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  • Weight Gain is Associated with Reduced Striatal Response to Palatable Food
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Because obese people generally have reduced striatal D2R density, such individuals may have relatively insensitive reward circuitry, especially as compared to lean humans. These obese individuals may then be more likely to overeat to compensate for the hypofunctioning reward circuitry, leading to a vicious spiral. Stice et al. performed functional magnetic resonance imaging studies to look at the link between overeating and striatal activation. They studied 26 women over the course of six months - they measured BMI and striatal activation via the milkshake paradigm twice, from baseline to the 6-month follow-up.

Figure 3 shows caudate activation differences in three groups: (1) subjects whose weight decreased, (2) subjects whose weight remained stable, and (3) subjects whose weight increased over the 6-month period. During the fMRI, subjects were shown images of milkshakes and water and then later allowed to consume a milkshake or a tasteless solution. The researchers studied activation in response to drinking the milkshake. Of interest is that only the subjects whose weight increased over the 6-month period had decreased caudate activation in response to the milkshake, while groups 1 and 2 had increased activation in response to the milkshake. The finding that striatal activation is reduced in response to palatable foods after only weight gain is quite novel. The Johnson and Kenny paper also shows similar data but in rats.

Note that this paper precedes the Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats article and offers interesting background to the above paper's findings that D2R density is reduced in the striatum. Perhaps this morphological change is the basis for the decreased activation.

Return to Neural Reward, Energy Homeostasis, and Addiction-like Compulsive Eating

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