PT  - JOURNAL ARTICLE
AU  - Buracas, Giedrius T.
AU  - Boynton, Geoffrey M.
TI  - The Effect of Spatial Attention on Contrast Response Functions in Human Visual Cortex
AID  - 10.1523/JNEUROSCI.3162-06.2007
DP  - 2007 Jan 03
TA  - The Journal of Neuroscience
PG  - 93--97
VI  - 27
IP  - 1
4099  - http://www.jneurosci.org/content/27/1/93.short
4100  - http://www.jneurosci.org/content/27/1/93.full
SO  - J. Neurosci.2007 Jan 03; 27
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.