The role of vestibular function on the representation of space and its impairment after central and peripheral lesions

Abstract

Our perception of space is based on the integration of signals from vestibular, visual, and somatosensory systems. These sensory modalities allow awareness of the displacements and positions of our body and body parts, as well as the locations of objects in extra-personal space. Brain lesions can produce severe deficits in the representation of personal or extra-personal space, as demonstrated by the syndrome of unilateral (left) spatial neglect after (right) hemisphere stroke. Many aspects of the neglect syndrome have been ascribed to pathological biases in the internal representation of space, some of which can also be observed in patients with dysfunction of the vestibular pathways, either in the peripheral or central nervous system. The recent studies showed for example, neglect patients like vestibular patients exhibit an ipsilesional (e.g. rightward) deviation of their subjective body midline when pointing straight-ahead, as well as ipsilesional biases in posture and abnormal perception of verticality. Therefore, it has been hypothesized that some impairment in the integration of vestibular signals at the brain level might contribute to impaired spatial cognition and neglect after focal hemispheric damage. A critical role for the vestibular system in neglect would be consistent with its central projections on multisensory integration areas in parietal and frontal cortex which are thought to be involved in the representation of space across egocentric and allocentric spatial frames of reference, and which are typically damaged in neglect patients.