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Sung Jun Joo, Geoffrey M. Boynton, Scott O. Murray; Stimulus predictability affects early sensory components of the ERP response. Journal of Vision 2012;12(9):436. doi: 10.1167/12.9.436.
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Predictive coding models suggest that neural responses in early visual areas can be reduced if incoming sensory input matches feedback from top-down predictions. If such feedback processes are occurring, then specific hypotheses can be made about their expected time-course and dependence upon stimulus timing. In particular, if surrounding flanking stimuli precede the onset of a target by a sufficient length of time, then the feedback process is likely to be in place and stabilized before the onset of the target. Thus, differences in flanking configurations that affect target predictability should appear early in the neural response to the target.
To test this, we measured event-related potentials (ERPs) to the onset of a briefly flashed (100 ms) oriented target. Target predictability was manipulated by changing the relative orientation of flanking stimuli. The flankers were presented 1~2 s before the target to ensure that any predictive, feedback process was in place before target onset. In Experiment 1, we found that the orientation relationship in a three element configuration (one target and two flankers) influenced early ERP responses (~150 ms) at electrode sites near the occipital pole (Oz, O1, O2, POz, PO3, and PO4). ERPs to targets that matched the flankers had lower amplitudes than targets that did not match the flankers. In Experiment 2, we measured ERPs to targets in three five-element conditions: same (VVVVV/HHHHH), orthogonal (HHVHH/VVHVV), and alternating (VHVHV/HVHVH). Importantly, the orientation relationship between the target and immediately adjacent flankers remains the same in the orthogonal and alternating conditions (e.g., HVH/VHV); only the orientation of the most distant flankers is changed. The early component of the ERPs showed lower amplitude in the same and alternating conditions (predictable target) compared to the orthogonal condition (unpredictable target). These results suggest that stimulus predictability can influence initial feedforward stimulus processing.
Meeting abstract presented at VSS 2012
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