TY - JOUR T1 - To Blink or Not to Blink: Fine Cognitive Tuning of the Defensive Peripersonal Space JF - The Journal of Neuroscience JO - J. Neurosci. SP - 12921 LP - 12927 DO - 10.1523/JNEUROSCI.0607-12.2012 VL - 32 IS - 37 AU - C. F. Sambo AU - B. Forster AU - S. C. Williams AU - G. D. Iannetti Y1 - 2012/09/12 UR - http://www.jneurosci.org/content/32/37/12921.abstract N2 - The blink reflex elicited by the electrical stimulation of the median nerve at the wrist [hand blink reflex (HBR)] is a subcortical, defensive response that is enhanced when the stimulated hand is inside the peripersonal space of the face. Such enhancement results from a tonic, top-down modulation of the excitability of the brainstem interneurons mediating the HBR. Here we aim to (1) characterize the somatotopical specificity of this top-down modulation and investigate its dependence on (2) cognitive expectations and (3) the presence of objects protecting the face, in healthy humans. Experiment 1 showed that the somatotopical specificity of the HBR enhancement is partially homosegmental, i.e., it is greater for the HBR elicited by the stimulation of the hand near the face compared with the other hand, always kept far from the face. Experiment 2 showed that the HBR is enhanced only when participants expect to receive stimuli on the hand close to the face and is thus strongly dependent on cognitive expectations. Experiment 3 showed that the HBR enhancement by hand–face proximity is suppressed when a thin wooden screen is placed between the participants' face and their hand. Thus, the screen reduces the extension of the defensive peripersonal space, so that the hand is never inside the peripersonal space of the face, even in the “near” condition. Together, these findings indicate a fine somatotopical and cognitive tuning of the excitability of brainstem circuits subserving the HBR, whose strength is adjusted depending on the context in a purposeful manner. ER -