ELECTROPHYSIOLOGICAL ANALYSIS OF THE REGISTRATION, STORAGE AND RETRIEVAL OF INFORMATION IN DELAYED MATCHING FROM SAMPLES

Brain processes of registration, storage in working memory and retriev al of different kinds of information were studied by analysis of EEG a nd ERP activity recorded during two delayed matches from sample tasks: (1) matching the digits in two series of six numbers, and (2) matchin g the sums of the same two series of six numbers. Each trial was compo sed of six intervals continuing six equally spaced visual stimuli: (1) control - observing a series of six fixation points, P1, on a compute r monitor; (2) priming - viewing a series, S-1, of six numbers; (3) de lay - observing a second series of six fixation points, P2; (4) matchi ng - viewing a second series, S-2, of six numbers; (5) response select ion - selecting the left button to press if S-1 contained all the item s in S-2 or the right button if any item appeared only in S-2, while o bserving six fixation points; (6) feedback - six color coded fixation points indicate correct or error. Each interval was 4 s in duration an d 20 trials were presented in each task. During each interval the visu al field flickered at a tracer frequency of 1.5/s, whether numbers or fixation points were on the monitor screen, Very narrow band power spe ctra (VNB), ERPs elicited by presentation of S-1 or S-2 information it ems, and non-contingent probes (NCP) elicited by presentation of fixat ion points were used to trace the processing of information by neural populations activated by the visual stimulation. Global field power ma xima identified latencies at which functional landscapes were analyzed . VNB, ERP, NCP and landscape differences were found between digits an d sums. However, though these differences were highly significant with in each subject (p<0.001), no consistency was found across individuals for the electrophysiological changes during the tasks. This suggests that utilization of brain resources in cognition varies greatly with i ndividual cognitive styles and strategies.