Klaus Hoffman lecture delivered at Science 2008
Last Thursday and Friday saw some of the most highly acclaimed researchers of the decade converge at the University of Pittsburgh’s annual science and technology showcase, Science 2008. One of the most notable parts of the event was the Klaus Hoffman lecture, which is presented annually in memory of Klaus Hoffman, a biochemist who made significant contributions to research at the University of Pittsburgh. This lecture has been a highly anticipated part of the event and has featured notable speakers such as last year’s Nobel Prize winner, Mario Capecchi.
This year’s lecture was delivered by Marcus Raichle, a professor of radiology, neurology, neurobiology, psychology, and biomedical engineering at Washington University in St. Louis. The lecture, “Two views of brain function,” gave insights into the rather mysterious workings of the brain.
Raichle’s lecture succeeded in surprising the audience as it revealed that, contrary to popular belief, the brain spends most of its energy performing intrinsic activities rather than in responding to external stimuli.
Raichle explained that the debate between these two views of brain function had been going on for a long time.
In order to find concrete evidence supporting either of the two theories, researchers looked at the general energy consumption in the brain when people were performing different activities. Elaborating on this concept, Raichle said, “The brain is rather expensive.” He explained this statement by saying that although the brain accounts for only 2 percent of the body’s weight, it uses up nearly 20 percent of the energy produced by the body. Hence, by assessing the “cost” of the brain for intrinsic activities as compared to the cost for responses to the environment, a firm conclusion could be drawn.
Raichle and his team assessed the energy consumption in people’s brains while they were responding to certain tasks and while they were in a resting state. Positron Emission Tomography (PET), which assesses the glucose consumption in the different parts of the brain, was used for this purpose. “[Our conclusion was that the] work of the brain is dominated by intrinsic activities,” Raichle said. The results were startling as they revealed that internal activities of the brain accounted for nearly 60 to 80 percent of the brain’s total energy consumption. There was constant activity going on in the brain even when the subjects were supposedly at rest.
“[There is a] beautiful [pattern] that emerges out of the brain even when it isn’t engaged in input/output,” Raichle said.
This conclusion raised the question of what the brain was using such large amounts of energy for. Most would view intrinsic activities in the brain simply as activities related to nourishing the brain cells.
As Raichle rhetorically asked, “[Was the high cost of energy] just for housekeeping?” However, as he later explained, a major part of intrinsic activities is communication between cells. Raichle joked that just as humans use up a lot of energy in talking to one another, cells need energy to communicate. Another ongoing internal activity in the brain is the formation of connections — called synapses— between the different neurons.
“Increase in glycolysis is linked to synaptogenesis,” Raichle said. Glycolysis is the first step in the process of glucose metabolism, which ultimately produces ATP, the basic source of energy for all cells.
What was interesting about the levels of glycolysis in the brain was that glycolysis levels increased during the day and decreased at night. Raichle’s inference from this discovery was that during the day, new synapses are built in the brain, but at night, the brain stocks up on energy and does not use too much glucose.
This finding also sheds light on why humans need to sleep. As Raichle aptly said, “We can’t afford not to sleep; it’s too expensive.” Although cell-to-cell communication and formation of synapses are very important, perhaps the most important function that the brain performs internally is that of the retention of information. Certain experiments showed that glycolysis is persistent a few hours after learning something new. Also, research with Alzheimer’s patients showed that the regions with amyloid deposits, which are deposits of fibrous protein that are responsible for Alzheimer’s disease, showed decreased rates of glycolysis. More research into these could perhaps lead to a better understanding of Alzheimer’s disease.
The Klaus Hoffman lecture was a perfect end to the Science 2008 event. As reported in Medical News Today, apart from lectures from renowned scientists, the event consisted of presentations from a variety of researchers from the University of Pittsburgh and Carnegie Mellon, poster presentations, professional development workshops, and showcases of new technology developed around Pittsburgh. The two-day event was enjoyable for many. According to Saudamini Roy, a graduate student in the psychology department at Carnegie Mellon, the lectures were a great learning experience.
“I think the talks were very interesting and covered a wide range of topics. Marcus Raichle’s talk was very good,” Roy said.
As far as the complexity of the lectures was concerned, Roy said, “It does require a certain level of background in psychology and neuroscience to understand the higher-level concepts, but I think a layman could get an overall summary of some of the talks. Some of the speakers were really good; they teased apart complicated concepts into two or three sentences [for the audience] to take home.”