REGIONAL VOLUMETRIC CORRELATES OF SPATIOTEMPORAL AND RECOGNITION MEMORY IMPAIRMENT IN AGED RHESUS MONKEYS.
1. Dept Neurosci, Mount Sinai, New York, NY, USA
2. Radiology, Univ California, Davis, CA, USA
3. CNPRC, Davis, CA, USA
4. Psychiatry, Univ California, Davis, CA, USA
5. NSMA, Univ Arizona, Tucson, AZ, USA
Spatiotemporal and recognition memory are vulnerable to aging in both humans and monkeys. To investigate whether these deficits are coupled with atrophic changes of memory-related brain regions, we acquired T1-weighted magnetic resonance images and quantified cerebral, ventricular, hippocampal, prefrontal cortical (PFC), striatal and calcarine sulcus volumes for 6 young (9-12 yrs) and 14 aged (24-29 yrs) rhesus monkeys (Macaca mulatta). Subjects were tested on a medial temporal lobe dependent recognition memory task (delayed non-matching to sample; DNMS), and a spatiotemporal memory procedure (delayed response; DR) that requires the PFC. Chronological age inversely correlated with the volume of the striatum (r= -0.57, p=0.01) and dorsolateral PFC (r=-0.55, p=0.01) when all subjects were included in the analysis, and cerebral volume declined selectively among the aged monkeys (r= -0.66, p=0.02). Although hippocampal volume was unrelated to DNMS performance (Shamy et al., 2006), it predicted initial acquisition scores for DR (r= -0.53, p=0.02), and DR accuracy across increased memory delays in aged subjects (r=0.59, p=0.03). Striatal volume correlated with age-related DNMS acquisition impairment (r=-0.52, p=0.02) and delay performance (r=0.57, p=0.01). For the PFC, total volume (r=0.61, p=0.03), and the volume of white (r=0.60, p=0.03) and gray matter (r=0.58, p=0.04) predicted DNMS accuracy. Regional analysis revealed that, across all monkeys, dorsolateral PFC volume was coupled with DNMS acquisition (r=-0.57, p=0.01) and delay scores (r=0.55, p=0.02), but not DR performance. When the aged group was considered alone, the volume of the ventrolateral PFC cortex was related to DNMS acquisition (r=-0.57, p=0.04), and performance across delays correlated with the volume of the superior frontal (r=0.61, p=0.03), dorsolateral (r=0.60, p=0.03) and ventromedial PFC (r=0.59, p=0.03). Finally, calcarine sulcus volume was preserved during aging and failed to predict any of the behavioral measures examined. This extensive volumetric analysis adds to growing evidence that morphometric alterations coupled with cognitive aging in primates include a complex constellation of region-specific vulnerability distributed across multiple memory-related systems.