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Published on: August 1, 2018
Functional rather than effector-specific organization of human posterior parietal cortex.
Tobias Heed1, Sabine M Beurze, Ivan Toni
1Biological Psychology and Neuropsychology, Department of Psychology, University of Hamburg, 20146 Hamburg, Germany. tobias.heed@uni-hamburg.de
Summary
The posterior parietal cortex (PPC) does not strictly separate eye and limb movement planning. Instead, its organization reflects computational differences between planning eye versus limb movements.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Neuroimaging
Background:
- Previous studies suggest the posterior parietal cortex (PPC) has modular, effector-specific organization for eye and hand movements.
- The unique functional and spatial requirements of eye movements may lead to specialized PPC subregions.
- Limb movements might show less distinct organization within the PPC compared to eye movements.
Purpose of the Study:
- To investigate the organization of the posterior parietal cortex (PPC) for planning movements of different effectors (eyes, hands, feet).
- To determine if the PPC exhibits effector-specific or a more generalized organization for movement planning.
- To compare brain activity patterns during memory-guided eye, hand, and foot movements using functional magnetic resonance imaging (fMRI).
Main Methods:
- Functional magnetic resonance imaging (fMRI) was employed to measure brain activity.
- Participants performed memory-guided eye, hand, and foot movements.
- Analysis focused on comparing activation patterns within the PPC across different effector movements.
Main Results:
- No significant activation differences were found in the PPC for planning hand versus foot movements, except in anterior PPC (BA 5, extending to BA 7/40) showing a lateral-to-medial gradient.
- Limb-unspecific PPC regions showed functional connectivity with hand and foot motor areas.
- A gradient-like organization was observed across the PPC for planning eye versus limb movements, with saccade planning activating occipitoparietal regions and limb movements activating superior parietal lobule regions more.
Conclusions:
- The posterior parietal cortex (PPC) does not exhibit a strict effector-specific organization for movement planning.
- The large-scale organization of the PPC appears to be influenced by the distinct computational demands of planning eye versus limb movements.
- Findings suggest a more nuanced understanding of PPC functional organization beyond simple modularity.
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