Associate Professor of Psychology Chantal Stern studies working memory in people using functional Magnetic Resonance Imaging. Psychology Professor Howard Eichenbaum studies the brains of rats as they solve complex problems. Psychology Professor Michael Hasselmo examines the intricacies of working memory on a cellular level.

Recent studies by Hasselmo and his colleague, Angel Alonso at the Montreal Neurological Institute and McGill University, reveal that contrary to previous expectations, individual neurons in the entorhinal cortex (an area of the brain near the hippocampus) fire single electrical impulses, or spikes, not only when they are activated by sensory input, for several seconds after sensory input ceases. This sustained neuronal activity indicates working memory, says Hasselmo.

The researchers most recent studies reveal that neurons in the deep layers of the entorhinal cortex not only sustain activity, but they do so at graded firing rates — if they start firing at 5 spikes per second (5Hz) they maintain firing at 5 Hz; if additional input pushes them to 7 Hz they maintain a 7 Hz level; and so forth. This ability, says Hasselmo, is important for storing information about continuous dimensions, such as keeping track of the headings of a compass and distant landmarks as you are navigating your kayak.

The researchers are now examining the relationship between sustained neuronal activity and the neurochemical acetylcholine — a substance known to activate neurons and which is depleted in the brains of individuals with Alzheimer’s disease. By better understanding the cellular processes underlying working memory, the researchers ultimately hope to find mechanisms that lead to effective treatments for Alzheimer’s disease.

This research was published in the November 14, 2002 issue of the journal Nature.

See also related story: BU Bridge, Research Briefs - for related studies by Sargent College Professor Gloria Waters.