VOLUMETRIC MRI ANALYSIS OF THE AMYGDALA AND THE HIPPOCAMPUS IN SUBJECTS WITH AGE-ASSOCIATED MEMORY IMPAIRMENT - CORRELATION TO VISUAL AND VERBAL MEMORY

Age-associated memory impairment (AAMI) is a common but disputed entit y. It is unclear whether AAMI is a phenomenon of normal aging or an ea rly sign of Alzheimer's disease. The present study aimed to identify p ossible structural abnormalities in the medial temporal lobe of AAMI s ubjects. We measured volumes of the hippocampus and amygdala by MRI in 16 AAMI subjects and in 16 age- and sex-matched controls and correlat ed the volumes with subjects' performance on two visual memory tasks ( the Benton and the Heaton visual retention tests) and on a verbal memo ry task (the Buschke-Fuld Selective Reminding Test). The mean hippocam pal and amygdaloid volumes normalized for brain size per se did not di ffer between the two study groups. In controls, but not in AAMI subjec ts, the right hippocampus was larger than the left. Accordingly, the v olumetric asymmetry between the right and left hippocampi was smaller in AAMI subjects than in controls (Student's t test, p < 0.05). The vo lume of the right hippocampus (r = 0.37, n = 32, p < 0.05) and the mag nitude of the asymmetry between the right and left hippocampi (r = 0.3 8, n = 32, p < 0.05) correlated with total score on the Benton test. W e also found significant correlations between the amygdaloid volumes a nd the performance on visual memory tests but not with score on the ve rbal memory test. Furthermore, a subgroup of seven AAMI subjects with the lowest visual memory scores (less than or equal to 5 on the Benton test) had smaller right and left amygdala (13%, p < 0.05) than the si x controls with the highest scores (=9 on the Benton test). Thus, we d emonstrate that minor structural changes are present in both the hippo campus and the amygdala in AAMI subjects compared with age-matched con trols. Follow-up of the subjects will be necessary to determine whethe r these minor structural abnormalities predict development of dementia or just reflect increased variability of cognitive performance in eld erly humans.