Neurophysiological Mechanisms of Orientation Feature Matching in a Working Memory Task

This study aimed to elucidate the mechanism of detecting differences between a current line orientations and line orientations retained in working memory (WM). The results were compared with the data obtained in a WM experiment for spatial patterns. The study involved 33 healthy subjects with normal vision. The subjects performed a WM task, and the visual event-related potentials (ERPs) and dipole simulation were analyzed in the interval 160–280 ms after the stimulus. An increase in ERP amplitude was identified as an informative marker of a mismatch between the current and retained stimuli. The increase arose simultaneously in the frontal and parietal-occipital cortical areas and was stimulus type independent. An analysis of distributed dipole sources showed that the topography of match vs. mismatch differences depends on the stimulus type. In the case of orientations, differences were more local and predominated in the caudal areas of the left hemisphere. In the case of spatial patterns, differences were more extended and prevailed in the right hemisphere. The results indicate that a common organization is characteristic of neural networks detecting a mismatch between current and retained stimuli and, on the other hand, that some rearrangements can arise in these neural networks depending on the type of information processed.