Journal of Neurophysiology

Caulfield, Kevin A.

doi: 10.1152/jn.00537.2019pmid: 31553674

A recent study by Williams et al. (Williams NR, Sudheimer KD, Bentzley BS, Pannu J, Stimpson KH, Duvio D, Cherian K, Hawkins J, Scherrer KH, Vyssoki B, DeSouza D, Raj KS, Keller J, Schatzberg AF. Brain 141: e18, 2018) used accelerated, high-dose intermittent theta burst stimulation (iTBS) to treat highly treatment-resistant depression patients. Remarkably, most patients remitted, but the durability of therapeutic response was weak and all patients relapsed within 2 wk posttreatment. This mini-review examines the “fast on, fast off” effects of accelerated, high-dose iTBS for depression and suggests a new treatment that would combine the strengths of multiple extant iTBS protocols.

Maxwell, David J.; Soteropoulos, Demetris S.

doi: 10.1152/jn.00347.2019pmid: 31693445

Commissural systems are essential components of motor circuits that coordinate left–right activity of the skeletomuscular system. Commissural systems are found at many levels of the neuraxis including the cortex, brainstem, and spinal cord. In this review we will discuss aspects of the mammalian spinal commissural system. We will focus on commissural interneurons, which project from one side of the cord to the other and form axonal terminations that are confined to the cord itself. Commissural interneurons form heterogeneous populations and influence a variety of spinal circuits. They can be defined according to a variety of criteria including, location in the spinal gray matter, axonal projections and targets, neurotransmitter phenotype, activation properties, and embryological origin. At present, we do not have a comprehensive classification of these cells, but it is clear that cells located within different areas of the gray matter have characteristic properties and make particular contributions to motor circuits. The contribution of commissural interneurons to locomotor function and posture is well established and briefly discussed. However, their role in other goal-orientated behaviors such as grasping, reaching, and bimanual tasks is less clear. This is partly because we only have limited information about the organization and functional properties of commissural interneurons in the cervical spinal cord of primates, including humans. In this review we shall discuss these various issues. First, we will consider the properties of commissural interneurons and subsequently examine what is known about their functions. We then discuss how they may contribute to restoration of function following spinal injury and stroke.

Aguilar, David D.; Strecker, Robert E.; Basheer, Radhika; McNally, James M.

doi: 10.1152/jn.00532.2019pmid: 31747354

Metabotropic glutamate receptor type 5 (mGluR5) knockout (KO) mice show several translationally relevant abnormalities in neural oscillatory activity associated with schizophrenia. These include deficits in sleep spindle density, sigma and alpha power, and 40-Hz task-evoked gamma power. The timing of these phenotypes suggests an impaired circadian process in these mice. Previously reported rapid eye movement sleep deficits in this model were not observed. These findings suggest mGluR5-enhancing drugs may improve sleep stability and sleep spindle density, which could impact memory and cognition.

Stepniewska, Iwona; Friedman, Robert M.; Miller, Daniel J.; Kaas, Jon H.

doi: 10.1152/jn.00576.2019pmid: 31693452

Long trains of electrical pulses applied simultaneously to two sites in motor cortical areas (motor and posterior parietal cortices) have shown that interactions of functionally matched domains (evoking similar movements) within these areas were additive to produce a specific complex movement. Interactions between functionally mismatched domains (evoking different movements) were mostly antagonistic, suggesting their involvement in mutual suppression of conflicting motor outputs to prevent competing movements. Simultaneous stimulation of unrelated domains (forelimb and face) produced both movements independently.

Avraham, Guy; Keizman, Matan; Shmuelof, Lior

doi: 10.1152/jn.00080.2019pmid: 31721646

The consistency of an external perturbation modulates error sensitivity and the motor response. The roles of explicit and implicit processes in this modulation are unknown. We show that when humans are asked to ignore the perturbation, they do not show increased error sensitivity in consistent environments. When the implicit system is manipulated by delaying feedback, sensitivity to a consistent perturbation does not change. Overall, our results suggest that consistency affects adaptation mainly through explicit control.

Higgin, Dwight; Krupka, Alexander; Maghsoudi, Omid Haji; Klishko, Alexander N.; Nichols, T. Richard; Lyle, Mark A.; Prilutsky, Boris I.; Lemay, Michel A.

doi: 10.1152/jn.00018.2019pmid: 31693435

Spinal locomotor networks locomotor trained on a flat surface can adapt the locomotor output to slope walking, up to ±25° of slope, even with total absence of supraspinal CONTROL. Autogenic length feedback (stretch reflex) shows signs of recovery in spinalized animals, contrary to results in spinally intact animals.

Soldado-Magraner, Saray; Brandalise, Federico; Honnuraiah, Suraj; Pfeiffer, Michael; Moulinier, Marie; Gerber, Urs; Douglas, Rodney

doi: 10.1152/jn.00506.2019pmid: 31721636

Although firing patterns are widely conserved across the animal phyla, it is still a mystery why nerve cells present such diversity of discharge dynamics upon somatic step currents. Adding a new timing dimension to the intrinsic plasticity literature, here we show that CA3 neurons rapidly adapt through the space of known firing patterns in response to the subthreshold signals that they receive from their embedding circuit, potentially adjusting their network processing to the temporal statistics of their circuit.

Basu, Debaleena; Murthy, Aditya

doi: 10.1152/jn.00545.2018pmid: 31721632

The execution of purposeful sequences underlies much of goal-directed behavior. How different brain areas accomplish sequencing is poorly understood. Using a modified double-step task to generate a rapid sequence of two saccades, we demonstrate that downstream movement neurons in the frontal eye field (FEF), a prefrontal oculomotor area, allow for coactivation of the first and second movement plans that constitute the sequence. These results provide fundamental insights into the neural control of action sequencing.

Ignatova, Irina I.; Saari, Paulus; Frolov, Roman V.

doi: 10.1152/jn.00365.2019pmid: 31721631

When stimulated by light, microvilli of rhabdomeric photoreceptors produce discrete signals characterized by variable latencies. We show that this intrinsic latency dispersion restricts signaling bandwidth and information rate of photoreceptors in Periplaneta americana. Profound differences are found between the properties of photoreceptor responses in vivo and in vitro.

Gourévitch, Boris; Mahrt, Elena J.; Bakay, Warren; Elde, Cameron; Portfors, Christine V.

doi: 10.1152/jn.00377.2019pmid: 31721644

GABAergic inhibition adds nonlinearity to neuronal response curves. This increases the neuronal range of evoked firing rate by reducing baseline firing. GABAergic inhibition prevents bursting responses from neurons in a spontaneous state, reducing noise in the temporal coding of the neuron. This could result in improved signal transmission to the cortex.