IC‐P‐113: RELEVANCE OF PARAHIPPOCAMPAL‐LOCUS COERULEUS CONNECTIVITY TO MEMORY DYSFUNCTION IN EARLY ALZHEIMER'S DISEASE

white matter (WM) connections. Evaluating this structural connectivity is a key part of understanding how AD affects specific brain networks. The considerable variation in early-onset sporadic AD (EOAD), from typical AD (episodic-memory loss) to posterior cortical atrophy (visual dysfunction) likely reflects differences in neuro-resilience and/or protection. Here we use techniques designed for effective longitudinal DTI analysis, conducting the first longitudinal comparison of WM structure in PCA and tAD to our knowledge. Methods: Participants were 16 PCA patients (mean age:61.6], disease-duration:4.9) 13 tAD patients (mean age:60.7, disease-duration:4.3) and 20 controls (mean age:60.4) with baseline and follow-up scans at w1-year interval. The DTI scan had two 64-direction sequences; voxel size1⁄42.5x2.5x2.5mm; b-value1⁄41000s/mm 2. Preprocessing included EPI-distortion correction, eddyand motion-correction. Longitudinal analysis used an unbiased framework utilising full-tensor information for improved registration (Keihaninejad et al., 2013 NeuroImage). Fractional anisotropy (FA) and mean diffusivity (MD) were extracted from 16 regions of interest (using ICBM-DTI-81