中文版

15 October 2004

CUHK Researchers Solve the Mystery of Long-term Memory

　　Scientists have known for a long time that memory can be divided into two main types: short-term memory and long-term memory. Short-term memory, which lasts for seconds to minutes, allows one to memorize, say, a rarely used telephone number long enough to make a call, but will be lost completely afterwards. Long-term memory, on the other hand, lasts much longer and is resistant to removal. It is long-term memory that is more important to our lives. Long-term memory is closely related to our learning process. Patients with Alzheimer's Disease lose their ability to memorize or recall old memories are not only handicapped in daily lives, they lose also their own identities.

　　Researchers at The Chinese University of Hong Kong, in collaboration with the National Institutes of Health (NIH) and Cornell University in the U.S., solves one of the long-standing mysteries in memory research: what is the mechanism that converts short-term memory to long-term memory? They found that a protein called brain-derived neurotrophic factor (BDNF), which is well known to be a trophic factor for the survival of neurons, is crucial in the formation of long-term memory. Their results will be published today (15 October) in the prestigious journal Science.

　　By applying electrophysiological techniques on normal and gene knock-out mice, these researchers show that in the hippocampus, a brain area important for memory formation, BDNF is the only key protein required for the expression of late-phase long-term potentiation, a cellular model of long-term memory. The researchers also found that the synthesis of the active form of BDNF is critically dependent on a seemingly unrelated enzyme system in the body known as tPA/ plasmin, which may provide hints for further research on the mechanism of long-term memory formation.

　　One could envisage that when we try to memorize, for instance, in preparation for an examination, there is increased production and release of BDNF in the brain. If the production of active BDNF is not functioning, long-term memory formation will be hindered. Professor Yung Wing Ho, Associate Professor at the Department of Physiology, CUHK and one of the authors of the study, pointed out that it is too early to talk about applications of the finding. But one thing is certain: the more we know about the process of memory formation, the more likely we could find drugs or other means to improve learning and memory in normal subjects and subjects with memory disorders.

　　The person who did the main part of the work is Ms Petti Pang, a PhD graduate of CUHK's Faculty of Medicine. With a degree in physics Ms Pang entered a PhD programme in the Physiology Department of CUHK with virtually no research experience in life science. She received more than a year of research training under the supervision of Professor Yung before embarking on a collaborative project in Professor Lu Bai's laboratory at the National Institute of Child Health and Human Development of NIH. She used only about 12 months of time to solve the mystery of long-term memory formation.

　　Dr Pang said: "The significance of this work is in pinpointing the key role played by BDNF in long-term memory formation. My next target is to work out the roles played by BDNF in other higher brain functions such as cognition, calculation and logical thinking".

　　The findings by CUHK researchers also have interesting implications in another, even more mysterious question: the mechanism of forgetting, which is the reverse of memorization. Specific hypotheses on this question are now under the scrutiny of the research team.

Ms Petti Pang, the PhD graduate of CUHK's Faculty of Medicine, who did the main part of the work.