A head of time

For the first time, neuroscientists find brain cells that keep track of time with extreme precision.


Keeping track of time is one of the brain's most important tasks. As the brain processes the flood of sights and sounds it encounters, it must also remember when each event occurred. But how does that happen? How does your brain recall that you brushed your teeth before you took a shower, and not the other way around?

For decades, neuroscientists have theorized that the brain "time stamps" events as they happen, allowing us to keep track of where we are in time and when past events occurred. However, they couldn't find any evidence that such time stamps really existed — until now.

An MIT team led by Institute Professor Ann Graybiel has found groups of neurons in the primate brain that code time with extreme precision. "All you do is time stamp everything, and then recalling events is easy: you go back and look through your time stamps until you see which ones are correlated with the event," she says.

That kind of precise timing control is critical for everyday tasks such as driving a car or playing the piano, as well as keeping track of past events. The discovery, reported in this week's issue of the Proceedings of the National Academy of Sciences, could lead to new treatments for diseases such as Parkinson's disease, where the ability to control the timing of movements is impaired.

Construction of time

The research team trained two macaque monkeys to perform a simple eye-movement task. After receiving the "go" signal, the monkeys were free to perform the task at their own speed. The researchers found neurons that consistently fired at specific times — 100 milliseconds, 110 milliseconds, 150 milliseconds and so on — after the "go" signal.

"Soon enough we realized we had cells keeping time, which everyone has wanted to find, but nobody has found them before," says Graybiel, who is also an investigator in MIT's McGovern Institute for Brain Research. The neurons are located in the prefrontal cortex and the striatum, both of which play important roles in learning, movement and thought control.

The new work is an elegant demonstration of how the brain represents time, says Peter Strick, professor of neurobiology at the University of Pittsburgh, who was not involved in the research. "We have sensory receptors for light, sound, touch, hot and cold, and smell, but we don't have sensory receptors for time. This is a sense constructed by the brain," he says.

Key to the team's success was a new technique that allows researchers to record electrical signals from hundreds of neurons in the brain simultaneously, and a mathematical way to analyze the brain signals, spearheaded by team members Naotaka Fujii of the RIKEN Brain Institute in Japan and Dezhe Jin of Penn State. Though this study focused on the prefrontal cortex and striatum, Graybiel says she expects other regions of the brain may also have neurons that keep time.

Graybiel suggests that the new research could help patients with Parkinson's disease, who often behave as if their brains' timekeeping functions are impaired: they have trouble performing tasks that require accurate rhythm, such as dancing, and time appears to pass more slowly for them. Rhythmic stimuli such as tapping can help them to speak more clearly.

Targeting the timekeeping neurons with neural prosthetic devices or drugs — possibly including the natural brain chemicals dopamine and serotonin — may help treat those Parkinson's symptoms, she says.

Future studies in this area could shed light on how the brain produces these time stamps and how this function can control behavior and learning. The work also raises questions regarding how the brain interprets the passage of time differently under different circumstances.

"Sometimes time moves quickly, and in some situations time seems to slow down. All of this ultimately has a neural representation," says Strick.


Topics: Neuroscience, Bioengineering and biotechnology, McGovern Institute, Memory

Comments

As we descovered the "Quantum" property of the time tracking brain cells, there is probably an evidence of Quantum space and time to which nature is accustomed with. Therefore studying this kind of cell will probably make innovation in physics.
Maybe this has something to do with why we have less indifferent memories than highly pleasant or highly unpleasant.
Maybe it's too radical a thought. If you can say it with words, then you can find it, as in the words, ahead of time. Language has innate, inherent genius. Maybe we are actualizing the potential of words, of the letters, themselves. it's an old notion. But to ask the question, which it does seem, nobody truly asks, is to go to a deeper place. How is it we can do this alchemy with words? And do it, constantly?
Is it at all possible that this, dubbed, the sixth sense is subject to actualization? Can some people record time and the memories involved in it, even though they may not be significant memories? Emotion definitely plays a role with time-keeping in the brain. In emotionally stressful situations, time slows..but in the most pleasant of situations, time speeds. So, if we can control emotions by focusing the brain power towards that emotion and resisting any physiological change, could we then manipulate time in our own lives? Just thinking here...
Anyone want to comment on how this lends support to Kant's ideas about the Forms of Space and Time? I don't know Kantian metaphysics well enough to really know how this would fit into this theory. On the one hand, it seems like this discovery could support Kant. On the other, it may be that Kant wouldn't want the Form of Time to be embodied in human physiology.
So am I wrong to think that these time-stamping neurons actually stamp more often in the stressful situations making it seem as if the time has slowed and it stamps less often in the pleasurable situations making it seem as if the time was going really fast. What you think?
Going with what Maulik said, that is a very strong possibility. If neurons which stamp time are more repetitive in stressful situations it could explain why most can visualize memories that occurred during strenuous experiences (flashbulb memories). You usually remember the time and place where you were when something catastrophic happens, such as when the twin tower collapsed..I can imagine exactly where I was and what I was doing the time it happened. These neurons may have been stamping time more quickly slowing time down. I also may think adrenaline could stimulate time in a certain way, depending on the amount of adrenaline in someone while under questionable conditions.?
Is this the same time stamp that allows me to check my roast seconds before the stove timer goes on? And the one which allows me to tell myself that I have to wake up at 7am for something (without an alarm) and I miraculously do so? And why is it that some people have a great sense of timing and others don't (like ADD/ADHD people)? Are all of these affected by this time stamping? IMHO, I suspect that early training would hone up the neurons involved and that children can be taught this kind of time stamping. Music would be a start.
Back to the top