Insights Into Auditory Cortex Dynamics From Non-invasive Brain Stimulation

Abstract

Non-invasive brain stimulation (NIBS) has been widely used as a research tool to modulate cortical excitability of motor as well as non-motor areas, including auditory or language-related areas. NIBS, especially transcranial magnetic stimulation (TMS) and transcranial direct current stimulation, have also been used in clinical settings, with however variable therapeutic outcome, highlighting the need to better understand the mechanisms underlying NIBS techniques. TMS was initially used to address causality between specific brain areas and related behavior, such as language production, providing non-invasive alternatives to lesion studies. Recent literature however suggests that the relationship is not as straightforward as originally thought, and that TMS can show both linear and non-linear modulation of brain responses, highlighting complex network dynamics. In particular, in the last decade, NIBS studies have enabled further advances in our understanding of auditory processing and its underlying functional organization. For instance, NIBS studies showed that even when only one auditory cortex is stimulated unilaterally, bilateral modulation may result, thereby highlighting the influence of functional connectivity between auditory cortices. Additional neuromodulation techniques such as transcranial alternating current stimulation or transcranial random noise stimulation have been used to target frequency-specific neural oscillations of the auditory cortex, thereby providing further insight into modulation of auditory functions. All these NIBS techniques offer different perspectives into the function and organization of auditory cortex. However, further research should be carried out to assess the mode of action and long-term effects of NIBS to optimize their use in clinical settings.

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

“…1). Present NIBS techniques include the two most commonly utilized technologies, repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) [9]. NIBS guidelines for the clinic are key for making patient care decisions in rehabilitation procedures, but no consensus of best practices for different NP conditions currently exists [10][11][12][13][14][15][16].…”

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

“…These networks have predictable effects and worse outcomes with bilateral structural lesions affecting these pathways in both hemispheres. [68][69][70][71][72] Structural imaging can aid in assessing damage to nodal areas and their connections belonging to networks that are highly lateralized, such as language. Particular patterns of damage also correlate with clinical syndromes and outcome (e.g., Broca's, Wernicke's, conduction, transcortical and other classic aphasia syndromes), but clinical presentations and prospects for recovery are probably more variable and less predictable than for the corticospinal and primary visual pathways.…”

Oscillations in the auditory system and their possible role

“…how perception is affected by the manipulation of oscillations independently of other cerebral processes, such as spikes. This theoretical purpose has remained unreachable to date, but volitional control of oscillations (Engelhard et al, 2013;Fetz, 2013) and non-invasive brain stimulation J o u r n a l P r e -p r o o f techniques (Andoh et al, 2018;Heimrath et al, 2016;Neuling et al, 2012;Zoefel and Davis, 2017), even if mechanisms for this latter remain controversial (Karabanov et al, 2019;Liu et al, 2018), are promising attempts. For instance, the use of transcranial alternating current stimulation (tACS, Herrmann et al, 2013) at 40Hz in the auditory cortex selectively modulated speech perception (Rufener et al, 2016b), in an age dependent fashion (Rufener et al, 2016a).…”