Evidence from single cell recording studies in primates indicates that neurons encode spatial information in a variety of coordinate frames, which may be transformed to a single, common viewer (eye-) centered representation in posterior parietal cortex used for planning movements. Lesions studies in both monkeys and humans indicate that spatial representations with different coordinate frames can occasionally be separately disrupted by brain damage, variously impairing action or perception on the side contralateral to the brain lesion (causing different forms of hemispatial neglect). However, the cortical organization of such spatial representations is fundamentally different in primates and humans, as indicated by the fact that lesions in either hemisphere cause comparable hemispatial neglect in monkeys, whereas right cortical lesions cause more common, severe, and persistent neglect in humans. I will report evidence regarding the neural correlates of hemispatial neglect in humans, from studies utilizing MR perfusion weighted imaging (PWI) and diffusion weighted imaging (DWI) and concurrent testing of hemispatial neglect in hyperacute stroke. I will present evidence for proposing that distinct areas of human cortex are essential for computing spatial representations with different coordinate frames.

Possible suggested readings: Hillis, A.E. & Caramazza, A. (1995). A framework for interpreting distinct patterns of hemispatial neglect. Neurocase, 1, 189-207. Hillis, A.E., Wityk, R., Barker, P.B., Caramazza, A. (2003). Neural regions essential for writing verbs. Nature Neuroscience, 6, 19-20. Hillis, A.E., Wityk, R.J., Barker, P.B., Beauchamp, N.J., Gailloud, P., Murphy, K., Cooper, O., Metter, E.J. (2002). Subcortical aphasia and neglect in acute stroke: the role of cortical hypoperfusion, Brain, 125, 1094-1104.