EYE-CENTERED, HEAD-CENTERED, AND INTERMEDIATE CODING OF REMEMBERED SOUND LOCATIONS IN AREA LIP

1. The lateral intraparietal area (LIP) of the posterior parietal cort ex lies within the dorsal cortical stream for spatial vision and proce sses visual information to plan saccadic eye movements. We investigate d how LIP neurons respond when a monkey makes saccades to the remember ed location of sound sources in the absence of visual stimulation. 2. Forty-three (36%) of the 118 neurons sampled showed significant audito ry triggered activity during the memory period. This figure is similar to the proportion of cells showing visually triggered memory activity . 3. Of the cells showing auditory memory activity, 44% discharged in an eye-centered manner, similar to the way in which LIP cells discharg e for visually initiated saccades. Another 33% responded in head-cente red coordinates, and the remaining 23% had responses intermediate betw een the two reference frames. 4. For a substantial number of cells in all three categories, the magnitude of the response was modulated by e ye position. Similar orbital ''gain fields'' had been shown previously for visual saccades. 5. We propose that area LIP is either at the ori gin of, or participates in. the transformation of auditory signals for oculomotor purposes, and that orbital gains on the discharge are part of this process. 6. Finally, we suggest that, by the level of area LI P, cells are concerned with the abstract quality of where a stimulus i s in space, independent of the exact nature of the stimulus.