So what does this have to do with epigenetics? Li-Huei Tsai’s team at the Massachusetts Institute of Technology found evidence that environmental enrichment could lead to a fundamental change in the brain cell’s program – the instructions that describe how to make new cells. These changes are made to the actual shape of the packets of DNA in each cell, a modification to its epigenome.

To recap, changes that do not affect the DNA sequence are called epigenetic – they change the way DNA is wrapped up in the nucleus. DNA wraps around proteins called histones, like cotton around a spool, to make a package called chromatin. The characteristic features that change chromatin packaging are mostly chemical changes, either to the DNA itself, by the methylation of individual DNA bases; or to the histone packaging proteins they are wound around, by modifications such as acetylation, or methylation. These modifications can make regions of chromatin more tightly packaged, in which case the genes on the DNA in that region are silenced, or more open, which switches genes on. Tsai’s team showed that environmental enrichment increases acetylation of the histone spools, which makes the chromatin package more open, activating a large number of genes.

So how does this decrease dementia risk? Both Savonenko’s and Tsai’s teams measured the apparent improvement in brain performance using several markers:  the rate at which new brain cells are made; the number of newly-formed or re-established connections between cells; and the capacity of these connections to be conditioned for learning, termed ‘synaptic plasticity’. What they found was that mice kept in environmentally enriched conditions had an increased brain mass, due to new cells being made. In addition, microscopic investigations revealed that the number of connections increased, while  experiments using electrical signals in the brain demonstrated that synaptic plasticity became greater, with mouse subjects showing improved learning skills and memory recall.