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Nitzan Censor, Yoram Bonneh, Dov Sagi; Electrophysiological correlates of performance and learning in the backward-masked texture-discrimination task. Journal of Vision 2007;7(9):795. doi: https://doi.org/10.1167/7.9.795.
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© ARVO (1962-2015); The Authors (2016-present)
Experimental evidence from texture discrimination tasks using backward pattern masking shows performance dependence on the stimulus-to-mask onset asynchrony (SOA) as well as the amount of prior practice. In the following study we examine whether human event-related potentials (ERPs) correlate with the level of texture discrimination performance and thus enable to reveal underlying mechanisms of learning and backward masking effects on the level of performance. The standard texture stimulus was used, briefly presented (40 ms) and backward masked as in Karni and Sagi (1993). Observers decided whether an array of 3 diagonal bars embedded in a background of horizontal bars was horizontal or vertical. In each session the SOA decreased gradually to obtain a psychometric curve. ERPs were recorded over occipital electrode sites and time-locked to the onset of the target visual stimulus. Both naïve and experienced observers participated in the experiment. At large SOAs ([[gt]]200 ms) there was a clear separation between target responses and mask responses, with maximal response to the target at 100 ms. The latter was found to be constant in each observer, independent of SOA (60–340 ms) and performance level. Performance level was found to correlate with the temporal separation between target and mask responses which in turn depend on SOA and experience with the task. It seems that performance fails when the presented mask limits the effective processing of the target signal. The correlation found here between the ERP response and the discrimination performance may have an essential role in the underlying mechanism of backward masking effects on texture discrimination performance. Practice with the texture task seems to improve the temporal separation between target and mask.
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