Journal of Neurophysiology

von Maydell, Djuna; Jorfi, Mehdi

doi: 10.1152/jn.00395.2019pmid: 31365320

Microglia constitute ~10–20% of glial cells in the adult human brain. They are the resident phagocytic immune cells of the central nervous system and play an integral role as first responders during inflammation. Microglia are commonly classified as “HM” (homeostatic), “M1” (classically activated proinflammatory), or “M2” (alternatively activated). Multiple single-cell RNA-sequencing studies suggest that this discrete classification system does not accurately and fully capture the vast heterogeneity of microglial states in the brain. In fact, a recent single-cell RNA-sequencing study showed that microglia exist along a continuous spectrum of states. This spectrum spans heterogeneous populations of homeostatic and neuropathology-associated microglia in both healthy and Alzheimer’s disease (AD) mouse brains. Major risk factors, such as sex, age, and genes, modulate microglial states, suggesting that shifts along the trajectory might play a causal role in AD pathogenesis. This study provides important insight into the cellular mechanisms of AD and underlines the potential of novel cell-based therapies for AD.

Quinlan, K. A.; Reedich, E. J.; Arnold, W. D.; Puritz, A. C.; Cavarsan, C. F.; Heckman, C. J.; DiDonato, C. J.

doi: 10.1152/jn.00652.2018pmid: 31365319

Changes in spinal motoneuron physiologic function precede cell death in spinal muscular atrophy (SMA), but how they vary with maturational state and disease severity remains unknown. This study characterized motoneuron and neuromuscular electrophysiology from the Smn2B/− model of SMA. Motoneurons were hyperexcitable at postnatal day (P)9–10, and specific electrophysiological changes in Smn2B/− motoneurons preceded functional motor unit loss at P14, as determined by motor unit number estimation studies.

Backer, Kristina C.; Kessler, Andrew S.; Lawyer, Laurel A.; Corina, David P.; Miller, Lee M.

doi: 10.1152/jn.00868.2018pmid: 31268796

A novel electroencephalography paradigm enables the rapid, reliable, and noninvasive assessment of neural activity along both auditory and visual pathways concurrently. The paradigm uses an ecologically valid continuous speech stimulus for auditory evaluation and can simultaneously track visual activity to both parafoveal and peripheral visual space. This new methodology may be particularly appealing to researchers and clinicians working with infants and young children and with patient populations with limited communication abilities.

Unruh, Kathryn E.; Martin, Laura E.; Magnon, Grant; Vaillancourt, David E.; Sweeney, John A.; Mosconi, Matthew W.

doi: 10.1152/jn.00286.2019pmid: 31314644

This is the first known study to examine functional brain activation during precision visuomotor behavior in autism spectrum disorder (ASD). We replicate previous findings of elevated force variability in ASD and find these deficits are associated with atypical function of ventral premotor cortex, putamen, and posterolateral cerebellum, indicating cortical-striatal processes supporting action selection and cortical-cerebellar circuits involved in feedback-guided reactive adjustments of motor output may be key targets for understanding the neurobiology of ASD.

Levitan, David; Lin, Jian-You; Wachutka, Joseph; Mukherjee, Narendra; Nelson, Sacha B.; Katz, Donald B.

doi: 10.1152/jn.00357.2019pmid: 31339800

Here, we analyzed taste-related spiking activity in awake mouse gustatory cortical (GC) neural ensembles, revealing deep similarities between mouse cortical taste processing and that repeatedly demonstrated in rat: mouse GC ensembles code multiple aspects of taste in a coarse-coded, time-varying manner that is essentially invariant across the spatial extent of GC. These data demonstrate that, contrary to some reports, cortical network processing is distributed, rather than being separated out into spatial subregion.

Wadsley, Corey G.; Cirillo, John; Byblow, Winston D.

doi: 10.1152/jn.00310.2019pmid: 31339791

The temporal dynamics of an anticipated response task were manipulated to effect the difficulty of behavioral stopping and the underlying effects on motor neurophysiology. There were large response delays during trials where a subcomponent of an upcoming bimanual response was cued to stop in conditions where the anticipated action of the hands were synchronous, but not when asynchronous. Response delays reflected the integration of actions of both hands into a unitary response.

Milosevic, Luka; Dallapiazza, Robert F.; Munhoz, Renato P.; Kalia, Suneil K.; Popovic, Milos R.; Hutchison, William D.

doi: 10.1152/jn.00203.2019pmid: 31411948

Use of a dual-microelectrode technique enabled us to compare long-term potentiation (LTP)-like changes in a patient with lithium-induced tremor to that of patients with Parkinson’s disease. This study corroborated the findings in rodent brain slices that chronic lithium treatment may block LTP. Whereas a deficit in LTP may underlie the therapeutic mechanism for treating psychiatric disorders such as bipolar affective disorder, it may simultaneously contribute to consequent appearance of tremor.

Lothe, Lise R.; Raven, Tim J. L.; Sandbæk, Gunnar; Eken, Torsten

doi: 10.1152/jn.00004.2019pmid: 31365288

We implanted fine-wire electrodes in the deepest part of axial postural muscles in patients with acute low back pain and characterized their motor unit activity. We found less pronounced common drive to the two sides of the spine compared with pain-free subjects, suggesting a different postural control strategy in patients with acute low back pain. An unexpected finding was that common drive coefficient values appeared to consist of two partially overlapping populations of normal distributions.

Ott, Elizabeth P.; Baker, Sarah E.; Holbein, Walter W.; Shoemaker, J. Kevin; Limberg, Jacqueline K.

doi: 10.1152/jn.00319.2019pmid: 31389742

Our results demonstrate that, compared with normoxic end-expiratory apnea, hypoxic apnea increases the frequency and incidence of action potential spikes as well as the probability of multiple firing. We further show that this response is suppressed when individuals are hyperoxic. These data highlight the potentially important role of chemoreflex stress in neural firing and recruitment and may have implications for neural control of the circulation in recreational and/or clinical conditions prone to apnea.

Ohashi, Hiroki; Gribble, Paul L.; Ostry, David J.

doi: 10.1152/jn.00383.2019pmid: 31390294

We tracked somatosensory and motor cortical excitability during motor skill acquisition. Changes in both motor cortical and somatosensory excitability were observed during learning; however, the earliest changes were in somatosensory cortex, not motor cortex. Moreover, the earliest changes in somatosensory cortical excitability predict the extent of subsequent learning; those in motor cortex do not. This is consistent with the idea that plasticity in somatosensory cortex coincides with the earliest stages of human motor learning.