Experimental Medical Science

Faculty of Medicine | Lund University


Associative Learning


Germund Hesslow, Professor,
Research Group Leader
Tel: + 46 (0)46 2227750 
E-mail: Germund.Hesslow(at)med.lu.se

About a hundred year ago, the Russian physiologist Ivan Pavlov described a simple form of associative learning, today often called classical or Palovian conditioning. If one starts with an inborn reflex such as salivation elicited by food in the mouth or a blink elicited by a puff of air to the eye and let the food or the air puff repeatedly be preceded by a neutral stimulus such  as a tone, the tone will acquire the ability to elicit the response, which is then called a conditioned response. An interesting aspect of the conditioned response is that it is precisely timed. If the time between the tone and the air puff is increased, the conditioned blink will be delayed by a corresponding amount. It has been known for a couple of decades that the learning takes place in the cerebellum and our research group has identified the group of nerve cells in which the learning occurs. We are currently studying how properties of individual nerve cells change during learning. The purpose is to understand mechanisms underlying the learning and the timing of the conditioned responses. We have also discovered a feedback mechanism that regulates the learning and that blocks further learning when the conditioned response has reached a sufficient size. We are now trying to clarify the mechanisms and consequences of this feedback system.

There are several medical conditions that are suspected of involving a dysfunction of cerebellar mechanisms, for instance autism and speech and language disabilities. We are currently working on a project where we test cerebellar learning in children with various handicaps.

We have developed a theory of cognitive function called "the simulation theory" that builds on the assumption that the brain can simulate interaction with the external world and generate its own input. We are working on developing the consequences of this theory and apply the basic mechanism to robots.

Research Interests

  •  Physiological mechanisms underlying associative learning. Research is focused on the physiology of the cerebellum which contains the neural substrate for classical (Pavlovian) conditioning.
  • Mechanisms underlying consciousness and cognition, including robot simulations of cognition. 
  • The philosophy of science, mainly causality.

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