An important factor in schizophrenia and Alzheimer’s disease, as in concentration disorders like ADHD, is that memory circuits are easily distracted by other signals. Inhibitory cells are not active enough, in other words. Patients lose focus and find it difficult to “keep more than one ball in the air at a time.”

New experimental discoveries have shown that the signal substance dopamine can regulate the activity of inhibitory nerve cells so that we aren’t so easily distracted. In the PNAS article the scientists demonstrate how this mechanism can improve our short-term memory.

“Dopamine shortage leaves us less concentrated and hampers our short-term memory. We’re looking for a drug that influences exactly the right type of dopamine-secreting cells in the frontal lobe,” says Jesper Tegnér, professor of biological computing at Linköping University.

The frontal lobe is the site of the working memory, the ability to keep information active for short periods. Behind the model now being presented lie studies of how children with ADHD react to memory training, among other things.

“The training program has proven to produce lasting effects. Apparently permanent changes take place in nerve cell circuits,” says Jesper Tegnér.

Together with American colleagues, he has constructed a mathematical model, based on experimental data, that can be studied using computer simulations. It is a network model representing a circuit of 1,000 cells in the frontal front lobe in apes. The outcome of the model has been compared with experimental studies of the brain activity of apes. The simulations performed precise predictions about the effects of dopamine on the inhibitory cells. It is well known that patients with schizophrenia have disturbances in the dopamine-producing path systems. The new results can provide a basis for studies of schizophrenia and also for improving the training programs for children with ADHD.

The article is published in PNAS No. 5 2004.

Professor Jesper Tegnér can be reached at phone +46 13-282989 or at