Implicit integration in a case of integrative visual agnosia

Hillel Aviezer, Ayelet N. Landau, Lynn C. Robertson, Mary A. Peterson, Nachum Soroker, Yaron Sacher, Yoram Bonneh, Shlomo Bentin

Research output: Contribution to journalArticlepeer-review


We present a case (SE) with integrative visual agnosia following ischemic stroke affecting the right dorsal and the left ventral pathways of the visual system. Despite his inability to identify global hierarchical letters [Navon, D. (1977). Forest before trees: The precedence of global features in visual perception. Cognitive Psychology, 9, 353-383], and his dense object agnosia, SE showed normal global-to-local interference when responding to local letters in Navon hierarchical stimuli and significant picture-word identity priming in a semantic decision task for words. Since priming was absent if these features were scrambled, it stands to reason that these effects were not due to priming by distinctive features. The contrast between priming effects induced by coherent and scrambled stimuli is consistent with implicit but not explicit integration of features into a unified whole. We went on to show that possible/impossible object decisions were facilitated by words in a word-picture priming task, suggesting that prompts could activate perceptually integrated images in a backward fashion. We conclude that the absence of SE's ability to identify visual objects except through tedious serial construction reflects a deficit in accessing an integrated visual representation through bottom-up visual processing alone. However, top-down generated images can help activate these visual representations through semantic links.

Original languageEnglish
Pages (from-to)2066-2077
Number of pages12
Issue number9
StatePublished - 2007
Externally publishedYes


  • Grouping
  • Integrative agnosia
  • Local-global processing
  • TPJ
  • Visual agnosia


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