OS_35. Executive control
Sunday, October 02nd, 2011 [15:40 - 16:40]
OS_35.1 - Is awarness needed to achieve (partial) error cognitive control?
Rochet, N. , Casini, L. , Thierry, H. & Burle, B.
Laboratoire de Neurobiologie de la Cognition, Universite de provence/CNRS ,Marseille,France
In conflicting situations, incorrect responses tend to be activated. Subjects consciously and reliably detect suprathreshold activations leading to error commission (>90%). However, electromyographic recording in such tasks reveal that most of the incorrect activations remain subtreshold. In such trials, the subliminal activations were interrupted and corrected, revealing the involvement of cognitive control mechanisms. The question as to whether those subliminal incorrect activations are consciously perceived remains an important open issue since it has been argued that cognitive control processes require conscious experience. Awareness of incorrect response activation was assessed by asking the participants, after every trial, to report how confident they were to have activated the incorrect response. Signal Detection Theory was used to characterise subject detection performance. Mean d' and beta were high, indicating that subjects were able to detect their partial errors, but reported such detection only when they were certain. Furthermore, subjects took longer to correct detected incorrect activations. The amplitude of incorrect EMG activation correlates with subjects detection. This suggests that subjects are aware of having produced an incorrect motor command and that awareness delays correction. In most cases, cognitive processes implicated in partial error control remain unconscious.
OS_35.2 - Dissociating top-down and bottom-up influences on intentional decisions within the medial prefrontal cortex
Demanet, J. 1 , De Baene, W. 1 , Arrington, C. C. 2 & Brass, M. 1
1 Ghent University
2 Lehigh University
The question how top-down and bottom-up inlfuences of intentional decisions are implemented in the brain has never been systematically investigated. By combining voluntary task switching with functional magnetic resonance imaging, we investigated the involvement of the median pre-frontal cortex (PFC) in both components of intentional control. A bottom-up bias was established in a training phase by associating a subset of stimuli with one task and another subset of stimuli with another task. By comparing voluntary task choices that are compatible (stronger bottom-up component) or incompatible (stronger top-down component) to the stimulus-induced bias, we were able to capture the brain circuits related to both components. The imaging results showed evidence for a functional dissociation within the median PFC, with the rostral cingulate zone more involved in the top-down component and the ventro-median PFC (vmPFC) more involved in the bottom-up component. Especially the involvement of the vmPFC in intentional control is an intriguing finding because it suggests that this region may be hosting implicit processes that are responsible for the formation of intentions.
OS_35.3 - Top-down vs. bottom-up: When instructions overcome automatic retrieval
Kiesel, A. 1 , Waszak, F. 2 & Pfister, R. 1
1 University of Wuerzburg
2 University Paris Descartes & CNRS
Research on human action has extensively covered controlled and automatic processes in the transformation of stimulus information into motor action, and how conflict between both systems is solved. However, the question of whether automatic S-R translation per se depends on top-down control states has received comparatively little attention. The present study addressed this issue by manipulating top-down control state (instructed S-R mapping) and automatic bottom-up processing (retrieval of S-R memory traces) independently from each other. Using a color/shape task-switching paradigm, we compared cross-talk triggered by distractor stimuli, for which the instructed S-R mapping and the S-R associations compiled at the beginning of the experiment matched, with the cross-talk triggered by distractor stimuli, for which (re)instructed mapping and compiled S-R associations did not match. The results show that the latter kind of distractors did not yield any cross-talk at all, demonstrating that automatic S-R retrieval only takes place if the S-R associations concur with the currently valid S-R mapping.