Functional Organization of the Human Gustatory Cortex

Abstract

Neurological studies in patients with stroke or epilepsy have suggested that the human primary gustatory cortex is located in the insula and frontal operculum. Although electrophysiological studies in non-human primates have supported the above idea, these conventional approaches were inapplicable to systematically examine the human gustatory cortex. Recent non-invasive brain imaging techniques including positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have enabled us to explore the precise locations of gustation-related regions in the human brain. These non-invasive imaging studies have revealed the mechanism of not only “bottom-up” information processing, from the peripheral gustatory organs, taste buds, to the gustatory cortices, but also “top-down” processing in the gustatory system. Our group investigated the organization of neural systems for gustatory perception and gustatory imagery using fMRI. We found that gustatory imagery tasks activate the insula, showing predominant activation in the left hemisphere. Furthermore, gustatory imagery tasks activated the orbitofrontal, precentral, and middle/superior frontal gyri. On the other hand, gustatory imagery contrasted with visual imagery activated only the insula, orbitofrontal and precentral gyri. These results suggest the possibility that the source of “top-down” signals may be in the middle and superior frontal gyri, and that these signals may affect on neural activities in the insula, orbitofrontal, and precentral gyri.