Rodent posterior parietal cortex as a component of a cortical network mediating directed spatial attention

The rat posterior parietal cortex has been found to be a multimodal convergence area identifiable by its pattern of neuroanatomical connections with the cortex and thalamus. The rat posterior parietal cortex is part of a cortical network that also includes the medial agranular and ventrolateral orbital areas. Each of these three cortical areas is a region of multimodal convergence. Bilateral destruction of any of these areas produces deficits in spatial learning, whereas unilateral lesions induce deficits in directed attention. These findings suggest that together these cortical regions form an integrated network for spatial processing and orientation. In a recent test of this hypothesis, the posterior parietal area was selectively disconnected from the medial agranular cortex without direct damage to either area. This resulted in severe neglect which was qualitatively and quantitatively similar to that produced by unilateral destruction of wither cortical area, thereby supporting the network hypothesis. Some earlier conflicting reports bearing on the functional role of rat posterior parietal cortex may be explained in light of these disconnection data. The anatomical and behavioral findings suggest that in rats, as in primates, a parieto-frontal network mediates the integrated, dynamic spatial representations essential for normal directed attention and spatial orientation.