Spatial working memory in human extrastriate cortex

The performance of spatial working memory tasks is known to evoke activity in a set of higher-order association areas, including the prefrontal cortex, posterior parietal cortex and the frontal and supplementary, eye fields. Recent physiological studies in monkey have shown that memory-related activity also is found in extrastriate cortex [J. Neurophysiol. 84 (2000) 677]. We conducted functional magnetic resonance imaging studies to determine whether human extrastriate cortex contributes to the on-line maintenance of spatial information in an eye movement task. We found that performance of memory-guided saccades, as compared to visually guided saccades, elicited significant activation in two areas of extrastriate cortex: the posterior superior temporal sulcus (PST) and lateral occipitotemporal cortex (LOT). Both areas also were activated during the basic sensorimotor task of visually guided saccades as compared to fixation. We further determined that area LOT is close to but distinct from motion-sensitive area MT+. These findings demonstrate that areas PST and LOT, along with higher-level association cortex, help to encode and maintain spatial representations. (C) 2002 Elsevier Science Inc. All rights reserved.