There's a built-in stop-watch in the brain, according to MIT neuroscientists.
They have identified populations of neurons that code time with extreme precision in the primate brain. These neurons are found 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.
Although daily life is extremely dependent on precise timing - whether it's walking, speaking or playing the piano - surprisingly little has been known about how time is represented in the activity of brain cells.
The team 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 that consistently fired at specific times — 100 milliseconds, 110msec, 150msec, and so on — after the 'go' signal.
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 remarkable precision - less than 50 milliseconds.
More work is needed to establish how the brain produces this time code, and how it is used to control behavior and learning.
In the longer term, the ability to read the brain's natural time-code might help in 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 results are published in the Proceedings of the National Academy of Sciences.