ラットにおける間隔二等分課題の反応潜時

Interval timing, whose range is from a second to several minutes among the sense with respect to time, is related with feeding behavior, decision making and time estimation of animals. In this study, we used interval bisection task, which is a method for examining this interval timing quantitatively. First, rats learned left and right lever pressing associated with the tone stimuli of 2 seconds and 8 seconds for each. Second, probe stimulus tones (e. g. 2.5, 3.2, 4, 5, 6.4 seconds) were presented, and we observed which lever rats selected. When the proportion of the lever pressing associated with the 8 seconds tone is 50%, the point of subjective equality (PSE) can be obtained. The PSE is an indicator of decision making in time perception. In order to investigate whether the difference in the physical properties of the stimulus affects the time perception, we used two kinds of tones, a continuous tone and a 4 Hz pulse tone. The results suggest that the difference in physical properties between continuous tone and 4 Hz pulse tone does not affect time perception. As another index, response latency of lever pressing for each tone presented in the task was calculated. As a result, at the testing stage, a peak in a distribution of response latency was around 3.2 seconds or 4 seconds of probe stimulus. The durations of the peak was similar to PSE. From these results, it was suggested that response latency is an important indicator in decision making of which lever selected.