Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

What makes the brain tick, tick, tick. . .

31.10.2005


The brain is a "time machine," assert Duke neuroscientists Catalin Buhusi and Warren Meck. And understanding how the brain tracks time is essential to understanding all its functions. The brain’s internal clocks coordinate a vast array of activities from communicating, to orchestrating movement, to getting food, they said.



In a review article in the October 2005 Nature Reviews Neuroscience, Buhusi and Meck discuss the current state of understanding of one of the brain’s most important, and mysterious, clocks -- the one governing timing intervals in the seconds to minutes range. Such interval timing occupies the middle neurological ground between two other clocks -- the circadian clock that operates over the 24-hour light-dark cycle, and the millisecond clock that is crucial for such functions as motor control and speech generation and recognition. Meck is a professor and Buhusi is an assistant research professor in the Department of Psychological and Brain Sciences.

Interval timing is central to broader coordination of tasks such as walking, manipulating objects, carrying on a conversation and tracking objects in the environment, they said.


"Interval timing is necessary for us to understand temporal order of events, for example when carrying on a conversation," said Meck. "To understand speech, I not only have to process the millisecond intervals involved in voice onset time, but also the duration of vowels and consonants. Also, to respond, I need to process the pacing of speech, to organize my thoughts coherently and to respond back to you in a timely manner. That’s all interval timing, and in fact it’s hard to find any complex behavioral process that timing isn’t involved in."

Deciphering the neural mechanisms of such clocks may be even more fundamental to understanding the brain than figuring out, for example, neural processing of spatial position and movement, they said.

Said Buhusi, "I would argue that time is more fundamental than space, because one can just close one’s eyes and relive memories, going back in time; or prospectively go forward in time to predict something, without actually changing your position in space."

Understanding the machinery of interval timing is profoundly difficult because it is "amodal," said Buhusi and Meck. That is, the interval timing clock is independent of any sense -- touch, sight, hearing, taste or smell. Thus, it cannot be localized in a discrete brain area, as can the circadian clock, which has clear inputs from the visual system and outputs that control the cyclic release of circadian hormones.

"So, this process has to be distributed so it can integrate information from all the senses," said Meck. "But more importantly, because it’s involved in learning and memory, you could argue that time isn’t directly perceived, but that we make temporal discriminations relative to memories of previous durations. Such features have made the machinery of interval timing more elusive, and some even questioned whether an internal clock of this sort even exists."

In the 1980s Meck and his colleagues at Brown and Columbia Universities proposed what became the traditional theory for explaining interval timing which involved a "pacemaker-accumulator" model. This model holds that somewhere in the brain lurks an independent biological pacemaker that regularly emits neural timing pulses or "ticks." However, more recent research by Meck and his colleagues at Duke, has led to the development of a "striatal beat frequency" model of interval timing involving the "coincidence detection" of oscillatory patterns of neural activity. The striatum is a part of the brain structure known as the basal ganglia, which control basic body functions such as movement.

In this model, explained Buhusi, "each structure in the brain contributes its own resonance, and all these oscillations are monitored and integrated by the basal ganglia or striatal circuits. It’s like a conductor who listens to the orchestra, which is composed of individual musicians. Then, with the beat of his baton, the conductor synchronizes the orchestra so that listeners hear a coordinated sound."

Thus, in essence, the entire brain is an intricate interval timing machine, in which individual structures busy with their own neural tasks, generate resonances that integrate to become ticks of the neural clock.

Meck, Buhusi and their clockwork colleagues are using an array of experimental techniques to try to identify this "baton" timing signal and to refine the theory. These include studies using genetically modified mice, pharmacological tools, recording of electrical brain signals in ensembles of brain cells and functional magnetic resonance imaging of the brain.

For example, they are studying how the clock’s ticking changes in Parkinson’s patients as they change levels of their medication, which effects the amount of dopamine in their brains. Dopamine has been implicated as a key signaling molecule in the neuronal circuitry of the timing machinery.

"When Parkinson’s patients are on their medication, they time quite normally," said Meck. "But as their medication wears off, we can see their clock slow down by recording their brain signals."

Said Meck of their research, "We’re addressing two challenges. One is to find the molecular processes that underlie this internal clock. And the second challenge is to build more realistic models of how this timing process works, with constant, parallel input from throughout the brain." In such studies, the researchers face the daunting process of trying to monitor the intricate swirling of neural activity throughout the entire brain, said Meck.

"Looking at only one place in the brain for the interval clock is like the blind man feeling just the toe of the elephant and trying to describe how it works," he said. "While we’re very excited about our success so far, we want to be modest about our capabilities. We are blind men touching just one part of this elephant that is time.

"And our new review paper, to the best of our knowledge, is the first to try to integrate the different fields and levels of analysis that contribute to understanding timing and time perception, to help advance this exciting field."

Dennis Meredith | EurekAlert!
Further information:
http://www.duke.edu

More articles from Life Sciences:

nachricht Could this protein protect people against coronary artery disease?
17.11.2017 | University of North Carolina Health Care

nachricht Microbial resident enables beetles to feed on a leafy diet
17.11.2017 | Max-Planck-Institut für chemische Ökologie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>