Influence of late-life exposure to environmental enrichment or exercise on hippocampal function and CA1 senescent physiology

Abstract

Aged (20–22 months) male Fischer 344 rats were randomly assigned to sedentary (A-SED), environmentally enriched (A-ENR) or exercise (A-EX) conditions. After 10–12 weeks of differential experience, the three groups of aged rats and young sedentary controls were tested for physical and cognitive function. Spatial discrimination learning and memory consolidation, tested on the water maze, were enhanced in A-ENR compared to A-SED. A-EX exhibited improved and impaired performance on the cue and spatial task, respectively. Impaired spatial learning in A-EX was likely due to a bias in response selection associated with exercise training, as object recognition memory improved for A-EX rats. An examination of senescent hippocampal physiology revealed that enrichment and exercise reversed age-related changes in long-term depression (LTD) and long-term potentiation (LTP). Rats in the enrichment group exhibited an increase in cell excitability compared to the other two groups of aged animals. The results indicate that differential experience biased the selection of a spatial or a response strategy and factors common across the two conditions, such as increased hippocampal activity associated with locomotion, contribute to reversal of senescent synaptic plasticity.

Late enrichment maintains accurate recent and remote spatial memory only in aged rats that were unimpaired when middle aged

“…Although enrichment failed to protect learning against age-related deficit, it alleviated the deficit in short-term memory exhibited by SC aged rats. Thus, late enriched environment exposure mitigates age-related deficit, in agreement with previous studies (e.g., Kobayashi et al 2002;Harburger et al 2007;Freret et al 2012;Kumar et al 2012;Morse et al 2015;Fuchs et al 2016;but Bouet et al 2011). The present results also showed that, although EE young adults outperformed SC young adults on a measure of platform-search accuracy (annulus crossing), enrichment had no beneficial effects on the recent memory probe trial in aged subjects.…”

“…Conversely, impaired spatial memory is not a systematic hallmark of physiological aging and many experiments have highlighted the heterogeneity of individual performance at a given chronological age (e.g., Gage et al 1984;Gallagher et al 1993;McQuail and Nicolle 2015). Interestingly, several studies showed that a sustained exposure of middle-aged rodents to an enriched environment mitigated spatial memory deficit in old age (e.g., Kobayashi et al 2002;Harburger et al 2007;Freret et al 2012;Kumar et al 2012;Fuchs et al 2016;but Bouet et al 2011). However, whether housing middle-aged rodents in a more stimulating environment rescues spatial memory in already cognitively declining subjects or protects against further decline remains to be explored.…”

Reversal of age-associated cognitive deficits is accompanied by increased plasticity-related gene expression after chronic antidepressant administration in middle-aged mice

“…Furthermore, although we found some changes in growth factor levels after chronic antidepressant treatment in middle-aged mice, none of these are consistent with the observed changes in visuospatial memory. It has been reported elsewhere that improvement in spatial memory in aged rodents were not accompanied by a change in growth factor levels (Kumar et al, 2012). It is important to note that this does not preclude an important role for drug-induced changes in hippocampal growth factors in other behavioral domains not addressed here.…”

Activité aérobie et environnement enrichi : perspectives pour le patient Alzheimer

“…Si chez les rongeurs âgés, l'EE semble ne pas modifier l'expression des enzymes antioxydantes telles que les SOD-1 et la glutathion peroxydase (GPX-1), la diminution des taux de malondialdéhyde semble témoigner d'un stress oxydant moins important [28].…”

“…Enfin, Beauquis et al [31] ont réarrangé tous les 2 jours la cage utilisée pour présenter l'EE afin de renouveler les stimulations cognitives des rongeurs. Sur le plan cognitif, l'EE améliorerait les fonctions cognitives [28][29][30]32,33]. Néan-moins, ces effets sont très limités aux stades les plus avancés de la maladie [32].…”