Beating Back Depression With Neuroplasticity
Fire Together, Wire Together
You probably didn’t know this, but babies lose a ton of brain cells. That isn’t because anything is wrong; it’s because brains are basically just pattern-recognition machines, and babies are encountering the basic patterns of our world for the first time all day, every day. Cells that aren’t wired up the right way or don’t respond to the right kinds of stimulation die off, as do unhelpful connections between neurons. In total, we lose something like 15% of our brain cells to this basic “pruning” process between birth and adulthood.
The inverse of pruning is neuron growth, which is known in the brain science community as neurogenesis. Together, they are the two most dramatic forms of neuroplasticity, a sciencey word for changes in the physical structure of the brain. Our early lives produce an explosion of neuroplastic changes.
When you read about it in the press, though, neuroplasticity is more commonly associated with learning, and with ongoing change over the course of our lives. This is a different kind of plasticity (which just means “change,” by the way, and was first used in the context of brains by the extraordinary William James.) Learning-based neuroplasticity is mostly about changes in connections between neurons. New connections form, old connections are severed, and most often, the strength of connections changes.
The phrase you’ll hear in any intro neuroscience class is, “what fires together, wires together.” Modern neuroscientists talk about long-term potentiation. Basically, neurons are all linked to many other neurons by long, thin structures called axons and dendrites that meet up at connection points called synapses. Ions—electrically charged molecules—travel across synapses, often in waves. When they build up in sufficient concentrations around a single neuron, the difference in electrical charge between the cell’s inside and outside triggers a sort of flush, with ions flowing into and out of the cell en masse and sending waves of charged molecules on to other cells in turn. When cells are triggered in very close sequence, the connection between them gets more efficient at passing on ions.
If that last paragraph didn’t make a ton of sense, think about it like the first people traveling via carriage and forging a path. As more people need to travel via carriage, processes become streamlined; carriages are loaded more efficiently and depart more frequently. More carriages traveling on the same path make the path more established and easier to maneuver over. Below is a video from USC for a visual.
Over time, as we move and act and think and experience what’s around us, this process gradually reshapes whole networks of neurons. It forms memories, shapes our reactions, trains our muscles, and much more.
Healthy Brain, Healthy Mind
We’ve talked about depression before on this site, emphasizing that it’s a physical disease rooted in changes to the structure of our brains. It’s worth unpacking the details of that, just a little.
Remember, everyone has some symptoms of depression at least some of the time. Those symptoms usually come from environmental changes (like stress or poor diet) that lead to inflammation and cell death in our brains. Both neurons and microglia support cells are affected, and so many cells can die that some brain structures actually shrink on volume.
Antidepressants are effective, in part, because they appear to cool off that inflammation. Less inflammation means less cell death, which means more normal brain function, which means fewer symptoms.
This is a relatively new area of study, but it’s attracting interest quickly. The core idea is that neural inflammation stops neuroplasticity. If we can get the engine of neuroplasticity going again, we can reduce depressive symptoms. Unsurprisingly, all the same basic healthy habits that help with depression are also linked to later-in-life neuroplasticity: fresh food and varied diet, active social connections, and exercise.
Inspired by that link, scientists are proposing that we combine powerful neuroplasticity-enhancing treatment with more traditional “behavioral” treatments like talk therapy. We might give people ketamine, for instance, which changes how neurons interact with certain kinds of molecules and makes synaptic change easier. Combine that with a therapy or program designed to help people reshape negative thought patterns, and the therapy might work much better—your brain will have an easier time building new connections.
There are other tools to massively boost neuroplasticity. One is zapping your brain directly with electricity using either electroconvulsive therapy or transcranial brain stimulation (TBS). Another is increasing levels of brain-derived neurotrophic factor, a chemical that aids in neuron growth, which can be done by getting aerobic exercise, taking lactate injections, and other means. Finally, and least excitingly, regular antidepressants have some effect on neuroplasticity as well—probably for reasons linked to BDNF and increased signaling sensitivity.
In terms of practical advice, all of this points in a few different directions. One is overall health and good habits. Another is getting in touch with a psychiatrist to talk about the more intense options, like ketamine, lactate, or TBS. And last, of course, is general advice for neural health: keep your mind moving.
