We now know that declarative memory, the type of memory we use to remember facts, faces and events, is intimately associated with the brain's limbic system (including such structures as the hippocampus, the amygdala and the hypothalamus). Procedural memory is of a very different form, and is the type of memory we use to learn and perform basic and complex motor skills which help us to interact with our environment. This latter type of memory is now attributed, in part, to a very different part of the brain--the cerebellum. During the past several years Dr. Lavond and his colleagues have been involved in an extensive mapping of the cerebellum as pertains to its involvement in the acquisition of a classically (Pavlovian) conditioned response. The earlier studies involved making destructive lesions in selected brain nuclei, their inputs or outputs, and demonstrating that this destroys old memories and prevents the formation of new memories. A major drawback to this technique is that it is permanent: There is no way to restore destroyed brain tissue, and more importantly, it is impossible to distinguish between different loci which are involved in the learning versus the memorial process. Dr. Lavond is now utilizing a remarkable new technique which allows him to make "reversible lesions" of selected brain loci. He uses a miniaturized cooling probe to drop the temperature of precise brain regions: This renders the nerve cells temporarily inactive. Then, as the brain warms up, the functioning of that previously cooled part of the brain returns to normal. In one experiment, the acquisition of memory (learning) is being tested. Cooling the brain locus necessary for learning will prevent the brain activity essential for memory. When returned to normal temperature, there should be no recall or performance associated with having been trained. In another experiment, memory retention per se is being tested. If, in a previously trained animal, the memory locus itself is anesthetized then there will be no performance of learned activity. When returned to normal temperature, the performance will reappear. Results of these studies will help localize further the different brain loci involved in different aspects of learning and memory. This information will be useful in the design of yet more pragmatic therapeutic regimens for children with learning disabilities, those who have sustained traumatic brain injury, and for aged adults with senile dementia.
