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Hans Supèr, August Romeo; Backward-masking of figure-ground signal by feed forward inhibition. Journal of Vision 2010;10(7):1212. doi: 10.1167/10.7.1212.
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© ARVO (1962-2015); The Authors (2016-present)
In backward masking, a target stimulus is rendered less perceptible or even invisible through the presentation of a second stimulus, the mask. Feedforward inhibitory models explain backward masking by asserting that the second stimulus exerts an inhibitory influence on the responses of a neuron evoked by the target. Another set of theories argue that the masking interferes with recurrent or reentrant processing. Earlier neurpohysiological studies have demonstrated that the feedforward processing of the target remains largely intact. Strong evidence favoring the role of recurrent processing is backward masking of figure-ground textures. Figure-ground activity is believed to be contingent on feedback, and represents a neural correlate of visual perception. Rendering the figure invisible by backward masking abolishes the figure-ground modulated responses while leaving the detection of features intact. Thus, the results of figure-ground masking favor the hypothesis that backward masking blocks conscious processing by disrupting reentrant signals. Recently we described a computational spiking model that performs figure-ground segmentation of in a purely feed-forward manner. In this model global feedforward inhibition suppresses background responses but not the figure responses and can account for the segregation of textured figures. Here we used this model to test whether backward masking interrupts the feedforward segmentation of figure from ground. Our results show that feature extraction is intact while figure-ground segregation is interrupted in the pattern mask but not in the blank mask condition. These observations are very similar to the neuro-physiological findings in the primate visual cortex where figure-ground activity was specifically disrupted by a pattern mask but not by a blank mask. We further examined the behavior of the model by forward and backward masking using a surround mask. In conclusion our results show that feedforward inhibition can account for backward masking effects of figure-ground stimuli.
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