137. Inflammatory effects on human Rhinal cortex glucose metabolism predict subsequent spatial memory impairment

• Published in: Brain, behavior, and immunity behavior, and immunity, 2012-09, Vol.26, p.S38-S38
• Main Authors: Harrison, N.A, Doeller, C, Cooper, E, Burgess, N, Critchley, H.D
• Format: Article
• Language: English
• Subjects: Allergy and Immunology; Psychiatry
• ISSN: 0889-1591; 1090-2139
• DOI: 10.1016/j.bbi.2012.07.161

Rodent studies implicate inflammatory mediators in both physiological and pathological hippocampus-dependent memory processes (Yirmiya, BBI, 2011). Predominant effects on encoding or consolidation are uncertain, though recent transgenic mice data with selective hippocampal IL-1beta over-expression suggest early encoding effects (Moore, Neuroscience, 2009). To investigate this in humans, twenty healthy participants (24.7 ± 6.8 yrs) underwent 18 Fluorodeoxyglucose (18FDG)– PET scanning at baseline 4 and 8 h. After session 1 and 2 they learned and recalled the spatial location of objects in two separate PC-based virtual environments, completed a non-hippocampus dependent (control) mirror-tracing task then received Typhoid (Typhim Vi) vaccination followed by Saline (control) or vice versa. After session 3 they recalled the spatial location of objects learned at sessions 1 and 2. Inflammation at 4 h was associated with a discrete reduction in resting Rhinal-cortex metabolism: interaction group × time, P < 0.001 (sustained at 8 h) and an impairment in spatial but not control memory performance ( F (1,17) = 5.01, P = 0.039, F (1,17) = 1.38, p = 0.26). To investigate, whether inflammatory effects on resting Rhinal-cortex metabolism predicted subsequent spatial memory impairment we performed a regression analysis of our behavioural and PET data. Strikingly, this revealed that though Rhinal-cortex metabolism prior to encoding predicted subsequent spatial memory performance (both immediate and late) in controls ( P < 0.001) this relationship was disrupted following inflammation (significant interaction with group p < 0.01) suggesting that inflammatory effects on resting Rhinal-cortex metabolism may impair encoding in human spatial memory.