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Cognitive functioning depends on intact brain networks that can be assessed with functional magnetic resonance imaging (fMRI) techniques. We hypothesized that cognitive decrements in type 1 diabetes mellitus (T1DM) are associated with alterations in resting-state neural connectivity and that these changes vary according to the degree of microangiopathy. T1DM patients with (MA(+): n = 49) and without (MA(-): n = 52) microangiopathy were compared with 48 healthy control subjects. All completed a neuropsychological assessment and resting-state fMRI. Networks were identified using multisubject independent component analysis; specific group differences within each network were analyzed using the dual-regression method, corrected for confounding factors and multiple comparisons. Relative to control subjects, MA(-) patients showed increased connectivity in networks involved in motor and visual processes, whereas MA(+) patients showed decreased connectivity in networks involving attention, working memory, auditory and language processing, and motor and visual processes. Better information-processing speed and general cognitive ability were related to increased degree of connectivity. T1DM is associated with a functional reorganization of neural networks that varies, dependent on the presence or absence of microangiopathy. [ABSTRACT FROM AUTHOR]

Objective: Hyperglycemia-associated microvascular disease may underlie changes in cerebral functioning and cognitive performance in patients with type 1 diabetes. Functional connectivity, an indicator of functional interactions and information exchange between brain regions, provides a measure of cerebral functioning. This study addresses functional connectivity and cognition in type 1 diabetic patients with and without proliferative retinopathy, relative to healthy control subjects, using magnetoencephalography.Research Design and Methods: Fluctuations in magnetic field at scalp for Delta, theta, lower and upper alpha, beta, and lower and upper gamma frequency bands were measured using magnetoencephalography. Synchronization likelihood, a measure of functional connectivity, was computed. Using neuropsychological tests, cognitive functioning was assessed and its associations with functional connectivity were determined.Results: Compared with control subjects, type 1 diabetic patients performed poorer on general cognitive ability, information processing speed, and motor speed, irrespective of their microvascular complication status. Functional connectivity, however, was lowest for type 1 diabetic patients with retinopathy, compared with type 1 diabetic patients without microvascular complications and control subjects, whereas type 1 diabetic patients without microvascular complications showed an increase relative to control subjects. Positive associations were found between functional connectivity and executive functioning, memory, information processing speed, motor speed, and attention.Conclusions: Compared with healthy control subjects, functional connectivity and cognition differed in type 1 diabetic patients irrespective of microvascular complication status, indicating that chronic hyperglycemia, among other factors, may negatively affect brain functioning even before microvascular damage becomes manifest. The association found between synchronization likelihood and cognition suggests functional connectivity plays a significant role in cognitive functioning. [ABSTRACT FROM AUTHOR]

Individuals with type 1 diabetes have mild performance deficits on a range of neuropsychological tests compared with nondiabetic control subjects. The mechanisms underlying this cognitive deterioration are still poorly understood, but chronic hyperglycemia is now emerging as a potential determinant, possibly through microvascular changes in the brain. In 24 type 1 diabetic patients, we tested at euglycemia and at acute hypoglycemia whether the presence of proliferative diabetic retinopathy, as a marker of microvascular disease, adversely affects the ability of the brain to respond to standardized hypoglycemia, using functional magnetic resonance imaging with a cognitive task. Patients with retinopathy, compared with patients without, showed less deactivation (hence, an increased response) in the anterior cingulate and the orbital frontal gyrus during hypoglycemia compared with euglycemia (P < 0.05). Task performance and reaction time were not significantly different for either group. We conclude that microvascular damage in the brain of patients with retinopathy caused this increased brain response to compensate for functional loss. [ABSTRACT FROM AUTHOR]