Neural correlates of habituation to taste stimuli in healthy women.

Recent studies show that specific regions of the cortex contribute to modulation of appetitive behaviors. The purpose of this study was to determine whether neural response in these regions changes over time when a taste stimulus is administered repeatedly. Such a paradigm may be useful for determining whether altered habituation contributes to disturbed eating behavior. This study used a programmable syringe pump to compare administration of a 10% sucrose solution to distilled water in 11 healthy female subjects using functional magnetic resonance imaging. The stimuli were presented in either a sequential or pseudorandom order. An a priori 'Region of Interest' (ROI) based analysis method was used, with ROIs defined in the prefrontal cortex, insula, amygdala, and hippocampus. To test habituation, activation during the first half of each block was compared with activation during the second half. For the pseudorandom blocks, subjects showed habituation in almost all ROIs to water, but in none to sucrose. By contrast, for sequential blocks, both stimuli produced habituation in taste-related brain regions. These data suggest that habituation patterns in healthy subjects may depend on frequency and regularity of stimulus administration.