Humans offer an exceptional opportunity for studying hemispheric differences in gustatory processing because their subcortical taste pathway is arranged in a strictly ipsilateral fashion. The demonstration by Pritchard et al. (1999) that language-based taste tasks are performed in the left hemisphere suggests that other aspects of gustatory perception may be lateralized as well. This proposal addresses perception and expression of gustatory perception may be lateralized as well. This proposal addresses perception and expression of gustatory affect, an integral component of taste that is cortically based and reliant on another lateralized gustatory affect, an integral component of taste that is cortically based and reliant on another lateralized system: emotion. Psychophysical techniques will be used to assess gustatory affect in patients with damage to either the rostral insula (primary taste cortex) or the orbitofrontal cortex. The orbitofrontal cortex, which receive direct projections from primary gustatory cortex, has been implicated in perception of emotion contained in facial expression and voices. The proposed experiments will determine the respective contributions of the light and right hemispheres to the perception of gustatory affect. Consistent with other studies in the visual and auditory systems, we expect to find that the left and right hemispheres work in concert but that positive affect (e.g., happiness) is mediated primarily by the left hemisphere while negative affect (e.g., disgust) is processed primarily by the right hemisphere. We will determine if deficits if gustatory affect are independent of deficits in emotional perception in the visual and auditory systems. Patients with insular damage in the left hemisphere are expected to be impaired in naming of taste quality and verbal reports of taste affect. However, the same patients are expected to report taste affect accurately when using other non-language-based techniques that are organized in the right hemisphere. Combining psychophysical taste testing with high resolution (1mm) MRI-based reconstructions of the brain damage in our subjects will enable us to determine with greater accuracy the location of primary taste cortex in humans.
