• Nancy J Lobaugh, Hélène Chevalier, Magali Batty, and Margot J Taylor.
• Imaging Research and Cognitive Neurology, Sunnybrook and Women's College Health Sciences Centre, 2075 Bayview Avenue Room A421, Toronto, Ontario, Canada M4N 3M5.
• Neuroimage. 2005 Jul 15;26(4):986-95.

AbstractPsychological and neurophysiological models of visual processing have traditionally emphasized hierarchical models to explain how separate features of visual stimuli are combined. This concept has been challenged recently with the demonstration of simultaneous activation of multiple visual areas and rapid feedback to primary cortices. Here, we show human visual processing may involve similar mechanisms. Subjects discriminated targets from nontargets as a function of shape, color, or the conjunction of these features while event-related brain potentials (ERPs) were recorded. ERP components from 100 to 200 ms across posterior occipital-temporal cortices were fastest and largest for conjunction targets. These enhanced early responses were followed by task-specific sustained posterior activity (300-500 ms). Faster reaction times were correlated with enhanced and faster early processing in the visual ventral areas. These data demonstrate the human visual system conjoins features rapidly, accelerating and amplifying the processing of relevant stimulus dimensions.

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