August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Effects of motor preparation on category-specific representations in human cortex
Author Affiliations & Notes
  • Canhuang Luo
    University of Nevada, Reno
  • Edward Ester
    University of Nevada, Reno
  • Footnotes
    Acknowledgements  NSF 2050833
Journal of Vision August 2023, Vol.23, 5970. doi:https://doi.org/10.1167/jov.23.9.5970
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      Canhuang Luo, Edward Ester; Effects of motor preparation on category-specific representations in human cortex. Journal of Vision 2023;23(9):5970. https://doi.org/10.1167/jov.23.9.5970.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Categorization is the ability to classify physically similar yet conceptually different objects. The neural circuits responsible for categorization are unclear, with invasive electrophysiological studies in non-human primates pointing toward prefrontal and parietal cortex and human neuroimaging studies pointing towards early sensory areas. This discrepancy could result from task structure. Invasive studies in non-human primates typically rely on delayed-match-to-category (DMC) tasks, which allow researchers to track category-selective signals independently of motor preparation; in contrast, human neuroimaging studies typically employ category discrimination (CD) tasks that require speeded responses. Thus, an important difference between non-human primate and human experiments is that the former precludes motor preparation while the latter does not. To examine whether and how motor signals influence categorization, we used an inverted encoding model to track the evolution of category biases reconstructed from the alpha power of EEG activity while participants performed CD and DMC tasks. During the CD task, participants learned to categorize stimuli appearing at 12 positions into two discrete groups. Participants were free to respond following stimulus onset and instructed to prioritize accuracy and speed. During the DMC task, participants were required to determine whether two successive stimuli appearing in different spatial positions were drawn from the same category. Thus, in this task, participants cannot plan or execute a response until the second stimulus is presented. Reconstructions of stimulus position were systematically biased towards the center of the appropriate category during the CD and DMC tasks. However, biases emerged significantly earlier during the CD relative to the DMC task. Furthermore, the decrease of lateralized beta activity, which is used to track motor preparation, is temporally coincident with the time difference of category biases in both conditions. We interpret this difference as evidence that decision and/or motor preparation signals influence the development of category biases in human cortex.

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