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3.4 Indirect Benefits of Learning 45

VetBooks.ir cognitive environmental enrichment is able of behavioural tests (including the Morris
water maze and plus maze tests) at various
to delay onset of dementia because the brain
is able to utilise available neural structures
housed in enriched conditions showed better
which are active in those people who are still ages, 4, 13, and 25 months. Rats that were
learning (Milgram et al. 2006; see Figure 3.6). performance in the tasks at older ages com-
The cognitive reserve hypothesis relies on pared to rats housed in standard laboratory
the assumption that cognitive enrichment conditions. Enriched conditions comprised
early in life affects brain organisation in later of keeping groups of 10–12 animals in two
life, which is supported by MRIs of young adjoining wire‐mesh cages, with objects such
and old human patients (Milgram et al. 2006). as tunnels and toys which were changed five
Similar findings have also been reported in times a week. Harati et al. (2013) concluded
rodent models, where it has been shown that that their study demonstrated that enrich-
cognitive enrichment leads to a number of ment delayed the onset of short term memory
structural changes in the brain, such as an retention deficits. Whilst it can be assumed
increased number of neurons, synapses, and that the enrichment was providing animals
dendritic branches, especially in cortex and with learning opportunities, those rats
hippocampal formation (Würbel 2001). housed in enriched conditions will also likely
Rodent models are often used to better be more active, so it is possible that the activ-
understand the cellular mechanisms driving ity levels also contributed or were the cause of
the neural effects of enrichment and as a this positive effect. For example in humans,
result there is a wealth of literature investigat- cognitive activity during mid‐life is associated
ing the effects of providing animals with both with a reduced risk of developing Alzheimer’s
physical and cognitive challenges and the disease but social and physical activity are
resulting effects on both cognitive function also important (Milgram et al. 2006).
and brain physiology. For example Harati To address which component of environ-
et al. (2013) subjected female rats to a series mental enrichment (social/physical/cogni-

Figure 3.6 An illustration of enriched laboratory mouse enclosure. Source: reproduced with permission of the
Institute of Animal Technology/NC3Rs.