In March 2015 I finally started my last semester of the Master´s in Neurobiology. Courses-wise, the semester was actually not so intense, we just had two courses, but I finally got repaid of all the efforts I had to put into getting myself around Physics, Neurophysiology and some not-so-nice professors: I was eventually connecting all the dots and I was finally learning the neural bases of different behavioural processes and the mechanisms of drugs acting on the central nervous system (CNS), in respect to their use in Neurology and Psychiatry. Not everything was lost, I was finally having fun and I was eventually sure I chose the right Master´s.
As I mentioned in one of my first posts (have a look here and here if you missed them), I consider human behaviour no more than the result of an electrical and chemical exchange that happens in our brain and everything we do, we think, we say, is no more than the effect of neurotransmitters release in a certain area, that is connected to another area and another one, that will then result in us falling in love, getting angry, remember a moment of our life, show empathy and so on so forth. Therefore, beginning to study the cellular mechanisms and neuronal circuits that allow us to learn and remember, emotions, food intake, sexual and parental behaviour and language was giving me the comforting feeling of being close to mechanistically understand humans and myself in particular.
Since the content of this fascinating course was quite wide, I will definitely explore more of the topics we went through during the course. However, for today, I would like to introduce the SRF with a question: have you ever had the feeling of having an instinctive response to something because of the associations you have made with it over time? To be clearer, let’s make an example: which brand can you think of, when you spot a red poster of a big glass filled with sparkly, bubbly cola on ice? Most likely it is going to be Coca-Cola. Indeed, Coca-Cola’s marketing campaigns associate various activities and environmental factors, like dehydration and heat with their product, and the cold Coke has now become the signal for the arrival of the heat. So, how did they do that? They used the so-called Pavlovian conditioning.
“Science Related Fact” (SRF):
Pavlov was a Russian scientist who in 1904 won the Nobel Prize in Physiology or medicine “in recognition of his work on the physiology of digestion, through which knowledge on vital aspects of the subject has been transformed and enlarged”. But there is more about is work.
Like many great scientific advances, Pavlovian conditioning (aka classical conditioning) was discovered accidentally. Pavlov started from the idea that there are some things that a dog does not need to learn. For example, dogs do not learn to salivate whenever they see food. However, he noticed that dogs produce extra saliva when they believe food is on its way: in behaviourist terms, food is an unconditioned stimulus and salivation is an unconditioned response. (i.e., a stimulus-response connection that required no learning). However, he realised that dogs would begin to salivate whenever they heard the footsteps of his assistant who was bringing them the food, creating a learned and conditioned response. In the famous experiments that Ivan Pavlov conducted with his dogs, Pavlov found that objects or events could trigger a conditioned response.
He designed an experiment using a bell as a neutral stimulus. By itself the bell did not elicit a response from the dogs (in this case, it did not elicit salivation in the dogs). Next, Pavlov began the conditioning: as he gave food to the dogs, he rang the bell. After a number of repeats of this procedure, he tried ringing the bell without providing food to the dogs. On its own, an increase in salivation occurred: the sound of the bell on its own now caused an increase in salivation. The result of the experiment was a new conditioned response in the dogs: the dog had learned an association between the metronome and the food and a new behaviour had been learned (see picture below for a diagram of this experiment).
Incidentally, Pavlov got hungry himself (got conditioned himself) during these trials and, to keep himself away from the meat that was to be given to the dogs, he invented a filling dessert that has since been called the pavlova.
There are reports of pavlovian conditioning researches performed on human, even if we can see some effects of this conditioning on ourselves everyday, since we are constantly “attacked” by advertisements everywhere we look at. However, an interesting (still with questionable results) research on human conditioning was the one used by S. Rachman and his group in 1960s: they wanted to know if they could condition a sexual reflex in men by seeing pictures of boots. They first got volunteers and hooked them up to a device that measured tumescence. They then showed a sequence of slides that was always the same – naked women and then boots. Indeed, after some time, the scientists were pleased to see that the men responded to pictures of boots without ever seeing the naked women. Nonetheless, the results were questioned later, as boots were already very much en vogue for sexually attractive women at the time.