Cerebral Cortex Advance Access originally published online on April 16, 2009
Cerebral Cortex 2009 19(12):2970-2981; doi:10.1093/cercor/bhp070
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Additive Effects of Attention and Stimulus Contrast in Primary Visual Cortex
1 Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK, 2 The Netherlands Institute for Neuroscience, an institute of the Royal Netherlands Academy of Arts and Sciences, 1105 BA, Amsterdam, the Netherlands, 3 Department of Experimental Neurophysiology, Center for Neurogenomics and Cognitive Research, VU University, Amsterdam, the Netherlands
Address correspondence to email: alex.thiele{at}ncl.ac.uk.
Previous studies have proposed a variety of mechanisms by which attention influences neuronal activity. Here we investigated the mechanisms of attention in the striate cortex of monkeys performing a spatial or an object-based attention task at various stimulus contrasts and compared neuronal contrast response functions with and without attention. Our data are best described by an "additive" interaction: The influence of attention on the neuronal response is relatively independent of the stimulus contrast, at least when the stimulus has enough contrast to become visible. This shows that attention adds to the neuronal responses in a largely contrast invariant manner. These data support recent functional magnetic resonance imaging studies and suggest that feedback from higher areas exerts a constant attentional drive that is mostly task not stimulus driven.
Key Words: area V1 attentional modulation contrast gain contrast sensitivity response gain
4 Current address: Department of Psychology, School of Business, Law & Psychology, University of Sunderland, Sunderland, SR6 0DD, UK