Neuroscientists have discovered groups of neurons in the primate brain that are responsible for our timing of individual actions, such as speaking, driving a car, or throwing a football. These neurons help in activities that require very precise control
Researchers including 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) have said that the new discovery is an important step towards uncovering how brain cells keep track of time.
"This research is the first time that precise time-keeping activities have been identified in recordings of neuron activity," said Jin.
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.
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. 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," explained Jin.
"We suggest that time encoding is the essential function of the brain's neural networks," he said.
He claimed that 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 behaviour 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.
The study has been published this week in the Proceedings of the National Academy of Science.