Journal of Neurophysiology

Whitelaw, Brendan S.

doi: 10.1152/jn.00021.2017pmid: 28835520

It has recently become clear that microglia, the immune cells of the central nervous system, are far more active in the healthy brain than previously thought. Microglia facilitate many stages of brain development by shaping neuronal connectivity via synaptic elimination. Dysfunction of these same processes likely underlies a wide range of neurological and neurodevelopmental disorders.

Subramanian, Sandeep K.; Feldman, Anatol G.; Levin, Mindy F.

doi: 10.1152/jn.00362.2017pmid: 28904099

When arm movements were made outside, instead of inside, the range affected by spasticity, there was an immediate decrease in the number of trials needed to restore accuracy in response to a change in the external load. This suggests that motor learning processes may be preserved in patients with stroke but masked by the presence of spasticity in specific joint ranges. This has important implications for designing rehabilitation interventions predicated on motor learning principles.

Tillman, Mitchell; Ambike, Satyajit

doi: 10.1152/jn.00519.2017pmid: 28931612

We compared the stability of multifinger, isometric force-production tasks for trials in which force changes of unknown direction and timing were expected with trials in which there was no expectation of any force change. Mere expectation of a change caused the stability of the current motor state to drop. This novel result provides a much refined view of the processes that facilitate dexterous switching between motor states.

St George, R. J.; Gurfinkel, V. S.; Kraakevik, J.; Nutt, J. G.; Horak, F. B.

doi: 10.1152/jn.00582.2017pmid: 28978769

By studying an idiopathic camptocormia case with a detailed biomechanical and sensorimotor approach, we have demonstrated unique insights into the neural control of human bipedalism: 1) balance and postural control cannot be considered the same neural process, as there is a stereotyped abnormal flexed posture, without balance deficits, associated with camptocormia, and 2) posture during standing is controlled by automatic axial tone but “sensory tricks” involving sensory biofeedback to direct voluntary attention to postural alignment can override, when required.

Cardis, Marco; Casadio, Maura; Ranganathan, Rajiv

doi: 10.1152/jn.00158.2017pmid: 28954891

We examined the role of introducing variability during motor learning in a redundant task. The presence of redundancy allows variability to be introduced in different dimensions: the task space (where it affects task performance) or the null space (where it does not affect task performance). We found that introducing variability affected learning adversely, but the amount of variability was more critical than the dimension in which variability was introduced.

Hall, Stephen P.; Traub, Roger D.; Adams, Natalie E.; Cunningham, Mark O.; Schofield, Ian; Jenkins, Alistair J.; Whittington, Miles A.

doi: 10.1152/jn.00516.2017pmid: 28954894

Spike-and-wave-type discharges (SpW) are a common feature in many epilepsies. Their electrographic manifestation is highly varied, as are available genetic clues to associated underlying pathology. Using computational and in vitro models, we demonstrate that distinct subtypes of SpW are generated by lamina-selective disinhibition or enhanced interlaminar excitation. These subtypes could be detected in at least some noninvasive patient recordings, suggesting more detailed analysis of SpW may be useful in determining clinical pathology.

Massendari, Delphine; Lisi, Matteo; Collins, Thérèse; Cavanagh, Patrick

doi: 10.1152/jn.00229.2017pmid: 28954892

We compared the effect of a perceptual illusion on two types of saccades, visually guided vs. memory-guided saccades, and found that whereas visually guided saccades were almost unaffected by the perceptual illusion, memory-guided saccades exhibited a strong effect of the illusion. Our result is the first evidence in the literature to show that visually and memory-guided saccades use different spatial representations.

Newlands, Shawn D.; Abbatematteo, Ben; Wei, Min; Carney, Laurel H.; Luan, Hongge

doi: 10.1152/jn.00382.2017pmid: 28978765

This is the first study to systematically explore the interaction of rotational and translational signals in the vestibular nuclei through independent manipulation. The results of this study demonstrate nonlinear integration leading to maximum response amplitude when the timing and direction of peak rotational and translational responses are coincident.

Knowlton, Christopher; Kutterer, Sylvie; Roeper, Jochen; Canavier, Carmen C.

doi: 10.1152/jn.00351.2017pmid: 28978764

Recently identified distinct subpopulations of midbrain dopamine neurons exhibit differences in their two primary activity patterns in vivo: tonic (single spike) firing and phasic bursting. This study elucidates the biophysical basis of bursts specific to dopamine neurons in the medial substantia nigra, enabled by ATP-sensitive K+ channels and necessary for novelty-induced exploration. A better understanding of how dopaminergic signaling differs between subpopulations may lead to therapeutic strategies selectively targeted to specific subpopulations.

Ausborn, Jessica; Snyder, Abigail C.; Shevtsova, Natalia A.; Rybak, Ilya A.; Rubin, Jonathan E.

doi: 10.1152/jn.00550.2017pmid: 28978767

Our theoretical/modeling study focuses on the analysis of locomotor central pattern generators (CPGs) composed of conditionally bursting half-centers coupled with reciprocal inhibition and receiving independent external drives. We show that this CPG framework can operate in several regimes consistent with seemingly contradictory experimental data. In each regime, we study how intrinsic dynamics and phase-switching mechanisms control oscillation frequency and phase durations. Our results provide insights into the organization of spinal circuits controlling locomotion.