Conceptual Processing during the Conscious Resting State: A Functional MRI Study

Abstract

Localized, task-induced decreases in cerebral blood flow are a frequent finding in functional brain imaging research but remain poorly understood. One account of these phenomena postulates processes ongoing during conscious, resting states that are interrupted or inhibited by task performance. Psychological evidence suggests that conscious humans are engaged almost continuously in adaptive processes involving semantic knowledge retrieval, representation in awareness, and directed manipulation of represented knowledge for organization, problem-solving, and planning. If interruption of such 'conceptual' processes accounts for task-induced deactivation, tasks that also engage these conceptual processes should not cause deactivation. Furthermore, comparisons between conceptual and nonconceptual tasks should show activation during conceptual tasks of the same brain areas that are 'deactivated' relative to rest. To test this model, functional magnetic resonance imaging data were acquired during a resting state, a perceptual task, and a semantic retrieval task. A network of left-hemisphere polymodal cortical regions showed higher signal values during the resting state than during the perceptual task but equal values during the resting and semantic conditions. This result is consistent with the proposal that perceptual tasks interrupt processes ongoing during rest that involve many of the same brain areas engaged during semantic retrieval. As further evidence for this model, the same network of brain areas was activated in two direct comparisons between semantic and perceptual processing tasks. This same 'conceptual processing' network was also identified in several previous studies that contrasted semantic and perceptual tasks or resting and active states. The model proposed here offers a unified account of these findings and may help to explain several unanticipated results from prior studies of semantic processing.

Meta‐analyses of object naming: Effect of baseline

“…Our object-naming meta-analysis confirmed this prediction, but also revealed areas where activation was observed more when the baseline was high than when it was low. Although this reverse effect was less expected, it is consistent with the findings of Binder et al [1999], who demonstrated that resting baselines activate areas associated with semantic relative to phonological tasks.…”

“…For example, baselines that require subjects to say "OK" to meaningless visual stimuli may increase demands on working memory and executive task processes while decreasing attention to perceptual processing. Likewise, there may be unpredicted processing that occurs during low-level baselines more than that during high-level baselines [Binder et al, 1999]. Our comparison of high-and low-level baselines might then reveal activation in unexpected regions.…”

Auditory processing abnormalities in schizotypal personality disorder: An fMRI experiment using tones of deviant pitch and duration

“…Unfortunately, in fMRI aberrant activation patterns can result from subtraction. These areas of unusual activation may reflect "spontaneous neuronal activity", that is, areas not predicted by task demands, which cannot be experimentally controlled (Binder et al, 1999). A mismatch task is not cognitively demanding, in fact it is arguably pre-attentive (Naatanen 1990), possibly allowing for more "task-unrelated thoughts" (Binder et al, 1999).…”

“…These areas of unusual activation may reflect "spontaneous neuronal activity", that is, areas not predicted by task demands, which cannot be experimentally controlled (Binder et al, 1999). A mismatch task is not cognitively demanding, in fact it is arguably pre-attentive (Naatanen 1990), possibly allowing for more "task-unrelated thoughts" (Binder et al, 1999). These "task-unrelated thoughts" can result in changes in blood flow detected by BOLD method (Binder et al, 1999).…”

“…A mismatch task is not cognitively demanding, in fact it is arguably pre-attentive (Naatanen 1990), possibly allowing for more "task-unrelated thoughts" (Binder et al, 1999). These "task-unrelated thoughts" can result in changes in blood flow detected by BOLD method (Binder et al, 1999). In fact, the hemodynamic effect of such thoughts using the subtraction method has been demonstrated in a tone task (Binder et al, 1999).…”