Association between executive dysfunction and hippocampal volume in Alzheimer's disease

Background: Some previous research has hypothesized that executive dysfunction in patients with early Alzheimer's disease (AD) occurs as a result of a disconnection between different cerebral areas. The aim of the present study was to evaluate how the hippocampal volume influences executive function as a non-memory cognitive function. Methods: From 157 consecutive patients with AD or amnestic mild cognitive impairment (A-MCI), we recruited 107 subjects who had a global Clinical Dementia Rating (CDR) of 0.5 or 1.0 and whose degree of hippocampal atrophy had been measured using magnetic resonance imaging (MRI); the severity of atrophy was assessed using the voxel-based specific regional analysis for Alzheimer's disease (VSRAD) system. We divided the subjects into three groups: mild atrophy, 0 < Z-score < 1.0 (N = 21); moderate atrophy, 1.0 <= Z-score < 2.0 (N = 46); or severe atrophy, 2.0 <= Z-score < 4.0 (N = 40) according to the Z-score and compared the Frontal Assessment Battery (FAB) and its subtest scores between each atrophy group. Results: The results demonstrated that age, sex ratio, duration of illness, education years, MMSE score, Behave-AD score, and proportion of atrophy area in total brain (%) were not significantly different among the three groups. Only the go/no-go score among the six subtests was significantly lower for increasing atrophy severity (P < 0.05). Furthermore, hippocampal atrophy significantly influenced the go/no-go score independently of interactions from whether the diagnosis was early AD or A-MCI (P < 0.05). Conclusion: These results support a significant association between hippocampal atrophy and executive dysfunction as a non-memory cognitive impairment in patients with early AD and A-MCI.