Neurons in the lateral intraparietal area create a priority map by the combination of disparate signals
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Primates search for objects in the visual field with eye movements. We recorded the activity of neurons in the lateral intraparietal area (LIP) in animals performing a visual search task in which they were free to move their eyes, and reported the results of the search with a hand movement. We distinguished three independent signals: (1) a visual signal describing the abrupt onset of a visual stimulus in the receptive field; (2) a saccadic signal predicting the monkey’s saccadic reaction time independently of the nature of the stimulus; (3) a cognitive signal distinguishing between the search target and a distractor independently of the direction of the impending saccade. The cognitive signal became significant on average 27 ms after the saccadic signal but before the saccade was made. The three signals summed in a manner discernable at the level of the single neuron.
KeywordsParietal cortex Single neurons recording Monkey Saccades Visual search Priority map
We are grateful to Yana Pavlova for dedicated animal maintenance, to Drs. Mohammed Osman and Girma Asfaw for veterinary care, to Steve Dashnaw and Dr. Joy Hirsch for MR imaging, to Glen Duncan for electronic and computer support, to the members of the Mahoney Center for their trenchant comments on earlier drafts of this paper, and to Latoya Palmer for facilitating everything. Dr. Lance Optican of the Laboratory of Sensorimotor Research of the National Eye Institute wrote the Matlab functions which convert REX data files to Matlab structs. Dr. John McClurkin from the Laboratory of Sensorimotor Research helped us maintain REX, VEX, and MEX. This research was supported by grants from the National Eye Institute (1 R01 EY014978-01, and 1 R24 EY015634-01 to M.E.G.), the National Institute of Neurological, Communicative Diseases and Stroke (1 F31 NS058059-01 to A.L.G.) and the Keck and Dana Foundations; and from the National Science Foundation.
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