title: Training transfers the limits on perception from parietal to ventral cortex.
abstract: Visually guided behavior depends on (1) extracting and (2) discriminating signals from complex retinal inputs, and these perceptual skills improve with practice. For instance, training on aerial reconnaissance facilitated World War II Allied military operations; analysts pored over stereoscopic photographs, becoming expert at (1) segmenting pictures into meaningful items to break camouflage from (noisy) backgrounds, and (2) discriminating fine details to distinguish V-weapons from innocuous pylons. Training is understood to optimize neural circuits that process scene features (e.g., orientation) for particular purposes (e.g., judging position). Yet learning is most beneficial when it generalizes to other settings and is critical in recovery after adversity, challenging understanding of the circuitry involved. Here we used repetitive transcranial magnetic stimulation (rTMS) to infer the functional organization supporting learning generalization in the human brain. First, we show dissociable contributions of the posterior parietal cortex (PPC) versus lateral occipital (LO) circuits: extracting targets from noise is disrupted by PPC stimulation, in contrast to judging feature differences, which is affected by LO rTMS. Then, we demonstrate that training causes striking changes in this circuit: after feature training, identifying a target in noise is not disrupted by PPC stimulation but instead by LO stimulation. This indicates that training shifts the limits on perception from parietal to ventral brain regions and identifies a critical neural circuit for visual learning. We suggest that generalization is implemented by supplanting dynamic processing conducted in the PPC with specific feature templates stored in the ventral cortex.
authors.affiliation: McGill Vision Research, Department of Ophthalmology, McGill University, Montreal, QC H3A 1A1, Canada; School of Psychology, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Dorita H F
authors.initials: DH
authors.lastname: Chang
authors.affiliation: School of Psychology, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Carmel
authors.initials: C
authors.lastname: Mevorach
authors.affiliation: School of Psychology, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; Laboratory for Neuro- and Psychophysiology, KU Leuven, O&N II Herestraat 49, Box 1021, 3000 Leuven, Belgium; Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Kourtzi
authors.affiliation: School of Psychology, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK; Laboratory for Neuro- and Psychophysiology, KU Leuven, O&N II Herestraat 49, Box 1021, 3000 Leuven, Belgium; Department of Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK. Electronic address: aew69@cam.ac.uk.
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Welchman
mesh_terms: D002540:Cerebral Cortex / Q000502:physiology*; D055724:Electrophysiological Phenomena; D006801:Humans; D007858:Learning; D059906:Neuroimaging; D011597:Psychomotor Performance / Q000502:physiology*; D050781:Transcranial Magnetic Stimulation; D014796:Visual Perception / Q000502:physiology*