The time course of visual processing: from early perception to decision-making

J Cogn Neurosci. 2001 May 15;13(4):454-61. doi: 10.1162/08989290152001880.


Experiments investigating the mechanisms involved in visual processing often fail to separate low-level encoding mechanisms from higher-level behaviorally relevant ones. Using an alternating dual-task event-related potential (ERP) experimental paradigm (animals or vehicles categorization) where targets of one task are intermixed among distractors of the other, we show that visual categorization of a natural scene involves different mechanisms with different time courses: a perceptual, task-independent mechanism, followed by a task-related, category-independent process. Although average ERP responses reflect the visual category of the stimulus shortly after visual processing has begun (e.g. 75-80 msec), this difference is not correlated with the subject's behavior until 150 msec poststimulus.

MeSH terms

  • Adult
  • Animals
  • Behavior / physiology
  • Decision Making / physiology*
  • Evoked Potentials, Visual / physiology
  • Female
  • Humans
  • Male
  • Mental Processes / physiology*
  • Middle Aged
  • Perceptual Masking / physiology
  • Reaction Time / physiology
  • Transportation
  • Visual Perception / physiology*