Multiple representations of space in the brain
Lesions of posterior parietal cortex have long been known to produce visuo-spatial deficits in both humans and monkeys. Yet there is no known “map” of space in parietal cortex. Posterior parietal cortex projects to a number of other areas which are involved in specialized spatial functions. In these areas space is represented at the level of single neurons and in many of them there is a topographically organized map of space. These extra-parietal areas include premotor cortex and the putamen, involved in visuomotor space, the frontal eye fields and the superior colliculus, involved in oculomotor space, the hippocampus, involved in environmental space, and dorsolateral prefrontal cortex, involved in mnemonic space. In many of these areas, space is represented by means of a coordinate system that is fixed to a particular body part. Thus, the processing of space is not unitary, but is divided among several brain areas and several coordinate systems in addition to those in posterior parietal cortex.