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Where bottom-up meets top-down: neuronal interactions during perception and imagery
Andrea Mechelli1, Cathy J Price, Karl J Friston
1Wellcome Department of Imaging Neuroscience, Institute of Neurology, 12 Queen Square, London, WC1N 3BG, UK. andream@fil.ion.ucl.ac.uk
Cerebral Cortex (New York, N.Y. : 1991)
|June 12, 2004
Summary
Brain imaging reveals distinct neural pathways for visual perception versus imagery. Perception relies on bottom-up signals, while imagery uses top-down signals, showing task-dependent brain connectivity.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Neuroimaging
Background:
- Functional magnetic resonance imaging (fMRI) studies show category-selective regions in the ventral occipito-temporal cortex for faces and objects.
- The roles of bottom-up and top-down mechanisms in modulating these activations are not fully understood.
Purpose of the Study:
- To investigate neuronal interactions between occipito-temporal, parietal, and frontal regions during visual perception and imagery.
- To differentiate the roles of bottom-up and top-down mechanisms in category-selective brain activation.
Main Methods:
- Combined fMRI with dynamic causal modelling (DCM).
- Examined neural connectivity during visual perception and visual imagery tasks.
- Utilized stimuli including faces, houses, and chairs.
Main Results:
- Visual perception of categories is driven by bottom-up, content-sensitive forward connections from early visual areas.
- Visual imagery involves top-down, content-sensitive backward connections from the prefrontal cortex.
- Parietal cortex shows content-unrelated connectivity during both perception and imagery, suggesting a role in mental image maintenance.
Conclusions:
- Neuronal interactions are task- and stimulus-dependent.
- Sensory representations are mediated by bottom-up mechanisms during perception and top-down mechanisms during imagery.
- Non-selective top-down processes from parietal areas contribute to mental imagery generation and maintenance.