Behavioural relevance modulates access to spatial working memory in humans

Neurophysiological studies in monkeys suggest selective representation of b ehaviourally relevant information in working memory. So far, no behavioural evidence for this has been reported for humans. Here, we investigated the role of behavioural relevance for access to human visuospatial working memo ry by using delayed oculomotor response tasks. Subjects were presented two successive visual cues in different and unpredictable locations while fixat ing on a central fixation point. After a delay, an unpredictable auditory s ignal (one beep or two beeps) sounded and the central fixation point was tu rned off, initiating the oculomotor response (i.e. memory-guided saccade) p hase. Two groups of 10 subjects each were studied in two conditions: in the 'relevant' condition, subjects were instructed to memorize both visual cue s and to move the eyes to the remembered position of the first cue (one bee p) or the second cue (two beeps). The same stimuli were used in the 'irrele vant' condition, but subjects were instructed to memorize and move the eyes to the position of the first cue only, regardless of the second cue and th e auditory signal. In the 'relevant' condition, we found a significant incr ease in errors of memory-guided saccades to the first cue, when the second cue was located between central fixation point and first cue. This spatiall y selective interference effect disappeared in the 'irrelevant' condition, despite identical stimuli. On a behavioural level, these results show for t he first time the significance of behavioural relevance for access to human spatial working memory. These findings complement recent single-neuron stu dies in monkeys, showing that the neuronal substrates of working memory sel ectively represent behaviourally relevant perceptual information.