Object-centered spatial awareness - awareness of the location, relative to an object, of its parts - plays an important role in many aspects of perception, cognition and action. One possible basis for this form of spatial awareness is the existence in the brain of neurons with response fields defined relative to an object-centered reference frame. Evidence for such a mechanism has been provided by the finding that neurons in the supplementary eye field (SEF) fire differentially as a function of object-centered direction when monkeys make eye movements to the right or left end of a horizontal bar. Research carried out during the preceding and first support period of the current grant established object-centered direction selectivity in the SEF as a robust and replicable phenomenon and demonstrated, among other findings, that it was independent of visual stimulus selectivity and could not be accounted for in terms of body-centered motor signals. In addition, it extended into inferotemporal cortex (IT) the study of neural representations underlying the representation of object structure. Findings from this period have provided support for the general conclusion that there are neurons in the cerebral cortex which encode spatial information relative to an abstract non-motoric reference frame. Projects to be carried out during the next support period have as their twofold general aim: (1) to test the idea that object-centered representations in the SEF subserve cognitive processes more general than the selection of targets for eye movements; and (2) to compare directly object-centered activity in the SEF and in other, related cortical areas of the frontal and parietal lobes. Five main series of experiments will be carried out. Series 1 will assess the validity of the gain-field model according to which SEF neurons exhibit object-centered direction selectivity only during planning of eye movements into the classic motor field. Series 2 will assess whether SEF neurons carry object-centered signals when monkeys perform a task requiring them to remember object-centered locations without making movements to them. Series 3 will test the hypothesis that the object-centered neuronal activity in the SEF is correlated with object-centered visual attention as measured at the level of inferotemporal cortex. Series 4 will investigate whether neurons in the frontal eve field (FEF) carry object-centered signals.
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