The neuroimaging literature is littered with findings of functional
differences between the left and right amygdala. One side is active in
one task, the other during another task and with no real pattern or
consensus as to what this functional asymmetry might mean. The most
intriguing new finding in this area is that of gender differences in
amygdala activity in association with the formation of emotional
memories. Larry Cahill and colleagues recently published a paper in
Neurobiology of Learning and Memory (vol. 75 pp 1-9) which illustrates
that in women, activity in the left, but not right amygdala predicts
subsequent memory for emotional stimuli. The converse pattern is found
in men (right activity predicts memory). This finding replicates two
previous reports of same, so this is the most consistent finding of
human amygdala asymmetry that I know of. Work with lesion patients
subsequent to unilateral temporal lobectomy has shown some interesting
patterns in this regard. Namely, damage to the left amygdala results in
reduced memory for emotional verbal material and damage to the right
amygdala impairs memory for emotional pictures (as well as reducing
visuospatial performance in general). These studies are complicated by
the fact that it is not only the amygdala that resected in these
surgeries, but the temporal pole and a variable amount of temporal
cortex as well. I've also read of some functional asymmetries in fear
conditioning, but I can't remember what the pattern was...
--
Tony W. Buchanan
University of Iowa
