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Susan Boehnke, David Berg, Pierre Baldi, Laurent Itti, Doug Munoz; Adaptation and habituation of visual responses in the superficial and intermediate layers of the superior colliculus (SC). Journal of Vision 2007;7(9):188. doi: 10.1167/7.9.188.
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One neural correlate of visual attention is a decrease in the neural response to a target after prior presentation of an orienting ‘cue’ (e.g. inhibition of return). This decreased responding could be the result of repeated stimulation of a neuron's receptive field resulting in either ‘adaptation’ - a lower level mechanism related to neural fatigue, or ‘habituation’ - where an organism stops responding to an irrelevant stimulus but recovers the response after a change in stimulus properties. We dissociated adaptation from habituation in superficial (SCs) and intermediate (SCi) layer neurons of the SC, a hub of oculomotor and attentional processing. SCs receives visual input from the retina directly or via V1, while the SCi receives convergent input from visual and motor areas. Monkeys were rewarded for fixating a central point while a series of 7 successive stimuli were briefly flashed (100 ms duration; 100–400 ms interval) in the receptive field of the neuron. On 70% of trials all flashed stimuli were identical, while on others, the 4th was either brighter, dimmer or absent (10% each). If reduced neural response is due to habituation, some recovery of the response (dishabituation) should occur to any oddball stimulus. However, if the reduced response is due to adaptation, the response should be further reduced after the brighter, but recover after the dimmer or absent stimulus. The largest decrease in response (often [[gt]] than 50%) was to the second stimulus, and subsequent stimuli resulted in only small further reductions. The shorter the inter-flash interval, the greater these reductions. The pattern was globally similar in SCs and SCi, but there was a greater reduction to the 3–7th stimuli in SCi. Responses to oddball stimuli in SCs neurons were suggestive of adaptation, while responses in SCi neurons showed features of both adaptation and habituation.
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