title: Neural substrates of verbal memory impairments in adults with type 2 diabetes mellitus.
abstract: BACKGROUND
  Verbal memory impairment is well documented in type 2 diabetes mellitus (T2DM) but, to date, the neural substrates remain unclear. The present study evaluated verbal memory and ascertained the degree of frontal and temporal lobe involvement in the anticipated verbal memory impairment among adults with T2DM.
  
  
  METHODS
  Forty-six late-middle-aged and elderly adults with T2DM and 50 age-, sex-, and education-matched adults without T2DM underwent medical evaluation, verbal memory assessment, and brain magnetic resonance imaging (MRI) evaluations.
  
  
  RESULTS
  As anticipated, participants with T2DM had clear verbal memory impairments. Consistent with prior reports, we found volume reductions restricted to the hippocampus. Our diffusion tensor imaging analysis revealed that participants with T2DM had extensive cerebral gray and white matter microstructural abnormalities predominantly in the left hemisphere, with a larger concentration present in the temporal lobe. In contrast, we uncovered mostly nonspecific microstructural abnormalities in the absence of tissue loss in the frontal lobe. Of great importance, we present the first evidence among participants with T2DM linking verbal memory impairment and compromised microstructural integrity of the left parahippocampal gyrus, a key memory-relevant structure.
  
  
  CONCLUSIONS
  Our results suggest that the hippocampus and parahippocampal gyrus may be particularly vulnerable to the deleterious effects of T2DM. The parahippocampal gyrus in particular may play a crucial role in the verbal memory impairments frequently reported in T2DM. Future studies should employ methods such as resting state functional magnetic resonance imaging and diffusion tensor imaging tractography to better characterize network connectivity, which may help further characterize the verbal memory impairment frequently reported in T2DM.
authors.affiliation: a Department of Psychiatry , New York University School of Medicine , New York , NY , USA.
authors.forename: Po Lai
authors.initials: PL
authors.lastname: Yau
authors.forename: Alan
authors.initials: A
authors.lastname: Kluger
authors.forename: Joan C
authors.initials: JC
authors.lastname: Borod
authors.forename: Antonio
authors.initials: A
authors.lastname: Convit
mesh_terms: D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000503:physiopathology*; D056324:Diffusion Tensor Imaging / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D006624:Hippocampus / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology / Q000503:physiopathology*; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology; D009483:Neuropsychological Tests; D020534:Parahippocampal Gyrus / Q000473:pathology / Q000503:physiopathology; D014706:Verbal Learning / Q000502:physiology*