title: Extending peripersonal space representation without tool-use: evidence from a combined behavioral-computational approach.
abstract: Stimuli from different sensory modalities occurring on or close to the body are integrated in a multisensory representation of the space surrounding the body, i.e., peripersonal space (PPS). PPS dynamically modifies depending on experience, e.g., it extends after using a tool to reach far objects. However, the neural mechanism underlying PPS plasticity after tool use is largely unknown. Here we use a combined computational-behavioral approach to propose and test a possible mechanism accounting for PPS extension. We first present a neural network model simulating audio-tactile representation in the PPS around one hand. Simulation experiments showed that our model reproduced the main property of PPS neurons, i.e., selective multisensory response for stimuli occurring close to the hand. We used the neural network model to simulate the effects of a tool-use training. In terms of sensory inputs, tool use was conceptualized as a concurrent tactile stimulation from the hand, due to holding the tool, and an auditory stimulation from the far space, due to tool-mediated action. Results showed that after exposure to those inputs, PPS neurons responded also to multisensory stimuli far from the hand. The model thus suggests that synchronous pairing of tactile hand stimulation and auditory stimulation from the far space is sufficient to extend PPS, such as after tool-use. Such prediction was confirmed by a behavioral experiment, where we used an audio-tactile interaction paradigm to measure the boundaries of PPS representation. We found that PPS extended after synchronous tactile-hand stimulation and auditory-far stimulation in a group of healthy volunteers. Control experiments both in simulation and behavioral settings showed that the same amount of tactile and auditory inputs administered out of synchrony did not change PPS representation. We conclude by proposing a simple, biological-plausible model to explain plasticity in PPS representation after tool-use, which is supported by computational and behavioral data.
authors.affiliation: Laboratory of Cognitive Neuroscience, Department of Life Science, Center for Neuroprosthetics, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Dipartimento di Psicologia, Alma Mater Studiorum, Università di Bologna Bologna, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Serino
authors.affiliation: Laboratory of Cognitive Neuroscience, Department of Life Science, Center for Neuroprosthetics, Ecole Polytechnique Fédérale de Lausanne Lausanne, Switzerland ; Dipartimento di Psicologia, Centro Studi e ricerche in Neuroscienze Cognitive, Polo Scientifico Didattico di Cesena, Alma Mater Studiorum, Università di Bologna Bologna, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Canzoneri
authors.affiliation: Dipartimento di Psicologia, Centro Studi e ricerche in Neuroscienze Cognitive, Polo Scientifico Didattico di Cesena, Alma Mater Studiorum, Università di Bologna Bologna, Italy.
authors.forename: Marilena
authors.initials: M
authors.lastname: Marzolla
authors.affiliation: Dipartimento di Psicologia, Alma Mater Studiorum, Università di Bologna Bologna, Italy ; Dipartimento di Psicologia, Centro Studi e ricerche in Neuroscienze Cognitive, Polo Scientifico Didattico di Cesena, Alma Mater Studiorum, Università di Bologna Bologna, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: di Pellegrino
authors.affiliation: Interdepartmental Centre for Industrial Research in Health Sciences and Technologies, Alma Mater Studiorum, University of Bologna Bologna, Italy ; Department of Electrical, Electronic and Information Engineering "Guglielmo Marconi," Alma Mater Studiorum, University of Bologna Bologna, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Magosso
keywords: multisensory processing; neural network model; peripersonal space; plasticity; tool-use