Now, UCSF researchers have broken ground in understanding how the brain generates this tracking motion, a finding that offers a window, they say, into how neurons orchestrate all of the body’s movements.
The study, reported in the April 24 issue of Neuron, reveals that individual neurons do not fire independently across the entire duration of a motor function as traditionally thought. Rather, they coordinate their activity with other neurons, each firing at a particular moment in time.
“Scientists have known that neurons that connect to muscles initiate movement in a coordinated fashion. But they have not known how the neurons we are studying – which coordinate these front-line neurons -- commit the brain to move the eyes,”says co-lead author David Schoppik, PhD, who conducted the study while a doctoral candidate in the laboratory of senior author Stephen Lisberger, PhD, at the University of California, San Francisco.
“For decades, scientists have been asking, ‘Do the signals involve a handful of neurons or thousands? What is the nature of the commands?’ The classical understanding has been that one class of neuron is responsible for one movement, such as generating eye movement to the left, and that it remains active across the entire duration of a behavior,” he says.
“The new findings suggest a totally different way of looking at how movement is controlled across time,” says Lisberger, a Howard Hughes Medical Institute Investigator at UCSF, where he is professor of physiology, director of the W.M. Keck Foundation Center for Integrative Neuroscience, and co-director of the Sloan Center for Theoretical Neurobiology.
The findings, the researchers say, could inform efforts to develop neural prosthetics to treat paralysis and motor dysfunctions, such as those resulting from stroke. “The brain’s messages don’t reach the muscles in these conditions,” says Schoppik, “so it’s critical that the drive to these prosthetics reflect what the brain is trying to do to move muscles. Understanding how multiple neurons work together could influence the type of software created to drive these devices.”
The investigation of how neurons give rise to motor behaviorshas been stymied until now, says Schoppik, by the difficulties inherent in studying more than one neuron in action at a time during the course of a behavior. In the current study, the scientists overcame this obstacle in a study of macaque monkeys that had been trained to track a moving object with their eyes.
Basing their approach on two key pieces of information -- first, that when a neuron responds to a stimulus there is always a slight variation in its performance, a phenomenon that neuroscientists traditionally refer to as “noise,” and, second, that each attempt of the eye to pursue a moving target is also unique – they proposed that some aspects of neural variation may reflect behavioral variation.
They used this inherent variability as a probe. Using a formula from financial securities market analysis that looks at how individual stocks behave at a given time within the context of fluctuations in the larger financial market, they explored how individual neurons would behave relative to their neighbors.
They compared the deviations from the average spiking activity of single neurons and simultaneous deviations from the mean eye velocity. They also measured the degree to which variation shared across two pairs of concurrently active neurons.
The data demonstrated that individual neurons encode different aspects of behavior, controlling eye velocity fluctuations at particular moments during the course of eye movement, while the population of neurons collectively tiles the entire duration of the movement.
The analysis also revealed the strength of correlations in the eye movement predictions derived from pairs of simultaneously recorded neurons, and suggests, the researcher say, either that a small number of neurons are sufficient to drive the behavior at any given time or that many neurons operate collectively at each moment.
The finding, says Lisberger, underscores the importance of recording for more than one neuron at a time. “There is a lot that we can learn from how multiple neurons interact.”
The other co-author of the study was Katherine Nagel, PhD, at the time a doctoral candidate in the laboratory of Allison J. Doupe, MD, PhD, a professor of psychiatry and physiology and a member of the Keck Center for Integrative Neuroscience at UCSF.
The study was funded by the Howard Hughes Medical Institute and by a Conte Center for Neuroscience Research grant.
UCSF is a leading university dedicated to defining health worldwide through advanced biomedical research, graduate level education in the life sciences and health professions, and excellence in patient care.
Jennifer O’Brien | EurekAlert!
Europe’s Demographic Future. Where the Regions Are Heading after a Decade of Crises
10.08.2017 | Berlin-Institut für Bevölkerung und Entwicklung
Scientists reveal source of human heartbeat in 3-D
07.08.2017 | University of Manchester
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
17.08.2017 | Physics and Astronomy
17.08.2017 | Earth Sciences
17.08.2017 | Physics and Astronomy