Taste, Smell, and the Insular Cortex

Very specific regions of our brains process the sensations of taste and smell. Animal studies, neuroimaging, metabolic studies (such as PET), and an analysis of cerebral lesions in humans have shown that these sensations are processed bilaterally in the parietofrontal operculum and insula. However, there has been some debate as to which part of the insula is responsible for this important brain function. There are many reasons for this, including the fact that it is very difficult to test one of these sensations without activating another. For instance, noxious stimuli also will activate the trigeminal pathways. A small amount of liquid that is placed in the mouth will go into the nasopharynx, stimulating smell. Direct cortical stimulation eliminates these confounding factors and is likely to be a much more accurate way of identifying the regions of the brain responsible for processing the sensations of taste and smell. Mazzola et al, working at the University Hospital of Saint-Etienne (France),...