This question gets at the remarkable fact under our noses all day long: our ineffable thoughts and feelings are making concrete, physical, lasting changes in the structure and function of our brains. Neurons that fire together, wire together. This is learning, including the emotional, motivational, attitudinal and skills learning that is our focus in therapy. In other words, the making of memory – especially implicit memory, the storehouse of emotional residues of lived experience, knowing “how to,” expectations, assumptions, models of relationship, etc. distinct from explicit memory, the much smaller storehouse of specific recollections and knowing “about” – the gradual change of the structure and function of the brain.
In this context, any kind of mental change is evidence of neural change. Since neuroscience is a baby science, our current, noninvasive, imaging technologies have limited capacities to measure neural change in human beings – especially given how physically fine, fast, and complex these changes are. You could put five of the cell bodies of a typical neuron side by side in the width of just one of your hairs, and five thousand of the synapses, the connections, between neurons in the width of just one hair.
Nonetheless, even though the ethics of animal research trouble and even alarm many, including me, it is the case that more invasive research on animal learning – including emotional, motivational learning, that has some parallels to therapy – has established many fine-grained details of the ways in which experiences of stress, frustration, and trauma, as well as experiences of caring, success, and safety change the nervous system.
So we presume that neural change must be occurring if there is mental change. In this light, there are now many studies with human beings that show structural and functional changes after interventions such as training in mindfulness, compassion, body awareness, and psychotherapy. The cortex – the outer shell or “skin” of the brain – gets measurably thicker due to new synapses and greater infusion by capillaries for blood flow; key regions are more readily activated; there is also greater connectivity between regions, so they are more integrated and work better together; there are even changes in the expression of genes – tiny strips of atoms in the twisted up molecules of DNA in the nuclei of neurons.
And as your mind changes your brain for the better, these changes in your brain feed back to change your mind for the better as well. As these positive structural and functional changes in the brain occur, people become more capable and happy. For instance, training in mindfulness increases activation in the left prefrontal cortex, which supports a more positive mood.
As to new cell growth, I assume this is a reference to neurogenesis, the birth of new baby neurons, primarily in the hippocampus. We can encourage the birth of these neurons through exercise, and encourage their survival and wiring into memory networks through engaging in complexity and stimulation.
Here’s the takeaway: we can be confident in our own lives, and in our work with clients, that our efforts are bearing fruit in actual, physical changes in the nervous system. And since motivation is one of the primary factors shaping outcome in psychotherapy – and in life as a whole – this is heartening, wonderful news.