Attenuated long-term Arc expression in the aged fascia dentata.

One prominent component of aging is a defect in memory stabilization. To understand how the formation of enduring memories is altered in the aged brain, long-term markers of the biological events that may mediate memory consolidation were used to examine the activity dynamics of hippocampal circuits over extended intervals. The immediate early gene Arc, which is implicated in both durable memory and synaptic plasticity, is expressed in the fascia dentata (FD) for long periods following behavioral experience. To test the hypothesis that aging alters long-term Arc transcription in the FD, a region critical for spatial memory and impaired with progressive age, young and aged rats explored a novel environment twice, separated by an 8-hour interval, and FD Arc transcription was assessed. Relative to young rats, (a) fewer granule cells in the aged FD transcribe arc 8 hours after spatial exploration, and (b) this decrease is correlated with impaired spatial memory. These findings are consistent with behavioral evidence of age-related decline in hippocampal-dependent memory processing long after an event is to be remembered, and reaffirm the integral role of the FD in the neural circuits supporting durable memory.