Unequal representation of cardinal vs. oblique orientations in the middle temporal visual area

Xiangmin Xu, Christine E. Collins, Ilya Khaytin, Jon H. Kaas*, Vivien A. Casagrande

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


A possible neurobiological basis for the "oblique effect" is linked to the finding that more neural machinery is devoted to processing cardinal vs. oblique orientations in primary visual cortex (V1). We used optical imaging to determine whether more territory is devoted to processing horizontal and vertical orientations than oblique orientations in owl monkey middle temporal visual area (MT), a visual area highly sensitive to moving stimuli. We found that more of MT was devoted to representing cardinal than oblique orientations, and that the anisotropy was more prominent in parts of MT representing central vision (≤10°). Neural responses to orientations of 0° and 90° were also greater than those to 45° and 135°. In comparison, an overrepresentation of cardinal orientations in the representation of central vision in owl monkey V1 was relatively small and inconsistent. Our data could explain the greater sensitivity to motion discrimination when stimuli are moved along cardinal meridians and suggest that the neural machinery necessary to explain the motion oblique effect either originates in MT or is enhanced at this level.

Original languageEnglish (US)
Pages (from-to)17490-17495
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number46
StatePublished - Nov 14 2006


  • Oblique effect
  • Optical imaging
  • Orientation preference
  • Owl monkey
  • Visuotopic maps

ASJC Scopus subject areas

  • General


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