hand in view and a participant’s visually occluded hand. It involves visual, tactile, and proprioceptive multisensory integration and activates multisensory areas in the brain, including the posterior parietal cortex (PPC). Multisensory inputs are transformed into outputs for motor control in association areas such as PPC. A behavioral study reported decreased motor performance after RHI. However, it remains unclear whether RHI modifies the interactions between sensory and motor systems and between PPC and the primary motor cortex (M1). We used transcranial magnetic stimulation (TMS) and examined the functional connections from the primary somatosensory and association cortices to M1 and from PPC to M1 during RHI. In experiment 1, short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI) were measured before and immediately after a synchronous (RHI) or an asynchronous (control) condition. In experiment 2, PPC-M1 interaction was measured using two coils. We found that SAI and LAI were reduced in the synchronous condition compared with baseline, suggesting that RHI decreased somatosensory processing in the primary sensory and the association cortices projecting to M1. We also found that greater inhibitory PPC-M1 interaction was associated with stronger RHI assessed by questionnaire. Our findings suggest that RHI modulates both the early and late stages of processing of tactile afferent, which leads to altered M1 excitability by reducing the gain of somatosensory afferents to resolve conflicts among multisensory inputs. NEW & NOTEWORTHY Perception of one’s own body parts involves integrating different sensory information and is important for motor control. We found decreased effects of cutaneous stimulation on motor cortical excitability during rubber hand illusion (RHI), which may reflect decreased gain of tactile input to resolve multisensory conflicts. RHI strength correlated with the degree of inhibitory posterior parietal cortex-motor cortex interaction, indicating that parietal-motor connection is involved in resolving sensory conflicts and body ownership during RHI.

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Hashemirad, Fahimeh, Maryam Zoghi, Paul B. Fitzgerald, Masoumeh Hashemirad, and Shapour Jaberzadeh. "Site Dependency of Anodal Transcranial Direct-Current Stimulation on Reaction Time and Transfer of Learning during a Sequential Visual Isometric Pinch Task." Brain Sciences 14, no. 4 (April 22, 2024): 408. http://dx.doi.org/10.3390/brainsci14040408.

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Considering the advantages of brain stimulation techniques in detecting the role of different areas of the brain in human sensorimotor behaviors, we used anodal transcranial direct-current stimulation (a-tDCS) over three different brain sites of the frontoparietal cortex (FPC) in healthy participants to elucidate the role of these three brain areas of the FPC on reaction time (RT) during a sequential visual isometric pinch task (SVIPT). We also aimed to assess if the stimulation of these cortical sites affects the transfer of learning during SVIPT. A total of 48 right-handed healthy participants were randomly assigned to one of the four a-tDCS groups: (1) left primary motor cortex (M1), (2) left dorsolateral prefrontal cortex (DLPFC), (3) left posterior parietal cortex (PPC), and (4) sham. A-tDCS (0.3 mA, 20 min) was applied concurrently with the SVIPT, in which the participants precisely controlled their forces to reach seven different target forces from 10 to 40% of the maximum voluntary contraction (MVC) presented on a computer screen with the right dominant hand. Four test blocks were randomly performed at the baseline and 15 min after the intervention, including sequence and random blocks with either hand. Our results showed significant elongations in the ratio of RTs between the M1 and sham groups in the sequence blocks of both the right-trained and left-untrained hands. No significant differences were found between the DLPFC and sham groups and the PPC and sham groups in RT measurements within the SVIPT. Our findings suggest that RT improvement within implicit learning of an SVIPT is not mediated by single-session a-tDCS over M1, DLPFC, or PPC. Further research is needed to understand the optimal characteristics of tDCS and stimulation sites to modulate reaction time in a precision control task such as an SVIPT.

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Lyons, Michael J., Kazunori Morikawa, and Shigeru Akamatsu. "A linked aggregate code for processing faces." Facial Information Processing 8, no. 1 (May 17, 2000): 63–81. http://dx.doi.org/10.1075/pc.8.1.04lyo.

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A model of face representation, inspired by known biology of the visual system, is compared to experimental data on the perception of facial similarity. The face representation model uses aggregate primary visual cortex (V1) cell responses topographically linked to a grid covering the face, allowing comparison of shape and texture at corresponding points in two facial images. When a set of relatively similar faces was used as stimuli, this “linked aggregate code” (LAC) predicted human performance in similarity judgment experiments. When faces of different categories were used, natural facial dimensions such as sex and race emerged from the LAC model without training. The dimensional structure of the LAC similarity measure for the mixed-category task displayed some psychologically plausible features, but also highlighted shortcomings of the proposed representation. The results suggest that the LAC based similarity measure may be useful as an interesting starting point for further modeling studies of face representation in higher visual areas.

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Sellers, Kristin K., Davis V. Bennett, Axel Hutt, and Flavio Fröhlich. "Anesthesia differentially modulates spontaneous network dynamics by cortical area and layer." Journal of Neurophysiology 110, no. 12 (December 15, 2013): 2739–51. http://dx.doi.org/10.1152/jn.00404.2013.

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Anesthesia is widely used in medicine and research to achieve altered states of consciousness and cognition. Whereas changes to macroscopic cortical activity patterns by anesthesia measured at the spatial resolution of electroencephalography have been widely studied, modulation of mesoscopic and microscopic network dynamics by anesthesia remain poorly understood. To address this gap in knowledge, we recorded spontaneous mesoscopic (local field potential) and microscopic (multiunit activity) network dynamics in primary visual cortex (V1) and prefrontal cortex (PFC) of awake and isoflurane anesthetized ferrets ( Mustela putoris furo). This approach allowed for examination of activity as a function of cortical area, cortical layer, and anesthetic depth with much higher spatial and temporal resolution than in previous studies. We hypothesized that a primary sensory area and an association cortical area would exhibit different patterns of network modulation by anesthesia due to their different functional roles. Indeed, we found effects specific to cortical area and cortical layer. V1 exhibited minimal changes in rhythmic structure with anesthesia but differential modulation of input layer IV. In contrast, anesthesia profoundly altered spectral power in PFC, with more uniform modulation across cortical layers. Our results demonstrate that anesthesia modulates spontaneous cortical activity in an area- and layer-specific manner. These finding provide the basis for 1) refining anesthesia monitoring algorithms, 2) reevaluating the large number of systems neuroscience studies performed in anesthetized animals, and 3) increasing our understanding of differential dynamics across cortical layers and areas.

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Retter, Talia L., Michael A. Webster, and Fang Jiang. "Directional Visual Motion Is Represented in the Auditory and Association Cortices of Early Deaf Individuals." Journal of Cognitive Neuroscience 31, no. 8 (August 2019): 1126–40. http://dx.doi.org/10.1162/jocn_a_01378.

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Individuals who are deaf since early life may show enhanced performance at some visual tasks, including discrimination of directional motion. The neural substrates of such behavioral enhancements remain difficult to identify in humans, although neural plasticity has been shown for early deaf people in the auditory and association cortices, including the primary auditory cortex (PAC) and STS region, respectively. Here, we investigated whether neural responses in auditory and association cortices of early deaf individuals are reorganized to be sensitive to directional visual motion. To capture direction-selective responses, we recorded fMRI responses frequency-tagged to the 0.1-Hz presentation of central directional (100% coherent random dot) motion persisting for 2 sec contrasted with nondirectional (0% coherent) motion for 8 sec. We found direction-selective responses in the STS region in both deaf and hearing participants, but the extent of activation in the right STS region was 5.5 times larger for deaf participants. Minimal but significant direction-selective responses were also found in the PAC of deaf participants, both at the group level and in five of six individuals. In response to stimuli presented separately in the right and left visual fields, the relative activation across the right and left hemispheres was similar in both the PAC and STS region of deaf participants. Notably, the enhanced right-hemisphere activation could support the right visual field advantage reported previously in behavioral studies. Taken together, these results show that the reorganized auditory cortices of early deaf individuals are sensitive to directional motion. Speculatively, these results suggest that auditory and association regions can be remapped to support enhanced visual performance.

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HIGO, NORIYUKI, TAKAO OISHI, AKIKO YAMASHITA, KEIJI MATSUDA, and MOTOHARU HAYASHI. "Expression of MARCKS mRNA in lateral geniculate nucleus and visual cortex of normal and monocularly deprived macaque monkeys." Visual Neuroscience 19, no. 5 (September 2002): 633–43. http://dx.doi.org/10.1017/s0952523802195083.

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We performed a nonradioactive in situ hybridization histochemistry (ISH) study of the lateral geniculate nucleus (LGN) and the primary visual area (area 17) of the macaque monkey to investigate mRNA expression of the myristoylated alanine-rich C-kinase substrate (MARCKS), a major protein kinase C (PKC) substrate. In the LGN, intense hybridization signals were observed in both magnocellular neurons (layers 1 and 2) and parvocellular neurons (layers 3 to 6). Double labeling using ISH and immunofluorescence revealed that MARCKS mRNA was coexpressed with the α-subunit of type II calcium/calmodulin-dependent protein kinase, indicating that MARCKS mRNA is also expressed in koniocellular neurons in the LGN. GABA-immunoreactive neurons in the LGN did not contain MARCKS mRNA, indicating that MARCKS mRNA is not expressed in inhibitory interneurons. The signals were generally weak in area 17, and intense signals were restricted to large neurons in layers IVB, V, and VI. GABA-immunoreactive neurons in layers II–VI of area 17 did not contain MARCKS mRNA. Double-label ISH revealed that MARCKS mRNA was coexpressed with mRNA of GAP-43, another PKC substrate, in neurons of both the LGN and area 17. To determine whether the expression of MARCKS mRNA is regulated by retinal activity, we performed ISH in the LGN and area 17 of monkeys deprived of monocular visual input by tetrodotoxin. After monocular deprivation for 5 to 30 days, MARCKS mRNA was down-regulated in the LGN, but not in area 17. These results suggest that MARCKS mediates the activity-dependent changes in the excitatory relay neurons in the LGN.

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Muri, R. M., A. I. Vermersch, S. Rivaud, B. Gaymard, and C. Pierrot-Deseilligny. "Effects of single-pulse transcranial magnetic stimulation over the prefrontal and posterior parietal cortices during memory-guided saccades in humans." Journal of Neurophysiology 76, no. 3 (September 1, 1996): 2102–6. http://dx.doi.org/10.1152/jn.1996.76.3.2102.

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1. We used single-pulse transcranial magnetic stimulation (TMS) to explore the temporal organization of the cortical control of memory-guided saccades in eight humans. The posterior parietal cortex (PPC) or the dorsolateral prefrontal cortex (DPFC), which are both known to be involved in the control of such saccades, were stimulated on the right side at different time intervals after the presentation of a flashed lateral visual target. The memorization delay was 2,000 ms. Single pulses were applied at 160, 260, and 360 ms after the flashed target, during the period of 700 and 1,500 ms, and finally at 2,100 ms, i.e., 100 ms after the extinguishing of the central fixation point. The effects of TMS were evaluated by calculating the percentage of error in amplitude (PEA) and latency of memory-guided saccades. The PEA was determined for the primary saccade (motor aspect) and the final eye position, i.e., after the end saccade (mnemonic aspect). Stimulation over the occipital cortex at the same time intervals served as control experiments. 2. After PPC stimulation, a significant increase in the PEA of the primary saccade and final eye position existed for contralateral saccades, compared with the PEA without stimulation, when stimulation was applied 260 ms after target presentation, but not at other time intervals. There was no significant effect on ipsilateral saccades. Latency was significantly increased bilaterally when stimulation was performed 2,100 ms after target presentation. 3. After prefrontal stimulation, a significant increase in the PEA of the primary saccade and final eye position existed for contralateral saccades, when stimulation was applied between 700 and 1,500 ms after target presentation, but not at other time intervals. There was no significant effect on ipsilateral saccades. Latency was not affected by prefrontal TMS at any stimulation times. 4. Occipital stimulation resulted in no significant effect on the PEA and latency of ipsilateral or contralateral saccades, in particular including the application at 260 ms after target presentation or during the memorization phase. 5. From these results it may be concluded that the observed effects of TMS on saccade accuracy were specific to the stimulated region and specific to the stimulation time. The PPC seems to be involved in the preparation of saccade amplitude, during the early phase of the paradigm, i.e., the sensorimotor processing period, whereas the DPFC could play a role during the later phase of the paradigm, i.e., the memorization period. Therefore in humans these results support the experimental findings suggesting that sensorimotor integration is controlled by the PPC and spatial memory by the DPFC. Furthermore, our results suggest that the PPC, although not the DPFC, plays a role in saccade triggering.

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Yang, Fang-Chi, and Rebecca D. Burwell. "Neuronal Activity in the Rat Pulvinar Correlates with Multiple Higher-Order Cognitive Functions." Vision 4, no. 1 (March 1, 2020): 15. http://dx.doi.org/10.3390/vision4010015.

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The pulvinar, also called the lateral posterior nucleus of the thalamus in rodents, is one of the higher-order thalamic relays and the main visual extrageniculate thalamic nucleus in rodents and primates. Although primate studies report the pulvinar is engaged under attentional demands, there are open questions about the detailed role of the pulvinar in visuospatial attention. The pulvinar provides the primary thalamic input to the posterior parietal cortex (PPC). Both the pulvinar and the PPC are known to be important for visuospatial attention. Our previous work showed that neuronal activity in the PPC correlated with multiple phases of a visuospatial attention (VSA) task, including onset of the visual stimuli, decision-making, task-relevant locations, and behavioral outcomes. Here, we hypothesized that the pulvinar, as the major thalamic input to the PPC, is involved in visuospatial attention as well as in other cognitive functions related to the processing of visual information. We recorded the neuronal activity of the pulvinar in rats during their performance on the VSA task. The task was designed to engage goal-directed, top–down attention as well as stimulus-driven, bottom–up attention. Rats monitored three possible locations for the brief appearance of a target stimulus. An approach to the correct target location was followed by a liquid reward. For analysis, each trial was divided into behavioral epochs demarcated by stimulus onset, selection behavior, and approach to reward. We found that neurons in the pulvinar signaled stimulus onset and selection behavior consistent with the interpretation that the pulvinar is engaged in both bottom–up and top–down visuospatial attention. Our results also suggested that pulvinar cells responded to allocentric and egocentric task-relevant locations.

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Maywald, Maximilian, Marco Paolini, Boris Stephan Rauchmann, Christian Gerz, Jan Lars Heppe, Annika Wolf, Linda Lerchenberger, et al. "Individual- and Connectivity-Based Real-Time fMRI Neurofeedback to Modulate Emotion-Related Brain Responses in Patients with Depression: A Pilot Study." Brain Sciences 12, no. 12 (December 14, 2022): 1714. http://dx.doi.org/10.3390/brainsci12121714.

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Introduction: Individual real-time functional magnetic resonance imaging neurofeedback (rtfMRI NF) might be a promising adjuvant in treating depressive symptoms. Further studies showed functional variations and connectivity-related changes in the dorsolateral prefrontal cortex (dlPFC) and the insular cortex. Objectives: The aim of this pilot study was to investigate whether individualized connectivity-based rtfMRI NF training can improve symptoms in depressed patients as an adjunct to a psychotherapeutic programme. The novel strategy chosen for this was to increase connectivity between individualized regions of interest, namely the insula and the dlPFC. Methods: Sixteen patients diagnosed with major depressive disorder (MDD, ICD-10) and 19 matched healthy controls (HC) participated in a rtfMRI NF training consisting of two sessions with three runs each, within an interval of one week. RtfMRI NF was applied during a sequence of negative emotional pictures to modulate the connectivity between the dlPFC and the insula. The MDD REAL group was divided into a Responder and a Non-Responder group. Patients with an increased connectivity during the second NF session or during both the first and the second NF session were identified as “MDD REAL Responder” (N = 6). Patients that did not show any increase in connectivity and/or a decreased connectivity were identified as “MDD REAL Non-Responder” (N = 7). Results: Before the rtfMRI sessions, patients with MDD showed higher neural activation levels in ventromedial PFC and the insula than HC; by contrast, HC revealed increased hemodynamic activity in visual processing areas (primary visual cortex and visual association cortex) compared to patients with MDD. The comparison of hemodynamic responses during the first compared to during the last NF session demonstrated significantly increased BOLD-activation in the medial orbitofrontal cortex (mOFC) in patients and HC, and additionally in the lateral OFC in patients with MDD. These findings were particularly due to the MDD Responder group, as the MDD Non-Responder group showed no increase in this region during the last NF run. There was a decrease of neural activation in emotional processing brain regions in both groups in the last NF run compared to the first: HC showed differences in the insula, parahippocampal gyrus, basal ganglia, and cingulate gyrus. Patients with MDD demonstrated deceased responses in the parahippocampal gyrus. There was no significant reduction of BDI scores after NF training in patients. Conclusions: Increased neural activation in the insula and vmPFC in MDD suggests an increased emotional reaction in patients with MDD. The activation of the mOFC could be associated with improved control-strategies and association-learning processes. The increased lOFC activation could indicate a stronger sensitivity to failed NF attempts in MDD. A stronger involvement of visual processing areas in HC may indicate better adaptation to negative emotional stimuli after repeated presentation. Overall, the rtfMRI NF had an impact on neurobiological mechanisms, but not on psychometric measures in patients with MDD.

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Bhat, Jyoti, Lee M. Miller, Mark A. Pitt, and Antoine J. Shahin. "Putative mechanisms mediating tolerance for audiovisual stimulus onset asynchrony." Journal of Neurophysiology 113, no. 5 (March 1, 2015): 1437–50. http://dx.doi.org/10.1152/jn.00200.2014.

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Audiovisual (AV) speech perception is robust to temporal asynchronies between visual and auditory stimuli. We investigated the neural mechanisms that facilitate tolerance for audiovisual stimulus onset asynchrony (AVOA) with EEG. Individuals were presented with AV words that were asynchronous in onsets of voice and mouth movement and judged whether they were synchronous or not. Behaviorally, individuals tolerated (perceived as synchronous) longer AVOAs when mouth movement preceded the speech (V-A) stimuli than when the speech preceded mouth movement (A-V). Neurophysiologically, the P1-N1-P2 auditory evoked potentials (AEPs), time-locked to sound onsets and known to arise in and surrounding the primary auditory cortex (PAC), were smaller for the in-sync than the out-of-sync percepts. Spectral power of oscillatory activity in the beta band (14–30 Hz) following the AEPs was larger during the in-sync than out-of-sync perception for both A-V and V-A conditions. However, alpha power (8–14 Hz), also following AEPs, was larger for the in-sync than out-of-sync percepts only in the V-A condition. These results demonstrate that AVOA tolerance is enhanced by inhibiting low-level auditory activity (e.g., AEPs representing generators in and surrounding PAC) that code for acoustic onsets. By reducing sensitivity to acoustic onsets, visual-to-auditory onset mapping is weakened, allowing for greater AVOA tolerance. In contrast, beta and alpha results suggest the involvement of higher-level neural processes that may code for language cues (phonetic, lexical), selective attention, and binding of AV percepts, allowing for wider neural windows of temporal integration, i.e., greater AVOA tolerance.

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23

Lee, Seung Yeol, Jisu Seo, Cheong Hoon Seo, Yoon Soo Cho, and So Young Joo. "Gait Performance and Brain Activity Are Improved by Gait Automatization during Robot-Assisted Gait Training in Patients with Burns: A Prospective, Randomized, Single-Blinded Study." Journal of Clinical Medicine 13, no. 16 (August 16, 2024): 4838. http://dx.doi.org/10.3390/jcm13164838.

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Background: Patients with lower extremity burn injuries have decreased gait function. Gait dysfunctions are compensated by activation of executive areas such as the prefrontal cortex (PFC). Although robot-assisted gait training (RAGT) can improve gait function, the training mechanisms of RAGT are unknown. We aimed to determine the clinical effects of RAGT in patients with burns and investigate their underlying mechanisms. Methods: This single-blind, randomized controlled trial involved 54 patients with lower extremity burns. The RAGT group underwent RAGT using SUBAR® and conventional training. The control (CON) group underwent only conventional training. The primary outcome was cortical activity measured using a functional near-infrared spectroscopy device before and after 8 weeks of training to confirm the compensatory effect of gait dysfunction. The secondary outcomes were the functional ambulation category (FAC) to evaluate gait performance, 6-min walking test (6 MWT) distance to measure gait speed, isometric force and range of motion (ROM) of lower extremities to evaluate physical function, and the visual analog scale (VAS) score to evaluate subjective pain during gait. Results: PFC activation during the gait phase in the RAGT group decreased significantly compared with that of the CON. The VAS score decreased and FAC score improved after 8 weeks of training in both groups. The 6 MWT scores, isometric strengths (the left knee flexor and bilateral ankle plantar flexors), and the ROMs (the extensions of bilateral hip and bilateral knee) of the RAGT group were significantly improved compared with those of the CON. RAGT improved gait speed, lower extremity ROMs, and lower extremity muscles strengths in patients with burns. Conclusions: The improvement in gait speed and cerebral blood flow evaluation results suggests that the automatization of gait is related to the treatment mechanism during RAGT.

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Solbakk, Anne-Kristin, Ingrid Funderud, Marianne Løvstad, Tor Endestad, Torstein Meling, Magnus Lindgren, Robert T. Knight, and Ulrike M. Krämer. "Impact of Orbitofrontal Lesions on Electrophysiological Signals in a Stop Signal Task." Journal of Cognitive Neuroscience 26, no. 7 (July 2014): 1528–45. http://dx.doi.org/10.1162/jocn_a_00561.

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Behavioral inhibition and performance monitoring are critical cognitive functions supported by distributed neural networks including the pFC. We examined neurophysiological correlates of motor response inhibition and action monitoring in patients with focal orbitofrontal (OFC) lesions (n = 12) after resection of a primary intracranial tumor or contusion because of traumatic brain injury. Healthy participants served as controls (n = 14). Participants performed a visual stop signal task. We analyzed behavioral performance as well as event-related brain potentials and oscillations. Inhibition difficulty was adjusted individually to yield an equal amount of successful inhibitions across participants. RTs of patients and controls did not differ significantly in go trials or in failed stop trials, and no differences were observed in estimated stop signal RT. However, electrophysiological response patterns during task performance distinguished the groups. Patients with OFC lesions had enhanced P3 amplitudes to congruent condition go signals and to stop signals. In stop trials, patients had attenuated N2 and error-related negativity, but enhanced error positivity. Patients also showed enhanced and prolonged post-error beta band increases for stop errors. This effect was particularly evident in patients whose lesion extended to the subgenual cingulate cortex. In summary, although response inhibition was not impaired, the diminished stop N2 and ERN support a critical role of the OFC in action monitoring. Moreover, the increased stop P3, error positivity, and post-error beta response indicate that OFC injury affected action outcome evaluation and support the notion that the OFC is relevant for the processing of abstract reinforcers such as performing correctly in the task.

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Stern, Peter. "Another primary visual cortex." Science 363, no. 6422 (January 3, 2019): 39.16–41. http://dx.doi.org/10.1126/science.363.6422.39-p.

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Tong, Frank. "Primary visual cortex and visual awareness." Nature Reviews Neuroscience 4, no. 3 (March 2003): 219–29. http://dx.doi.org/10.1038/nrn1055.

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Beltramo, Riccardo. "A new primary visual cortex." Science 370, no. 6512 (October 1, 2020): 46.2–46. http://dx.doi.org/10.1126/science.abe1482.

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Stern, Peter. "Rethinking primary visual cortex function." Science 364, no. 6447 (June 27, 2019): 1247.14–1249. http://dx.doi.org/10.1126/science.364.6447.1247-n.

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Chan, Jane W. "The Cat Primary Visual Cortex." Journal of Neuro-Ophthalmology 26, no. 1 (March 2006): 70. http://dx.doi.org/10.1097/01.wno.0000206242.42410.de.

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Pigarev, I., D. Chelvanayagam, J. Cappello, and T. Vidyasagar. "Primary visual cortex and memory." Experimental Brain Research 140, no. 3 (October 1, 2001): 311–17. http://dx.doi.org/10.1007/s002210100825.

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31

Posner, M. I., and C. D. Gilbert. "Attention and primary visual cortex." Proceedings of the National Academy of Sciences 96, no. 6 (March 16, 1999): 2585–87. http://dx.doi.org/10.1073/pnas.96.6.2585.

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32

Konovenko, Nadiia, and Valentin Lychagin. "Invariants for primary visual cortex." Differential Geometry and its Applications 60 (October 2018): 156–73. http://dx.doi.org/10.1016/j.difgeo.2018.04.009.

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33

Sengpiel, Frank, and Mark Hübener. "Visual perception: Spotlight on the primary visual cortex." Current Biology 9, no. 9 (May 1999): R318—R321. http://dx.doi.org/10.1016/s0960-9822(99)80202-4.

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34

Silvanto, Juha. "Is primary visual cortex necessary for visual awareness?" Trends in Neurosciences 37, no. 11 (November 2014): 618–19. http://dx.doi.org/10.1016/j.tins.2014.09.006.

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35

Henriksen, Sid, Seiji Tanabe, and Bruce Cumming. "Disparity processing in primary visual cortex." Philosophical Transactions of the Royal Society B: Biological Sciences 371, no. 1697 (June 19, 2016): 20150255. http://dx.doi.org/10.1098/rstb.2015.0255.

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The first step in binocular stereopsis is to match features on the left retina with the correct features on the right retina, discarding ‘false’ matches. The physiological processing of these signals starts in the primary visual cortex, where the binocular energy model has been a powerful framework for understanding the underlying computation. For this reason, it is often used when thinking about how binocular matching might be performed beyond striate cortex. But this step depends critically on the accuracy of the model, and real V1 neurons show several properties that suggest they may be less sensitive to false matches than the energy model predicts. Several recent studies provide empirical support for an extended version of the energy model, in which the same principles are used, but the responses of single neurons are described as the sum of several subunits, each of which follows the principles of the energy model. These studies have significantly improved our understanding of the role played by striate cortex in the stereo correspondence problem. This article is part of the themed issue ‘Vision in our three-dimensional world’.

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Leopold, David A. "Primary Visual Cortex: Awareness and Blindsight." Annual Review of Neuroscience 35, no. 1 (July 21, 2012): 91–109. http://dx.doi.org/10.1146/annurev-neuro-062111-150356.

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37

Barone, Pascal. "Is the primary visual cortex multisensory?" Physics of Life Reviews 7, no. 3 (September 2010): 291–92. http://dx.doi.org/10.1016/j.plrev.2010.07.002.

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Földiák, Peter. "Stimulus optimisation in primary visual cortex." Neurocomputing 38-40 (June 2001): 1217–22. http://dx.doi.org/10.1016/s0925-2312(01)00570-7.

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39

Li, Wu, Valentin Piëch, and Charles D. Gilbert. "Contour Saliency in Primary Visual Cortex." Neuron 50, no. 6 (June 2006): 951–62. http://dx.doi.org/10.1016/j.neuron.2006.04.035.

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MacEvoy, S. P., and M. A. Paradiso. "Lightness constancy in primary visual cortex." Proceedings of the National Academy of Sciences 98, no. 15 (July 10, 2001): 8827–31. http://dx.doi.org/10.1073/pnas.161280398.

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41

Zipser, Karl, Victor A. F. Lamme, and Peter H. Schiller. "Contextual Modulation in Primary Visual Cortex." Journal of Neuroscience 16, no. 22 (November 15, 1996): 7376–89. http://dx.doi.org/10.1523/jneurosci.16-22-07376.1996.

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Zayyad, Zaina A., John H. R. Maunsell, and Jason N. MacLean. "Normalization in mouse primary visual cortex." PLOS ONE 18, no. 12 (December 18, 2023): e0295140. http://dx.doi.org/10.1371/journal.pone.0295140.

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When multiple stimuli appear together in the receptive field of a visual cortical neuron, the response is typically close to the average of that neuron’s response to each individual stimulus. The departure from a linear sum of each individual response is referred to as normalization. In mammals, normalization has been best characterized in the visual cortex of macaques and cats. Here we study visually evoked normalization in the visual cortex of awake mice using imaging of calcium indicators in large populations of layer 2/3 (L2/3) V1 excitatory neurons and electrophysiological recordings across layers in V1. Regardless of recording method, mouse visual cortical neurons exhibit normalization to varying degrees. The distributions of normalization strength are similar to those described in cats and macaques, albeit slightly weaker on average.

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Richter, David, Dirk van Moorselaar, and Jan Theeuwes. "Distractor suppression in primary visual cortex." Journal of Vision 24, no. 10 (September 15, 2024): 411. http://dx.doi.org/10.1167/jov.24.10.411.

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Iacaruso, M. Florencia, Ioana T. Gasler, and Sonja B. Hofer. "Synaptic organization of visual space in primary visual cortex." Nature 547, no. 7664 (July 2017): 449–52. http://dx.doi.org/10.1038/nature23019.

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Tong, F. "Representations of Visual Imagery in Human Primary Visual Cortex." Journal of Vision 4, no. 8 (August 1, 2004): 46. http://dx.doi.org/10.1167/4.8.46.

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46

Heeger, David J. "The Representation of Visual Stimuli in Primary Visual Cortex." Current Directions in Psychological Science 3, no. 5 (October 1994): 159–63. http://dx.doi.org/10.1111/1467-8721.ep10770661.

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Morris, Adam P., and Bart Krekelberg. "A Stable Visual World in Primate Primary Visual Cortex." Current Biology 29, no. 9 (May 2019): 1471–80. http://dx.doi.org/10.1016/j.cub.2019.03.069.

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Beltramo, Riccardo, and Massimo Scanziani. "A collicular visual cortex: Neocortical space for an ancient midbrain visual structure." Science 363, no. 6422 (January 3, 2019): 64–69. http://dx.doi.org/10.1126/science.aau7052.

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Visual responses in the cerebral cortex are believed to rely on the geniculate input to the primary visual cortex (V1). Indeed, V1 lesions substantially reduce visual responses throughout the cortex. Visual information enters the cortex also through the superior colliculus (SC), but the function of this input on visual responses in the cortex is less clear. SC lesions affect cortical visual responses less than V1 lesions, and no visual cortical area appears to entirely rely on SC inputs. We show that visual responses in a mouse lateral visual cortical area called the postrhinal cortex are independent of V1 and are abolished upon silencing of the SC. This area outperforms V1 in discriminating moving objects. We thus identify a collicular primary visual cortex that is independent of the geniculo-cortical pathway and is capable of motion discrimination.

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van den Hurk, Job, Marc Van Baelen, and Hans P. Op de Beeck. "Development of visual category selectivity in ventral visual cortex does not require visual experience." Proceedings of the National Academy of Sciences 114, no. 22 (May 15, 2017): E4501—E4510. http://dx.doi.org/10.1073/pnas.1612862114.

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To what extent does functional brain organization rely on sensory input? Here, we show that for the penultimate visual-processing region, ventral-temporal cortex (VTC), visual experience is not the origin of its fundamental organizational property, category selectivity. In the fMRI study reported here, we presented 14 congenitally blind participants with face-, body-, scene-, and object-related natural sounds and presented 20 healthy controls with both auditory and visual stimuli from these categories. Using macroanatomical alignment, response mapping, and surface-based multivoxel pattern analysis, we demonstrated that VTC in blind individuals shows robust discriminatory responses elicited by the four categories and that these patterns of activity in blind subjects could successfully predict the visual categories in sighted controls. These findings were confirmed in a subset of blind participants born without eyes and thus deprived from all light perception since conception. The sounds also could be decoded in primary visual and primary auditory cortex, but these regions did not sustain generalization across modalities. Surprisingly, although not as strong as visual responses, selectivity for auditory stimulation in visual cortex was stronger in blind individuals than in controls. The opposite was observed in primary auditory cortex. Overall, we demonstrated a striking similarity in the cortical response layout of VTC in blind individuals and sighted controls, demonstrating that the overall category-selective map in extrastriate cortex develops independently from visual experience.

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Burg, Max F., Santiago A. Cadena, George H. Denfield, Edgar Y. Walker, Andreas S. Tolias, Matthias Bethge, and Alexander S. Ecker. "Learning divisive normalization in primary visual cortex." PLOS Computational Biology 17, no. 6 (June 7, 2021): e1009028. http://dx.doi.org/10.1371/journal.pcbi.1009028.

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Divisive normalization (DN) is a prominent computational building block in the brain that has been proposed as a canonical cortical operation. Numerous experimental studies have verified its importance for capturing nonlinear neural response properties to simple, artificial stimuli, and computational studies suggest that DN is also an important component for processing natural stimuli. However, we lack quantitative models of DN that are directly informed by measurements of spiking responses in the brain and applicable to arbitrary stimuli. Here, we propose a DN model that is applicable to arbitrary input images. We test its ability to predict how neurons in macaque primary visual cortex (V1) respond to natural images, with a focus on nonlinear response properties within the classical receptive field. Our model consists of one layer of subunits followed by learned orientation-specific DN. It outperforms linear-nonlinear and wavelet-based feature representations and makes a significant step towards the performance of state-of-the-art convolutional neural network (CNN) models. Unlike deep CNNs, our compact DN model offers a direct interpretation of the nature of normalization. By inspecting the learned normalization pool of our model, we gained insights into a long-standing question about the tuning properties of DN that update the current textbook description: we found that within the receptive field oriented features were normalized preferentially by features with similar orientation rather than non-specifically as currently assumed.

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Journal articles on the topic 'Primary Visual Cortex (PVC)'

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