Effects of working memory demands on frontal slow waves in time-interval reproduction tasks in humans

Very few studies have examined the event-related potentials associated with the retention of temporal information for later use. In the present experiment, event-related potentials were recorded during two duration reproduction tasks in which a delay was introduced between the encoding and the reproduction phases. Furthermore, working memory demands were varied during the delay (number of durations to be memorized and degree of manipulation of the durations). These variables had no significant effect on the amplitude of the contingent negative variation observed during duration encoding. By contrast, the amplitude of the slow wave recorded over middle frontal regions during the delay increased with working memory demands, which confirms the key role played by these frontal regions in the cognitive processes engaged during the retention of duration in working memory.