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Aniruddha Das; Task-related Responses in Intrinsic-Signal Optical Imaging. Journal of Vision 2015;15(12):1415. doi: 10.1167/15.12.1415.
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© 2017 Association for Research in Vision and Ophthalmology.
There is a growing appreciation of the importance of endogenous, task-related processes such as attention and arousal even at the earliest stages of sensory processing. By combining intrinsic-signal optical imaging with simultaneous electrode recordings we earlier demonstrated a particular task-related response – distinct from stimulus-evoked responses – in primary visual cortex (V1) of macaque monkeys engaged in visual tasks. The task-related response powerfully reflects behavioral correlates of the task, independent of visual stimulation; it entrains to task timing, increasing progressively in amplitude and duration with temporal anticipation; and it correlates with both task-related rewards, and performance.
Notably, however, the effect of the task-related response on stimulus-evoked responses – such as the contrast response function (CRF) – remains an open question. For tasks that are stereotyped and independent of visual stimulation, the task- and stimulus-related responses are linearly separable: the task-related component can be subtracted away leaving an imaged contrast response function that is robustly linear with stimulus-evoked spiking. When the task-related response is modified – such as, by increasing the reward size – the effect is largely additive: the baseline imaging response increases, without, to first order, changing the CRF of the stimulus-evoked component. Thus the important question remains: are there other reliable measures of changes in neural activity, such as changes in signal or noise correlation, rather than local spike rate or LFP magnitude, that can better characterize the task-related response?
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