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Neurogenesis Not Needed for Environmental Enrichment Effects
French researchers, which found that turning off neurogenesis blocked
environment-induced memory enhancement in rats.
While differences between studies, or the existence of different pathways
to learning, might account for opposite outcomes, the new evidence
means the jury must re-evaluate the role of adult neurogenesis in modify-
ing learning and behavior.
The verdict is of interest to Alzheimer researchers, because environmen-
tal enrichment has been shown to decrease both amyloid pathology and
cognitive defects in mouse models of AD.
To investigate the role of neurogenesis in environment, joint first authors
Dar Meshi, Michael Drew, and their colleagues used targeted radiation to
kill off neuronal progenitors in the hippocampus before upgrading their
mice to deluxe accommodations.
The researchers showed that bromodeoxyuridine and doublecortin—neu-
rogenesis markers that otherwise appear in the hippocampus after envi-
ronmental enrichment—were absent from irradiated animals.
Six weeks later, the irradiated and control mice were put through several
behavioral tests, including those for anxiety, habituation to a new envi-
ronment, and for spatial learning in the Morris water maze.
In each case, environmental enrichment improved the animals’ perfor-
mance, and that improvement was unaffected by previous irradiation.
From this the authors concluded that, at least for these tasks, the effects
of environment do not require adult neurogenesis.
Odds and ends - themes and trends 460