Dynamic Shaping of the Defensive Peripersonal Space through Predictive Motor Mechanisms: When the "Near" Becomes "Far".
The hand blink reflex is a subcortical defensive response, known to dramatically increase when the stimulated hand is statically positioned inside the defensive peripersonal space (DPPS) of the face. Here, we tested in a group of healthy human subjects the hand blink reflex in dynamic conditions, investigating whether the direction of the hand movements (up-to/down-from the face) could modulate it. We found that, on equal hand position, the response enhancement was present only when the hand approached to (and not receded from) the DPPS of the face. This means that, when the hand is close to the face but the subject is planning to move the hand down, the predictive motor system can anticipate the consequence of the movement: the "near" becomes "far." We found similar results both in passive movement condition, when only afferent (visual and proprioceptive) information can be used to estimate the final state of the system, and in motor imagery task, when only efferent (intentional) information is available to predict the consequences of the movement. All these findings provide evidence that the DPPS is dynamically shaped by predictive mechanisms run by the motor system and based on the integration of feedforward and sensory feedback signals.SIGNIFICANCE STATEMENTThe defensive peripersonal space (DPPS) has a crucial role for survival, and its modulation is fundamental when we interact with the environment, as when we move our arms. Here, we focused on a defensive response, the hand blink reflex, known to increase when a static hand is stimulated inside the DPPS of the face. We tested the hand blink reflex in dynamic conditions (voluntary, passive, and imagined movements) and we found that, on equal hand position, the response enhancement was present only when the hand approached to (and not receded from) the DPPS of the face. This suggests that, through the integration of efferent and afferent signals, the safety boundary around the body is continuously shaped by the predictive motor system.
Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy, and.
Ambra
0000-0002-9385-1714
A
Bisio
SpAtial, Motor and Bodily Awareness-Research Group, Psychology Department, University of Turin, 10123 Turin, Italy marco.bove@unige.it fra.garbarini@gmail.com.
Francesca
0000-0003-1210-0175
F
Garbarini
Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy, and.
Monica
0000-0001-5800-4643
M
Biggio
SpAtial, Motor and Bodily Awareness-Research Group, Psychology Department, University of Turin, 10123 Turin, Italy.
Carlotta
0000-0001-8145-006X
C
Fossataro
Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy, and.
Piero
0000-0001-5939-1489
P
Ruggeri
Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy, and marco.bove@unige.it fra.garbarini@gmail.com.
Marco
0000-0001-8129-4298
M
Bove
D000328:Adult; D000704:Analysis of Variance; D001767:Blinking / Q000502:physiology; D003674:Defense Mechanisms; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D056228:Feedback, Sensory; D005260:Female; D006225:Hand; D006801:Humans; D007092:Imagination; D008297:Male; D009068:Movement / Q000502:physiology*; D010550:Personal Space; D012867:Skin / Q000294:innervation; D013028:Space Perception / Q000502:physiology*; D014953:Wrist / Q000294:innervation; D055815:Young Adult
defensive peripersonal space; hand blink reflex; motor imagery; movement