Quadrantic deficit reveals anatomical constraints on selection

Thomas A. Carlson*, George A. Alvarez, Patrick Cavanagh

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)


Our conscious experience is of a seamless visual world, but many of the cortical areas that underlie our capacity for vision have a fragmented or asymmetrical representation of visual space. In fact, the representation of the visual field is fragmented into quadrants at the level of V2, V3, and possibly V4. In theory, this division could have no functional consequences and therefore no impact on behavior. Contrary to this expectation, we find robust quadrant-level interference effects when attentively tracking two moving targets. Performance improves when target objects appear in separate quadrants (straddling either the horizontal or vertical meridian) compared with when they appear the same distance apart but within a single quadrant. These quadrant-level interference effects would not be predicted by cognitive theories of attention and tracking that do not take anatomical constraints into account. Quadrant-level interference strongly suggests that cortical areas containing a noncontiguous representation of the four quadrants of the visual field (i.e., V2, V3, and V4) impose an important constraint on attentional selection and attentive tracking.

Original languageEnglish
Pages (from-to)13496-13500
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number33
Publication statusPublished - 14 Aug 2007
Externally publishedYes


  • Attentional interference
  • Extrastriate cortex
  • Multifocal attention
  • Visual attention


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