Time-keeping brain neurons discovered

October 21, 2009

Groups of neurons that precisely keep time have been discovered in the primate brain by a team of researchers that includes Dezhe Jin, assistant professor of physics at Penn State University and two neuroscientists from the RIKEN Brain Science Institute in Japan and the Massachusetts Institute of Technology (MIT). "This research is the first time that precise time-keeping activities have been identified in recordings of neuron activity," Jin said. The time-keeping neurons are in two interconnected brain regions, the prefrontal cortex and the striatum, both of which are known to play critical roles in learning, movement, and thought control.

The timing of individual actions, like speaking, driving a car, or throwing a football, requires very precise control. Although the lives of humans and other primates are extremely dependent on this remarkable capability, surprisingly little has been known about how brain cells keep track of time. This new discovery, published this week in the Proceedings of the National Academy of Sciences, is an important step toward answering this fundamental question.

To make the discovery, Jin analyzed thousands of neural-activity recordings made by Naotaka Fujii, from RIKEN, who then was a postdoctoral researcher in the lab of Ann Graybiels, an institute professor at MIT. Jin developed the computational tools that enabled the discovery of the novel results to emerge from the team's vast data set.

"The key finding is that neurons in the prefrontal cortex and the striatum encode the time information associated with sensory cues," Jin explained. "Visual cues, for example, elicit a variety of responses in a particular population of neurons. We found that the brain is able to tell the passage of time from the visual cues because different neurons are active at different times. Most remarkably we found that there are neurons that are active at precise times after a particular visual cue, and these neurons act like clocks that mark time."

The team of researchers trained two macaque monkeys to perform a simple eye-movement task. After receiving a "go" signal, the monkeys were free to perform the task at their own speed. The researchers found that neurons in the prefrontal cortex and the striatum consistently fired at specific times after the "go" signal -- at 100 milliseconds, 110 milliseconds, 150 milliseconds, and other intervals. Like a stopwatch, these neurons provided a fine-scale coverage over a period of several seconds. The combined activity of these neurons provided "time stamps" that could specify any given time point with a remarkable precision of less than 50 milliseconds, which is more than sufficient to account for most behaviors.

"Another key finding of our work is that the brains of the monkeys constructed neural activities to encode time even though timing was not required for the experimental task," Jin said. "We suggest that time encoding is the essential function of the brain's neural networks."

Jin said this kind of time-keeping activity long had been suggested in theories of how animals learn to recognize a stimulus that leads to delayed rewards, but his team's work is the first experimental demonstration of this Time-keeping function using recordings of neuron activity.

The discovery opens the door to many investigations, including how the brain produces this time code, and how the time code is used to control behavior and learning. In the longer term, the ability to read the brain's natural time code may facilitate the development of neural prosthetic devices for conditions such as Parkinson's disease, in which neurons in the prefrontal cortex and basal ganglia are disrupted and the ability to control the timing of movements is impaired.
-end-
This research was supported by the National Eye Institute, the National Parkinson Foundation, the Alfred P. Sloan Foundation, and the Huck Institutes of the Life Sciences at Penn State University.

CONTACTS
Dezhe Jin: (+1)814-863-6673, dzj2@psu.edu
Barbara Kennedy (PIO): 814-863-4682, science@psu.edu

WEB PAGE
http://www.science.psu.edu/alert/Jin10-2009.htm

Penn State

Related Neurons Articles from Brightsurf:

Paying attention to the neurons behind our alertness
The neurons of layer 6 - the deepest layer of the cortex - were examined by researchers from the Okinawa Institute of Science and Technology Graduate University to uncover how they react to sensory stimulation in different behavioral states.

Trying to listen to the signal from neurons
Toyohashi University of Technology has developed a coaxial cable-inspired needle-electrode.

A mechanical way to stimulate neurons
Magnetic nanodiscs can be activated by an external magnetic field, providing a research tool for studying neural responses.

Extraordinary regeneration of neurons in zebrafish
Biologists from the University of Bayreuth have discovered a uniquely rapid form of regeneration in injured neurons and their function in the central nervous system of zebrafish.

Dopamine neurons mull over your options
Researchers at the University of Tsukuba have found that dopamine neurons in the brain can represent the decision-making process when making economic choices.

Neurons thrive even when malnourished
When animal, insect or human embryos grow in a malnourished environment, their developing nervous systems get first pick of any available nutrients so that new neurons can be made.

The first 3D map of the heart's neurons
An interdisciplinary research team establishes a new technological pipeline to build a 3D map of the neurons in the heart, revealing foundational insight into their role in heart attacks and other cardiac conditions.

Mapping the neurons of the rat heart in 3D
A team of researchers has developed a virtual 3D heart, digitally showcasing the heart's unique network of neurons for the first time.

How to put neurons into cages
Football-shaped microscale cages have been created using special laser technologies.

A molecule that directs neurons
A research team coordinated by the University of Trento studied a mass of brain cells, the habenula, linked to disorders like autism, schizophrenia and depression.

Read More: Neurons News and Neurons Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.