title: Functional versus effector-specific organization of the human posterior parietal cortex: revisited.
abstract: It has been proposed that the posterior parietal cortex (PPC) is characterized by an effector-specific organization. However, strikingly similar functional MRI (fMRI) activation patterns have been found in the PPC for hand and foot movements. Because the fMRI signal is related to average neuronal activity, similar activation levels may result either from effector-unspecific neurons or from intermingled subsets of effector-specific neurons within a voxel. We distinguished between these possibilities using fMRI repetition suppression (RS). Participants made delayed, goal-directed eye, hand, and foot movements to visual targets. In each trial, the instructed effector was identical or different to that of the previous trial. RS effects indicated an attenuation of the fMRI signal in repeat trials. The caudal PPC was active during the delay but did not show RS, suggesting that its planning activity was effector independent. Hand and foot-specific RS effects were evident in the anterior superior parietal lobule (SPL), extending to the premotor cortex, with limb overlap in the anterior SPL. Connectivity analysis suggested information flow between the caudal PPC to limb-specific anterior SPL regions and between the limb-unspecific anterior SPL toward limb-specific motor regions. These results underline that both function and effector specificity should be integrated into a concept of PPC action representation not only on a regional but also on a fine-grained, subvoxel level.
authors.affiliation: Biological Psychology and Neuropsychology, University of Hamburg, Hamburg, Germany; and Biological Psychology and Cognitive Neuroscience, Bielefeld University, Bielefeld, Germany tobias.heed@uni-bielefeld.de.
authors.forename: Tobias
authors.identifier: 0000-0001-5632-6091
authors.initials: T
authors.lastname: Heed
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Frank T M
authors.initials: FT
authors.lastname: Leone
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: Ivan
authors.identifier: 0000-0003-0936-3601
authors.initials: I
authors.lastname: Toni
authors.affiliation: Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors.forename: W Pieter
authors.initials: WP
authors.lastname: Medendorp
mesh_terms: D000328:Adult; D001931:Brain Mapping; D053483:Eye Movement Measurements; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology*; D006040:Goals; D006225:Hand / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009434:Neural Pathways / Q000000981:diagnostic imaging / Q000502:physiology; D009483:Neuropsychological Tests; D010296:Parietal Lobe / Q000000981:diagnostic imaging / Q000502:physiology*; D011930:Reaction Time; D055815:Young Adult
keywords: cortical organization; foot; parietal cortex; pointing; sensorimotor processing