A new University of Otago – Ōtākou Whakaihu Waka-led study has put its own spin on the Pavlov’s Dog experiment, shining a light on how our brain learns new things.
In the original 1890s experiment, physiologist Ivan Pavlov trained dogs to associate the sound of a click or a bell with the imminent delivery of food by repeatedly feeding them after the sound. The dogs were so used to this pairing that they would salivate when hearing the sound, even if they were not fed.
In the new study, researchers replicated this on rodents by pairing a flash of light with a reward.
In doing so, they discovered a mechanism in the brain that explains how the light – which previously had no inherent value – gains significance as something positive, and the role this mechanism plays in the learning process.
Professor John Reynolds
Lead author Professor John Reynolds, of the Department of Anatomy, says when something important and valuable happens, our brain constantly tries to discover what we did to cause it.
“If we work that out, we can turn it into a habit so that we don’t have to use our scarce brain resources all the time,” he says.
“We found the response in a sensory area of the brain, the superior colliculus, to the visual cue became stronger with repeated pairing and stayed strengthened unless the light flash was then repeatedly delivered without reward.”
The process of strengthening the superior colliculus required the combined actions of two major neurochemicals, dopamine and serotonin, he says.
“We further found that once strengthened, the visual signal began to channel through the colliculus to directly drive the release of dopamine itself into areas where the learning of actions lead to delivery of reward.
“Hence, the initial formation of a strong representation of the reward value of the light through classical conditioning begins to contribute to the processes of operant conditioning, teaching the brain the actions that are required to earn the reward.”
Professor Reynolds says despite being a century old, the neural mechanisms underlying sensory conditioning by reward are not fully understood.
“It might seem that how cues gain significance would be well-known, however we have discovered that it happens in a very primitive part of the brain that is the first to see the light – the superior colliculus – rather than the much bigger and more sophisticated cerebral cortex.”
The study is published in the journal Nature Communications and believed to be the first report of a mechanism directly linking the processes of classical and operant conditioning at the cellular level.
Publication:
Yan-Feng Zhang, Jean-Philippe Dufour, Peter Zatka-Haas, Peter Redgrave, Melony J. Black, Armin Lak, Ed Mann, Stephanie J. Cragg, Wickliffe C. Abraham & John NJ Reynolds
Nature Communications
