Aftertaste - Aftertaste Processing in The Cerebral Cortex

Aftertaste Processing in The Cerebral Cortex

The primary taste perception areas in the cerebral cortex are located in the insula and regions of the somatosensory cortex; the nucleus of the solitary tract located in the brainstem also plays a major role in taste perception. These regions were identified when human subjects were exposed to a taste stimulus and their cerebral blood flow measured with magnetic resonance imaging. Although these regions have been identified as the primary zones for taste processing in the brain, other cortical areas are also activated during eating, as other sensory inputs are being signaled to the cortex.

For aftertaste, much is unclear about the cortical processing related to its perception. The first neuroimaging study to evaluate the temporal taste profile of aspartame, an artificial sweetener, in humans was published in 2009. In it, the insula was observed to be activated for a longer period of time than other sensory processing areas in the brain when the aftertaste profile of aspartame was measured. Subjects were administered a solution of aspartame for a specific amount of time before being instructed to swallow the solution. Functional magnetic resonance images of the blood flow in the subjects’ brains were recorded before and after they swallowed the aspartame solution. Before swallowing, the amygdala, somatosensory cortex, thalamus, and basal ganglia were all activated. After swallowing, only the insula remained activated and the response of the other brain regions was not evident. This suggests that the insula may be a primary region for aftertaste sensation because it was activated even after the aspartame solution was no longer present in the mouth. This finding aligns with the insula’s identification as a central taste processing area and simply expands its function. An explanation for less activation of the amygdala was that because it is a reward center in the brain, less reward would be experienced by the subjects during prolonged exposure to the aspartame solution.