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Journal of Neurophysiology

Christopher J Hasson, Sarah E Goodman
This work aims to understand the sensorimotor processes used by humans when learning how to manipulate a virtual model of locomotor dynamics. Prior research shows that when interacting with novel dynamics, humans develop internal models that map neural commands to limb motion, and vice-versa. Whether this can be extrapolated to locomotor rehabilitation, a continuous and rhythmic activity that involves dynamically complex interactions is unknown. In this case, humans could default to model-free strategies. These competing hypotheses were tested with a novel interactive locomotor simulator that reproduced the dynamics of hemiparetic gait...
November 7, 2018: Journal of Neurophysiology
Masakazu Igarashi, Jeffery R Wickens
Bimanual coordination - in which both hands work together to achieve a goal - is crucial for the basic needs of life, such as gathering and feeding. Such coordinated motor skill is highly developed in primates, where it has been most extensively studied. Rodents also exhibit remarkable dexterity and coordination of forelimbs during food handling and consumption. However, rodents have been less commonly used in the study of bimanual coordination because of limited quantitative measuring techniques. Here we describe a high-resolution tracking system that enables kinematic analysis of rat forelimb movement...
November 7, 2018: Journal of Neurophysiology
Noam Roth, Nicole C Rust
Task performance is determined not only by the amount of task-relevant signal present in our brains, but also by the presence of noise, which can arise from multiple sources. Internal noise, or "trial variability", manifests as trial-by-trial variations in neural responses under seemingly identical conditions. External factors can also translate into noise, particularly when a task requires extracting a particular type of information from our environment amid changes in other task-irrelevant, "nuisance" parameters...
November 7, 2018: Journal of Neurophysiology
Eli Brenner, Jeroen B J Smeets
This paper reviews our understanding of the interception of moving objects. Interception is a demanding task that requires both spatial and temporal precision. The required precision must be achieved on the basis of imprecise and sometimes biased sensory information. We argue that people make precise interceptive movements by continuously adjusting their movements. Initial estimates of how the movement should progress can be quite inaccurate. As the movement evolves, the estimate of how the rest of the movement should progress gradually becomes more reliable as prediction is replaced by sensory information about the progress of the movement...
October 31, 2018: Journal of Neurophysiology
Hongwei Mao, Yuan Yuan, Jennie Si
To better understand the neural cortical underpinnings that explain behavioral differences in learning rate, we recorded single unit activity in rat primary motor (M1) and secondary motor (M2) areas while rats learned to perform a directional (left or right) operant visuomotor association task. Analysis of neural activity during the early portion of the cue period showed that neural modulation in the motor cortex was most strongly associated with two task factors: the previous trial outcome (success or error) and the current trial's directional choice (left or right)...
October 31, 2018: Journal of Neurophysiology
Michael Elliott Shinder, Jeffrey Steven Taube
Head direction (HD) cells fire when the animal faces that cell's preferred firing direction (PFD) in the horizontal plane. The PFD response when the animal is oriented outside the earth-horizontal plane could result from cells representing direction in the plane of locomotion or as a three-dimensional (3D), global-referenced direction anchored to gravity. To investigate these possibilities, anterodorsal thalamic HD cells were recorded from restrained rats while they were passively positioned in various 3D orientations...
October 31, 2018: Journal of Neurophysiology
Giorgia Ponsi, Bianca Monachesi, Vincenzo Panasiti, Salvatore Maria Aglioti, Maria Serena Panasiti
Recent studies show that sympathetic nervous system (SNS) activity can be heavily impacted not only by basic threats to survival, but by threats to social bonds. Herein we explored the behavioral and physiological consequences of social exclusion/inclusion in patients with psoriasis, a disease frequently associated with the experience of being ostracized and deficient emotion regulation skills. We employed a virtual ball-tossing game (Cyberball) to induce the experience of social exclusion/inclusion. We then used a Trust game to measure the effects of this social modulation on trust...
October 31, 2018: Journal of Neurophysiology
Spencer A Murphy, Francesco Negro, Dario Farina, Tanya Onushko, Matthew J Durand, Sandra K Hunter, Brian D Schmit, Allison S Hyngstrom
Following stroke, hyperexcitable sensory pathways, such as the group III/IV afferents that are sensitive to ischemia, may inhibit paretic motor neurons during exercise. We quantified the effects of whole leg ischemia on paretic vastus lateralis motor unit firing rates during sub-maximal isometric contractions. Ten chronic stroke survivors (>1 year post stroke) and 10 controls participated. During conditions of whole leg occlusion, the discharge timings of motor units were identified from decomposition of high-density surface EMG signals during repeated sub-maximal knee extensor contractions...
October 31, 2018: Journal of Neurophysiology
Laurent Goffart, Clara Bourrelly, Jean-Charles Quinton
In this article, we perform a critical examination of assumptions which led to assimilate measurements of the movement of a rigid body in the physical world to parameters encoded within the brain activity. In many neurophysiological studies of goal-directed eye movements, equivalence has indeed been made between the kinematics of the eyes or of a targeted object and the associated neuronal processes. Such a way of proceeding brings up the reduction encountered in projective geometry when a multidimensional object is being projected onto a one-dimensional segment...
October 31, 2018: Journal of Neurophysiology
Marissa J Rosenberg, Raquel C Galvan-Garza, Torin K Clark, David P Sherwood, Laurence R Young, Faisal Karmali
Precise motion control is critical to human survival on Earth and in space. Motion sensation is inherently imprecise, and the functional implications of this imprecision are not well understood. We studied a "vestibular" manual control task in which subjects attempted to keep themselves upright using a rotational hand controller (i.e., joystick) to null out pseudo-random, roll tilt motion disturbances of their chair in the dark. Objective 1: Study the relationship between intersubject differences in manual control performance and sensory precision, determined by measuring vestibular perceptual thresholds...
October 31, 2018: Journal of Neurophysiology
Stephanie Naufel, Joshua I Glaser, Konrad P Koerding, Eric J Perreault, Lee E Miller
Whether delicately placing a contact lens on the surface of the eye, or lifting a heavy weight from the floor, the motor system must produce a wide range of forces under different dynamical loads. How does the motor cortex, with neurons that have a limited activity range, function effectively under these widely varying conditions? Here, we explored the interaction of activity in primary motor cortex (M1) and muscles (EMGs) of two male rhesus monkeys for wrist movements made during three tasks requiring different dynamical loads and forces...
October 31, 2018: Journal of Neurophysiology
Ryan J Colquhoun, Patrick M Tomko, Mitchel A Magrini, Tyler W D Muddle, Nathaniel David Moyer Jenkins
INTRODUCTION: Decomposition of the surface electromyographic (sEMG) signal is commonly used to examine motor unit (MU) firing behavior. However, the intra- and inter-day reliability of these measurements has yet to be quantified or reported. This investigation 1) examined the effect of input excitation on the mean firing rate (MFR) versus recruitment threshold (RT) relationship and 2) determined the inter- and intra-day reliability of the MFR versus RT relationship at 30%, 50%, and 70% of maximum voluntary isometric strength (MVIC)...
October 24, 2018: Journal of Neurophysiology
Ananda Sidarta, Floris van Vugt, David J Ostry
Recent studies using visuomotor adaptation and sequence learning tasks have assessed the involvement of working memory in the visuospatial domain. The capacity to maintain previously performed movements in working memory is perhaps even more important in reinforcement-based learning in order to repeat accurate movements and avoid mistakes. Using this kind of task in the current work we tested the relationship between somatosensory working memory and motor learning. The first experiment involved separate memory and motor learning tasks...
October 24, 2018: Journal of Neurophysiology
Paul M Briley, Elizabeth B Liddle, Madeleine J Groom, Helen J F Smith, Peter G Morris, Giles L Colclough, Matthew J Brookes, Peter F Liddle
Functional activity in the human brain is intrinsically organised into independently active, connected brain regions. These networks include sensorimotor systems, as well as higher-order cognitive networks such as the default mode network (DMN), which dominates activity when the brain is at rest, and the fronto-parietal (FPN) and salience (SN) networks, that are often engaged during demanding tasks. Evidence from functional magnetic resonance imaging (fMRI) suggests that while sensory systems are mature by the end of childhood, the integrity of the FPN and SN develop throughout adolescence...
October 24, 2018: Journal of Neurophysiology
Jeffrey B Thuma, Scott L Hooper
Choline chloride is often, and N-methyl-D-glucamine (NMDG) sometimes, used to replace sodium chloride in studies of sodium-activated potassium channels. Given the high concentrations used in sodium replacement protocols, it is essential to test that it is not the replacement substances themselves, as opposed to the lack of sodium, that cause any observed effects. We therefore compared, in lobster stomatogastric neurons and leech Retzius cells, the effects of applying salines in which choline chloride replaced sodium chloride, and in which choline hydroxide or sucrose was added to normal saline...
October 24, 2018: Journal of Neurophysiology
Evan J Lockyer, Ryan J Benson, Audrey P Hynes, Lynsey R Alcock, Alyssa-Joy Spence, Duane C Button, Kevin E Power
The present study investigated the effects of cadence and power output on corticospinal excitability to the biceps (BB) and triceps brachii (TB) during arm cycling. Supraspinal and spinal excitability were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract, respectively. Motor evoked potentials (MEPs) elicited by TMS and cervicomedullary motor evoked potentials (CMEPs) elicited by TMES were recorded at two positions during arm cycling corresponding to mid-elbow flexion and mid-elbow extension (i...
October 24, 2018: Journal of Neurophysiology
Raquel C Galvan-Garza, Torin K Clark, David Sherwood, Ana Diaz Artiles, Marissa J Rosenberg, Alan Natapoff, Faisal Karmali, Charles M Oman, Laurence R Young
Overestimation of roll tilt in hyper-gravity ("G-Excess" illusion) has been demonstrated, but corresponding sustained hypo-gravic conditions are impossible to create in ground laboratories. Here we describe the first systematic experimental evidence that in a hypo-gravity analog, humans underestimate roll tilt. We studied perception of self-roll tilt in nine subjects, who were supine, but spun on a centrifuge to create a hypo-gravity analog. By varying the centrifuge rotation rate, we modulated the centripetal acceleration (Gc) at the subject's head location (0...
October 17, 2018: Journal of Neurophysiology
Nikola Grujic, Nils Brehm, Cordula Gloge, Weijie Zhuo, Ziad M Hafed
Saccadic eye movements, which dramatically alter retinal images, are associated with robust peri-movement perceptual alterations. Such alterations, thought to reflect brain mechanisms for maintaining perceptual stability in the face of saccade-induced retinal-image disruptions, are often studied by asking subjects to localize brief stimuli presented around the time of horizontal saccades. However, other saccade directions are not usually explored. Motivated by recently discovered asymmetries in upper and lower visual field representations in the superior colliculus, a structure important for both saccade generation and visual analysis, here we observed significant differences in peri-saccadic perceptual alterations for upward saccades relative to other saccade directions...
October 17, 2018: Journal of Neurophysiology
Ellen Teresa Koch, Cameron L Woodard, Lynn Alison Raymond
Glutamate is the main excitatory neurotransmitter in the brain, and impairments in its signaling are associated with many neurological disorders, including Huntington's Disease (HD). Previous studies in HD mouse models demonstrate altered glutamate receptor distribution and signaling at cortico-striatal synapses, and some studies suggest glutamate release is altered; however, traditional methods to study synaptic glutamate release are indirect or have poor temporal resolution. Here we utilize iGluSnFR, a modified GFP reporter for real-time imaging of glutamate transmission, to study presynaptic modulation of cortical glutamate release in the striatum of the YAC128 HD mouse model...
October 17, 2018: Journal of Neurophysiology
Neil P M Todd, Sendhil Govender, James Gordon Colebatch
We recorded evoked potentials (EPs) from over the posterior fossa and in parallel ocular vestibular evoked myogenic potentials (OVEMPs) during visuo-vestibular stimulation in a sample of 7 male and 11 female human subjects. In 9 of the 18 subjects we were able to record EPs reliably in the form of an early biphasic positive-negative wave with latencies about 12 and 17 ms ipsilateral to head acceleration direction (P12-N17) and a slightly later, contralateral, biphasic positive-negative wave with latencies about 19 and 23 ms (P19-N23)...
October 17, 2018: Journal of Neurophysiology
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