Abstract
Hemodynamic recordings from visual cortex contain powerful endogenous task-related responses that may reflect task-related arousal, or “task engagement” distinct from attention. We tested this hypothesis with hemodynamic measurements (intrinsic-signal optical imaging) from monkey primary visual cortex (V1) while the animals’ engagement in a periodic fixation task over several hours was varied through reward size and as animals took breaks. With higher rewards, animals appeared more task-engaged; task-related responses were more temporally precise at the task period (approximately 10–20 seconds) and modestly stronger. The 2–5 minute blocks of high-reward trials led to ramp-like decreases in mean local blood volume; these reversed with ramp-like increases during low reward. The blood volume increased even more sharply when the animal shut his eyes and disengaged completely from the task (5–10 minutes). We propose a mechanism that controls vascular tone, likely along with local neural responses in a manner that reflects task engagement over the full range of timescales tested.
Highlights
Hemodynamic recordings from visual cortex contain powerful endogenous task-related responses that may reflect task-engagement distinct from attention
Using intrinsic-signal optical imaging and electrophysiology, we looked for effects on the measured task-related hemodynamic response at multiple time scales: of individual trials (~10-20 seconds); of blocks of trials (150-300 seconds), and of extended segments of task engagement vs. disengagement as the animal switched between working, as vs. resting with eyes closed
All experimental procedures were performed in accordance with the NIH Guide for the Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committees (IACUC) of Columbia University and the New York State Psychiatric Institute
Summary
Hemodynamic recordings from visual cortex contain powerful endogenous task-related responses that may reflect task-engagement distinct from attention. It appears to be distinct from selective attention It entrains to task structure and extends over large sections of cortical areas (e.g. primary visual cortex, i.e. V1) independent of the stimulus[16,31,32,33], where it can even be substantially stronger than stimulus-selective responses[34]. The observed task-related response entrained to task timing independent of visual stimulation, with amplitudes that could compare with or even exceed vigorous visually evoked responses[44] It appeared to be spatially non-selective, being homogeneous over the optical imaging window and presumably extending beyond[32]. At a vascular level, this response corresponded to a coordinated contraction-dilation cycle engaging the arterial blood supply into the imaged cortical region[31] These observations suggested an underlying mechanism distinct from exogenous, stimulus-evoked responses
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