Computer Simulated Brain

Swedish researchers at the Karolinska Institutet (KI) have managed to build a model that shows the mathematical activity of the anterior and superior parts of the brain. The scientists believe this model will lead to greater understanding of how much working memory the brain holds and will teach us how the billions of neurons interact inside the brain. The study is a multidisciplinary project that is a collaboration of two KI teams, lead by Torkel Klinberg and Jesper Tegner. The majority of the work on this project was undertaken by Fredrik Edin and Albert Compte.

Limited Capacity

Working memory is our active, conscious memory and serves to hold onto and process information. We need our working memory for most of our cognitive actions, including language, planning, and thinking. There are limits to what our working memory can hold. For instance, the Swedish scientists discovered that the brain sets a limit on the number of items humans can store in their working memory to seven items at a time.

Magnetic resonance imaging (MRI) has shown that the frontal and parietal lobes of the brain are awakened when two pictures are shown in a sequence. The working memory can hold the images for a short time. But we don't know the mechanism that enables nerve cells to cope with such tasks.

The scientists borrowed techniques from a variety of scientific fields to analyze data on the biochemical and electrophysiological workings of nerve cells and synapses. The researchers then used mathematical tools to produce a computer model of the human brain. The computational data contributing to the workings of the model were developed through fMRI experiments. The use of fMRI also enabled the scientists to check that the data generated by the model was accurate. "It's like a computer programme for aircraft designers," comments Fredrik Edin, whose field is computational neuroscience. "Before testing the design for real, you feed in data on material and aerodynamics and so on to get an idea of how the plan's going to fly."

Memory Storage

Watching the model brain at work, the team was able to reveal what happens to limit the working memory to retaining only 2-7 pictures at the same time. As the working memory begins to fill with information, the neurons located in the parietal lobe start to block the activity of cells in the vicinity. This inhibition of the natural activity and interaction of the neurons gathers strength and stops the brain from adopting added visual information. This effect can be counteracted in part through the stimulation of the frontal lobes. The researchers believe that the frontal lobes may therefore be useful in regulating the memory storage of the parietal lobes.

Dr. Edin believes that intense stimulation of the frontal lobes may improve working memory. He comments that his team was able to demonstrate this effect on humans during their follow-up experiments. Edin states his opinion that the working memory serves as a "bottleneck" for the brain's ability to process information and believes that the study results give scientists some understanding about the structure of this bottleneck.