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Journal of Neurophysiology

Lie Wang, Giri Kumar Chandaka, Robert C Foehring, Joseph C Callaway, William E Armstrong
Oxytocin (OT) neurons exhibit larger afterhyperpolarizations (AHPs) following spike trains during pregnancy and lactation, when these neurons burst and release more OT. Calcium-dependent AHPs mediated by SK channels show this plasticity, and are reduced when the channel is phosphorylated by casein kinase 2 (CK2), and increased when dephosphorylated by protein phosphatase 2A (PP2A), by altering Ca2+ sensitivity. We compared AHP currents in supraoptic OT neurons after CK2 inhibition with 4,5,6,7-tetrabromobenzotriazole (TBB), or PP1-PP2A inhibition with okadaic acid (OA) focusing on the peak current at 100 ms representing the SK-mediated, medium AHP (ImAHP )...
March 14, 2018: Journal of Neurophysiology
Zarrar Shehzad, Gregory McCarthy
Whether category information is discretely localized or represented widely in the brain remains a contentious issue. Early functional MRI studies supported the localizationist perspective that category information was represented in discrete brain regions. More recent fMRI studies using machine learning pattern classification techniques provide evidence for widespread distributed representations. However, these latter studies have not typically accounted for shared information. Here, we find strong support for distributed representations when brain regions are considered separately...
March 14, 2018: Journal of Neurophysiology
Shahaf Weiss, Dori Derdikman
Since their discovery, mammalian head-direction (HD) cells have been extensively researched in terms of sensory origins, external cue control and circuitry. However, the relationship of HD cells to behavior is not yet fully understood. In the current review, we examine the anatomical clues for information flow in the HD circuit, and an emerging body of evidence that links between neural activity of HD cells and spatial orientation. We hypothesize from results obtained in spatial orientation tasks involving HD cells, that when properly aligned with available external cues, the HD signal could be used for guiding rats to a goal location...
March 14, 2018: Journal of Neurophysiology
Taryn Klarner, E Paul Zehr
Evidence first described in reduced animal models over 100 years ago led to deductions about the control of locomotion through spinal locomotor central pattern generating (CPG) networks. These discoveries in nature were contemporaneous with another form of deductive reasoning found in popular culture-that of Arthur Conan Doyle's detective "Sherlock Holmes". Since the invasive methods used in reduced non-human animal preparations are not amenable to study in humans, we are left instead with deducing from other measures and observations...
March 14, 2018: Journal of Neurophysiology
Irina I Ignatova, Andrew S French, Roman V Frolov
Natural visual scenes are rarely random. Instead, intensity and wavelength change slowly in time and space over many regions of the scene, so that neighboring temporal and spatial visual inputs are more correlated, and contain less information than truly random signals. It has been suggested that sensory optimization to match these higher order correlations (HOC) occurs at the earliest visual stages, and that photoreceptors can process temporal natural signals more efficiently than random signals. We tested this early stage hypothesis by comparing the information content of Calliphora vicina photoreceptor responses to naturalistic inputs before and after removing HOC by randomizing phase...
March 14, 2018: Journal of Neurophysiology
Peter James Holland, Olivier Codol, Joseph M Galea
Despite increasing interest in the role of reward in motor learning, the underlying mechanisms remain ill-defined. In particular, the contribution of explicit processes to reward-based motor learning is unclear. To address this, we examined subject's (n=30) ability to learn to compensate for a gradually introduced 25⁰ visuomotor rotation with only reward-based feedback (binary success/failure). Only two-thirds of subjects (n=20) were successful at the maximum angle. The remaining subjects initially followed the rotation but after a variable number of trials began to reach at an insufficiently large angle and subsequently returned to near baseline performance (n=10)...
March 14, 2018: Journal of Neurophysiology
Jean-Paul Noel, Olaf Blanke, Elisa Magosso, Andrea Serino
Interactions between the body and the environment occur within the Peri-Personal Space (PPS), the space immediately surrounding the body. The PPS is encoded by multisensory (audio-tactile, visual-tactile) neurons that possess receptive fields (RFs) anchored on the body and restricted in depth. The extension in depth of PPS neurons' RFs has been documented to change dynamically as a function of the velocity of incoming stimuli, but the underlying neural mechanisms are still unknown. Here, by integrating a psychophysical approach with neural network modeling, we propose a mechanistic explanation behind this inherent dynamic property of PPS...
March 14, 2018: Journal of Neurophysiology
Seth W Holwerda, Rachel E Luehrs, Allene L Gremaud, Nealy A Wooldridge, Amy K Stroud, Jess G Fiedorowicz, Francois M Abboud, Gary L Pierce
Relative burst amplitude of muscle sympathetic nerve activity (MSNA) is an indicator of augmented sympathetic outflow and contributes to greater vasoconstrictor responses. Evidence suggests anxiety-induced augmentation of relative MSNA burst amplitude in patients with panic disorder, thus we hypothesized that acute stress would result in augmented relative MSNA burst amplitude and vasoconstriction in individuals with chronic anxiety. Eighteen participants with chronic anxiety (ANX, 8 men/10 women, 32{plus minus}2 years) and 18 healthy controls with low/no anxiety (CON, 8 men/10 women, 39{plus minus}3 years) were studied...
March 14, 2018: Journal of Neurophysiology
Kevin A Day, Kristan A Leech, Ryan T Roemmich, Amy J Bastian
Acquiring new movements requires the capacity of the nervous system to remember previously experienced motor patterns. The phenomenon of faster re-learning after initial learning is termed 'savings'. Here we studied how savings of a novel walking pattern develops over several days of practice, and how this process can be accelerated. We introduced participants to a split-belt treadmill adaptation paradigm for 30 minutes for 5 consecutive days. After 5 training days, participants were able to produce near-perfect performance when switching between split and tied-belt environments...
March 14, 2018: Journal of Neurophysiology
Gaspar Epro, Andreas Mierau, Christopher McCrum, Michael Leyendecker, Gert-Peter Bruggemann, Kiros Karamanidis
The plantar flexors play a crucial role in recovery from sudden disturbances to gait. The objective of this study was to investigate whether medium (months) or long-term (years) exercise-induced enhancement of triceps surae (TS) neuromuscular capacities affects older adults' ability to retain improvements in reactive gait stability during perturbed walking acquired from perturbation training sessions. Thirty-four female adults (65{plus minus}7y) were recruited to a perturbation training group (n=13) or a group which additionally completed 14 weeks of TS neuromuscular exercise (n=21), 12 of whom continued with the exercise for 1...
March 14, 2018: Journal of Neurophysiology
Paola Contessa, John Letizi, Gianluca De Luca, Joshua C Kline
The control of motor unit firing behavior during fatigue is still debated in the literature. Most studies agree that the central nervous system increases the excitation to the motoneuron pool to compensate for decreased force contributions of individual motor units and sustain muscle force output during fatigue. However, some studies claim that motor units may decrease their firing rates despite increased excitation, contradicting the direct relationship between firing rates and excitation that governs the voluntary control of motor units...
March 14, 2018: Journal of Neurophysiology
Eleftherios Neromyliotis, Adonis K Moschovakis
We studied the phasic saccade related discharges of single neurons (S neurons) of the premotor cortex of female rhesus monkeys, mostly in the caudal bank of the arcuate sulcus. As described in previous work from our laboratory (Neromyliotis and Moschovakis, 2017b), some of these cells emitted phasic discharges for coordinated movements of the eyes and hand as well as for movements of either effector executed in isolation (motor equivalence -Meq). Other cells (S), did not emit phasic discharges for hand movements unaccompanied by saccades...
March 14, 2018: Journal of Neurophysiology
Erik Summerside, Reza Shadmehr, Alaa A Ahmed
Making a movement may be thought of as an economic decision in which one spends effort in order to acquire reward. Time discounts reward, which predicts that the magnitude of reward should affect movement vigor: we should move faster, spending greater effort, when there is greater reward at stake. Indeed, saccade peak velocities are greater and reaction-times are shorter when a target is paired with reward. Here, we focused on human reaching and asked whether movement kinematics were affected by expectation of reward...
March 14, 2018: Journal of Neurophysiology
Christopher H Mullens, David A Brown
Individuals who have experienced a stroke often demonstrate inappropriate muscle activity phasing in the paretic leg during locomotion. Past research has demonstrated that inappropriate paretic phasing varies between behavioral contexts, and is reduced during unilateral pedaling with the non-paretic leg inactive. We investigated whether individuals could voluntarily alter activity in a target muscle of the paretic limb in a consistent behavioral context, and whether this voluntary change differed between bilateral and unilateral pedaling...
March 14, 2018: Journal of Neurophysiology
Ibis M Agosto, Nicole L Nichols, Gordon S Mitchell
Although systemic inflammation induced by even a low dose of lipopolysaccharide (LPS, 100uL/kg) impairs respiratory motor plasticity, little is known concerning cellular mechanisms giving rise to this inhibition. Phrenic motor facilitation (pMF) is a form of respiratory motor plasticity elicited by pharmacological agents applied to the cervical spinal cord, or by acute intermittent hypoxia (AIH; 3, 5 min hypoxic episodes); when elicited by AIH, pMF is known as phrenic long-term facilitation (pLTF). AIH consisting of moderate hypoxic episodes (mAIH, PaO2 = 35-55 mmHg) elicits pLTF via the Q- pathway to pMF, a mechanism that requires spinal serotonin (5HT2) receptor activation and new BDNF protein synthesis...
March 7, 2018: Journal of Neurophysiology
Robert Naumann, Patricia Preston-Ferrer, Michael Brecht, Andrea Burgalossi
Following the groundbreaking discovery of grid cells, the medial entorhinal cortex (MEC) has become the focus of intense anatomical, physiological, and computational investigations. Whether and how grid activity maps onto cell types and cortical architecture is still an open question. Fundamental similarities in microcircuits, function and connectivity suggest a homology between rodent MEC and human posteromedial entorhinal cortex. Both are specialized for spatial processing and display similar cellular organization, consisting of layer 2 pyramidal/calbindin cell patches superimposed on scattered stellate neurons...
March 7, 2018: Journal of Neurophysiology
Yoshiko Izawa, Hisao Suzuki
Focal stimulation in the frontal eye field (FEF) evoked eye movements that were often accompanied by neck movements. Experiments were performed with concurrent recording of both movements in trained monkeys. We recorded neck forces under a head-restrained condition using a force-measuring system. With the system, we measured forces along the x, y, and z axes and torque about the z axis. Torque about the z axis that represented yaw rotation of the head was significantly affected by stimulation. We found that stimulation generated two types of motor actions of the eyes and neck...
March 7, 2018: Journal of Neurophysiology
Sirui Liu, Peter Ulric Tse, Patrick Cavanagh
When a Gabor patch moves along a path in one direction while its internal texture drifts orthogonally to this path, it can appear to deviate from its physical path by 45 ̊ or more. This double-drift illusion is different from other motion-induced position shift effects in several ways: it has an integration period of over a second; the illusory displacement that accumulates over a second or more is orthogonal to rather than along the motion path; the perceptual deviations are much larger; and they have little or no effect on eye movements to the target...
March 7, 2018: Journal of Neurophysiology
Seong-Cheol Park, Chun Kee Chung
BACKGROUND AND PURPOSE: The objective of this study was to introduce a new machine learning guided by outcome of resective epilepsy surgery defined as the presence/absence of seizures to improve data mining for interictal pathologic activities in neocortical epilepsy. METHODS: Electrocorticographies for 39 patients with medically intractable neocortical epilepsy were analyzed. We separately analyzed 38 frequencies from 0.9 to 800 Hz including both high-frequency activities and low-frequency activities to select bands related to seizure outcome...
March 7, 2018: Journal of Neurophysiology
Peng Yuan, Vincent Koppelmans, Patricia Reuter-Lorenz, Yiri De Dios, Nichole Gadd, Roy Riascos, Igor Kofman, Jacob Bloomberg, Ajitkumar Mulavara, Rachael D Seidler
Head-down tilt bed rest (HDBR) has been used as a spaceflight analog to study some of the effects of microgravity on human physiology, cognition, and sensorimotor functions. Previous studies have reported declines in balance control and functional mobility after spaceflight and HDBR. Here we investigated how the brain activation for foot movement changed with HDBR. Eighteen healthy men participated in the current HDBR study. They were in a 6{degree sign} head-down tilt position continuously for 70 days. Functional MRI scans were acquired to estimate brain activation for foot movement pre-, during- and post-HDBR...
February 28, 2018: Journal of Neurophysiology
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