Genetically determined differences in brain response to a primary food reward

Area of Science:

• Neuroscience
• Genetics
• Behavioral Science

Background:

• Individual differences in neurophysiology and disease vulnerability can be understood by combining genetic and neuroimaging techniques.
• The TaqIA A1 allele is linked to reduced dopamine D(2) receptor density, increased body mass, and altered food reinforcement, potentially predisposing individuals to overeating.
• It remains unclear whether this predisposition stems from fundamental neurophysiological differences or covarying factors like impulsivity and eating style.

Purpose of the Study:

• To investigate the direct association between the TaqIA A1 polymorphism and neural responses to palatable food ingestion.
• To differentiate between a direct neurophysiological effect of the A1 allele and the influence of related behavioral factors on reward processing and eating behavior.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed to measure brain activity in healthy subjects with (A1+) and without (A1-) the TaqIA A1 allele.
• Participants underwent fMRI scanning during the ingestion of a palatable, caloric milkshake and a tasteless/odorless baseline.
• Subject groups were carefully matched for age, gender, education, body mass index, impulsivity, eating style, and perceptual responses to control for confounding variables.

Main Results:

• A significant interaction between TaqIA genotype (A1+ vs A1-) and stimulus (milkshake vs baseline) was observed in the midbrain, thalamus, and orbital frontal cortex.
• Individuals without the A1 allele (A1-) exhibited increased neural responses to the milkshake, while those with the A1 allele (A1+) showed decreased responses relative to baseline.
• These neural differences were apparent despite comparable self-reported ratings of milkshake pleasantness, intensity, and familiarity between the groups.

Conclusions:

• The study concludes a specific association between the TaqIA A1 polymorphism and altered brain response patterns during the ingestion of palatable food.
• This finding supports a direct neurophysiological link between the TaqIA A1 genotype and the brain's processing of food rewards, independent of subjective taste perception.