抄録
We recorded single-cell activity from lateral frontal cortex of a rhesus monkey discriminating relative durations and distances. In the duration task, two different visual stimuli appeared sequentially at the monkey's fixation point (screen center), each followed by a delay period (D1 after the first stimulus and D2 after the second). Stimulus durations ranged from 50 ms to 3.2 s. After D2, the two stimuli appeared simultaneously,one to the left and one to the right of screen center. To receive a reward, the monkey had to choose the stimulus that had persisted longer in its initial presentation. In the distance task, the two stimuli appeared sequentially at different distances from screen center, one above and one below it. Matching the duration task, the stimuli later appeared simultaneously, and the monkey had to choose the stimulus that had been located farther from the center. We used one-way ANOVA (p<0.05) on neuronal activity during the first 400 ms of D2, with relative duration or distance as the factor. In the duration task, 21% of 182 neurons encoded relative duration: shorter and longer in roughly equal numbers. In the distance task, 21% of 312 neurons encoded relative distance from screen center: nearer and farther in roughly equal numbers. For 37 significant neurons studied in both tasks, 12 encoded only relative duration, 19 only relative distance, and 6 both. These findings indicate that during comparative judgments, frontal neurons can contribute to decisions about relative magnitude in both the spatial and temporal domains. [J Physiol Sci. 2007;57 Suppl:S25]
