0126 NEUROIMAGING OF CIRCUIT-SPECIFIC PROTEIN SYNTHESIS IN HUMAN SUBJECTS DURING SLEEP-DEPENDENT MEMORY CONSOLIDATION

Abstract Introduction: The notion that memory consolidation depends on protein synthesis is based on demonstrations that protein synthesis inhibitors prevent consolidation. We sought to demonstrate directly that protein synthesis is affected during sleep-dependent memory consolidation. We used L-[1-(11)C]leucine positron emission tomography (PET) to measure circuit-specific brain protein synthesis during a daytime nap opportunity. Methods: Subjects completed the texture discrimination task (TDT) before and after the nap opportunity. We randomized 34 subjects to either wakefulness or sleep and counterbalanced training to either left or right visual field. In accord with the retinotopic specificity of the TDT, we considered ipsilateral V1 as the untrained within-subject control. Following training on the TDT, subjects underwent the PET scan with simultaneous polysomnography. V1 was drawn on magnetic resonance volumes and transferred to corresponding PET volumes to compute average rates of protein synthesis in left and right V1. Results: If we disregard visual field trained (left, right), the Condition (wakefulness, sleep) x Local State (untrained, trained) interaction was not statistically significant (F[1,32]=0.07,p=0.79,f^2=0.002). Consideration of visual field trained indicates that the Condition x Visual Field Trained x Local State interaction was statistically significant (F[1,30]=9.08,p=0.005,f^2=0.30). Side-to-side differences were statistically significant only in the sleep condition: protein synthesis in the trained hemisphere was significantly higher if training was in left visual field and significantly lower if training was in right visual field. Another way to view these results is protein synthesis was higher in the right V1 during sleep-dependent memory consolidation regardless of the location of training. Conclusion: If we disregard visual field trained, our study could indicate sleep-dependent memory consolidation depends on processes other than protein synthesis such as synaptic renormalization. Consideration of visual field trained, however, may indicate that each hemisphere has inherent properties requiring either reduced or elevated protein synthesis for memory consolidation to occur during sleep. Support (If Any): Intramural Research Program of the National Institute of Mental Health, Intramural Research Program of the National Institute of Neurological Disorders and Stroke, and Military Operational Medicine Research Program of the Unit