In Jabar & Anderson (2015), we saw that orientation probability affected perceptual precision, and based on the data, we hypothesized that this was due to V1 tuning changes. We thought of a way to test that hypothesis by looking at the C1 ERP potential, which is thought to index early V1 activity. As it turns out, the electrophysiological data is concordant with our specific hypothesis.

The C1 ERP dampens for high-probability orientations, and this happens within about 15 minutes into the task. This matches our prediction that neurons preferring these orientations benefit from a 'sharpened' V1 tuning, which should decrease overall activity, while increasing perceptual precision. We are currently attempting to computationally model how this sharpening occurs over the stimulus exposures. [Stay tuned for updates on this]

While probability has been thought of as the product of attentional mechanisms or of shifts in decisional criteria, we demonstrate that probability effects can affect low-level perception. Still, an increased P300 (a later fronto-parietal ERP component) is commonly associated with rare targets, and we do see that trend with our low-probability orientations as well. Of interest though is that there appears to be a correlation between C1 and P300 amplitudes. Speculatively, it might be that differences that arise in early perceptual loci drives later decisional processes.

The article is available online at Vision Research. Update: Here is the link to the article. Feel free to contact us if there are any queries.