Cerebral representations for egocentric space - Functional-anatomical evidence from caloric vestibular stimulation and neck vibration

The internal representation of space involves the integration of different sensory inputs-visual, somatosensory/proprioceptive, vestibular-yielding re ference frames which are not based on individual peripheral sensory codes, being organized instead in ego-centred (e,g, head, trunk, arm) and object- or environment-centred coordinates, Lateralized or direction-specific stimu lation of peripheral sensory systems, such as caloric vestibular stimulatio n (CVS), posterior neck muscle mechanical vibration (NV) and optokinetic st imulation, can induce a distortion of egocentric coordinates, causing, for example, a deviation of the subjective straight ahead in pointing tasks, Ap propriate forms of this stimulation can also temporarily improve a variety of pathological manifestations of unilateral neglect, We used PET measureme nts of regional cerebral blood flow changes in normal volunteers to measure the brain responses shared by CVS and NV, We show that somatosensory areas of the perisylvian cortex including the insula and retroinsular cortex, th e temporoparietal junction and somatosensory area II receive signals from b oth sensory channels, We propose that these anatomical sites contribute to egocentric representation of space.