Journal articles on the topic 'Double-step task'
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Oostwoud Wijdenes, Leonie, Eli Brenner, and Jeroen B. J. Smeets. "Exposing sequence learning in a double-step task." Experimental Brain Research 234, no. 6 (February 12, 2016): 1701–12. http://dx.doi.org/10.1007/s00221-016-4566-z.
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Jin, Zhenlan, Shulin Yue, Junjun Zhang, and Ling Li. "Task-irrelevant emotional faces impair response adjustments in a double-step saccade task." Cognition and Emotion 32, no. 6 (October 5, 2017): 1347–54. http://dx.doi.org/10.1080/02699931.2017.1386621.
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Kapoor, Vishal, and Aditya Murthy. "Covert inhibition potentiates online control in a double-step task." Journal of Vision 8, no. 1 (January 29, 2008): 20. http://dx.doi.org/10.1167/8.1.20.
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Sharika, K. M., Arjun Ramakrishnan, and Aditya Murthy. "Control of Predictive Error Correction During a Saccadic Double-Step Task." Journal of Neurophysiology 100, no. 5 (November 2008): 2757–70. http://dx.doi.org/10.1152/jn.90238.2008.
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We explored the nature of control during error correction using a modified saccadic double-step task in which subjects cancelled the initial saccade to the first target and redirected gaze to a second target. Failure to inhibit was associated with a quick corrective saccade, suggesting that errors and corrections may be planned concurrently. However, because saccade programming constitutes a visual and a motor stage of preparation, the extent to which parallel processing occurs in anticipation of the error is not known. To estimate the time course of error correction, a triple-step condition was introduced that displaced the second target during the error. In these trials, corrective saccades directed at the location of the target prior to the third step suggest motor preparation of the corrective saccade in parallel with the error. To estimate the time course of motor preparation of the corrective saccade, further, we used an accumulator model (LATER) to fit the reaction times to the triple-step stimuli; the best-fit data revealed that the onset of correction could occur even before the start of the error. The estimated start of motor correction was also observed to be delayed as target step delay decreased, suggesting a form of interference between concurrent motor programs. Taken together we interpret these results to indicate that predictive error correction may occur concurrently while the oculomotor system is trying to inhibit an unwanted movement and suggest how inhibitory control and error correction may interact to enable goal-directed behaviors.
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Norouzi-Gheidari, Nahid, and Philippe Archambault. "Absence of equifinality of hand position in a double-step unloading task." Experimental Brain Research 205, no. 2 (July 10, 2010): 167–82. http://dx.doi.org/10.1007/s00221-010-2350-z.
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Wong, Aaron L., and Mark Shelhamer. "Using prediction errors to drive saccade adaptation: the implicit double-step task." Experimental Brain Research 222, no. 1-2 (August 1, 2012): 55–64. http://dx.doi.org/10.1007/s00221-012-3195-4.
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Thakkar, Katharine N., Jeffrey D. Schall, Gordon D. Logan, and Sohee Park. "Response inhibition and response monitoring in a saccadic double-step task in schizophrenia." Brain and Cognition 95 (April 2015): 90–98. http://dx.doi.org/10.1016/j.bandc.2015.01.007.
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Berman, Rebecca A., Laura M. Heiser, Catherine A. Dunn, Richard C. Saunders, and Carol L. Colby. "Dynamic Circuitry for Updating Spatial Representations. III. From Neurons to Behavior." Journal of Neurophysiology 98, no. 1 (July 2007): 105–21. http://dx.doi.org/10.1152/jn.00330.2007.
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Each time the eyes move, the visual system must adjust internal representations to account for the accompanying shift in the retinal image. In the lateral intraparietal cortex (LIP), neurons update the spatial representations of salient stimuli when the eyes move. In previous experiments, we found that split-brain monkeys were impaired on double-step saccade sequences that required updating across visual hemifields, as compared to within hemifield. Here we describe a subsequent experiment to characterize the relationship between behavioral performance and neural activity in LIP in the split-brain monkey. We recorded from single LIP neurons while split-brain and intact monkeys performed two conditions of the double-step saccade task: one required across-hemifield updating and the other required within-hemifield updating. We found that, despite extensive experience with the task, the split-brain monkeys were significantly more accurate for within-hemifield than for across-hemifield sequences. In parallel, we found that population activity in LIP of the split-brain monkeys was significantly stronger for the within-hemifield than for the across-hemifield condition of the double-step task. In contrast, in the normal monkey, both the average behavioral performance and population activity showed no bias toward the within-hemifield condition. Finally, we found that the difference between within-hemifield and across-hemifield performance in the split-brain monkeys was reflected at the level of single-neuron activity in LIP. These findings indicate that remapping activity in area LIP is present in the split-brain monkey for the double-step task and covaries with spatial behavior on within-hemifield compared to across-hemifield sequences.
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Bedore, Christopher D., Jasmine Livermore, Hugo Lehmann, and Liana E. Brown. "Comparing three portable, tablet-based visuomotor tasks to laboratory versions: An assessment of test validity." Journal of Concussion 2 (January 2018): 205970021879914. http://dx.doi.org/10.1177/2059700218799146.
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The assessment of visuomotor function can provide important information about neurological status. Many tasks exist for testing visuomotor function in the laboratory, but the availability of portable, easy-to-use versions that allow reliable, accurate, and precise measurement of movement timing and accuracy has been limited. We developed a tablet application that uses three laboratory visuomotor tests: the double-step task, interception task, and stop-signal task. We asked the participants to perform both the lab and tablet versions of each task and compared their response patterns across equipment types to assess the validity of the tablet versions. On the double-step task, the participants adjusted to the displaced target adequately in both the lab and tablet versions. On the interception task, the participants intercepted nonaccelerating targets and performed worse on accelerating targets in both versions of the task. On the stop-signal task, the participants successfully inhibited their reaching movements on short stop-signal delays (50–150 ms) more frequently than on long stop-signal delays (200 ms) in both versions of the task. Our findings suggest that the tablet version of each task assesses visuomotor processing in the same way as their respective laboratory version, thus providing the research community with a new tool to assess visuomotor function.
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de Brouwer, Anouk J., W. Pieter Medendorp, and Jeroen B. J. Smeets. "Contributions of gaze-centered and object-centered coding in a double-step saccade task." Journal of Vision 16, no. 14 (November 16, 2016): 12. http://dx.doi.org/10.1167/16.14.12.
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Gopal, Atul, and Aditya Murthy. "Eye-hand coordination during a double-step task: evidence for a common stochastic accumulator." Journal of Neurophysiology 114, no. 3 (September 2015): 1438–54. http://dx.doi.org/10.1152/jn.00276.2015.
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Many studies of reaching and pointing have shown significant spatial and temporal correlations between eye and hand movements. Nevertheless, it remains unclear whether these correlations are incidental, arising from common inputs (independent model); whether these correlations represent an interaction between otherwise independent eye and hand systems (interactive model); or whether these correlations arise from a single dedicated eye-hand system (common command model). Subjects were instructed to redirect gaze and pointing movements in a double-step task in an attempt to decouple eye-hand movements and causally distinguish between the three architectures. We used a drift-diffusion framework in the context of a race model, which has been previously used to explain redirect behavior for eye and hand movements separately, to predict the pattern of eye-hand decoupling. We found that the common command architecture could best explain the observed frequency of different eye and hand response patterns to the target step. A common stochastic accumulator for eye-hand coordination also predicts comparable variances, despite significant difference in the means of the eye and hand reaction time (RT) distributions, which we tested. Consistent with this prediction, we observed that the variances of the eye and hand RTs were similar, despite much larger hand RTs (∼90 ms). Moreover, changes in mean eye RTs, which also increased eye RT variance, produced a similar increase in mean and variance of the associated hand RT. Taken together, these data suggest that a dedicated circuit underlies coordinated eye-hand planning.
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Honda, H. "Interaction of extraretinal eye position signals in a double-step saccade task: psychophysical estimation." Experimental Brain Research 113, no. 2 (February 1997): 327–36. http://dx.doi.org/10.1007/bf02450330.
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de Brouwer, Anouk J., and Miriam Spering. "Eye-hand coordination during online reach corrections is task dependent." Journal of Neurophysiology 127, no. 4 (April 1, 2022): 885–95. http://dx.doi.org/10.1152/jn.00270.2021.
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Eye movements support hand movements in many situations. Here, we used variations of a double-step task to investigate temporal coupling of corrective hand and eye movements in response to target displacements. Correction latency coupling depended on the visual and cognitive processing demands of the task. The hand started correcting before the eye, especially when the task required decoding a symbolic cue. These findings highlight the flexibility and task dependency of eye-hand coordination.
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Goldberg, M. E., and C. J. Bruce. "Primate frontal eye fields. III. Maintenance of a spatially accurate saccade signal." Journal of Neurophysiology 64, no. 2 (August 1, 1990): 489–508. http://dx.doi.org/10.1152/jn.1990.64.2.489.
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1. We studied the activity of single neurons in the monkey frontal eye fields during oculomotor tasks designed to assess the activity of these neurons when there was a dissonance between the spatial location of a target and its position on the retina. 2. Neurons with presaccadic activity were first studied to determine their receptive or movement fields and to classify them as visual, visuomovement, or movement cells with the use of the criteria described previously (Bruce and Goldberg 1985). The neurons were then studied by the use of double-step tasks that dissociated the retinal coordinates of visual targets from the dimensions of saccadic eye movements necessary to acquire those targets. These tasks required that the monkeys make two successive saccades to follow two sequentially flashed targets. Because the second target disappeared before the first saccade occurred, the dimensions of the second saccade could not be based solely on the retinal coordinates of the target but also depended on the dimensions of the first saccade. We used two versions of the double-step task. In one version neither target appeared in the cell's receptive or movement field, but the second eye movement was the optimum amplitude and direction for the cell (right-EM/wrong-RF task). In the other the second stimulus appeared in the cell's receptive field, but neither eye movement was appropriate for the cell (wrong-EM/right-RF task). 3. Most frontal-eye-field cells discharged in the right-EM/wrong-RF version of the double-step task. Their discharge began after the first saccade and continued until the second saccade was made. They usually discharged even on occasional trials in which the monkey failed to make the second saccade. They discharged much less, or not at all, in the wrong-EM/right-RF version of the double-step paradigm. Thus most presaccadic cells in the frontal eye fields were tuned to the dimensions of saccadic eye movements rather than to the coordinates of retinal stimulation. 4. Eleven movement cells (including 1 which also had independent postsaccadic activity for saccades opposite its presaccadic movement field) were studied, and all had significant activity in the right-EM/wrong-RF task. 5. Almost all (28/32) visuomovement cells, including 12 with independent postsaccadic activity, discharged in the right-EM/wrong-RF task. None of the four that failed had independent postsaccadic activity. 6. The majority (26/40) of visual cells were responsive in the right-EM/wrong-RF task.(ABSTRACT TRUNCATED AT 400 WORDS)
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Messerschmidt, Emily L., Eric E. Hall, Caroline J. Ketcham, Kirtida Patel, and Srikant Vallabhajosula. "Gait Assessment in College Athletes: Do Concussion History, Symptoms, Gender, and Type of Sport Matter?" Journal of Sport Rehabilitation 30, no. 7 (September 1, 2021): 988–99. http://dx.doi.org/10.1123/jsr.2019-0331.
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Context: Though previous research has focused on examining the effects of concussion history using a dual-task paradigm, the influence of factors like symptoms (unrelated to concussion), gender, and type of sport on gait in college athletes is unknown. Objective: To examine the effect of concussion history, symptoms, gender, and type of sport (noncontact/limited contact/contact) individually on gait among college athletes. Design: Exploratory cross-sectional study. Setting: Laboratory. Participants: In total, 98 varsity athletes (age, 18.3 [1.0] y; height, 1.79 [0.11] m; mass, 77.5 [19.2] kg; 27 with concussion history, 58 reported at least one symptom, 44 females; 8 played noncontact sports and 71 played contact sports) walked under single- and dual-task (walking while counting backward by 7) conditions. Interventions: Not applicable. Main Outcome Measures: Dual-task cost (DTC; % difference between single task and dual task) of gait speed, cadence, step length and width, percentage of swing and double-support phases, symptom score, and total symptom severity score. Independent samples t tests and 1-way analysis of variance were conducted (α value = .05). Results: Self-reported concussion history resulted in no significant differences (P > .05). Those who reported symptoms at testing time showed significantly greater DTC of step length (mean difference [MD], 2.7%; 95% confidence interval [CI], 0.3% to 5.1%; P = .012), % of swing phase (MD, 1.0%; 95% CI, −0.2 to 2.1%; P = .042), and % of double-support phase (MD, 3.9%; 95% CI, 0.2% to 7.8%; P = .019). Females demonstrated significantly higher DTC of gait speed (MD, 5.3%; 95% CI, 1.3% to 9.3%; P = .005), cadence (MD, 4.0%; 95% CI, 1.4% to 6.5%; P = .002), % of swing phase (MD, 1.2%; 95% CI, 0.1% to 2.3%; P = .019), and % of double-support phase (MD, 4.1%; 95% CI, 0.4% to 7.9%; P = .018). Noncontact sports athletes had significantly greater step width DTC than contact sports athletes (MD, 14.2%; 95% CI, 0.9% to 27.6%; P = .032). Conclusions: Reporting symptoms at testing time may influence gait under dual-task conditions. Additionally, female athletes showed more gait changes during a dual task. Sports medicine professionals should be aware that these variables, while unrelated to injury, may affect an athlete’s gait upon analysis.
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Lajoie, Kim, and Trevor Drew. "Lesions of Area 5 of the Posterior Parietal Cortex in the Cat Produce Errors in the Accuracy of Paw Placement During Visually Guided Locomotion." Journal of Neurophysiology 97, no. 3 (March 2007): 2339–54. http://dx.doi.org/10.1152/jn.01196.2006.
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We developed a novel locomotor task in which cats step over obstacles that move at a different speed from that of the treadmill on which the cat is walking: we refer to this as a visual dissociation locomotion task. Slowing the speed of the obstacle with respect to that of the treadmill sometimes led to a major change in strategy so that cats made two steps with the hindlimbs before stepping over the obstacle (double step strategy) instead of the single step (standard strategy) observed when the obstacle was at the same speed as the treadmill. In addition, in the step preceding the step over the obstacle, the paws were placed significantly closer to the obstacle in the visual dissociation task than when the treadmill and the obstacle were at the same speed. After unilateral lesion of area 5 of the posterior parietal cortex (PPC), the cats frequently hit the obstacle as they stepped over it, especially in the visual dissociation task. This locomotor deficit was linked to significant differences in the location in which the forelimbs were placed in the step preceding that over the obstacle compared with the prelesion control. Cats also frequently hit the obstacle with their hindlimbs even when the forelimbs negotiated the obstacle successfully; this suggests an important role for the posterior parietal cortex in the coordination of the forelimbs and hindlimbs. Together, these results suggest an important contribution of the PPC to the planning of visually guided gait modifications.
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Jor’dan, Azizah J., Brad Manor, Ikechukwu Iloputaife, Daniel A. Habtemariam, Jonathan F. Bean, Farzaneh A. Sorond, and Lewis A. Lipsitz. "Diminished Locomotor Control Is Associated With Reduced Neurovascular Coupling in Older Adults." Journals of Gerontology: Series A 75, no. 8 (January 8, 2019): 1516–22. http://dx.doi.org/10.1093/gerona/glz006.
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Abstract Background Walking, especially while dual-tasking, requires functional activation of cognitive brain regions and their connected neural networks. This study examined the relationship between neurovascular coupling (NVC), as measured by the change in cerebral blood flow in response to performing a cognitive executive task, and dual-task walking performance. Methods Seventy community-dwelling older adults aged 84 ± 5 years within the Maintenance of Balance, Independent Living, Intellect and Zest in the Elderly (MOBILIZE) Boston Study were divided into LOW (n = 35) and HIGH (n = 35) NVC. NVC was quantified by transcranial Doppler ultrasound and stratified by the median change in cerebral blood flow velocity of the middle cerebral artery induced by the performance of the n-back task of executive function. Walking metrics included walking speed, step width, stride length, stride time, stride time variability, and double-support time from single- and dual-task walking conditions, as well as the “cost” of dual-tasking. Results During both single- and dual-task walking, older adults with LOW NVC displayed narrower step width (p = .02 and p = .02), shorter stride length (p = .01 and p = .02), and longer double-support time (p = .03 and p = .002) when compared with the HIGH group. During single-task walking only, LOW NVC was also linked to slower walking speed (p = .02). These associations were independent of age, height, hypertension, atrial fibrillation, and assistive device. The LOW and HIGH NVC groups did not differ in dual-task costs to walking performance. Conclusion In older adults, diminished capacity to regulate cerebral blood flow in response to an executive function task is linked to worse walking performance under both single- and dual-task conditions, but not necessarily dual-task costs.
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Koo, Dong-Kyun, Tae-Su Jang, and Jung-Won Kwon. "Effects of Dual-Task Training on Gait Parameters in Elderly Patients with Mild Dementia." Healthcare 9, no. 11 (October 26, 2021): 1444. http://dx.doi.org/10.3390/healthcare9111444.
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This study aimed to investigate the effectiveness of dual-task training (DTT) compared to single-task training (STT), on gait parameters in elderly patients with mild dementia (MD). Twenty-four elderly patients with MD were randomly assigned to the DTT (n = 13) or the STT group (n = 11). The DTT group performed a specific cognitive-motor DTT, while the STT group received only motor task training. Both training sessions lasted 8 weeks, with a frequency of 3 days per week, and the cognitive functions and gait parameters were measured. A statistically significant interaction effect was found between the two groups in stride length, stride velocity, cadence, step length, swing phase, stance phase, and double support phase (p < 0.05). After 8 weeks, the DTT group showed significant improvement in spatiotemporal parameters, except for the kinematic parameters (p < 0.05). In the between-group analysis, the DTT group showed more improvement than the STT group in stride velocity, step length, swing phase, stance phase, and double support (p < 0.05). These findings suggest that improvements in spatiotemporal gait parameters after DTT are reported in patients with MD. Our results can guide therapists to include dual tasks in their gait rehabilitation programs for the treatment of mild dementia.
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KLAPDOR-KLEINGROTHAUS, H. V. "LESSONS AFTER THE EVIDENCE FOR NEUTRINOLESS DOUBLE BETA DECAY — THE NEXT STEP." International Journal of Modern Physics E 17, no. 03 (March 2008): 505–17. http://dx.doi.org/10.1142/s0218301308009823.
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This paper describes the lessons we have to draw after the observation of neutrinoless ββ decay by the enriched 76 Ge experiment, for present and future experiments so as (a) to fulfill the task to confirm the present result (b) to deliver additional information on the main contributions of effective neutrino mass and right-handed weak currents etc. to the 0νββ amplitude. It is shown that presently running and planned experiments are probably not sensitive enough to check the evidence on a reasonable time scale. It is further demonstrated that, the only way to get more information on the individual contributions of m, η, λ etc. to the 0νββ amplitude is to go to completely different types of experiments, rather than those under construction and preparation at present, e.g. to mixed-mode β+/ EC decay experiments, such as 124 Xe decay. It is pointed out that the sometimes observed "tension" between the result of 0νββ decay and cosmological experiments like WMAP, SDSS etc. does not exist and is an artificial product of improper analysis of the latter.
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Hagner-Derengowska, Magdalena, Krystian Kałużny, Wojciech Hagner, Anna Kałużna, Bartosz Kochański, Alina Borkowska, and Jacek Budzyński. "The Effect of Two Different Cognitive Tests on Gait Parameters during Dual Tasks in Healthy Postmenopausal Women." BioMed Research International 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/1205469.
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Introduction. The paper aims to evaluate the influence of two different demanding cognitive tasks on gait parameters using BTS SMART system analysis.Patients and Methods. The study comprised 53 postmenopausal women aged 64.5 ± 6.7 years (range: 47–79). For every subject, gait analysis using a BTS SMART system was performed in a dual-task study design under three conditions: (I) while walking only (single task), (II) walking while performing a simultaneous simple cognitive task (SCT) (dual task), and (III) walking while performing a simultaneous complex cognitive task (CCT) (dual task). Time-space parameters of gait pertaining to the length of a single support phase, double support phase, gait speed, step length, step width, and leg swing speed were analyzed.Results. Performance of cognitive tests during gait resulted in a statistically significant prolongation of the left (by 7%) and right (by 7%) foot gait cycle, shortening of the length of steps made with the right extremity (by 4%), reduction of speed of swings made with the left (by 11%) and right (by 8%) extremity, and reduction in gait speed (by 6%).Conclusions. Performance of cognitive tests during gait changes its individual pattern in relation to the level of the difficulty of the task.
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Lim, Jongil, Jiyeon Kim, Kyoungho Seo, Richard E. A. van Emmerik, and Sukho Lee. "The Effects of Mobile Texting and Walking Speed on Gait Characteristics of Normal Weight and Obese Adults." Motor Control 24, no. 4 (October 1, 2020): 588–604. http://dx.doi.org/10.1123/mc.2020-0006.
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The aim of this study was to examine how usage of mobile devices while simultaneously walking affects walking characteristics and texting performance of normal weight (NW) and obese (OB) individuals. Thirty-two OB (body mass index [BMI] = 34.4) and NW (BMI = 22.7) adults performed two 60-s walking trials at three-step frequencies along a rectangular walkway in two conditions (No Texting and Texting). Dual-task cost as well as unadjusted spatial and temporal gait characteristics were measured. Dual-task costs for the gait parameters as well as texting performance were not different between the groups, except for the lateral step variability showing a larger variability at the preferred frequency in OB individuals. For the unadjusted variables, OB exhibited longer double support, longer stance time, and lower turn velocity compared with NW. Overall, the results highlight a similar dual-task cost for the OB individuals compared with the NW individuals, in spite of underlying differences in gait mechanics.
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Estevez, Julian, Jose Manuel Lopez-Guede, Gorka Garate, and Manuel Graña. "A Hybrid Control Approach for the Swing Free Transportation of a Double Pendulum with a Quadrotor." Applied Sciences 11, no. 12 (June 13, 2021): 5487. http://dx.doi.org/10.3390/app11125487.
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In this article, a control strategy approach is proposed for a system consisting of a quadrotor transporting a double pendulum. In our case, we attempt to achieve a swing free transportation of the pendulum, while the quadrotor closely follows a specific trajectory. This dynamic system is highly nonlinear, therefore, the fulfillment of this complex task represents a demanding challenge. Moreover, achieving dampening of the double pendulum oscillations while following a precise trajectory are conflicting goals. We apply a proportional derivative (PD) and a model predictive control (MPC) controllers for this task. Transportation of a multiple pendulum with an aerial robot is a step forward in the state of art towards the study of the transportation of loads with complex dynamics. We provide the modeling of the quadrotor and the double pendulum. For MPC we define the cost function that has to be minimized to achieve optimal control. We report encouraging positive results on a simulated environmentcomparing the performance of our MPC-PD control circuit against a PD-PD configuration, achieving a three fold reduction of the double pendulum maximum swinging angle.
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Reyes-Puerta, Vicente, Roland Philipp, Werner Lindner, Lars Lünenburger, and Klaus-Peter Hoffmann. "Influence of Task Predictability on the Activity of Neurons in the Rostral Superior Colliculus During Double-Step Saccades." Journal of Neurophysiology 101, no. 6 (June 2009): 3199–211. http://dx.doi.org/10.1152/jn.90983.2008.
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Target probability has been shown to modulate motor preparatory activity of neurons in the caudal superior colliculus (SC) of the primate. Here we tested whether top-down processes, such as task predictability, influence the activity of neurons also at the rostral pole of the SC (rSC), classically related to fixation. To investigate this, double-step saccade tasks were embedded in two different paradigms, one containing unpredictable and another containing predictable tasks. During predictable tasks the animals could develop some expectation about the forthcoming second target jump, i.e., anticipate when and where to make the second saccade. Neuronal responses were recorded during both paradigms and compared, revealing the influence of task predictability on the activity of rSC neurons during specific periods of fixation. In particular, neuronal activity stayed significantly lower during the fixation period between two successive saccades in predictable than in unpredictable tasks. In addition there was a learning effect within a session during predictable conditions, i.e., the intersaccadic activity was higher in the early than in the late trials. Further, reaction times for the second saccade were shorter in predictable than in unpredictable tasks. However, we demonstrated that this difference in reaction times cannot be solely accounted for by the reported difference in neural activity, which was mainly influenced by the predictability of the tasks. With these results we show that top-down processes such as predictability are imposed on the activity of neurons in the rostral pole of the primate SC.
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Donath, Lars, Oliver Faude, Stephanie A. Bridenbaugh, Ralf Roth, Martin Soltermann, Reto W. Kressig, and Lukas Zahner. "Transfer Effects of Fall Training on Balance Performance and Spatiotemporal Gait Parameters in Healthy Community-Dwelling Older Adults: A Pilot Study." Journal of Aging and Physical Activity 22, no. 3 (July 2014): 324–33. http://dx.doi.org/10.1123/japa.2013-0010.
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This study examined transfer effects of fall training on fear of falling (Falls Efficacy Scale—International [FES–I]), balance performance, and spatiotemporal gait characteristics in older adults. Eighteen community-dwelling older adults (ages 65–85) were randomly assigned to an intervention or control group. The intervention group completed 12 training sessions (60 min, 6 weeks). During pre- and posttesting, we measured FES–I, balance performance (double limb, closed eyes; single limb, open eyes; double limb, open eyes with motor-interfered task), and gait parameters (e.g., velocity; cadence; stride time, stride width, and stride length; variability of stride time and stride length) under single- and motor-interfered tasks. Dual tasks were applied to appraise improvements of cognitive processing during balance and gait. FES–I (p = .33) and postural sway did not significantly change (0.36 < p < .79). Trends toward significant interaction effects were found for step width during normal walking and stride length variability during the motor dual task (p = .05, ηp2 = .22). Fall training did not sufficiently improve fear of falling, balance, or gait performance under single- or dual-task conditions in healthy older adults.
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Lünenburger, Lars, and Klaus-Peter Hoffmann. "Arm movement and gap as factors influencing the reaction time of the second saccade in a double-step task." European Journal of Neuroscience 17, no. 11 (June 2003): 2481–91. http://dx.doi.org/10.1046/j.1460-9568.2003.02653.x.
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Fallahtafti, Farahnaz, Hyeon Jung Kim, Jennifer M. Yentes, Dawn Venema, and Julie Blaskewicz Boron. "OPTIC FLOW IMPROVES SPATIAL GAIT FUNCTIONING ESPECIALLY IN MEDIOLATERAL DIRECTION." Innovation in Aging 3, Supplement_1 (November 2019): S658. http://dx.doi.org/10.1093/geroni/igz038.2439.
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Abstract Instances where multiple tasks are completed simultaneously are considered high cognitive load situations (HCLS, also called dual-task), potentially affecting gait performance in older adults. Walking while talking is a common HCLS that requires additional cognitive resources. Optic flow (OF) provides visual information about speed and direction of self-motion, and thus, may ameliorate gait deficits under HCLS. This study aimed to identify the effect of HCLS, as well as OF, on gait performance in older adults. The HCLS included walking while talking on the phone, compared to walking alone. Fifteen older adults (70.86±4.7yrs) underwent four experimental conditions: walking alone with(1) and without OF(2), as well as walking while talking with(3) and without OF(4). Step width, step length, and double support time were measured and examined with 2(HCLS) x 2(OF) repeated-measures ANOVAs. There was a main effect of OF; step width was narrower with OF compared to without OF (p=0.048). For step length, there was a significant interaction between HCLS and OF (p=0.045). Without OF, there were no differences in step length; however, with OF step length was significantly longer when walking alone compared to when walking while talking (p=0.002). Double support time was not affected by HCLS or OF. Considering younger adults have longer and narrower steps compared to older adults, OF may have enhanced step width regardless of HCLS and step length when walking only. Using OF in training programs designed for older adults, could be a potential factor to improve spatial gait function, more so in the mediolateral direction.
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Beck, Eric N., Brittany N. Intzandt, and Quincy J. Almeida. "Can Dual Task Walking Improve in Parkinson’s Disease After External Focus of Attention Exercise? A Single Blind Randomized Controlled Trial." Neurorehabilitation and Neural Repair 32, no. 1 (December 20, 2017): 18–33. http://dx.doi.org/10.1177/1545968317746782.
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Background. It may be possible to use attention-based exercise to decrease demands associated with walking in Parkinson’s disease (PD), and thus improve dual task walking ability. For example, an external focus of attention (focusing on the effect of an action on the environment) may recruit automatic control processes degenerated in PD, whereas an internal focus (limb movement) may recruit conscious (nonautomatic) control processes. Thus, we aimed to investigate how externally and internally focused exercise influences dual task walking and symptom severity in PD. Methods. Forty-seven participants with PD were randomized to either an Externally (n = 24) or Internally (n = 23) focused group and completed 33 one-hour attention-based exercise sessions over 11 weeks. In addition, 16 participants were part of a control group. Before, after, and 8 weeks following the program (pre/post/washout), gait patterns were measured during single and dual task walking (digit-monitoring task, ie, walking while counting numbers announced by an audio-track), and symptom severity (UPDRS-III) was assessed ON and OFF dopamine replacement. Pairwise comparisons (95% confidence intervals [CIs]) and repeated-measures analyses of variance were conducted. Results. Pre to post: Dual task step time decreased in the external group (Δ = 0.02 seconds, CI 0.01-0.04). Dual task step length (Δ = 2.3 cm, CI 0.86-3.75) and velocity (Δ = 4.5 cm/s, CI 0.59-8.48) decreased (became worse) in the internal group. UPDRS-III scores (ON and OFF) decreased (improved) in only the External group. Pre to washout: Dual task step time ( P = .005) and percentage in double support ( P = .014) significantly decreased (improved) in both exercise groups, although only the internal group increased error on the secondary counting task (ie, more errors monitoring numbers). UPDRS-III scores in both exercise groups significantly decreased ( P = .001). Conclusions. Since dual task walking improvements were found immediately, and 8 weeks after the cessation of an externally focused exercise program, we conclude that externally focused exercise may improve on functioning of automatic control networks in PD. Internally focused exercise hindered dual tasking ability. Overall, externally focused exercise led to greater rehabilitation benefits in dual tasking and motor symptoms compared with internally focused exercise.
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Marković, Vladana, Iva Stanković, Saša Radovanović, Igor Petrović, Milica Ječmenica Lukić, Nataša Dragašević Mišković, Marina Svetel, and Vladimir Kostić. "Gait alterations in Parkinson’s disease at the stage of hemiparkinsonism—A longitudinal study." PLOS ONE 17, no. 7 (July 21, 2022): e0269886. http://dx.doi.org/10.1371/journal.pone.0269886.
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Background Progressive gait impairment in Parkinson’s disease (PD) leads to significant disability. Quantitative gait parameters analysis provides valuable information about fine gait alterations. Objectives To analyse change of gait parameters in patients with early PD at the stage of hemiparkinsonism and after 1 year of follow up, taking into account clinical asymmetry. Methods Consecutive early PD outpatients with strictly unilateral motor features underwent clinical and neuropsychological assessment at the study entry and after 1 year of follow up. Gait was assessed with GAITRite walkway using dual-task methodology. Spatiotemporal gait parameters (step time and length, swing time and double support time) and their coefficients of variation (CV), gait velocity and heel-to-heel base support were evaluated. Results We included 42 PD patients with disease duration of 1.3 years (±1.13). Progression of motor and non-motor symptoms, without significant cognitive worsening, was observed after 1 year of follow up. Significant shortening of the swing time, prolongation of the double support and increase of their CVs were observed during all task conditions similarly for most parameters on symptomatic and asymptomatic bodysides, except for CV for the swing time under the combined task. Conclusion Alterations of the swing time and double support time are already present even at the asymptomatic body side, and progress similarly, or even at faster pace, at this side, despite dopaminergic treatment These parameters deserve further investigation in larger, prospective studies to address their potential to serve as markers of progression in interventional disease modifying trials with early PD patients.
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Murthy, Aditya, Supriya Ray, Stephanie M. Shorter, Jeffrey D. Schall, and Kirk G. Thompson. "Neural Control of Visual Search by Frontal Eye Field: Effects of Unexpected Target Displacement on Visual Selection and Saccade Preparation." Journal of Neurophysiology 101, no. 5 (May 2009): 2485–506. http://dx.doi.org/10.1152/jn.90824.2008.
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The dynamics of visual selection and saccade preparation by the frontal eye field was investigated in macaque monkeys performing a search-step task combining the classic double-step saccade task with visual search. Reward was earned for producing a saccade to a color singleton. On random trials the target and one distractor swapped locations before the saccade and monkeys were rewarded for shifting gaze to the new singleton location. A race model accounts for the probabilities and latencies of saccades to the initial and final singleton locations and provides a measure of the duration of a covert compensation process—target-step reaction time. When the target stepped out of a movement field, noncompensated saccades to the original location were produced when movement-related activity grew rapidly to a threshold. Compensated saccades to the final location were produced when the growth of the original movement-related activity was interrupted within target-step reaction time and was replaced by activation of other neurons producing the compensated saccade. When the target stepped into a receptive field, visual neurons selected the new target location regardless of the monkeys’ response. When the target stepped out of a receptive field most visual neurons maintained the representation of the original target location, but a minority of visual neurons showed reduced activity. Chronometric analyses of the neural responses to the target step revealed that the modulation of visually responsive neurons and movement-related neurons occurred early enough to shift attention and saccade preparation from the old to the new target location. These findings indicate that visual activity in the frontal eye field signals the location of targets for orienting, whereas movement-related activity instantiates saccade preparation.
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Medendorp, W. P., G. F. I. Kramer, O. Jensen, R. Oostenveld, J. M. Schoffelen, and P. Fries. "Oscillatory Activity in Human Parietal and Occipital Cortex Shows Hemispheric Lateralization and Memory Effects in a Delayed Double-Step Saccade Task." Cerebral Cortex 17, no. 10 (December 26, 2006): 2364–74. http://dx.doi.org/10.1093/cercor/bhl145.
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Van der Stigchel, Stefan, Robert D. Rafal, and Janet H. Bultitude. "Temporal dynamics of error correction in a double step task in patients with a lesion to the lateral intra-parietal cortex." Neuropsychologia 51, no. 14 (December 2013): 2988–94. http://dx.doi.org/10.1016/j.neuropsychologia.2013.10.010.
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Lau, Lay Khoon, Jagadish Ullal Mallya, Wei Jun Benedict Pang, Kexun Kenneth Chen, Khalid bin Abdul Jabbar, Wei Ting Seah, Philip Lin Kiat Yap, Tze Pin Ng, and Shiou Liang Wee. "Physiological and Cognitive Determinants of Dual-Task Costs for Gait Parameters: The Yishun Study." Gerontology 67, no. 4 (2021): 457–66. http://dx.doi.org/10.1159/000514171.
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<b><i>Background:</i></b> Studies indicate that physiological and cognitive aging are causally related and functionally interdependent. However, the relative contribution of physiological factors and cognition to dual-task costs (DTC) of gait parameters has not been well studied. In this cross-sectional study, we examined the trajectory of DTC of gait parameters across the adult age spectrum for both sexes and identified the contributions of physical and cognitive performance to DTC of gait. <b><i>Methods:</i></b> A total of 492 community-dwelling adults, aged 21–90 years, were randomly recruited into the study. Participants were divided into 7 age groups, with 10-year age range for each group. Demographic data, height, body mass, education level, and information on comorbidities were recorded. Cognition was measured using the Repeatable Battery for the Assessment of Neuropsychological Status. Physical performance included visual contrast sensitivity, postural sway, hand reaction time, handgrip strength, knee extensor strength, and single-task and dual-task gait assessments. Stepwise multivariable regression was used to examine the association between physical and cognitive performance with DTC of gait parameters. <b><i>Results:</i></b> Women were found to have significantly higher DTC of gait speed (<i>p</i> = 0.01), cadence (<i>p</i> < 0.01), and double support time (<i>p</i> < 0.01) than men. However, significant aging effect on DTC of gait speed (<i>p</i> = 0.01), step length (<i>p</i> = 0.01), and double support time (<i>p</i> = 0.01) was observed in men but not in women. Immediate memory was the primary determinant for the DTC of gait speed (β = −0.25, <i>p</i> < 0.01), step length (β = −0.22<i>, p</i> < 0.01), and cadence (β = −0.15<i>, p</i> = 0.03) in men. Besides immediate memory, postural sway (β = −0.13, <i>p</i> = 0.03) and hand reaction (β = 0.14, <i>p =</i> 0.02) were also significantly associated with DTC of step length and cadence, respectively, in women. <b><i>Conclusion:</i></b> There were sex differences in the amplitude and trajectories of DTC of gait parameters. The DTC increased with age in men but not in women. Immediate memory was the primary determinant of DTC of gait parameters in men while immediate memory, postural sway, and reaction time were associated with DTC of gait in women. Future studies should investigate the clinical implications of the sex differences in the DTC with fall risks.
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Nikolić, Božidar, Ivanka Milošević, Tatjana Vuković, Nataša Lazić, Saša Dmitrović, Zoran Popović, and Milan Damnjanović. "Irreducible and site-symmetry-induced representations of single/double ordinary/grey layer groups." Acta Crystallographica Section A Foundations and Advances 78, no. 2 (February 4, 2022): 107–14. http://dx.doi.org/10.1107/s205327332101322x.
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Considered are 80 sets of layer groups, each set consisting of four groups: ordinary single and double, and grey single and double layer groups. The structural properties of layer groups (factorization into cyclic subgroups and the existence of grading according to the sequence of halving subgroups) enable efficient symbolic computation (by the POLSym code) of the relevant properties, real and complex irreducible and allowed (half-)integer (co-)representations in particular. This task includes, as the first step, classification of the irreducible domains based on the group action in the Brillouin zone combined with torus topology. Also, the band (co-)representations induced from the irreducible (co-)representations of Wyckoff-position stabilizers (site-symmetry groups) are decomposed into the irreducible components. These, and other layer group symmetry related theoretical data relevant for physics, layered materials in particular, are tabulated and made available through the web site https://nanolab.group/layer/.
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Haputhanthirige, Nadeesha Kalyani Hewa, Karen Sullivan, Gene Moyle, Sandy Brauer, Erica Rose Jeffrey, and Graham Kerr. "Effects of dance on gait and dual-task gait in Parkinson’s disease." PLOS ONE 18, no. 1 (January 24, 2023): e0280635. http://dx.doi.org/10.1371/journal.pone.0280635.
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Background Gait impairments in Parkinson’s disease (PD) limit independence and quality of life. While dance-based interventions could improve gait, further studies are needed to determine if the benefits generalise to different terrains and when dual-tasking. The aim was to assess the effects of a dance intervention, based on the Dance for PD® (DfPD®) program, on gait under different dual-tasks (verbal fluency, serial subtraction) and surfaces (even, uneven), and to determine if a larger scale follow-up RCT is warranted. Methods A dance group (DG; n = 17; age = 65.8 ± 11.7 years) and a control group (CG: n = 16; age = 67.0 ± 7.7 years) comprised of non-cognitively impaired (Addenbrooke’s score: DG = 93.2 ± 3.6, CG = 92.6 ± 4.3) independently locomoting people with PD (Hoehn & Yahr I-III). The DG undertook a one-hour DfPD®-based class, twice weekly for 12 weeks. The CG had treatment as usual. The spatiotemporal variables of gait were assessed at baseline and post-intervention while walking on two surfaces (even, uneven) under three conditions: regular walking; dual-task: verbal-fluency (DTVERB), and serial-subtraction (DTSUBT). The data were analysed by means of a linear mixed model. Results At baseline, there was no significant group difference for any spatiotemporal gait variable. The DG improved significantly compared to the CG with and without a dual task when walking on even surface. During regular walking, DG improved in gait velocity (p = 0.017), cadence (p = 0.039), step length (p = 0.040) and stride length (p = 0.041). During DTVERB significant improvements were noted in gait velocity (p = 0.035), cadence (p = 0.034) and step length (p = 0.039). The DG also exhibited significant improvement compared to the CG during DTSUBT in the measures of gait velocity (p = 0.012), cadence (p = 0.021), step length (p = 0.018), and stride length (p = 0.151). On the uneven surface, improvements were noted when walking while performing serial subtractions only. During regular walking, improvements were noted for the CG but not for the DG. CG has spent less time in double support following the intervention than DG. While DTVERB condition had no significant group differences for any gait parameter (p’s >0.05), in the DTSUBT condition, the DG improved significantly compared to the controls on gait velocity (p = 0.048), cadence (p = 0.026), and step length (p = 0.051). Conclusions DfPD®-based classes produced clinically significant improvement in spatiotemporal gait parameters under dual-task conditions and on uneven surfaces. This could arise from improved movement confidence and coordination; emotional expression; cognitive skills (planning, multitasking), and; utilisation of external movement cues. A large-scale RCT of this program is warranted. Trial registration A protocol for this study has been registered retrospectively at the Australian New Zealand Clinical Trials Registry. Identifier: ACTRN12618001834246.
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Higuchi, Ai, Junichiro Shiraishi, Yuichi Kurita, and Tomohiro Shibata. "Effects of Gait Inducing Assist for Patients with Parkinson’s Disease on Double Support Phase During Gait." Journal of Robotics and Mechatronics 32, no. 4 (August 20, 2020): 798–811. http://dx.doi.org/10.20965/jrm.2020.p0798.
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Parkinson’s disease (PD) is a common progressive neurodegenerative disease that affects a wide range of motor and non-motor symptoms. Freezing of gait (FOG) is such a motor symptom of PD that frequently results in falling, and almost half of PD patients suffer from FOG. In this study, we investigated the effectiveness of a robotic assistance system called UPS-PD, which was developed to suppress FOG. The double limb support phase (DLS) in a 10-m straight-line walking task, the gait time and step counts were measured in five PD subjects. In addition, the safety of the UPS-PD in a healthy person was investigated using OpenSim, and the DLS parameters in four healthy elderly subjects were evaluated. In the experiment with the PD patients, the DLS parameters of two subjects showed an improvement. Furthermore, the step length of one subject and the step length and walking speed of the other subject were improved. Moreover, there were no problems in terms of instability of gait in both the PD patients. The UPS-PD did not adversely affect the gait of healthy elderly subjects and the walking of a healthy subject model in the simulation. Therefore, the UPS-PD is considered to be a useful device for improving walking in PD patients.
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Mathar, David, Mani Erfanian Abdoust, Tobias Marrenbach, Deniz Tuzsus, and Jan Peters. "The catecholamine precursor Tyrosine reduces autonomic arousal and decreases decision thresholds in reinforcement learning and temporal discounting." PLOS Computational Biology 18, no. 12 (December 22, 2022): e1010785. http://dx.doi.org/10.1371/journal.pcbi.1010785.
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Supplementation with the catecholamine precursor L-Tyrosine might enhance cognitive performance, but overall findings are mixed. Here, we investigate the effect of a single dose of tyrosine (2g) vs. placebo on two catecholamine-dependent trans-diagnostic traits: model-based control during reinforcement learning (2-step task) and temporal discounting, using a double-blind, placebo-controlled, within-subject design (n = 28 healthy male participants). We leveraged drift diffusion models in a hierarchical Bayesian framework to jointly model participants’ choices and response times in both tasks. Furthermore, comprehensive autonomic monitoring (heart rate, heart rate variability, pupillometry, spontaneous eye-blink rate) was performed both pre- and post-supplementation, to explore potential physiological effects of supplementation. Across tasks, tyrosine consistently reduced participants’ RTs without deteriorating task-performance. Diffusion modeling linked this effect to attenuated decision-thresholds in both tasks and further revealed increased model-based control (2-step task) and (if anything) attenuated temporal discounting. On the physiological level, participants’ pupil dilation was predictive of the individual degree of temporal discounting. Tyrosine supplementation reduced physiological arousal as revealed by increases in pupil dilation variability and reductions in heart rate. Supplementation-related changes in physiological arousal predicted individual changes in temporal discounting. Our findings provide first evidence that tyrosine supplementation might impact psychophysiological parameters, and suggest that modeling approaches based on sequential sampling models can yield novel insights into latent cognitive processes modulated by amino-acid supplementation.
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Kaditis, Athanasios G., Maria Luz Alonso Alvarez, An Boudewyns, Emmanouel I. Alexopoulos, Refika Ersu, Koen Joosten, Helena Larramona, et al. "Obstructive sleep disordered breathing in 2- to 18-year-old children: diagnosis and management." European Respiratory Journal 47, no. 1 (November 5, 2015): 69–94. http://dx.doi.org/10.1183/13993003.00385-2015.
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This document summarises the conclusions of a European Respiratory Society Task Force on the diagnosis and management of obstructive sleep disordered breathing (SDB) in childhood and refers to children aged 2–18 years. Prospective cohort studies describing the natural history of SDB or randomised, double-blind, placebo-controlled trials regarding its management are scarce. Selected evidence (362 articles) can be consolidated into seven management steps. SDB is suspected when symptoms or abnormalities related to upper airway obstruction are present (step 1). Central nervous or cardiovascular system morbidity, growth failure or enuresis and predictors of SDB persistence in the long-term are recognised (steps 2 and 3), and SDB severity is determined objectively preferably using polysomnography (step 4). Children with an apnoea–hypopnoea index (AHI) >5 episodes·h−1, those with an AHI of 1–5 episodes·h−1and the presence of morbidity or factors predicting SDB persistence, and children with complex conditions (e.g.Down syndrome and Prader–Willi syndrome) all appear to benefit from treatment (step 5). Treatment interventions are usually implemented in a stepwise fashion addressing all abnormalities that predispose to SDB (step 6) with re-evaluation after each intervention to detect residual disease and to determine the need for additional treatment (step 7).
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Moroz, V. M., M. V. Yoltukhivskyy, O. V. Vlasenko, G. S. Moskovko, O. V. Bogomaz, I. L. Rokunets, I. V. Tyshchenko, L. V. Kostyuk, and K. V. Suprunov. "Sex-related features of walking with cognitive tasks." Reports of Morphology 25, no. 2 (June 26, 2019): 5–15. http://dx.doi.org/10.31393/morphology-journal-2019-25(2)-01.
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The organization of walking and its disorders remain one of the most difficult sections of the physiology of the nervous system and neurology. The purpose of the work is to analyze the sexual features of the spatio-temporal parameters of the person walking and the directions of their changes in the conditions of performing additional cognitive tasks. Sex-related features of human walking with cognitive tasks are investigated. 608 individuals of both sexes aged 12-43 years were examined by GAITRite®. Consistent naming of animals and consistent subtraction of 7 starting at 100 were used as cognitive tasks. Statistical processing of the obtained results was performed in the license package “STATISTICA 5.5” using parametric estimation methods. At performing the first (simpler) cognitive task in all age groups of men step length, stride length, step extremity ratio, support base, toe-in-out were increased. Temporal parameters in adolescents of both genders did not differ. Girls have longer step time, cycle time, single support, swing time and a slower velocity. The integral index of walking quality (FAP) tended to decrease in all examined groups: in adolescent males by 13.3±3.9 %; in young men by 14.6±2.2 %; in adolescent women by 15.3±1.8 %; in young women by 14.4±1.1 %; in middle-aged women 7.3±4.8 %. Boys and girls performed more complex cognitive tasks with reduced spatial and temporal parameters (primarily by increasing the double support and swing time), the support base and toe-in-out were stable. The step cycle was rebuilt. The support base and toe-in-out remained unchanged both in boys and girls. The boys were moving at a faster velocity, taking more steps per minute. The step time right, cycle time for each leg, single support time and double support time in girls lasted much longer. FAP declined sharply by 30.4 % in boys and by 33.4 % in girls, indicating a major reorganization of basic mechanisms for regulating walking stability. Such a decrease in FAP leads to a decrease in the level of the balance maintaining and a decrease in body stability during movement, which means that it increases the risk of falls. A complex cognitive task led to a decrease in walking performance and a more critical decrease in the quality of walking in favor of moving forward and maintaining the balance. Thus, walking is not an automated process, but requires the use of a variety of additional CNS resources, primarily attention and cognitive resources.
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Buonocore, Antimo, and David Melcher. "Disrupting saccadic updating: visual interference prior to the first saccade elicits spatial errors in the secondary saccade in a double-step task." Experimental Brain Research 233, no. 6 (April 2, 2015): 1893–905. http://dx.doi.org/10.1007/s00221-015-4261-5.
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Moroz, V. M., M. V. Yoltukhivskyy, O. V. Vlasenko, G. S. Moskovko, O. V. Bogomaz, I. L. Rokunets, I. V. Tyshchenko, L. V. Kostyuk, and K. V. Suprunov. "Age-related features of walking with cognitive tasks." Biomedical and Biosocial Anthropology, no. 34 (February 28, 2019): 68–76. http://dx.doi.org/10.31393/bba34-2019-10.
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Human walking is considered as a complex cognitive act. The research purpose is an analysis of age-related features of spatio-temporal parameters of human walking and directions of their changes at walking with dual (cognitive) tasks. The walking spatio-temporal indexes were studied in 608 individuals of both sexes aged 12-43 years by GAITRite® (CIR Systems Inc.,Clifton, NJ) under normal walking at individually comfortable velocity and under additional cognitive tasks: 1) sequentially pronounce aloud any known animals; 2) starting from a number 100, subtract 7 and pronounce the result aloud. The statistical processing of the got results was carried out in the licensed software “STATISTICA 5.5”. At performing the first, simpler, task, the spatial parameters had no significant changes in all age groups. Most of the temporal parameters changed: cycle time, swing time, single support time, and double support time increased. Therefore, equilibrium maintaining at walking with naming animals is realized with a longer overall support period, reducing the walking cadence and velocity. The constant width of the support base and the angle of the feet turn indicate that the magnitudes of the functional support base and angle of the feet turn at normal walking is sufficient to maintain posture and balance at walking with simultaneous performance of the cognitive task, as well as more rigid mechanisms of regulation of these two parameters. The walking temporal parameters are more labile than spatial parameters. With age, the percentage of the integral index of walking quality (FAP) decreases especially in females: in girls by 15.3 %, in young women by 14.4 %, in middle-aged women by 7.4 %. At performing the second, more complex, arithmetic task, in young men and young girls support base, toe-in-out, step length difference had no significant changes only. The mean velocity, cadence, step length, stride length, step extremity ratio decreased. The count of steps, all temporal parameters, and stance percentage increased. FAP declined critically by 30.4 % in young men and 33.4 % in young women, indicating a decrease in balance and body stability under walking with cognitive task and increasing the risk of falls. Therefore, a significant reduction in FAP can be used as a diagnostic criterion in neurological practice.
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Parr, Nicholas D., Chris J. Hass, and Mark D. Tillman. "Cellular Phone Texting Impairs Gait in Able-bodied Young Adults." Journal of Applied Biomechanics 30, no. 6 (December 2014): 685–88. http://dx.doi.org/10.1123/jab.2014-0017.
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Cellular phone texting has become increasingly popular, raising the risk of distraction-related injuries. The purpose of this study was to compare alterations in gait parameters during normal gait as opposed to walking while texting. Thirty able-bodied young adults (age = 20 ± 2 y, height = 171 ± 40 cm, mass = 61.7 ± 11.2 kg) who reported texting on a regular basis were tested using an 11-camera optical motion capture system as they walked across an 8 m, obstacle-free floor. A reduction in velocity (P < .05) was seen along with additional significant changes in spatial and temporal parameters. Specifically, step width and double stance time increased, while toe clearance, step length, and cadence decreased. Although many of the changes in spatial and temporal parameters generally accompany slowed gait, the complex distraction task used here may have amplified these potentially deleterious effects. The combination of the slower gait velocity and decrease in attention to the surrounding environment suggests that an individual who is texting while walking could be at a greater risk of injury. Tripping injuries while texting could be more likely due to the decreased toe clearance. In addition, increased step width may increase the likelihood of stepping on an unstable surface or colliding with obstacles in close proximity.
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Gao, Xin, Xueyuan Li, Qi Liu, Zirui Li, Fan Yang, and Tian Luan. "Multi-Agent Decision-Making Modes in Uncertain Interactive Traffic Scenarios via Graph Convolution-Based Deep Reinforcement Learning." Sensors 22, no. 12 (June 17, 2022): 4586. http://dx.doi.org/10.3390/s22124586.
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As one of the main elements of reinforcement learning, the design of the reward function is often not given enough attention when reinforcement learning is used in concrete applications, which leads to unsatisfactory performances. In this study, a reward function matrix is proposed for training various decision-making modes with emphasis on decision-making styles and further emphasis on incentives and punishments. Additionally, we model a traffic scene via graph model to better represent the interaction between vehicles, and adopt the graph convolutional network (GCN) to extract the features of the graph structure to help the connected autonomous vehicles perform decision-making directly. Furthermore, we combine GCN with deep Q-learning and multi-step double deep Q-learning to train four decision-making modes, which are named the graph convolutional deep Q-network (GQN) and the multi-step double graph convolutional deep Q-network (MDGQN). In the simulation, the superiority of the reward function matrix is proved by comparing it with the baseline, and evaluation metrics are proposed to verify the performance differences among decision-making modes. Results show that the trained decision-making modes can satisfy various driving requirements, including task completion rate, safety requirements, comfort level, and completion efficiency, by adjusting the weight values in the reward function matrix. Finally, the decision-making modes trained by MDGQN had better performance in an uncertain highway exit scene than those trained by GQN.
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Berman, Rebecca A., Laura M. Heiser, Richard C. Saunders, and Carol L. Colby. "Dynamic Circuitry for Updating Spatial Representations. I. Behavioral Evidence for Interhemispheric Transfer in the Split-Brain Macaque." Journal of Neurophysiology 94, no. 5 (November 2005): 3228–48. http://dx.doi.org/10.1152/jn.00028.2005.
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Internal representations of the sensory world must be constantly adjusted to take movements into account. In the visual system, spatial updating provides a mechanism for maintaining a coherent map of salient locations as the eyes move. Little is known, however, about the pathways that produce updated spatial representations. In the present study, we asked whether direct cortico-cortical links are required for spatial updating. We addressed this question by investigating whether the forebrain commissures—the direct path between the two cortical hemispheres—are necessary for updating visual representations from one hemifield to the other. We assessed spatial updating in two split-brain monkeys using the double-step task, which involves saccades to two sequentially appearing targets. Accurate performance requires that the representation of the second target be updated to take the first saccade into account. We made two central discoveries regarding the pathways that underlie spatial updating. First, we found that split-brain monkeys exhibited a selective initial impairment on double-step sequences that required updating across visual hemifields. Second, and most surprisingly, these impairments were neither universal nor permanent: the monkeys were ultimately able to perform the across-hemifield sequences and, in some cases, this ability emerged rapidly. These findings indicate that direct cortical links provide the main substrate for updating visual representations, but they are not the sole substrate. Rather, a unified and stable representation of visual space is supported by a redundant cortico-subcortical network with a striking capacity for reorganization.
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Bey, Katharina, Julia V. Lippold, Behrem Aslan, René Hurlemann, and Ulrich Ettinger. "Effects of lorazepam on prosaccades and saccadic adaptation." Journal of Psychopharmacology 35, no. 1 (December 4, 2020): 91–99. http://dx.doi.org/10.1177/0269881120972424.
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Background: Benzodiazepines have reliable adverse effects on saccadic eye movements, but the impact of sex as a potential modulator of these effects is less clear. A recent study reported stronger adverse effects on the spatial consistency of saccades in females, which may reflect sex differences in cerebellar mechanisms. Aims: We aimed to further examine the role of sex as a potential modulator of benzodiazepine effects by employing the saccadic adaptation paradigm, which is known to be sensitive to cerebellar functioning. Methods: A total of n=50 healthy adults performed a horizontal step prosaccade task and a saccadic adaptation task under 0.5 mg lorazepam, 1 mg lorazepam and placebo in a double-blind, within-subjects design. Results: In the prosaccade task, lorazepam had adverse effects on measures of peak velocity, latency and spatial consistency. The administration of 0.5 mg lorazepam led to significant reductions in gain-decrease adaptation, while a dose of 1 mg did not impair adaptation learning. Gain-increase adaptation was generally less pronounced, and unaffected by the drug. There were no significant drug×sex interactions in either task. Conclusions: We conclude that a low dose of lorazepam impairs gain-decrease adaptation independent of sex. At higher doses, however, increasing fatigue may facilitate adaptation and thus counteract the adverse effects observed at lower doses. With regards to prosaccades, our findings confirm peak velocity as well as latency and spatial measures as sensitive biomarkers of GABAergic effects.
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Gomes, Gisele de Cássia, Luci Fuscaldi Teixeira-Salmela, Flávia Alexandra Silveira de Freitas, Maria Luísa Morais Fonseca, Marina de Barros Pinheiro, Viviane Aparecida de Carvalho Morais, and Paulo Caramelli. "Gait performance of the elderly under dual-task conditions: Review of instruments employed and kinematic parameters." Revista Brasileira de Geriatria e Gerontologia 19, no. 1 (February 2016): 165–82. http://dx.doi.org/10.1590/1809-9823.2016.14159.
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Introduction The physiological deterioration associated with ageing exposes elderly persons to greater risks of falls, especially during the performance of simultaneous tasks during gait. Objectives To evaluate the effects of dual tasks (DT) on spatiotemporal gait parameters and to identify the tools and tasks most commonly used to assess the performance of DT among the elderly. Method Searches of the MEDLINE, PsycINFO, CINAHL, and SciELO databases were conducted. Observational studies, which evaluated gait changes during the performance of DT, published up to April 2014, were selected. Results A total of 385 articles were found, of which 28 were selected. Decreases in speed and increases in stride variability, stride time, step width, and double support time were observed under DT conditions. Motion analysis systems, such as the GAITRite walkway(r) system were the mostly commonly used instruments for the analyses of kinematic parameters (16 studies). DT was most commonly assessed by arithmetic calculations in 20 studies, followed by verbal fluency, in nine studies. The gait parameters most commonly assessed were speed (19 studies), followed by stride variability (14 studies). Conclusion The elderly showed changes in spatiotemporal gait parameters under DT conditions. Gait speed and stride variability were often assessed and, together, were considered good indicators of risks of falls.
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Chen, Yue, Lin Lv, and Jie Shen. "Effects of Intake Port Optimization on Soot Emission from Diesel Engine." Applied Mechanics and Materials 535 (February 2014): 333–39. http://dx.doi.org/10.4028/www.scientific.net/amm.535.333.
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All future engine developments must consider the primary task of achieving the required emission levels. An important step towards the development of combustion engines is the optimization of the flow in the intake ports. The charging movement in the combustion chamber, which is generated by the intake flow, considerably influences the quality of the combustion engine. In this paper, steady CFD analysis were applied to different structures of double-tangent-port. The swirl ratio can be improved while flow coefficient remains unchanged if port eccentricity is 34.4 mm. By defining three characteristic parameters, the speed non-uniformity index, standard deviation and mixture concentration standard deviation and equivalent ratio range, quantitatively describing the combustion process in cylinder, and then compared with transient CFD three-dimensional contours, we can see that characteristic parameters can be more accurate and comprehensive in analyzing the influence of inlet structure of soot formation. Effects of different intake ports on fuel-air mixing in a turbocharged diesel direct injection engine during intake and compression strokes are analyzed. It turns out that the optimized double-tangent-port has the highest uniformity of velocity, in the meanwhile, air/fuel mixing is relatively uniform. On the other hand, mixed-port and double-helix-port can cause uneven flow field which is bad for combustion, even though the swirl ratio can increase largely. Finally, the simulation results show that soot emissions of the optimized double-tangent-port have significantly lower levels, at 2200 r/min under full load.
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Dragalina-Chernaya, Elena G., and Elena N. Lisanyuk. "The incomprehensible effectiveness of logic, or The scandal of Francis Bacon’s true induction." Vestnik of Saint Petersburg University. Philosophy and Conflict Studies 38, no. 3 (2022): 307–18. http://dx.doi.org/10.21638/spbu17.2022.303.
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We take seriously a statement of Francis Bacon (1561-1626) that what is he creating is no new philosophy, but a new logic. The demarcation of the disciplinary boundaries of the experimental natural science and the new logic, ‘the art of questioning and interpreting nature’, turns out to be the key task of the grandiose reform of scientific knowledge initiated by his ‘Novum Organum’, the 400-th anniversary of which was celebrated in 2020. Bacon proposes his ‘logic of discovering’ including the true induction as the first part of the four parts of logic three other parts of which have been invented before him. This task involves a design of a double transition, from the experimental data in the ‘lower axioms’ though the ‘middle axioms’ to a particular logical system with its ‘higher axioms’, and vice versa, from the logical system to the experimental data. We consider Bacon's true induction as a conceptual technology for eliminating of the ‘vague abstractions’ in a conversation with nature about the truth. Based on the generalization of data from the examples of presence, absence, and degree, the true induction through the data refinement and validation relates its outcomes to probabilistic and plausible reasonings about reasonings. Technological devices of Baconian conceptual design are constructed to provide the imperfect cognitive agent with instructions for the interface design of sequential step-by-step ascent through the levels of abstraction from initial experimental data to true knowledge, thus presumably guaranteeing the comprehensible effectiveness of logical knowledge.
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Bhutani, Neha, Supriya Ray, and Aditya Murthy. "Is saccade averaging determined by visual processing or movement planning?" Journal of Neurophysiology 108, no. 12 (December 15, 2012): 3161–71. http://dx.doi.org/10.1152/jn.00344.2012.
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Saccadic averaging that causes subjects' gaze to land between the location of two targets when faced with simultaneously or sequentially presented stimuli has been often used as a probe to investigate the nature of computations that transform sensory representations into an oculomotor plan. Since saccadic movements involve at least two processing stages—a visual stage that selects a target and a movement stage that prepares the response—saccade averaging can either occur due to interference in visual processing or movement planning. By having human subjects perform two versions of a saccadic double-step task, in which the stimuli remained the same, but different instructions were provided (REDIRECT gaze to the later-appearing target vs. FOLLOW the sequence of targets in their order of appearance), we tested two alternative hypotheses. If saccade averaging were due to visual processing alone, the pattern of saccade averaging is expected to remain the same across task conditions. However, whereas subjects produced averaged saccades between two targets in the FOLLOW condition, they produced hypometric saccades in the direction of the initial target in the REDIRECT condition, suggesting that the interaction between competing movement plans produces saccade averaging.
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Alrowaili, Ziyad A., Mustafa M. Ali, Abdelraheem Youssef, Hossam H. H. Mousa, Ahmed S. Ali, Gamal T. Abdel-Jaber, Mohammed Ezzeldien, and Fatma Gami. "Robust Adaptive HCS MPPT Algorithm-Based Wind Generation System Using Model Reference Adaptive Control." Sensors 21, no. 15 (July 30, 2021): 5187. http://dx.doi.org/10.3390/s21155187.
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To treat the stochastic wind nature, it is required to attain all available power from the wind energy conversion system (WECS). Therefore, several maximum power point tracking (MPPT) techniques are utilized. Among them, hill-climbing search (HCS) techniques are widely implemented owing to their various features. Regarding current HCS techniques, the rotor speed is mainly perturbed using predefined constants or objective functions, which makes the selection of step sizes a multifaceted task. These limitations are directly reflected in the overall dynamic WECS performance such as tracking speed, power fluctuations, and system efficiency. To deal with the challenges of the existing HCS techniques, this paper proposes a new adaptive HCS (AD-HCS) technique with self-adjustable step size using model reference adaptive control (MRAC) based on the PID controller. Firstly, the mechanical power fluctuations are detected, then the MRAC continuously optimizes the PID gains so as to generate an appropriate dynamic step size until harvesting the maximum power point (MPP) under the optimal tracking conditions. Looking specifically at the simulation results, the proposed AD-HCS technique exhibits low oscillations around the MPP and a small settling time. Moreover, WECS efficiency is increased by 5% and 2% compared to the conventional and recent HCS techniques, respectively. Finally, the studied system is confirmed over a 1.5 MW, gird-tied, double-fed induction generator (DFIG) WECS using MATLAB/Simulink.
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Ettinger, Ulrich, Inga Meyhöfer, Mitul A. Mehta, Veena Kumari, Philip J. Corr, Steven CR Williams, and Adam M. Perkins. "Effects of lorazepam on saccadic eye movements: the role of sex, task characteristics and baseline traits." Journal of Psychopharmacology 32, no. 6 (May 21, 2018): 678–90. http://dx.doi.org/10.1177/0269881118772450.
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Background: Saccadic eye movements are controlled by a network of parietal, frontal, striatal, cerebellar and brainstem regions. The saccadic peak velocity is an established biomarker of benzodiazepine effects, with benzodiazepines reliably reducing the peak velocity. Aims: In this study, we aimed to replicate the effects of benzodiazepines on peak velocity and we investigated effects on previously less studied measures of saccades. We also explored the roles of sex, task characteristics and the baseline variables age, intelligence and trait anxiety in these effects. Method: Healthy adults ( N = 34) performed a horizontal step prosaccade task under 1 mg lorazepam, 2 mg lorazepam and placebo in a double-blind, within-subjects design. Results: We replicated the dose-dependent reduction in peak velocity with lorazepam and showed that this effect is stronger for saccades to targets at smaller eccentricities. We also demonstrated that this effect is independent of sex and other baseline variables. Lorazepam effects were widespread, however, occurring on mean and variability measures of most saccadic variables. Additionally, there were sex-dependent lorazepam effects on spatial consistency of saccades, indicating more adverse effects in females. Conclusions: We conclude that saccadic peak velocity is a sensitive and robust biomarker of benzodiazepine effects. However, lorazepam has pronounced effects also on other parameters of horizontal saccades. Sex-dependent drug effects on spatial consistency may reflect cerebellar mechanisms, given the role of the cerebellum in saccadic spatial accuracy.