Problem-solving abilities and frontal lobe cortical thickness in healthy aging and mild cognitive impairment

Mild cognitive impairment (MCI) is considered a transitional state between normal aging and Alzheimer disease. Most MCI subjects present disturbances in multiple neuropsychological domains, including executive function. This study aimed at exploring frontal lobe cortical thinning in MCI and healthy controls, and its relationship with problem-solving abilities. Twenty-three MCI patients and 30 elderly controls underwent MRI and neuropsychological assessment. Cortical thickness was measured by means of FreeSurfer. Problem-solving was assessed by means of the Tower of London (TOL) task. MCI showed a global thinning of the cortex. With regard to specific regions of interest, a thinning in the left frontal lobe and the bilateral posterior cingulate gyri was found. Partial correlations, after controlling for age, education, Mini-Mental Status Examination, and non-frontal mean thickness revealed negative significant correlations between frontal lobe thickness and executive outcomes in the control group. This counterintuitive relationship was not observed in the MCI group, suggesting that the frontal cortical atrophy observed in MCI entails a specific pathology-related relationship with high-level executive outcomes that is qualitatively different from that observed in healthy aging.