Defensive peripersonal space is modified by a learnt protective posture

Abstract

The Hand Blink Reflex (HBR) is a subcortical defensive response, elicited by the electrical stimulation of the median nerve. HBR increases when the stimulated hand is inside the defensive peripersonalspace (DPPS) of the face. However, the presence of a screen protecting the face could reduce the amplitude of this response. This work aimed to investigate whether the learning of a posture intended to protect the head could modulate the HBR responses. Boxing athletes learn a defensive posture consisting of blocking with arms opponent’s blow towards the face. Two groups were recruited: 13 boxers and 13 people naïve to boxing. HBR response was recorded and elicited in three hand positions depending on the distance from the face. A suppression of HBR enhancement in the static position close to the face was observed in boxer group, contrary to the control group. Also, the higher years of practice in boxing, the higher suppression occurred. However, this suppression was not observed when boxers were asked to move the hand up-to/down-from the face. These findings might suggest that the sensorimotor experience related to a previously learnt protective posture can modify the HBR and thus shape the dimension of the DPPS.

Transcutaneous trigeminal nerve stimulation modulates the hand blink reflex

“…In this condition, because of their potential to evoke a painful sensation, trigeminal stimuli could modify the spatial properties of the face DPPS by increasing it in response to a continuous alarm 3 . Other conditions, such as the personality trait, the psychic state, threat and the cognitive expectations of the subject may modulate the amplitude of HBR 7 , 14 , 15 . Interestingly, the locus coeruleus, which is a target for TNS 27 , can modulate the occurrence of blinking, depending on the arousal state, emotions or alertness 45 .…”

“…The enhancement of the HBR response when the hand enters the DPPS is due to a cortico-bulbar facilitation of the polysynaptic medullary pathways that relay somatosensory inputs to the heterosegmentally specific HBR interneurons in the brainstem 12 . The power of this facilitation is determined by cognitive factors, which demonstrates the behavioral relevance of this subcortical reflex and how such fine top-down modulation is expression of its defensive value 12,15 . In our study, the TNS depressive action on the HBR was not significantly larger in the near (29.9%) than far (21.7%) hand positions of the reflex.…”

“…Other conditions, such as the personality trait, the psychic state, threat and the cognitive expectations of the www.nature.com/scientificreports/ subject may modulate the amplitude of HBR 7,14,15 . Interestingly, the locus coeruleus, which is a target for TNS 27 , can modulate the occurrence of blinking, depending on the arousal state, emotions or alertness 45 .…”

“…In particular, HBR amplitude increases more when the stimulated hand enters the subject’s DPPS around the face (near-HBR) than when the same stimulated hand is placed far from it (far-HBR). Further, HBR amplitude can be also modulated by internal factors that may influence the perception of the external stimuli, such as personality traits and cognitive expectations 7 , pain perception 3 , and acquired sensorimotor experience 15 .…”

Machine learning for exploring neurophysiological functionality in multiple sclerosis based on trigeminal and hand blink reflexes

“…The main characteristic of HBR is that the proximity of the stimulated hand to the face modulates this reflex. In particular, the size of the reflex increases when the hand is inside the defensive peripersonal space (DPPS) of the face [14][15][16][17] . Since the novelty of HBR exploration in MS, we hypothesize that it could be introduced in clinical practice in MS to explore brainstem functionality.The goal of this work is to test whether Machine Learning (ML) techniques could be combined with neurophysiological approaches based on TBR and HBR to improve their clinical information and favour early MS detection.…”