How does PTSD or taste aversion make a change in the brain from one single experience?
By Lauren Bosch UA’24 and Jim Stellar
We know that the brain changes with experience. Typically it takes some time for the learning to take place. Think about the multiple repetitions that are required before Pavlov’s dogs learned to salivate when he rang the bell. So, how can one experience like in PTSD or in taste aversion learning produce such dramatic changes and what does that tell us neurologically about cognitive-emotional integration? Finally, how does that inform our thinking in this blog series about how students learn from internships or other direct experience what they want to study, or not to study, going forward in their program of classes.
Taste Aversion Learning: Imagine going to a nice restaurant and ordering a steak. It comes with sauce béarnaise, which you have never had before. Then later that night you start vomiting. It will turn out that you had a stomach virus that hit you just then, but your brain will attach that gastric illness to your first taste of sauce béarnaise and it will become repulsive to you the next time you even smell it. You will have a disgust reaction even to the smell of sauce béarnaise after just that one pairing and even with the hours separating the stimulus (sauce béarnaise) and the reaction (gastric illness). Pavlov not only had to pair the bell with the meat for his dogs multiple times but he had to give the meat shortly after the bell. So, what is happening here? At the psychological level, this taste-aversion learning is said to be “evolutionarily prepared” learning, possibly because poisoning from spoiled food or toxic plants is not uncommon and important to survival. A prominent learning psychologist, experienced this taste aversion with this same sauce béarnaise stimulus discussed above, confirming personally with this stimulus earlier research on taste-aversion learning. So how does it work?
Post Traumatic Stress Disorder: Before going there, consider PTSD (post-traumatic stress disorder). Again, this can be a long-term learning phenomenon that can start from a single experience. The experience can come from anywhere but one of the most discussed types is something dramatic that happened in a war zone that leaves the person intact and alive but traumatized and unable to function back home. The therapist will work with the patient, sometimes for years to get them to not be so anxious, afraid, disturbed in normal areas of life. Yet it can all start with a single experience.
Synaptic Plasticity: So what evidence is there in the brain that these experiences change the brain’s structure? This has been the subject of much research and theory. We know that neurons communicate with each other through connections called synapses where one neuron releases a chemical (a neurotransmitter) on the other. These synapses change with how much the neuron fires and that can leave a lasting difference in the potency of the connection. That changing their connectivity provides for learning in a very complex brain circuit where the changes that underlie our habits and memories. Every neuron can do that, even in the spinal cord. So, it can happen in the limbic system which can lead to changes that can drive the behaviors of Taste Aversion Learning and of PTSD. If that is true, then the trick then is how can the cognitive systems in the neocortex interact with these limbic systems to correct that imbalance? Of course the cognitive systems have the same neuroplasticity and that may be the structural manifestations, probably very subtle, that underlie any effectiveness of talking therapy.
Now Something Positive: Now let’s move to something positive. As a student in one of JS’s classes, LB began meeting with JS about classwork, which quickly turned into a mentor relationship. Before this experience, LB had never had a mentor, let alone met with a professor outside of class on a consistent basis. Now, even after graduating, LB and JS still meet to discuss continuing career development. Having a mentor figure that she can count on has given LB more confidence in her work as well as her potential for her future in a career within the psychology field. Without this relationship to lean on for both support and advice, LB feels that she would have had a much different experience both in the classroom setting and out. While it seems common for relationships like this to occur in university, most students do not and have not had an opportunity where they felt comfortable enough with a professor to reach out even after graduation. Similar to the therapist and patient from the previous paragraph, the mentor relationship is beneficial in helping a student realize their potential in a setting where they are almost always doubting it.
It is an article of faith for us that mentoring can rapidly change a student’s perspective. JS is well-known among his students for telling his own story of being mentored when he was their age. As a result, he walked away from a long held premedical plan for himself and into a neuroscience research plan that ultimately led to his being a professor and now working with LB.
Sometimes, when one can see something, it all becomes clearer. Unfortunately, we cannot see the effect on the brain from mentoring. But we can see (and feel) its effects on decisions, confidence, and even direction. For students, a mentor relationship can be the push needed to allow them to believe in themselves. Many people, especially young people, struggle with the ability to feel that they are doing the right work and are on the right path. Having someone older and more experienced than you guiding you as well as encouraging you can eliminate that self doubt and allow a student to reach higher potential.
So, what is going on in the brain when this “rapport” happens and a mentoring relationship develops rapidly? This is a good subject for our next blog.
