Epigenetic effects on memory: insects to mammals

System-Like Consolidation of Olfactory Memories in Drosophila
Isaac Cervantes-Sandoval, Alfonso Martin-Pena, Jacob A. Berry, and Ronald
L. Davis J. Neurosci. 2013;33 9846-9854 [subscription required]

Abstract excerpt: “These results argue that system consolidation is not a unique feature of the mammalian brain and memory systems, but rather a general and conserved feature of how different temporal memories are encoded from relatively simple to complex brains.”

My comment: Their findings fit within the context of what is currently known about the role of olfaction, odor receptors, hormones, and behavior across species. Nutrient-dependent pheromone-controlled epigenetic effects on hormone-organized and hormone-activated brain development enable the required plasticity during behavioral development of invertebrates and vertebrates via similar molecular mechanisms. The similarities exist regardless of brain size or complexity. Indeed, their data suggest to me that the molecular mechanisms of neurogenic and socio-cognitive niche construction are the same as those of ecological and social niche construction.

One difference is noteworthy. Immediate-early gene activation appears to lead to protein synthesis-dependent short-term memory in mammals that is protein synthesis-independent in flies. Speculatively, this could enable a more rapid response to changes in odor concentrations perceived by flies. All that’s required may be an epigenetic change in the microRNA/messenger RNA balance of neurons in the insect brain compared to changes in nutrient-dependent pheromone-controlled protein synthesis in gonadotropin releasing hormone (GnRH) neurosecretory neurons of the mammalian brain (e.g., in my model).

Article excerpt: “Nevertheless, the model for system consolidation processing of olfactory memories in Drosophila uses the same principles of interaction and reorganization between brain circuits, with early and late memories being supported by different brain regions. ”

My comment: In my model of nutrient-dependent/pheromone-controlled adaptive evolution, it is clear that invertebrate and vertebrate learning and memory are hormone-organized and hormone-activated. It is equally clear that classical conditioning of effects on hormones that affect behavior links olfaction and pheromones to the development of behavior associated with multisensory input (e.g., visual, auditory, tactile). As always, however, tone and foot shock pairing experiments by behaviorists do not exemplify classical conditioning in any species.

Difference between insects and mammals and claims that mammals, including humans, are not classically conditioned to respond to visual, auditory, and tactile input via associations with food odors and pheromones, just suffered another embarrassing refutation because the same molecular mechanisms are common to species from microbes to man. Thus, the insect-to-mammal learning and memory connection in this article  makes it more difficult for human pheromone-deniers to deny the similarities across species that clearly have again been demonstrated in the context of the molecular mechanisms of learning, memory, and hormone-driven organized and hormone-activated behavior.

Author: James Kohl

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