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Lore Thaler, Melvyn A. Goodale; The Allocentric Brain in Action. Journal of Vision 2011;11(11):939. doi: https://doi.org/10.1167/11.11.939.
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© ARVO (1962-2015); The Authors (2016-present)
The current study investigated which brain areas are involved in allocentric (scene-based) as compared to egocentric (viewer-based) coding for visually guided hand movements. Using an fMRI block-design, we scanned the brains of 14 subjects while they performed hand movements in either egocentric or allocentric tasks. Using a whole brain analysis we found that performance in both tasks elicited reliable BOLD signals in a sensorimotor network encompassing occipito-temporal, parietal and frontal cortices and the cerebellum. Contrasting BOLD between egocentric and allocentric tasks revealed that the allocentric task led to an increase in BOLD signals in portions of the sensorimotor network, in particular the fundus of the left intraparietal sulcus (IPS), posterior right IPS and bilateral dorsal premotor cortex (PMd). The comparison also showed that the allocentric task led to an increase in BOLD in ventral visual stream areas in lateral occipital cortex (LO) and the fusiform gyrus (FFG) that were separate from the sensorimotor network. We did not find activity specific for the egocentric task. The finding that ventral-occipital areas were recruited during the allocentric, but not the egocentric task, is consistent with neuropsychological data that link the integrity of these areas to successful performance in allocentric movement tasks. The data therefore suggest that areas LO and FFG are essential for the processing of visual information in a scene-based reference frame during visually guided movements. In contrast, activity in the IPS has been linked to the representation of magnitude and visual-spatial processing, and activity in PMd has been linked to the representation and selection of movement parameters. Thus an increase in activity in those areas during the allocentric task might suggest that, compared to the egocentric task, the allocentric task places a higher load on mechanisms that transform visual information about extent and spatial layout into movement parameters.
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