I got out one of my neuroscience books today to look something up, and I found some research linked to Saskatchewan (where I live) that made me sit up and notice, so today's an ode to my home province's contribution to this fascinating field.
In 2005, the University of Saskatchewan made a contribution to neuroscience research for its testing of marijuana on rats, and looking at their brains' ability to generate new neurons in response to the drug. I'm assuming they've made more contributions than just this one, but this 2005 study was given special mention in Wikipedia. Apparently pot could have a salutary effect on our capacity to retain memories as we get older... similar to the effect on the brain that exercise has.
We've all heard of neuroplasticity by now, which is a catchall term for a bunch of different processes: the generation of new neurons, synaptic pruning or rewiring; basically anything that changes the anatomy (structure) or physiology (function) of the brain in response to new experiences-- good or bad-- is an element of neuroplasticity (Siegel, 2007).
For the most part, when people talk about neuroplasticity today, they're talking about what their synapses and supporting cells are doing. Whether you're talking about the effect that mindfulness or your Luminosity app have on your brain, or how one part of your brain compensated for a damaged part after an accident, synaptogenesis is when two neurons who are neighbors to each other decide to form a link so information can flow between them.
Neurogenesis, on the other hand, is the process by which entirely new brain neurons are created- the byproduct of neural stem cells and progenitor cells coming together. Although adult neurogenesis was proved possible in 1965, we're still learning why the brain creates more neurons, as the function of new neurons still isn't very clear. Most of our neurons were generated while we were still in the womb, but now we know there are three parts of the brain in adult where neurogenesis occurs on a regular basis: the Dentate Gyrus in the Hippocampus, the Olfactory Bulb, and the Cerebellum.
Because there are a lot of "parent cells" [ie. neural stem cells and progenitor cells] that can give birth to new neurons in the Dentate Gyrus area of the hippocampus, researchers have focussed a lot on that area for their neurogenesis studies. (Students of mindfulness may know that the Hippocampus is where short- and long-term memories are stored; the Dentate Gyrus is one of the interlocking parts holding the two hypocampi together).
The U of S discovered that, in the Dentate Gyrus, where a class of cell membrane receptors called cannabinoid receptors are "involved in a variety of physiological processes including appetite, pain-sensation, mood, and memory", the receptors attached to synthetic cannabis and created new neurons. The cannabinoid-induced increase in hippocampal neurogenesis had an "anxiolytic and antidepressant effect."
I don't know where that leaves us, as my only interpretation that I can come to is that smoking a sane amount of pot here and there can help us grow new neurons, which helps us become less anxious and less depressed. Or is it the other way around, that marijuana helps us become less anxious and less depressed, and the extra neurons are just a byproduct of feeling good? If you're a scientist, you can read the study and e-mail me.
Either way, scientists are interested in this Dentate Gyrus area because- as it was mentioned- the area deals with memory, and because neurogenesis happens here specifically, in this tiny little area of the brain, they're wondering if there are any implications here for Alzheimer's patients. Who knows, maybe when we're all older, some of us will be smoking pot to extend the lifetime of our memories, and we'll be able to thank the U of S for that. Others of us will just be exercising, as that seems to stimulate neurogenesis too, at least in mice.