A Neurocomputational Model of an Imitation Deficit Following Brain Lesion

Abstract

Abstract. This paper investigates the neural mechanisms of visuo-motor imitation in humans through convergent evidence from neuroscience. In particular, we consider a deficit in imitation following callosal brain lesion, based on the rational that looking at how imitation is impaired can unveil its underlying neural principles. We ground the functional architecture and information flow of our model in brain imaging studies and use findings from monkey brain neurophysiological studies to drive the choice of implementation of our processing modules. Our neural model of visuo-motor imitation is based on self-organizing maps with associated activities. Patterns of impairment of the model, realized by adding uncertainty in the transfer of information between the networks, account for the scores found in a clinical examination of imitation [1]. The model also allows several interesting predictions.

Neurocomputational modeling of imitation deficits

“…The information flow and implementation details of the model are consistent with evidence from brain imaging and neurophysiological studies [4,5]. To simulate callosal apraxia, we added uncertainty in the transfer of information between sensory representations localized in different hemispheres, successfully reproducing the results found in [3].…”

“…The information flow and implementation details of the model are consistent with evidence from brain imaging and neurophysiological studies [4,5]. To simulate callosal apraxia, we added uncertainty in the transfer of information between sensory representations localized in different hemispheres, successfully reproducing the results found in [3].To summarize, our model makes hypotheses on the type of neural representations used and the computational mechanisms underlying human visuo-motor imitation and could possibly help to gain more understanding in the occurrence and nature of imitation errors in patients with brain lesions. In addition, to further test and validate the model against human motion experimental data, we conduct, in collaboration with the Geneva University Hospital (HUG) and Vaud University Hospital Center (CHUV), kinematic studies with brain damaged adults specifically disabled in gesture imitation.…”

“…These observations brought us to consider modeling of the information pathway across the two hemispheres and the type of connectivity impairment which would account for them. We have thus developed a leaky integrator neurocomputational model of the neural representations of different sensory information (e.g., visual, tactile or proprioceptive) and reciprocal nonlinear transformations necessary to perform the imitation task [3]. The sensory representations in our model are selforganizing maps whose interconnections are trained with anti-hebbian learning.…”

Revisiting a study of callosal apraxia: The right hemisphere can imitate the orientation but not the position of the hand

“…In a previous work, we proposed a neuro-anatomical model for the information flow across hemispheres during the imitation of meaningless gestures (Petreska & Billard, 2006). The model made predictions about the brain areas and neural processes that support this information flow, based on evidence from brain imaging and brain lesion studies (see Fig.…”

Abstraction Levels for Robotic Imitation: Overview and Computational Approaches

“…Examples include models of language and culture [3,15], curiosity drives resulting in imitation behaviors [68], behavior switching in children and chimpanzees [79]. There have also been studies of imitation deficits relying on models of brain connections [110,124] We also note that there are other social learning mechanisms that fall outside the "imitation realm" in biological research. Often imitation is seen as a fundamental mental process for acquiring complex social skills but other mechanisms, although cognitively simpler, may have their own evolutionary advantages [89,104,105].…”