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Rachel Denison, Karen Tian, David Heeger, Marisa Carrasco; Voluntary temporal attention and MEG visual cortical responses. Journal of Vision 2020;20(11):618. https://doi.org/10.1167/jov.20.11.618.
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Visual attention fluctuates across both space and time. Voluntary temporal attention is the goal-directed prioritization of visual information at specific points in time. Temporal attention selectively improves perceptual sensitivity at attended times. Here, we investigated the neural mechanisms underlying these perceptual improvements using MEG. We assessed how voluntary temporal attention affects the timing reliability of human visual cortical responses.
Observers performed an orientation discrimination task. On each trial, two grating targets (T1 and T2) appeared sequentially at the fovea for 50 ms, separated by a 300 ms stimulus onset asynchrony. A precue tone (75% validity) instructed observers to attend to T1 or T2. A response cue tone after the targets instructed them to report the orientation (CW/CCW) of either T1 or T2. Thus, on each trial, one target was attended and the other was unattended.
The targets were embedded in 20 Hz flickering noise. The flicker generated a 20 Hz steady state visual evoked field (SSVEF) response in visual cortex, which served as a probe of visual cortical responses throughout the trial. We used a wavelet analysis to measure 20 Hz stimulus-locked oscillations across time. We calculated the intertrial phase coherence (ITPC) of the SSVEF signal, which indexes neural timing reliability.
[Results and Conclusion]
Temporal attention improved orientation discrimination performance, more for T1 than T2. Each target was followed by a brief change in ITPC, which we call the evoked ITPC response. Temporal attention increased the magnitude of the evoked ITPC response for T1 but not T2. In conclusion, voluntary temporal attention affected the timing reliability of the T1 response.
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