Activation of SI is modulated by attention: a random effects fMRI study using mechanical stimuli

Animal experiments on tactile attention suggest a modulation of sensory processing on the level of sensory representations but correspondent neuroimaging data in humans is inconclusive. The present experiment used mechanical stimuli to study tactile processing while varying the focus of attention. Activations were contrasted between attend and ignore conditions, both of which employed identical stimulation characteristics and an active task. Random effects analysis revealed significant attention effects in area SI (primary somatosensory cortex) in that the blood oxygenation level-dependent response was greater for attended than for ignored stimuli. Modulations were further found in the secondary somatosensory cortex and the middle temporal gyrus. These findings suggest that stimulus processing at the level of primary representations in area SI is modulated by attention.