The Control of Movements via Motor Gamma Oscillations

The ability to perform movements is vital for our daily life. Our actions are embedded in a complex environment where we need to deal efficiently in the face of unforeseen events. Neural oscillations play an important role in basic sensorimotor processes related to the execution and preparation of movements. In this review, I will describe the state of the art regarding the role of motor gamma oscillations in the control of movements. Experimental evidence from electrophysiological studies has shown that motor gamma oscillations accomplish a range of functions in motor control beyond merely signaling the execution of movements. However, these additional aspects associated with motor gamma oscillation remain to be fully clarified. Future work on different spatial, temporal and spectral scales is required to further understand the implications of gamma oscillations in motor control.

Functional subgroups of rat and human sensory neurons: a systematic review of electrophysiological properties

Sensory neurons are responsible for the generation and transmission of nociceptive signals from the periphery to the central nervous system. They encompass a broadly heterogeneous population of highly specialized neurons. The understanding of the molecular choreography of individual subpopulations is essential to understand physiological and pathological pain states. Recently, it became evident that species differences limit transferability of research findings between human and rodents in pain research. Thus, it is necessary to systematically compare and categorize the electrophysiological data gained from human and rodent dorsal root ganglia neurons (DRGs). In this systematic review, we condense the available electrophysiological data defining subidentities in human and rat DRGs. A systematic search on PUBMED yielded 30 studies on rat and 3 studies on human sensory neurons. Defined outcome parameters included current clamp, voltage clamp, cell morphology, pharmacological readouts, and immune reactivity parameters. We compare evidence gathered for outcome markers to define subgroups, offer electrophysiological parameters for the definition of neuronal subtypes, and give a framework for the transferability of electrophysiological findings between species. A semiquantitative analysis revealed that for rat DRGs, there is an overarching consensus between studies that C-fiber linked sensory neurons display a lower action potential threshold, higher input resistance, a larger action potential overshoot, and a longer afterhyperpolarization duration compared to other sensory neurons. They are also more likely to display an infliction point in the falling phase of the action potential. This systematic review points out the need of more electrophysiological studies on human sensory neurons.

Miller fisher syndrome – A rare complication of covid-19 infection

The COVID-19 virus can present with various neurological signs and symptoms involving both the central and peripheral nervous systems. Miller Fisher syndrome (M.F.S.), a variant of Landry Guillain Barre Syndrome (L.G.B.S.), presents with ataxia, areflexia, and ophthalmoplegia. It can develop during and after COVID-19 illness. We are reporting a case of the Miller Fisher variant of L.G.B.S. following a COVID-19 infection. We found no difference in clinical presentation, electrophysiological studies, severity, recovery, and treatment in our patient compared to a non-covid related M.F.S. Our goal is to add a case of the COVID-19-associated Miller Fisher variant of L.G.B.S. to already existing limited literature through this case report.

Us and Mri Neurography Assessment of Diagnostic Criteria in Patients With Carpal Tunnel Syndrome Using Electrophysiological Tests as Gold Standard: A Prospective Study

BackgroundPeripheral neuropathy evaluation depends mainly on physical examination, patient history, electrophysiological studies, with evoked potential abnormalities. High-resolution US has the advantage of being fast, non-invasive modality with nerve dynamic assessment allowing examination of long part of nerve. MR imaging serve better in examination of deeper nerves with higher contrast resolution. It shows great benefit in patient with atypical presentation, Equivocal diagnosis and suspicious of secondary cause and post-surgical relapse.MethodsThis study was conducted prospectively on 32 patients, presented with carpal tunnel syndrome diagnosed by electrophysiological tests. Superficial US of the wrist joint was done to all participants followed by MRI within 1 weeks of the US.We aimed to assess the measurements & criteria of both US & MRN in diagnosis of CTS, depending mainly on the three-measurement assessed by Buchberger et al., then to find the agreement between US & MR Neurography (MRN)ResultsUs proved to have higher rate of CTS prediction, the three main parameters CSA measurement, distal nerve flattening and flexor retinaculum bowing indices showed positive occurrence of 93.7%,59.4% &59.4% respectively. While we found that decreased nerve echotexture was positive in 90.6% of patients.Regarding MRI it showed less diagnostic ability when using CSA measurement as it was positive in 81.2% of patients, also distal tunnel nerve increased flattening and bowed flexor retinaculum positive results were slightly decreased to 56.2% for each. In contrast to high T2 signal of median nerve which was positive in 90.6% of patients.In agreement study, we found statically significant difference supporting US as the primary diagnostic modality of CTS depending mainly on the three measurement CSA, Flattening and bowing indices. Yet, for cases of secondary CTS and detection of underlying entrapping cause as well as innervated muscle early abnormality detection and better tissue characterization, MRI was better diagnostic modality with statistically significant difference. ConclusionsOur results proved that ultrasound examination can be used as first imaging modality after physician evaluation with comparable results to electrophysiological studies in evaluating CTS and try to find the cause. MRN examination came as second step in patients with suspected muscle denervation changes that could not be elicited by US or equivocal cases for detection of secondary cause in clinically suspected patient.

Historical aspects of the development of the theory of ventricular preexcitation

The paper conducts a review of the literature on the problem of cognition of the nature of the syndrome of preexcitation of the ventricles. Despite the data of early publications, supporting the theory of bypass as a substrate of preexcitation, disputes and searches for the nature of this clinical syndrome continued until 1970, until surgical procedures and the first electrophysiological studies confirmed the “bypass” of the normal conducting system. Article describes the chronology of events related to the understanding of the syndrome, which bears the name Wolff-Parkinson-White.

The Role of Neurophysiological Biomarkers in Obsessive-Compulsive Disorder

Background: Obsessive-compulsive disorder is a highly debilitating psychiatric disorder with a high rate of treatment resistance. Biomarkers for obsessive-compulsive disorder may assist clinicians by predicting response to treatments and prognosis. Objective: To review the literature with regards to two of the more easily ascertainable and relatively inexpensive physiological biomarkers, i.e. heart rate variability and electroencephalography. Methods: Narrative review of the literature. Results: Decreased heart rate variability has been associated with increased symptom severity of obsessive-compulsive disorder. Findings from electroencephalography have also predicted response to pharmacotherapy and it is likely that biomarkers for OCD will have their greatest utility in predicting response to different pharmacological agents. However, the number of studies is small and results are inconsistent. Conclusions: More research is required to determine whether heart rate variability and electrophysiological studies have a clinical role as biomarkers for obsessive-compulsive disorder.

Reunification of Object and View-Center Background Information in the Primate Medial Temporal Lobe

Recent work has shown that the medial temporal lobe (MTL), including the hippocampus (HPC) and its surrounding limbic cortices, plays a role in scene perception in addition to episodic memory. The two basic factors of scene perception are the object (“what”) and location (“where”). In this review, we first summarize the anatomical knowledge related to visual inputs to the MTL and physiological studies examining object-related information processed along the ventral pathway briefly. Thereafter, we discuss the space-related information, the processing of which was unclear, presumably because of its multiple aspects and a lack of appropriate task paradigm in contrast to object-related information. Based on recent electrophysiological studies using non-human primates and the existing literature, we proposed the “reunification theory,” which explains brain mechanisms which construct object-location signals at each gaze. In this reunification theory, the ventral pathway signals a large-scale background image of the retina at each gaze position. This view-center background signal reflects the first person’s perspective and specifies the allocentric location in the environment by similarity matching between images. The spatially invariant object signal and view-center background signal, both of which are derived from the same retinal image, are integrated again (i.e., reunification) along the ventral pathway-MTL stream, particularly in the perirhinal cortex. The conjunctive signal, which represents a particular object at a particular location, may play a role in scene perception in the HPC as a key constituent element of an entire scene.

A comparison of three different methods of eliciting rapid activity-dependent synaptic plasticity at the Drosophila NMJ

The Drosophila NMJ is a system of choice for investigating the mechanisms underlying the structural and functional modifications evoked during activity-dependent synaptic plasticity. Because fly genetics allows considerable versatility, many strategies can be employed to elicit this activity. Here, we compare three different stimulation methods for eliciting activity-dependent changes in structure and function at the Drosophila NMJ. We find that the method using patterned stimulations driven by a K+-rich solution creates robust structural modifications but reduces muscle viability, as assessed by resting potential and membrane resistance. We argue that, using this method, electrophysiological studies that consider the frequency of events, rather than their amplitude, are the only reliable studies. We contrast these results with the expression of CsChrimson channels and red-light stimulation at the NMJ, as well as with the expression of TRPA channels and temperature stimulation. With both these methods we observed reliable modifications of synaptic structures and consistent changes in electrophysiological properties. Indeed, we observed a rapid appearance of immature boutons that lack postsynaptic differentiation, and a potentiation of spontaneous neurotransmission frequency. Surprisingly, a patterned application of temperature changes alone is sufficient to provoke both structural and functional plasticity. In this context, temperature-dependent TRPA channel activation induces additional structural plasticity but no further increase in the frequency of spontaneous neurotransmission, suggesting an uncoupling of these mechanisms.