Habituation of auditory startle reflex is a new sign of minimally conscious state

Abstract

Neurological examination of non-communicating patients relies on a few decisive items that enable the crucial distinction between vegetative state (VS)—also coined unresponsive wakefulness syndrome (UWS)—and minimally conscious state. Over the past 10 years, this distinction has proven its diagnostic value as well as its important prognostic value on consciousness recovery. However, clinicians are currently limited by three factors: (i) the current behavioural repertoire of minimally conscious state items is limited and restricted to a few cognitive domains in the goldstandard revised version of the Coma Recovery Scale; (ii) a proportion of ∼15–20% clinically VS/UWS patients are actually in a richer state than VS/UWS as evidenced by functional brain imaging; and (iii) the neurophysiological and cognitive interpretation of each minimally conscious state item is still unclear and debated. In the current study we demonstrate that habituation of the auditory startle reflex (hASR) tested at bedside constitutes a novel, simple and powerful behavioural sign that can accurately distinguish minimally conscious state from VS/UWS. In addition to enlarging the minimally conscious state items repertoire, and therefore decreasing the low sensitivity of current behavioural measures, we also provide an original and rigorous description of the neurophysiological basis of hASR through a combination of functional (high density EEG and 18F-fluorodeoxyglucose PET imaging) and structural (diffusion tensor imaging MRI) measures. We show that preservation of hASR is associated with the functional and structural integrity of a brain-scale fronto-parietal network, including prefrontal regions related to control of action and inhibition, and meso-parietal areas associated with minimally conscious and conscious states. Lastly, we show that hASR predicts 6-month improvement of consciousness. Taken together, our results show that hASR is a cortically-mediated behaviour, and suggest that it could be a new clinical item to clearly and accurately identify non-communicating patients who are in the minimally conscious state.

Mapping the emergence of visual consciousness in the human brain via brain-wide intracranial electrophysiology

“…The classification ability of iEEG signals at each recording site was measured via the area under the receiver operating characteristic curve (AUC). 28 , 29 , 30 A higher AUC indicates better performance in discriminating different conscious states. A permutation-based statistic was used to determine the significance of the AUC in each transition for all recording sites by randomly permuting the phase labels and repeating the procedure 500 times, which produced a null AUC distribution that was used to obtain a p value for each actual AUC.…”

Importance, limits and caveats of the use of “disorders of consciousness” to theorize consciousness

“…2008 ); (ii) trace conditioning effects, that require working memory resources postulated to be a specific property of conscious processing, can be probed at the bedside ( Bekinschtein et al. 2009b ); (iii) the habituation of the auditory startle response that relies on the preservation of the frontal cortex inhibition linked to conscious processing was explored at the bedside and demonstrated a powerful diagnostic value to identify MCS or CS patients as well as a prognostic value to predict consciousness recovery ( Hermann et al. 2020 ); (iv) olfactory sniffing response that requires cognitive resources was tested at the bedside and demonstrated both a diagnostic and a prognostic value ( Arzi et al.…”

Myoclonus and other jerky movement disorders

“…The auditory startle reflex and its associated studies, especially pre-pulse inhibition (PPI; see Section 2.3.5 ), have been used in fundamental research focused on the sensorimotor gating mechanisms of the central nervous system in various neurological and psychiatric disorders, including parkinsonian syndromes, dystonia, tics disorders, functional movement disorders, schizophrenia, and obsessive–compulsive disorders ( Gironell et al, 2000 , Gómez-Nieto et al, 2020 , Kiziltan et al, 2015 , Schleyken et al, 2020 , Valldeoriola et al, 1998 , Vidailhet et al, 1992 ). In some disorders (e.g., post-traumatic stress disorder, minimally conscious state), it has found a place amidst the diagnostic process ( Glover et al, 2011 , Hermann et al, 2020 ). Most of these patients do not exhibit a clinical exaggerated or excessive startle reflex and are therefore not considered startle syndromes.…”