Insights Into Auditory Cortex Dynamics From Non-invasive Brain Stimulation

Reduced connectivity of primary auditory and motor cortices during exposure to auditory white noise

Auditory white noise (WN) is widely used in daily life for inducing sleep, and in neuroscience to mask unwanted environmental noise and cues. However, WN was recently reported to influence corticospinal excitability and behavioral performance. Here, we expand previous preliminary findings on the influence of WN exposure on cortical functioning, and we hypothesize that it may modulate cortical connectivity. We tested our hypothesis by performing magnetoencephalography in 20 healthy subjects. WN reduces cortical connectivity of the primary auditory and motor regions with very distant cortical areas, showing a right lateralized connectivity reduction for primary motor cortex. The present results, together with previous finding concerning WN impact on corticospinal excitability and behavioral performance, further support the role of WN as a modulator of cortical function. This suggest avoiding its unrestricted use as a masking tool, while purposely designed and controlled WN application could be exploited to harness brain function and to treat neuropsychiatric conditions.

Transcranial direct current and transcranial magnetic stimulations for chronic pain

PURPOSE OF REVIEW

Chronic pain is debilitating and difficult to treat with pharmacotherapeutics alone. Consequently, exploring alternative treatment methods for chronic pain is essential. Noninvasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are increasingly being investigated for their neuropharmacological effects in the treatment of chronic pain. This review aims to examine and evaluate the present state of evidence regarding the use of tDCS and TMS in the treatment of chronic pain.

RECENT FINDINGS

Despite conflicting evidence in the early literature, evidence from recent rigorous research supports the use of tDCS and TMS in treating chronic pain conditions. For both tDCS and TMS, standardized stimulation parameters have been identified with the recommendation for repeated maintenance stimulation to ensure that the analgesic effect is sustained beyond discontinuation of therapy.

SUMMARY

Due to a lack of defined stimulation protocols, early findings on the efficacy of tDCS and TMS are mixed. Although the application of tDCS and TMS as pain relief approaches is still in its early stages, the introduction of standardized stimulation protocols is paving the way for more robust and informed research.

Analgesic Effect of Noninvasive Brain Stimulation for Neuropathic Pain Patients: A Systematic Review

Introduction

The objective of this review is to systematically summarize the consensus on best practices for different NP conditions of the two most commonly utilized noninvasive brain stimulation (NIBS) technologies, repetitive transcranial magnetic stimulation (rTMS), and transcranial direct current stimulation (tDCS).

Methods

PubMed was searched according to the predetermined keywords and criteria. Only English language studies and studies published up to January 31, 2020 were taken into consideration. Meta-analyses, reviews, and systematic reviews were excluded first, and those related to animal studies or involving healthy volunteers were also excluded. Finally, 29 studies covering 826 NP patients were reviewed.

Results

The results from the 24 enrolled studies and 736 NP patients indicate that rTMS successfully relieved the pain symptoms of 715 (97.1%) NP patients. Also, five studies involving 95 NP patients (81.4%) also showed that tDCS successfully relieved NP. In the included studied, the M1 region plays a key role in the analgesic treatment of NIBS. The motor evoked potentials (MEPs), the 10–20 electroencephalography system (EEG 10/20 system), and neuro-navigation methods are used in clinical practice to locate therapeutic targets. Based on the results of the review, the stimulation parameters of rTMS that best induce an analgesic effect are a stimulation frequency of 10–20 Hz, a stimulation intensity of 80–120% of RMT, 1000–2000 pulses, and 5–10 sessions, and the most effective parameters of tDCS are a current intensity of 2 mA, a session duration of 20–30 min, and 5–10 sessions.

Conclusions

Our systematically reviewed the evidence for positive and negative responses to rTMS and tDCS for NP patient care and underscores the analgesic efficacy of NIBS in patients with NP. The treatment of NP should allow the design of optimal treatments for individual patients.

Clinical Neurorehabilitation: Using Principles of Neurological Diagnosis, Prognosis, and Neuroplasticity in Assessment and Treatment Planning

Neurorehabilitation aspires to restore a person to his or her fullest potential after incurring neurological dysfunction. In medical rehabilitation, diagnosis involves assessment of medical conditions and their effects on functioning. It is usually a team effort that involves an amalgam of diagnostic assessments by multiple disciplines, leading to a collection of rehabilitative treatment plans and goals. This article discusses a clinical neurological paradigm, using rigorous clinical assessment of neuropathological and clinical diagnosis, along with prognostication of natural history and recovery. In the context of the role of neuroplasticity in recovery, this paradigm can add significant value to rehabilitation team management and planning. It contributes to enhanced understanding of neurological impairments and syndromes as they relate to functional disability, aiding in targeting deficits and setting treatment goals. Rehabilitation strategies and goals should be informed by natural history and prognosis, and viewed in the framework of the stage of recovery. Prognostic formulations should suggest an emphasis on restorative versus compensatory strategies for functional problems. Treatment planning should be informed by evidence on how interventions modulate brain reorganization in promoting recovery. Strategies that promote adaptive neuroplasticity should be favored, especially with restorative efforts, and evidence supporting optimal techniques, timing, and dosing of rehabilitation should be considered in treatment planning.

Oscillations in the auditory system and their possible role

GOURÉVITCH, B., C. Martin, O. Postal, J.J. Eggermont. Oscillations in the auditory system, their possible role. NEUROSCI BIOBEHAV REV XXX XXX-XXX, 2020. - Neural oscillations are thought to have various roles in brain processing such as, attention modulation, neuronal communication, motor coordination, memory consolidation, decision-making, or feature binding. The role of oscillations in the auditory system is less clear, especially due to the large discrepancy between human and animal studies. Here we describe many methodological issues that confound the results of oscillation studies in the auditory field. Moreover, we discuss the relationship between neural entrainment and oscillations that remains unclear. Finally, we aim to identify which kind of oscillations could be specific or salient to the auditory areas and their processing. We suggest that the role of oscillations might dramatically differ between the primary auditory cortex and the more associative auditory areas. Despite the moderate presence of intrinsic low frequency oscillations in the primary auditory cortex, rhythmic components in the input seem crucial for auditory processing. This allows the phase entrainment between the oscillatory phase and rhythmic input, which is an integral part of stimulus selection within the auditory system.