Modality-specific neural effects of selective attention to taste and odor.

The insular cortex is implicated in general attention and in taste perception. The effect of selective attention to taste on insular responses may therefore reflect a general effect of attention or it may be (taste) modality specific. To distinguish between these 2 possibilities, we used functional magnetic resonance imaging to evaluate brain response to tastes and odors while subjects passively sampled the stimuli or performed a detection task. We found that trying to detect a taste (attention to taste) resulted in activation of the primary taste cortex (anterior and mid-dorsal insula) but not in the primary olfactory cortex (piriform). In contrast, trying to detect an odor (attention to odor) increased activity in primary olfactory but not primary gustatory cortex. However, we did identify a region of far anterior insular cortex that responded to both taste and odor "searches." These results demonstrate modality-specific activation of primary taste cortex by attention to taste and primary olfactory cortex by attention to odor and rule out the possibility that either response reflects a general effect of attentional deployment. The findings also support the existence of a multimodal region in far anterior insular cortex that is sensitive to directed attention to taste and smell.