[P1–429]: FUNCTIONAL MRI OF TABLET‐BASED COMPUTERIZED PAIRED ASSOCIATE LEARNING (PAL) WITH IMPROVED ECOLOGICAL VALIDITY

Administered with a computerized touch-screen display, PAL assists in characterizing memory and learning deficits in patients with probable early Alzheimer's disease (AD) (Blackwell Dement-Geriatr-Cogn-Disord 2003). FMRI may clarify the relationship between PAL performance and brain activity, but ecological validity is a concern during complex motor tasks. Previously, we developed an fMRI-compatible tablet including visual feedback of hand position (VFHP) and an augmented reality display (Tam HBM-2011; Karimpoor Frontiers-2015) to address this issue for AD patients with impaired motor planning (Ghilardi BrainRes-2000). The purpose of the present work is to characterize brain activity for an ecologically valid fMRI computerized PAL test. Prior to testing AD patients, initial work involved young adults. The PAL test involves making associative judgements of an increasing number of patterns (1–6 patterns) and their locations on the screen (Fig.1). Each task is repeated twice in a mixed fMRI design interspersed with baseline visual fixation. Ten young healthy right-handed adults performed PAL at 3T. The PRONTO toolkit was used to optimize fMRI preprocessing pipelines (Churchill PloSone-2015), and obtain Z-scored maps of retrieval phase vs. baseline, using a uni-variate Gauss Naïve Base (GNB) model. Principal Component Analysis (PCA) was performed on the Z-scored activation maps to obtain brain patterns explaining maximum variance across the group. Fig 2.a shows group maps during retrieval of 3 patterns (3pat) vs. baseline. Fig 2.b shows 6 patterns (6pat) vs. baseline. Increased activity in medial temporal lobe and dorsolateral prefrontal cortex is observed during 6pat compared to 3pat, consistent with the different difficulty levels. Activation of left ventral premotor cortex is consistent with visually-guided hand actions. Extensive activation of the left middle frontal gyrus, superior parietal lobule, and basal ganglia is observed during 6pat, compared to 3pat; consistent with differences in complex motor planning and visuospatial understanding. Results suggest that the fMRI-compatible tablet with VFHP enables PAL tests with good ecological validity involving complex fine motor movements. These methods and findings are relevant to future fMRI studies of AD patients; involving batteries of tasks required to probe different cognitive domains during limited scan time. fMRI-compatible PAL test. The first principal component depicting brain activity for 10 subjects performing PAL. a) Retrieval 3 patterns vs. baseline. b) Retrieval 6 patterns vs. baseline.

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