Please use this identifier to cite or link to this item: http://hdl.handle.net/1893/23177
Appears in Collections:Psychology Journal Articles
Peer Review Status: Refereed
Title: Perceptual decisions regarding object manipulation are selectively impaired in apraxia or when tDCS is applied over the left IPL
Authors: Evans, Carys
Edwards, Martin G
Taylor, Lawrence
Ietswaart, Magdalena
Contact Email: magdalena.ietswaart@stir.ac.uk
Keywords: Perception and action
Apraxia
left inferior parietal lobe
dorsal and ventral streams
motor imagery
object manipulation
Issue Date: Jun-2016
Citation: Evans C, Edwards MG, Taylor L & Ietswaart M (2016) Perceptual decisions regarding object manipulation are selectively impaired in apraxia or when tDCS is applied over the left IPL, Neuropsychologia, 86, pp. 153-166.
Abstract: This study evaluated whether apraxia can be understood as due to impaired motor representations or motor imagery necessary for appropriate object-use, imitation, and pantomime. The causal role of the left inferior parietal lobe (IPL), which is heavily implicated in apraxia, is also evaluated. These processes are appraised in light of the proposed ventro-dorsal sub-stream of the classic two visual pathway model, where perceptual information from the ventral stream and the dorsal action stream are integrated and essential for object manipulation. Using a task assessing object-use perception, stroke patients with apraxia demonstrated a selective deficit during perceptual decisions reliant on the integration of visible and known object properties to select the appropriate grasp for object-use. This deficit increased with apraxia severity. A dissociation was evident in these patients showing intact non-motoric perceptual decisions regarding the functional semantic relationship between two objects in the absence of the actor (e.g. how a hammer hits a nail). Converging evidence was found using a modified version of the same task in a neuromodulation study that directly targeted the left IPL in healthy participants using transcranial direct current stimulation (tDCS). Application of inhibitory stimulation over the left IPL reduced performance during perceptual decisions regarding object manipulation whilst performance was unaffected during functional semantic decisions. Excitatory stimulation of the left IPL did not affect performance in either task. Combined, these results suggest that the left inferior parietal lobe is critical for motor imagery, and that apraxia may be caused by an inability to use internal motor representations of object manipulation. These results are discussed in terms of motoric and non-motoric perceptual processes and the proposal of an additional ventro-dorsal sub-stream within the dorsal and ventral visual pathways model.
DOI Link: http://dx.doi.org/10.1016/j.neuropsychologia.2016.04.020
Rights: This item has been embargoed for a period. During the embargo please use the Request a Copy feature at the foot of the Repository record to request a copy directly from the author. You can only request a copy if you wish to use this work for your own research or private study. Accepted refereed manuscript of: Evans C, Edwards MG, Taylor L & Ietswaart M Perceptual decisions regarding object manipulation are selectively impaired in apraxia or when tDCS is applied over the left IPL, Neuropsychologia, 86, pp. 153-166. DOI: 10.1016/j.neuropsychologia.2016.04.020 © 2016, Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/

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