Enabling global processing in simultanagnosia by psychophysical biasing of visual pathways

Cibu Thomas, Kestutis Kveraga, Elisabeth Huberle, Hans Otto Karnath, Moshe Bar

Research output: Contribution to journalArticlepeer-review

49 Scopus citations


A fundamental aspect of visual cognition is our disposition to see the 'forest before the trees'. However, damage to the posterior parietal cortex, a critical brain region along the dorsal visual pathway, can produce a neurological disorder called simultanagnosia, characterized by a debilitating inability to perceive the 'forest' but not the 'trees' (i.e. impaired global processing despite intact local processing). This impairment in perceiving the global shape persists even though the ventral visual pathway, the primary recognition pathway, is intact in these patients. Here, we enabled global processing in patients with simultanagnosia using a psychophysical technique, which allowed us to bias stimuli such that they are processed predominantly by the intact ventral visual pathway. Our findings reveal that the impairment in global processing that characterizes simultanagnosia stems from a disruption in the processing of low-spatial frequencies through the dorsal pathway. These findings advance our understanding of the relationship between visuospatial attention and perception and reveal the neural mechanism mediating the disposition to see the 'forest before the trees'.

Original languageEnglish
Pages (from-to)1578-1585
Number of pages8
Issue numberPt 5
StatePublished - May 2012

Bibliographical note

Funding Information:
Bundesministerium für Bildung und Forschung (BMBF-Verbund Grant Number 01GW0654 to H-O.K.) and by the National Institutes of Health (Grant Number R01EY019477 to M.B.).


  • brain circuits
  • cerebral ischaemia
  • dorsal stream
  • neurological disorders
  • visual system


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