Key result
Muscular effort in certain hand postures increases Hand-Blink Reflex magnitude less than eye-hand proximity.
Why the study?
The hand-blink reflex (HBR) magnitude may be influenced by lower-level factors such as muscular effort, which could confound interpretations of its behavioural relevance.
Muscular effort increases the magnitude of the hand-blink reflex, a confounding factor that should be accounted for in future experiments mapping defensive peripersonal space.
Muscular effort confounds HBR magnitude in peripersonal space mapping; extends low-level reflex modulation data but leaves open clinical relevance.
Defensive motor responses elicited by sudden environmental stimuli are finely modulated by their behavioural relevance to maximise the organism's survival. One such response, the blink reflex evoked by intense electrical stimulation of the median nerve (Hand-Blink Reflex; HBR), has been extensively used to derive fine-grained maps of defensive peripersonal space. However, as other subcortical reflexes, the HBR might also be modulated by lower-level factors that do not bear direct relevance to the defensive value of blinking, thus posing methodological and interpretive problems. Here, we tested whether HBR magnitude is affected by the muscular effort present when holding the hand in certain postures. We found that HBR magnitude increases with muscular effort, an effect most likely mediated by the increased corticospinal drive. However, we found strong evidence that this effect is substantially smaller than the well-known effect of eye-hand proximity on HBR magnitude. Nonetheless, care should be taken in future experiments to avoid erroneous interpretations of the effects of muscular effort as indicators of behaviour relevance.
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Bufacchi et al. (2018) studied this question. Muscular effort was evaluated on Hand-Blink Reflex (HBR) magnitude. Muscular effort when holding the hand in certain postures increases Hand-Blink Reflex magnitude, though this effect is smaller than the effect of eye-hand proximity.
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