Task-induced deactivation identified by SPM and Group Independent Component Analysis

Task-induced deactivation (TID) refers to some regional decrease in blood oxygenation level-dependent (BOLD) signal during a cognitive task compared to a baseline. Several functional imaging studies have found co-activation in a distributed network cortical regions, including ventral anterior cingulate cortex (vACC) and posterior cingulate cortex (PPC) that characterizes the default mode of human brain. This founding led to a hypothesis that these regions constitute a network supporting a TID mode network of brain function. In this study, two complementary methods, one applying the general linear model and the other a data driven approach called group independent component analysis (ICA), were utilized to analyze the fMRI data obtained two tasks, Chinese verb generation and the English noun word reading. Both methods yielded similar, but not identical, results and detected a network of robustly activated some midline regions including anterior and posterior cingulate cortex and precuneus. However, the ICA method segregated functional elements into two separate maps and identified ventral cingulate component and a fronto-parietal component. The results suggest that these two components in tasks induced deactivation might be linked to different mental function and play a significant role during "resting" or "passive" baseline.