The influence of obesity on structure, biochemistry and function of brain regions involved in cognition

While there are many clinical findings associating obesity with cognitive deficits, this relationship has not been fully characterized in animal models. Using an animal model of diet induced obesity (DIO), we can assay cognitive behaviors in obese versus normal weight rats. In the current study, adult rats were maintained on a nutritionally complete, palatable, high-fat diet for 8 weeks. At this point, obesity, defined as elevated body weight, increased fat pad accrual and increased serum triglyceride levels, was obvious in the high-fat consuming rats compared to age and weight matched rats maintained on standard rodent chow. After obesity onset, behavioral tasks that are dependent on brain regions important in cognition and memory, including the medial prefrontal cortex (mPFC), perirhinal cortex (PRC), and hippocampus (HIP), were implemented. Rats were also tested for performance on standard sensory and locomotor tasks, to eliminate confounding behavioral deficits that might present as cognitive deficits. Obese rats showed deficits on behavioral tasks requiring the mPFC and PRC, but not HIP. Further, obese rats showed no deficits on sensory or locomotor tasks compared to controls. These results indicate a correlation between obesity and performance on cognitive functions requiring the mPFC and PRC. The data also provide a model, as well as motivation, to further explore potential cellular and structural