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Diana Tonin, Vincenzo Romei, Rachel Lambert, Andre Bester, Janak Saada, Stephanie Rossit; The causal role of the lateral occipital (LO) cortex and anterior intraparietal sulcus (aIPS) in real and pantomimed grasping: an fMRI-guided TMS study. Journal of Vision 2017;17(10):14. doi: https://doi.org/10.1167/17.10.14.
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© ARVO (1962-2015); The Authors (2016-present)
Milner and Goodale (1995) propose a model of vision that makes a distinction between vision for perception and vision for action. One strong claim of this model is that the visual processing of objects for real grasping depends on dorsal stream areas whereas the processing of objects for pantomimed actions depends on the ventral stream regions. However, and even more that 20 years after its formulation, this claim is largely based on a single-case neuropsychological study: visual form agnosic patient DF can scale her grip aperture to different object sizes during real visually-guided grasping, but her grip scaling is impaired when performing pantomimed grasping in a location adjacent to these same objects. Here we used fMRI-guided transcranial magnetic stimulation (TMS) to shed light on the specific role of the lateral occipital (LO) cortex, a key ventral stream area in object perception, and the anterior intraparietal sulcus (aIPS), a key dorsal stream region in grip scaling, in real and pantomimed grasping. We applied theta burst TMS over left aIPS, left LO or vertex in three separate sessions before 16 participants performed real object grasping and pantomimed grasping in an adjacent location to the presented object. Grasping movements were performed in open loop with the right-hand in response to 3D Efron blocks presented in the right visual field. For real grasping, TMS over aIPS significantly weakened the relationship between object size and grip aperture when compared to TMS over LO and TMS over vertex, whereas TMS over LO had no effects. For pantomimed grasping, TMS over both aIPS and LO considerably reduced the relationship between object size and grip aperture when compared to vertex stimulation. Our results show that while aIPS is causally involved in grip scaling for both real and pantomime grasping, LO is only involved in pantomimed grasping.
Meeting abstract presented at VSS 2017
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