Reanalysis of the obesity-related attenuation in the left dorsolateral prefrontal cortex response to a satiating meal using gyral regions-of-interest.

Objective: The left dorsolateral prefrontal cortex (LDLPFC), which includes the inferior (IFG), middle (MFG), and superior (SFG) frontal gyri, has been implicated in satiation. Using a voxel-based approach, we previously identified an LDLPFC region (as reported as peak voxel) in which a reduced neuronal response to a meal was associated with obesity. In this study, we sought to determine which gyri in the LDLPFC best distinguished the neuronal responses to a meal using a different statistical approach.

Methods: We reanalyzed brain responses to a meal using the hypothesis-driven region-of-interest-based (ROI) approach. Regional cerebral blood flow (rCBF), a marker of neuronal activity in the LDLPFC and its 3 gyri, was acquired in 2 conditions (hunger and after the satiating meal) using (15)O-water positron emission tomography scans. rCBF was extracted and estimated using masks of the 3 gyri that were created in MRIcro and Statistical Parametric Mapping 5 software.

Results: Using the ROI approach, a satiation-related reduction in LDLPFC rCBF was observed in the obese (p = 0.04) and tended to be significantly greater than that in lean subjects (p = 0.07). The rCBF reduction was greater in the obese subjects than in the lean subjects in the left IFG (p = 0.03) and MFG (p = 0.004) after adjustment was made for age, sex, and number of voxels in these gyri, but not in the SFG (p = 0.5).

Conclusions: Our results are consistent with those obtained by the voxel-based approach in showing the association between obesity and a satiation-related reduction in LDLPFC activity. This LDLPFC response preferentially involves the IFG and MFG. We suggest that these brain regions could be targeted by new therapeutic interventions.