This 2015 Alabama combined animal and human review noted:
“Memories can last a lifetime, yet the proteins that enable synaptic plasticity, allowing for the establishment and maintenance of the memory trace, are subject to perpetual turnover.
DNA methylation may likely serve as the principle cellular information storage device capable of stably and perpetually regulating cellular phenotype.”
The authors developed a framework for understanding disparate findings of DNA methylation and demethylation concerning memory. The dependencies expressed in the framework among the numerous factors, with their relative strengths, timings, and durations reminded me of this video:
If such an error-prone framework accurately reflected the evolved architecture of our memory, we wouldn’t have the variety and number and intensity of memories that we have. The framework also neither accounted for prenatal memory processes nor differentiated emotional memories, although some of the referenced studies’ findings were applicable.
DNA methylation and demethylation aren’t the entirety of memory formation explanations. For example, they don’t explain state-dependent memories that can be instantiated, reactivated, and amnesia induced without involving “the proteins that enable synaptic plasticity” described in the authors’ framework. For completeness, the authors could have assessed the relative contributions of other memory processes, or at least enumerated them.
Similarly, DNA methylation and demethylation explanations don’t cover all epigenetic biochemical processes. There are also placental interactions, histone protein interactions, microRNA interactions, etc. For completeness, the authors could have placed the review’s topic within appropriate contexts of other epigenetic processes that influence memory.
This review of DNA methylation and demethylation roles in memory formation opened up a few slats in the blind covering one window. There’s more to be done to fully open that blind, and more window blinds to be opened before the workings of our memory are illuminated.
http://nro.sagepub.com/content/21/5/475.full “DNA Methylation in Memory Formation: Emerging Insights”