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Sirawaj Itthipuripat, Kai-Yu Chang, Vy Vo, Stephanie Nelli, John Serences; Dissociable effects of stimulus strength, task demands, and training on occipital and parietal EEG signals during perceptual decision-making. Journal of Vision 2017;17(10):37. doi: 10.1167/17.10.37.
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In most tasks, behavioral performance depends on several factors including stimulus strength, task demands, and also the amount of expertise. Here, we investigated how these different factors impacted neural modulations of early sensory and post-sensory processing. To address this question, we recorded encephalography (EEG) from human subjects performing a perceptual decision-making task and used two event-related potentials (ERPs): an early visual negativity (VN) and a late centro-parietal positivity (CPP) as neuromarkers for early sensory and post-sensory processing, respectively. Across four days, subjects discriminated the orientation of a patch of oriented lines as we manipulated stimulus strength (0-60% coherence) and task demands (number of possible target orientations: 2 or 4 choices). While behavioral performance improved with increased stimulus coherence, reduced choice number, and increased training duration, we observed distinguishable modulations of the VN and CPP components. Specifically, the amplitudes of the VN and CPP increased multiplicatively with increased stimulus coherence. On the other hand, reducing the task demands did not alter the VN amplitude, but increased the ramping rate of the CPP. Similar to increasing stimulus coherence, training amplified the VN amplitude, however; it reduced the CPP amplitude. The data suggest that altering task demands can produce an effect on post-sensory processing that is similar to changing stimulus strength but in the absence of changes in early sensory processing. On the other hand, training and increasing stimulus strength can produce similar effects on early sensory processing with different patterns of neural modulations at post-sensory stages.
Meeting abstract presented at VSS 2017
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