Two Distinct Neural Mechanisms for Category-selective Responses

The cognitive and neural mechanisms mediating category-selective responses in the human brain remain controversial. Using functional magnetic resonance imaging and effective connectivity analyses (Dynamic Causal Modelling), we investigated animal- and tool-selective responses by manipulating stimulu...

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Bibliographic Details
Published in:Cerebral cortex (New York, N.Y. 1991) N.Y. 1991), 2006-03, Vol.16 (3), p.437-445
Main Authors: Noppeney, Uta, Price, Cathy J., Penny, Will D., Friston, Karl J.
Format: Article
Language:English
Subjects:
Adult
Brain Mapping - methods
category selectivity
Cerebral Cortex - physiology
Computer Simulation
dynamic causal modelling
effective connectivity
Female
functional imaging
Humans
Male
Models, Neurological
Nerve Net - physiology
Neural Pathways - physiology
semantic memory
Speech Perception - physiology
Visual Perception - physiology
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Summary:The cognitive and neural mechanisms mediating category-selective responses in the human brain remain controversial. Using functional magnetic resonance imaging and effective connectivity analyses (Dynamic Causal Modelling), we investigated animal- and tool-selective responses by manipulating stimulus modality (pictures versus words) and task (implicit versus explicit semantic). We dissociated two distinct mechanisms that engender category selectivity: in the ventral occipito-temporal cortex, tool-selective responses were observed irrespective of task, greater for pictures and mediated by bottom-up effects. In a left temporo-parietal action system, tool-selective responses were observed irrespective of modality, greater for explicit semantic tasks and mediated by top-down modulation from the left prefrontal cortex. These distinct activation and connectivity patterns suggest that the two systems support different cognitive operations, with the ventral occipito-temporal regions engaged in structural processing and the dorsal visuo-motor system in strategic semantic processing. Consistent with current semantic theories, explicit semantic processing of tools might thus rely on reactivating their associated action representations via top-down modulation. In terms of neuronal mechanisms, the category selectivity may be mediated by distinct top-down (task-dependent) and bottom-up (stimulus-dependent) mechanisms.
ISSN:1047-3211
1460-2199
DOI:10.1093/cercor/bhi123