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1st appeared
24
January 2001
Eye Movement Study -- Insight into Way Brain Decides The eye has long been evoked as a window into the soul, but in a real sense, it also offers insight into the brain – particularly the way the brain makes the decisions that allow us to function in the world. This is the finding of a UCSF study, which reveals a region of the brain of rhesus monkeys that controls the degree to which the eyes respond to and keep up with an object passing in front of them. The study, reported in the January 11 issue of Nature, is significant in itself, for it most likely reveals an aspect of the neural strategy both in monkeys -- and humans – involved in making a key motor decision – whether or not to look at a moving target. But the finding also offers hints about decision making for other motions, as well, including the hands, arms, legs and posture, the researchers say, and the tests used in the current study could be applied to these other motor systems. "Our finding identifies a neural region involved in making the decision to focus the attention of the brain on a visual target," says the senior author of the study, Stephen Lisberger, PhD, a Howard Hughes Medical Institute Investigator, UCSF professor of physiology and a member of the W.M. Keck Foundation Center for Integrative Neuroscience at UCSF. Lead author of the study was Masaki Tanaka, PhD, an associate of the Howard Hughes Medical Institute and a postdoctoral fellow in Lisberger's lab. "The study examines a very specific aspect of planning for a particular kind of eye movement," said Lisberger. "But if we can understand the fundamental principles of how the brain moves the eye then we also know something about the fundamental principles of how the brain does other things." The idea of a motor system making a "decision" may sound counter-intuitive, as the term is more generally applied to such higher cortical processes as thought and reflection. But while a person may not be aware of it, the motor systems – the foot soldiers of the brain – are ceaselessly navigating the body through its sensory environment, monitoring external stimuli and reacting in a way that is advantageous. The current finding puts researchers a step closer to piecing together the steps that the brain takes in completing a motion -- from sensing a visual stimulus, to deciding whether to respond to it, to provoking the muscles of the system. "The goal of systems neuroscientists is to learn how humans decide what to do and how they do it. And as the basic building blocks of behavior are neural circuits, we try to select behaviors and identify the neural circuits that are responsible for those behaviors, in order to understand how those neural circuits work," says Lisberger. "The question of ‘how’ must always be preceded by answering the question of ‘where.’ The results of our study give us a pretty good idea of ‘where’ the decision gets made for a particular aspect of eye movement. Now we can begin to answer the question "how?" Links: Howard Hughes Medical Institute W.M. Keck Foundation Center for Integrative Neuroscience Source: Jennifer O'Brien, News Services |
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