comparison of the choice effect and the distance effect in a number-comparison task by fmri比较选择效应和距离效应的fmri number-comparison任务.pdf

Comparison of the Choice Effect and the Distance Effect in a Number-Comparison Task by fMRI 1 2 3 1 Yousuke Ogata *, Takahiro Horaguchi , Noriya Watanabe , Miyuki Yamamoto 1 Comprehensive Human Science, University of Tsukuba, Tsukuba, Ibaraki, Japan, 2 Physiology, Center for Medical Science, Ibaraki Prefectural University of Health Science, Inashiki, Ibaraki, Japan, 3 Graduate School of Engineering, Tamagawa University, Tokyo, Japan Abstract Behavioral and neurophysiological studies of numerical comparisons have shown a ‘‘distance effect,’’ whereby smaller numerical distances between two digits are associated with longer response times and higher activity in the parietal region. In this experiment, we introduced a two-choice condition (between either the smaller/lower or the larger/higher of two digits) and examined its effect on brain activity by fMRI. We observed longer response times and greater activity with the choice of smaller numbers (‘‘choice effect’’) in several brain regions including the right temporo–parietal region, (pre)cuneus, superior temporal sulcus, precentral gyrus, superior frontal gyrus, bilateral insula, and anterior cingulate cortex. These regions correspond to areas that have been suggested to play a role in attentional shift and response conflict. However, brain activity associated with the distance effect disappeared even though the behavioral distance effect remained. Despite the absence of the distance effect on brain activity, several areas changed activity in relation to response time, including regions that were reported to change activity in both a distance effect and a reaction-time-related manner. The result suggested that