Publications (2)13.09 Total impact
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Article: Unconscious priming instructions modulate activity in default and executive networks of the human brain.
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ABSTRACT: During task executions, brain activity increases in executive networks (ENs) and decreases in default-mode networks (DMNs). Here, we examined whether these large-scale network dynamics can be influenced by unconscious cognitive information processing. Volunteers saw instructions (cues) to respond either ipsilaterally or contralaterally to a subsequent lateralized target. Unbeknownst to them, each cue was preceded by a masked stimulus (prime), which could be identical (congruent), or opposite (incongruent) to the cue, or neutral (not an instruction). Behaviorally, incongruent primes interfered with performance, even though they were not consciously perceived. With functional magnetic resonance imaging, we individuated the anticorrelated ENs and DMNs involved during task execution. With effective connectivity analyses, we found that DMNs caused activity in ENs throughout the task. Unconscious interference during incongruent trials was associated with a specific activity increase in ENs and an activity drop in DMNs. Intersubject efficiency in performance during incongruent trials was correlated with functional connectivity between specific ENs and DMNs. These results indicate that unconscious instructions can prime activity in ENs and DMNs and suggest that the DMNs play a key role in unconscious monitoring of the environment in the service of efficient resource allocation for task execution.Cerebral Cortex 06/2011; 22(3):639-49. · 6.54 Impact Factor -
Article: A neuronal basis for task-negative responses in the human brain.
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ABSTRACT: Neuroimaging studies have revealed a number of brain regions that show a reduced blood oxygenation level-dependent (BOLD) signal during externally directed tasks compared with a resting baseline. These regions constitute a network whose operation has become known as the default mode. The source of functional magnetic resonance imaging (fMRI) signal reductions in the default mode during task performance has not been resolved, however. It may be attributable to neuronal effects (neuronal firing), physiological effects (e.g., task vs. rest differences in respiration rate), or even increases in neuronal activity with an atypical blood response. To establish the source of signal decreases in the default mode, we used the calibrated fMRI method to quantify changes in the cerebral metabolic rate of oxygen (CMRO₂) and cerebral blood flow (CBF) in those regions that typically show reductions in BOLD signal during a demanding cognitive task. CBF:CMRO₂ coupling during task-negative responses were linear, with a coupling constant similar to that in task-positive regions, indicating a neuronal source for signal reductions in multiple brain areas. We also identify, for the first time, two modes of neuronal activity in this network; one in which greater deactivation (characterized by metabolic rate reductions) is associated with more effort and one where it is associated with less effort.Cerebral Cortex 04/2011; 21(4):821-30. · 6.54 Impact Factor
