Environmental enrichment enhances episodic-like memory in association with a modified neuronal activation profile in adult mice.
PLoS ONE. 2012-10-22; 7(10): e48043
DOI: 10.1371/journal.pone.0048043
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Leger M(1), Quiedeville A, Paizanis E, Natkunarajah S, Freret T, Boulouard M, Schumann-Bard P.
Author information:
(1)Groupe Mémoire et Plasticité Comportementale-GMPc, Université de Caen Basse-Normandie, EA 4259, Caen, France.
Although environmental enrichment is well known to improve learning and memory in
rodents, the underlying neuronal networks’ plasticity remains poorly described.
Modifications of the brain activation pattern by enriched condition (EC),
especially in the frontal cortex and the baso-lateral amygdala, have been
reported during an aversive memory task in rodents. The aims of our study were to
examine 1) whether EC modulates episodic-like memory in an object recognition
task and 2) whether EC modulates the task-induced neuronal networks. To this end,
adult male mice were housed either in standard condition (SC) or in EC for three
weeks before behavioral experiments (n = 12/group). Memory performances were
examined in an object recognition task performed in a Y-maze with a 2-hour or
24-hour delay between presentation and test (inter-session intervals, ISI). To
characterize the mechanisms underlying the promnesiant effect of EC, the brain
activation profile was assessed after either the presentation or the test
sessions using immunohistochemical techniques with c-Fos as a neuronal activation
marker. EC did not modulate memory performances after a 2 h-ISI, but extended
object recognition memory to a 24 h-ISI. In contrast, SC mice did not
discriminate the novel object at this ISI. Compared to SC mice, no activation
related to the presentation session was found in selected brain regions of EC
mice (in particular, no effect was found in the hippocampus and the perirhinal
cortex and a reduced activation was found in the baso-lateral amygdala). On the
other hand, an activation of the hippocampus and the infralimbic cortex was
observed after the test session for EC, but not SC mice. These results suggest
that the persistence of object recognition memory in EC could be related to a
reorganization of neuronal networks occurring as early as the memory encoding.