The effect of stimulus rate and task requirements on hemispheric differences in the processing of serial nonverbal stimuli

In this experiment, functional differences of left (LH) and right hemisphere (RH) in temporal coding for serial nonverbal stimuli were examined in three different memory tasks. The pairs of nonsense shapes were presented, one in left (LVF) and another in right visual field (RVF), successively at three different presentation rate. After the list, to-be-judged items were presented, and subjects were required to judge on (a) whether or not these items were presented in the list (recognition task), (b) serial position in the list (order judgments), or (c) relative recency of two items (recency judgments). In recognition task, in which the processing and retention of order information of each item was not necessary, the reaction time to items presented in RVF were longer than those to items in LVF. In contrast, both the number of correct response and the reaction time showed RVF/LH superiority in the order judgment task that required precise order information. These results suggest that LH and RH were different in temporal coding for serial nonverbal stimuli, and that its difference implicated how differently LH and RH responded to temporal aspects of information