title: Allocentric coding in ventral and dorsal routes during real-time reaching: Evidence from imaging-guided multi-site brain stimulation.
abstract: Recent evidence has revealed an advantage for movements to last target positions in a structured visual display, suggesting a mediating role of allocentric, in addition to egocentric, information in goal-directed reaching. This notion is accommodated by the recently updated perception-action model (Milner and Goodale, 2008), which postulates functional roles of ventral and dorsal neural areas in allocentric coding. In the present study, we used imaging-guided multi-site continuous theta burst stimulation (cTBS) over regions of the ventral and dorsal processing streams to unravel their functional contribution on visually guided reaching in two display conditions: the "egocentric" condition where the target appeared in an empty display and the "allocentric" condition where the target appeared in a structured display with placeholders marking possible target locations. Cortical sites for cTBS were identified individually for each participant via coregistration with magnetic resonance scans. Results indicated that cTBS in the egocentric condition did not affect movement time, but cTBS in the allocentric condition modulated movement time contingent on stimulation site and target position. In particular, cTBS over the lateral occipital cortex (part of the ventral stream) and over the angular gyrus (part of the dorsal stream) eliminated the last-target advantage by slowing down reaching to the salient last target position. cTBS over the superior parietal occipital cortex did not affect the last-target advantage. These outcomes provide the first causal evidence for allocentric coding in ventral and dorsal routes during real-time reaching, thereby supporting the updated perception-action model.
authors.affiliation: Faculty of Health, Medicine and Life Sciences, Maastricht University, The Netherlands. Electronic address: jos.adam@maastrichtuniversity.nl.
authors.forename: J J
authors.initials: JJ
authors.lastname: Adam
authors.affiliation: Faculty of Health, Medicine and Life Sciences, Maastricht University, The Netherlands.
authors.forename: T J H
authors.initials: TJ
authors.lastname: Bovend'Eerdt
authors.affiliation: Faculty of Psychology and Neuroscience, Maastricht University, The Netherlands; Maastricht Brain Imaging Center, Maastricht, The Netherlands.
authors.forename: Teresa
authors.initials: T
authors.lastname: Schuhmann
authors.affiliation: Faculty of Psychology and Neuroscience, Maastricht University, The Netherlands; Maastricht Brain Imaging Center, Maastricht, The Netherlands.
authors.forename: A T
authors.initials: AT
authors.lastname: Sack
mesh_terms: D000328:Adult; D001132:Arm / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009778:Occipital Lobe / Q000033:anatomy & histology / Q000502:physiology*; D010296:Parietal Lobe / Q000033:anatomy & histology / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation / Q000379:methods; D055815:Young Adult
keywords: Allocentric; Dorsal stream; Egocentric; Frames of reference; Reaching; Ventral stream