RT Journal Article
SR Electronic
T1 The Effect of Spatial Attention on Contrast Response Functions in Human Visual Cortex
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 93
OP 97
DO 10.1523/JNEUROSCI.3162-06.2007
VO 27
IS 1
A1 Buracas, Giedrius T.
A1 Boynton, Geoffrey M.
YR 2007
UL http://www.jneurosci.org/content/27/1/93.abstract
AB Previous electrophysiology data suggests that the modulation of neuronal firing by spatial attention depends on stimulus contrast, which has been described using either a multiplicative gain or a contrast-gain model. Here we measured the effect of spatial attention on contrast responses in humans using functional MRI. To our surprise, we found that the modulation of blood oxygenation level-dependent (BOLD) responses by spatial attention does not greatly depend on stimulus contrast in visual cortical areas tested [V1, V2, V3, and MT+ (middle temporal area)]. An additive model, rather than a multiplicative or contrast-gain model best describes the attentional modulations in V1. This inconsistency with previous single-unit electrophysiological data has implications for the population-based neuronal source of the BOLD signal.