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Journal of Neurophysiology

Nathan D Crosby, John J Janik, Warren M Grill
Kilohertz-frequency spinal cord stimulation (KHF-SCS) is a potential paresthesia-free treatment for chronic pain. However, the effects of KHF-SCS on spinal dorsal column (DC) axons and its mechanisms of action remain unknown. The objectives of this study were to quantify activation and conduction block of DC axons by KHF-SCS across a range of kHz frequencies (1, 5, 10, or 20 kHz) and waveforms (biphasic pulses or sinusoids). Custom platinum electrodes delivered SCS to the T10/T11 DCs of anesthetized male Sprague-Dawley rats...
October 19, 2016: Journal of Neurophysiology
Ayako Yamaguchi, Jessica Cavin Barnes, Todd Appleby
Central pattern generators (CPG) in the brainstem are considered to underlie vocalizations in many vertebrate species, but the detailed mechanisms underlying how motor rhythms are generated, coordinated, and initiated remain unclear. We addressed these issues using isolated brain preparations of Xenopus laevis from which fictive vocalizations can be elicited. Advertisement calls of male X. laevis that consist of fast and slow trills are generated by vocal CPGs contained in the brainstem. Brainstem central vocal pathways consist of a premotor nucleus (DTAM) and a laryngeal motor nucleus (n...
October 19, 2016: Journal of Neurophysiology
Joshua G A Cashaback, Heather R McGregor, Henry C H Pun, Gavin Buckingham, Paul L Gribble
The human sensorimotor system is routinely capable of making accurate predictions about an object's weight, which allows for energetically efficient lifts and prevents objects from being dropped. Often however, poor predictions arise when the weight of an object can vary and sensory cues about object weight are sparse (e.g., picking up an opaque water bottle). The question arises, what strategies does the sensorimotor system use to make weight predictions when dealing with an object whose weight may vary? For example, does the sensorimotor system use a strategy that minimizes prediction error (minimal squared error) or one that selects the weight that is most likely to be correct (maximum a posteriori)? Here we dissociated the predictions of these two strategies by having participants lift an object whose weight varied according to a skewed probability distribution...
October 19, 2016: Journal of Neurophysiology
Richard F Lewis
Damage to the peripheral vestibular system can result in debilitating postural, perceptual, and visual symptoms. A new potential treatment for this clinical problem is to replace some aspects of peripheral vestibular function with an implant that senses head motion and provides this information to the brain by stimulating branches of the vestibular nerve. In this review I consider animal studies performed at our institution over the past fifteen years, which have helped elucidate how the brain processes information provided by a vestibular (semicircular canal) implant and how this information could be used to improve the problems experienced by patients with peripheral vestibular damage...
October 19, 2016: Journal of Neurophysiology
Samuel A Neymotin, Benjamin A Suter, Salvador Dura-Bernal, Gordon M G Shepherd, Michele Migliore, William W Lytton
Corticospinal neurons (SPI), thick-tufted pyramidal neurons in motor cortex layer 5B that project caudally via the medullary pyramids, display distinct class-specific electrophysiological properties in vitro: strong sag with hyperpolarization, lack of adaptation, and a nearly linear frequency-current (FI) relationship. We used our electrophysiological data to produce a pair of large archives of SPI neuron computer models in two model classes: 1. Detailed models with full reconstruction; 2. Simplified models with 6 compartments...
October 19, 2016: Journal of Neurophysiology
Katelyn N Benthall, Ryan A Hough, Andrew D McClellan
Following spinal cord injury (SCI) in the lamprey, there is virtually complete recovery of locomotion within a few weeks, but interestingly, axonal regeneration of reticulospinal (RS) neurons is mostly limited to short distances caudal to the injury site. To explain this situation, we hypothesize that descending propriospinal (PS) neurons relay descending drive from RS neurons to indirectly activate spinal central pattern generators (CPGs). In the present study, the contributions of PS neurons to locomotor recovery were tested in the lamprey following SCI...
October 19, 2016: Journal of Neurophysiology
Haitao Yu, Rishi R Dhingra, Thomas E Dick, Roberto Fernandez Galan
Neural activity generally displays irregular firing patterns even in circuits with apparently regular outputs, such as motor pattern generators, in which the output frequency fluctuates randomly around a mean value. This "circuit noise" is inherited from the random firing of single neurons, which emerges from stochastic ion-channel gating (channel noise), spontaneous neurotransmitter release, and its diffusion and binding to synaptic receptors. Here, we demonstrate how to expand conductance-based network models that are originally deterministic to include realistic, physiological noise, focusing on stochastic ion-channel gating...
October 19, 2016: Journal of Neurophysiology
Clarissa J Whitmire, Daniel C Millard, Garrett B Stanley
Sensory stimulation drives complex interactions across neural circuits as information is encoded and then transmitted from one brain region to the next. In the highly interconnected thalamocortical circuit, these complex interactions elicit repeatable neural dynamics in response to temporal patterns of stimuli that provide insight into the circuit properties that generated them. Here, using a combination of in-vivo voltage sensitive dye (VSD) imaging of cortex, single unit recording in thalamus, and optogenetics to manipulate thalamic state in the rodent vibrissa pathway, we probed the thalamocortical circuit with simple temporal patterns of stimuli delivered either to the whiskers on the face (sensory stimulation) or to the thalamus directly via electrical or optogenetic inputs (artificial stimulation)...
October 19, 2016: Journal of Neurophysiology
Carey D Balaban, Joseph M Furman
This study provides the first clear evidence that the generation of optokinetic nystagmus fast phases is a decision process that is influenced by performance of a concurrent disjunctive reaction time task (DRT). Ten subjects performed an auditory DRT during constant velocity optokinetic stimulation. Eye movements were measured in three dimensions with a magnetic search coil. Slow phase (SP) durations were defined as the interval between fast phases (FPs). There were three main findings. Firstly, human optokinetic nystagmus SP durations are consistent with a model of a Gaussian basic interval generator (a type of biological clock), such that FPs can be triggered randomly at the end of a clock cycle (mean duration: 200-250 ms); Kolmogorov-Smirnov tests could not reject the modeled cumulative distribution for any data trials...
October 19, 2016: Journal of Neurophysiology
Encarni Marcos, Satoshi Tsujimoto, Aldo Genovesio
The estimation of space and time can interfere with each other, and neuroimaging studies have shown overlapping activation in the parietal and prefrontal cortical areas. We used duration and distance discrimination tasks to determine whether space and time share resources in prefrontal cortex (PF) neurons. Monkeys were required to report which of 2 stimuli, a red circle or blue square, presented sequentially, was longer and farther, respectively, in the duration and distance tasks. In a previous study, we showed that relative duration and distance are coded by different populations of neurons and that the only common representation is related to goal coding...
October 19, 2016: Journal of Neurophysiology
Rodrigo S Maeda, Shawn M O'Connor, J Maxwell Donelan, Daniel S Marigold
As we walk, we must accurately place our feet to stabilize our motion and to navigate our environment. We must also achieve this accuracy despite imperfect sensory feedback and unexpected disturbances. Here we tested whether the nervous system uses state estimation to beneficially combine sensory feedback with forward model predictions to compensate for these challenges. Specifically, subjects wore prism lenses during a visually guided walking task, and we used trial-by-trial variation in prism lenses to add uncertainty to visual feedback and induce a reweighting of this input...
October 19, 2016: Journal of Neurophysiology
Jean-Jacques Orban de Xivry, Valery Legrain, Philippe Lefèvre
Motor planning is the process of preparing the appropriate motor commands in order to achieve a goal. This process has largely been thought to occur before movement onset and traditionally has been associated with reaction time. However, in a virtual line bisection task, we observed an overlap between movement planning and execution. In this task performed with a robotic manipulandum, we observed that participants (N=30) made straight movements when the line was in front of them (near target), but often made curved movements when the same target was moved sideways (far target, which had the same orientation) in such a way that they crossed the line perpendicular to its orientation...
October 12, 2016: Journal of Neurophysiology
Kévin Marche, Paul Apicella
Recent works highlight the importance of local inhibitory interneurons in regulating the function of the striatum. In particular, fast-spiking interneurons (FSIs), which likely correspond to a subgroup of GABAergic interneurons, have been involved in the control of movement by exerting strong inhibition on striatal output pathways. However, little is known about the exact contribution of these presumed interneurons in movement preparation, initiation, and execution. We recorded the activity of FSIs in the striatum of monkeys as they performed reaching movements to a visual target under two task conditions: one in which the movement target was presented at unsignaled left or right locations, and another in which advance information about target location was available, thus allowing monkeys to react faster...
October 12, 2016: Journal of Neurophysiology
Tarkeshwar Singh, Julius Fridriksson, Christopher Perry, Sarah C Tryon, Angela Ross, Stacy Fritz, Troy M Herter
Successful execution of many motor skills relies on well-organized visual search (voluntary eye movements that actively scan the environment for task-relevant information). Although impairments of visual search that result from brain injuries are linked to diminished motor performance, the neural processes that guide visual search within this context remain largely unknown. The first objective of this study was to examine how visual search in healthy adults and stroke survivors is used to guide hand movements during the Trail Making Test (TMT), a neuropsychological task that is a strong predictor of visuomotor and cognitive deficits...
October 12, 2016: Journal of Neurophysiology
N Apurva Ratan Murty, Sripati Panditaradhyula Arun
We have no difficulty seeing a straight line drawn on a paper even when the paper is bent, but this inference is in fact nontrivial. Doing so requires either matching of local features or representing the pattern after factoring out the surface shape. Here we show that single neurons in the monkey inferior temporal cortex show invariant responses to patterns across rigid and non-rigid changes of surfaces. We recorded neuronal responses to stimuli in which the pattern and the surrounding surface were varied independently...
October 12, 2016: Journal of Neurophysiology
Maike Vollmer, Ralph Eugene Beitel, Christoph E Schreiner, Patricia A Leake
In profoundly deaf cats, behavioral training with intracochlear electric stimulation (ICES) can improve temporal processing in the primary auditory cortex (AI). To investigate whether similar effects are manifest in the auditory midbrain, ICES was initiated in neonatally deafened cats either during development after short durations of deafness (8 wk of age) or in adulthood after long durations of deafness (≥3.5 yr). All of these animals received behaviorally-meaningless, 'passive' ICES. Some animals also received behavioral training with ICES...
October 12, 2016: Journal of Neurophysiology
Raza Naseem Malik, Rachel Cote, Tania Lam
BACKGROUND: Skilled walking, such as obstacle crossing, is an essential component of functional mobility. Sensorimotor integration of visual and proprioceptive inputs is important for successful obstacle crossing. The objective of this study was to understand how proprioceptive deficits affect obstacle-crossing strategies when controlling for variations in motor deficits in ambulatory individuals with spinal cord injury (SCI). METHODS: 15 ambulatory individuals with SCI and 15 able-bodied controls were asked to step over an obstacle scaled to their motor abilities under full and obstructed vision conditions...
October 12, 2016: Journal of Neurophysiology
Edyta K Bichler, Courtney C Elder, Paul S García
Antibiotics are used in the treatment and prevention of bacterial infections, but effects on neuron excitability have been documented. A recent study demonstrated that clarithromycin alleviates daytime sleepiness in hypersomnia patients (Trotti et al. 2014). To explore the potential application of clarithromycin as a stimulant, we performed whole cell patch clamp recordings in rat pyramidal cells from the CA3 region of hippocampus. In the presence of the antibiotic, rheobase current was reduced by 50%, F-I relationship (number of action potentials as a function of injected current) was shifted to the left, and the resting membrane potential was more depolarized...
October 12, 2016: Journal of Neurophysiology
Naomi Onisawa, Hiroyuki Manabe, Kensaku Mori
During slow-wave sleep, inter-areal communications via coordinated slow oscillatory activities occur in the large-scale networks of the mammalian neocortex. Because olfactory cortex (OC) areas, which belong to paleocortex, show characteristic sharp-wave activity during slow-wave sleep, we examined whether OC sharp-waves in freely behaving rats occur in temporal coordination with up- and down-states of the orbitofrontal cortex (OFC) slow oscillation. Simultaneous recordings of local field potentials and spike activities in the OC and OFC showed that during the down-state in the OFC, the OC also exhibited down-state with greatly reduced neuronal activity and suppression of sharp-wave generation...
October 12, 2016: Journal of Neurophysiology
Samuel B Tomlinson, Arun Venkataraman
Surgical intervention often fails to achieve seizure-free results in patients with intractable epilepsy. Identifying features of the epileptic brain that dispose certain patients to unfavorable surgical outcomes is a central challenge for epilepsy researchers. In this NeuroForum, we review evidence suggesting that pathways of secondary seizure generalization distinguish patients with favorable (i.e., seizure-free) versus unfavorable (i.e., seizure-persistent) surgical outcomes. The network underpinnings and clinical implications of these findings are then discussed...
October 5, 2016: Journal of Neurophysiology
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