Journal
NEUROIMAGE
Volume 29, Issue 4, Pages 1185-1191Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.neuroimage.2005.09.030
Keywords
fMRI; task-induced deactivation; resting state processing; task-unrelated thoughts; task difficulty
Funding
- NCRR NIH HHS [M01 RR000058, M01 RR00058] Funding Source: Medline
- NIMH NIH HHS [P01 MH051358, P0 MH51358] Funding Source: Medline
- NINDS NIH HHS [R01 NS33576, R01 NS033576] Funding Source: Medline
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In functional neuroimaging, a local decrease in blood flow during an active task, relative to a resting baseline, is referred to as task-induced deactivation (TID). TID may occur when resources shift from ongoing, internally generated processing typical of resting states to processing required by an exogenous task. We previously found specific brain regions in which TID increased as task processing demands increased. When engaged in an exogenous cognitive task, reallocation of resources from areas involved in internal processing should result in suspension of that processing. Self-reported thought content has been used as an indicator of the extent of internal processing activity. We investigated the relationship between TID and task-unrelated thought (TUT) frequency using an auditory target detection task with seven levels of task difficulty. At varied intervals during task performance, subjects indicated whether they were experiencing a TUT. We expected TUT frequency to decrease as task demands increased and for this pattern to correlate with TID magnitude across conditions. Generally, fewer TUTs were reported during difficult task conditions than during easier conditions. As TID magnitude increased across task conditions, the frequency of TUTs declined (r = 0.90, P = 0.005). Four left hemisphere regions (posterior parieto-occipital cortex, anterior cingulate gyros, fusiform gyrus, and middle frontal gyros) showed strong relationships between TUTs and TID (r > 0.79, P < 0.05 corrected). As these regions have been implicated in semantic processing and self-referential thought, the findings support the suspension of internal cognitive processing as one mechanism for TID. (c) 2005 Elsevier Inc. All rights reserved.
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