engleski

Adaptive resonance theory explains how expectations influence perception

Recently, several fMRI studies showed that conceptual processing creates expectations that modulate activity in the visual cortex. Based on these findings, it is concluded that expectations directly alter perception. However, if there is a strong overlap between bottom-up sensory information and top-down expectations, cognitive system would not be able to distinguish between perception and hallucination. In the current work, we offer an alternative explanation of the observed findings based on the adaptive resonance theory (ART). The ART was designed to solve the problem of stability of learning and memory in non-stationary environment. The problem is how to protect previously learned information from erosion when faced with new information that should be learned. The ART network consists of three layers labelled as F0, F1 and F2. The F0 layer represents purely sensory response that is not affected by expectations. The F1 layer serves as a matching point between bottom-up and top-down signals arriving from the F2 layer. Finally, the F2 layer represents category or knowledge level. Important property of the ART design is that it does not have feedback projections from the F2 to F0 layer or from the F1 to F0 layer. Therefore, the F0 layer could not be perturbed by the top-down signals. In other words, the F0 layer provides veridical or reference signal that is supplied to F1 layer for detecting match or mismatch with the top-down signals from the F2 layer. Computer simulations showed that it is possible to observe increased neural signal that arise from the read-out of top-down expectations in the F1 layer without noticeable effect on the perception when the whole network enter into the resonant state. Furthermore, our explanation is consistent with electrophysiological studies revealing that some but not all neurons in the visual cortex are subject to top-down modulations. We conclude that the observed cortical modulations arise from the subthreshold stimulation of the F1 layer that do not necessarily influence suprathreshold perception.

brightness perception ; grounded cognition ; magnitude representation ; mental arithmetic ; mental number line

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