Audiomotor Integration in Minimally Conscious State: Proof of Concept!

Abstract

Patients suffering from chronic disorders of consciousness (DOC) are characterized by profound unawareness and an impairment of large-scale cortical and subcortical connectivity. In this study, we applied an electrophysiological approach aimed at identifying the residual audiomotor connectivity patterns that are thought to be linked to awareness. We measured some markers of audiomotor integration (AMI) in 20 patients affected by DOC, before and after the application of a repetitive transcranial magnetic stimulation protocol (rTMS) delivered over the left primary motor area (M1), paired to a transauricular alternating current stimulation. Our protocol induced potentiating of the electrophysiological markers of AMI and M1 excitability, paired to a clinical improvement, in all of the patients with minimally conscious state (MCS) but in none of those suffering from unresponsive wakefulness syndrome (UWS). Our protocol could be a promising approach to potentiate the functional connectivity within large-scale audiomotor networks, thus allowing clinicians to differentiate patients affected by MCS from UWS, besides the clinical assessment.

Toward Improving Diagnostic Strategies in Chronic Disorders of Consciousness: An Overview on the (Re-)Emergent Role of Neurophysiology

“…Interestingly, we found that the evaluation and modulation of SMI through NIBS was useful in UWS-fLIS differential diagnosis. We evaluated functional visuo-premotor-motor FC in UWS and MCS sample before and after the administration of an associative stimulation protocol composed of tDCS on the dorsolateral prefrontal cortex and parieto-occipital areas and trans-orbital alternating current stimulation [96,97]. Such an approach confirmed the clinically-based differential diagnosis with the exception of one patient in UWS who electrophysiologically behaved as those in MCS, and who regained consciousness some months later.…”

“…Such an approach confirmed the clinically-based differential diagnosis with the exception of one patient in UWS who electrophysiologically behaved as those in MCS, and who regained consciousness some months later. Therefore, passive audiomotor and visuomotor integration could be a promising tool to stimulate sensory networks FC, thus enabling physicians in the differential diagnosis among MCS, UWS, and fLIS [96,97]. Based on our studies, we can argue that patients UWS showing an improvement in cortical FC and motor output after a SMI-based NIBS approach should be considered as suffering from fLIS rather than UWS.…”

“…Furthermore, the study of large-scale sensory-motor integration (SMI) processes subtending awareness can be useful to identify patients with fLIS [89,96,97]. The usefulness of studying SMI processes concerning awareness detection relies on the fact that SMI depends on large cortical-subcortical networks carrying information at a conscious level [98,99].…”

Facilitation of Auditory Comprehension After Theta Burst Stimulation of Wernicke's Area in Stroke Patients: A Pilot Study

“…A few preliminary TMS and transcranial direct current stimulation approaches targeting the left temporal region in chronic aphasic patients showed indeed significant improvement in language abilities (18,(64)(65)(66). An alternative promising approach to foster audiomotor integration ability, tested so far only in patients with disorder of consciousness due to severe brain injury, consisted in pairing auditory with transcranial magnetic stimuli on the primary motor area, using the stimulation paradigm known as paired associative stimulation, which induces associative LTP or LTD-like neuronal plasticity (67).…”

A Short Commentary on Non-invasive Brain Stimulation in Chronic Disorder of Consciousness Differential Diagnosis

“…Indeed, it has been shown in DOC samples that TMS and tDCS can unmask residual covert connectivity patterns in parallel to a behavioral responsiveness improvement [14,15]. Moreover, audiomotor and visuomotor stimulation could be promising tools to potentiate the functional connectivity within large-scale sensorymotor networks [16,17]. These new approaches exploring covert behaviors and functional connectivity may yield further insight into DOC pathophysiology and improve the differential diagnosis.…”