Mike Anderson

Diabetes mellitus type 1 (T1DM) has been associated with cognitive dysfunction and structural abnormalities across the cortex. It has been argued that there are critical periods in the lifespan where the brain is particularly vulnerable to the neural insults of Diabetes (Biessels, Deary & Ryan, 2008). In this MRI study, we used voxel-based morphometry to compare a group of T1DM patients to sibling controls during young adulthood. We had previously shown that when 7 years younger there was no effect of T1DM on IQ (Strudwick et al., 2005) and while there was still no effect on IQ, there was a suggestion of difficulties in executive functioning (EF; Ly et al., 2011). In this follow-up study we explored whether differences in brain structure related to T1DM might explain the difference in EF. There were 61 participants (Mage = 19.3) who participated in the MRI scanning (T1DM N = 31) with an approximately equal gender balance (54% female). Participants' T1-weighted volumes at 1mm3 voxel size were obtained from a 3T Siemens scanner. MRI scans were analysed using the SPM8 toolbox (Wellcome Trust) in MATLAB (The Mathworks, Inc). When performing voxel-wise comparisons across the cortex, there were no significant differences in grey matter density between T1DM and sibling controls (corrected p =. 05). Lowering the statistical criteria to an uncorrected p =. 001 revealed sibling controls had higher grey matter density in four left-lateralised clusters (middle temporal gyrus, cuneus, superior frontal gyrus and postcentral gyrus). The largest effects were for T1DM patients to have reduced grey matter density in the middle temporal gyrus"”a cortical region associated with semantic processing and risk factor for developing Dementia, and in the superior frontal gyrus"”a cortical region implicated in EF. These results reveal consistent, yet subtle, structural brain differences between T1DM patients and controls in young adulthood.

Diabetes mellitus type 1 (T1DM) has been associated with cognitive dysfunction and structural abnormalities across the cortex. It has been argued that there are critical periods in the lifespan where the brain is particularly vulnerable to the neural insults of Diabetes (Biessels, Deary & Ryan, 2008). In this MRI study, we used voxel-based morphometry to compare a group of T1DM patients to sibling controls during young adulthood. We had previously shown that when 7 years younger there was no effect of T1DM on IQ (Strudwick et al., 2005) and while there was still no effect on IQ, there was a suggestion of difficulties in executive functioning (EF; Ly et al., 2011). In this follow-up study we explored whether differences in brain structure related to T1DM might explain the difference in EF. There were 61 participants (Mage = 19.3) who participated in the MRI scanning (T1DM N = 31) with an approximately equal gender balance (54% female). Participants' T1-weighted volumes at 1mm3 voxel size were obtained from a 3T Siemens scanner. MRI scans were analysed using the SPM8 toolbox (Wellcome Trust) in MATLAB (The Mathworks, Inc). When performing voxel-wise comparisons across the cortex, there were no significant differences in grey matter density between T1DM and sibling controls (corrected p =. 05). Lowering the statistical criteria to an uncorrected p =. 001 revealed sibling controls had higher grey matter density in four left-lateralised clusters (middle temporal gyrus, cuneus, superior frontal gyrus and postcentral gyrus). The largest effects were for T1DM patients to have reduced grey matter density in the middle temporal gyrus"”a cortical region associated with semantic processing and risk factor for developing Dementia, and in the superior frontal gyrus"”a cortical region implicated in EF. These results reveal consistent, yet subtle, structural brain differences between T1DM patients and controls in young adulthood.

Background: Executive functions (EFs) are commonly theorised to be related yet separable constructs in adults, and specific EFs, such as prepotent response inhibition and working memory, are thought to have clear and distinct neural underpinnings. However, recent evidence suggests that EFs are unitary in children up to about 9 years of age. The aim of the current study was to test the hypothesis that event-related potential (ERP) components of individual EFs are related to behavioural performance, despite EFs being psychometrically indistinguishable in children. Specifically, P3b ERP (associated with updating of working memory), N2 ERP, and N2 difference waveform (both associated with inhibition) latent variables were created and entered into confirmatory factor analysis and structural equation models with a unitary executive functioning factor. Methods: Children aged 7-9 years (N = 215) completed eight measures of inhibition, working memory, and shifting. A modified flanker task was also completed during which EEG data were recorded. Results: The P3b ERP and the N2 difference waveform factors both significantly correlated with (and were predictors of) the executive functioning factor; however, the N2 ERP factor was not. Discussion: These results provide support for the utility of ERPs as a counterpoint to psychometric measures of executive functioning, and, more broadly, for the relationship between brain and behaviour.