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Hand-Selective Visual Regions Represent How to Grasp 3D Tools: Brain Decoding during Real Actions

Authors
  • Knights, Ethan
  • Mansfield, Courtney
  • Tonin, Diana
  • Saada, Janak
  • Smith, Fraser W.
  • Rossit, Stéphanie
Type
Published Article
Journal
Journal of Neuroscience
Publisher
Society for Neuroscience
Publication Date
Jun 16, 2021
Volume
41
Issue
24
Pages
5263–5273
Identifiers
DOI: 10.1523/JNEUROSCI.0083-21.2021
PMID: 33972399
PMCID: PMC8211542
Source
PubMed Central
Keywords
Disciplines
  • Research Articles
  • Behavioral/Cognitive
License
Unknown

Abstract

Most neuroimaging experiments that investigate how tools and their actions are represented in the brain use visual paradigms where tools or hands are displayed as 2D images and no real movements are performed. These studies discovered selective visual responses in occipitotemporal and parietal cortices for viewing pictures of hands or tools, which are assumed to reflect action processing, but this has rarely been directly investigated. Here, we examined the responses of independently visually defined category-selective brain areas when participants grasped 3D tools ( N = 20; 9 females). Using real-action fMRI and multivoxel pattern analysis, we found that grasp typicality representations (i.e., whether a tool is grasped appropriately for use) were decodable from hand-selective areas in occipitotemporal and parietal cortices, but not from tool-, object-, or body-selective areas, even if partially overlapping. Importantly, these effects were exclusive for actions with tools, but not for biomechanically matched actions with control nontools. In addition, grasp typicality decoding was significantly higher in hand than tool-selective parietal regions. Notably, grasp typicality representations were automatically evoked even when there was no requirement for tool use and participants were naive to object category (tool vs nontools). Finding a specificity for typical tool grasping in hand-selective, rather than tool-selective, regions challenges the long-standing assumption that activation for viewing tool images reflects sensorimotor processing linked to tool manipulation. Instead, our results show that typicality representations for tool grasping are automatically evoked in visual regions specialized for representing the human hand, the primary tool of the brain for interacting with the world.

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