Imagined locomotion in the blind: an functional magnetic resonance imaging study

Abstract

Objective: Previous functional magnetic resonance imaging (fMRI) studies in sighted individuals showed parahippocampal and fusiform activations during locomotor imagery, which were interpreted to reflect visuospatial navigation. Concurrent deactivations in multisensory vestibular and somatosensory cortical areas were interpreted to reflect suppression of vestibular and somatosensory input, in order to prevent adverse interactions of sensory signals with the optimized automated locomotion pattern. Blind subjects may use distinct sensorimotor strategies for locomotor control. Methods: We performed an fMRI study to compare blood oxygen level dependent (BOLD) activations and deactivations during the kinesthetic imagery of standing, walking, and running in seven congenitally totally blind subjects and seven sighted age-matched controls. Imagined lying served as the rest condition. Training of experimental tasks was performed before the fMRI experiment in all subjects. Results: As opposed to their sighted controls, congenitally totally blind individuals activated multisensory vestibular areas in the posterior insula and superior temporal gyrus during imagined locomotion. Congenitally blind individuals did not show activations in parahippocampal and fusiform regions during locomotor tasks. In the intergroup comparisons, congenitally blind subjects exhibited higher BOLD activity levels than sighted subjects in multisensory vestibular (posterior insula and adjacent temporal sites), somatosensory (postcentral gyrus), and primary motor cortical areas, while sighted subjects showed higher activity levels in the parahippocampal and fusiform gyri. Discussion: Our findings indicate that blind subjects rely more on vestibular and somatosensory feedback for locomotion control than sighted subjects. This appeared to be accompanied by enhanced voluntary motor control and enhanced motor-kinesthetic processing in the blind. Thus, we provide neuroimaging evidence of distinct sensorimotor strategies in the blind for locomotor control.