New Study Explains How Brain Measures Time

Monica Wilson November 02, 2012

The human perception of time has always been based on external cues – night and day, morning and afternoon, today and tomorrow. But for the purpose of accuracy, we look at the clock to determine the time. But, is it possible to do certain tasks on time without any external cue?

Scientists from the University of Minnesota’s Centre for Magnetic Resonance Research (CMRR) have discovered a group of neurons in the brain that is involved in measuring time – a process that has always been difficult to perform in lab tests.

For their study, the researchers developed an activity in which monkeys could only rely on their internal sense of time. While there were many trials such as this carried out in the past, this experiment was the first to eliminate all external cues which give the subjects a guide in indentifying the passage of time.

The study involved training the monkeys to move their eyes constantly on regular time intervals without using any external cue or immediate expectation of reward. The researchers found that the monkeys were remarkably precise in their behaviour despite the lack of sensory information.

How does the brain measure time?

Based on the research, the animals’ ability to measure time lies on a specific region of the brain called lateral intraparietal area (LIP). This region is found in the intraparietal sulcus of the brain, and is involved in eye movement. The LIP is also believed to contribute in the working memory.

The researchers found that the LIP activity during their experiment was different from that of the previous studies that failed to eliminate external cues or expectation of rewards.

According to the lead author, Dr Geoffrey Ghose, associate professor of neuroscience at the University of Minnesota, the LIP activity decreases at a constant rate between time movements, which is in contrast to the previous studies that observed a build-up of activity linked to the passage of time. Also, the animals’ timing varied after these neurons were, more or less, active, he said.

Such activity of the LIP serves like an internal hourglass in the animal’s brain.

Their findings also reveal that the brain has no “central clock” that is relied upon for all tasks involving timing. According to the researchers, it appears that each of the brain circuit responsible for certain functions is capable of producing an accurate timing signal.

The challenge for future studies is to explore how such timing signals arise as a result of learning and practise, and if there are clear effects on behaviour when the signals are changed.

Source of this article:

Timing and Sequence of Brain Activity in Top-Down Control of Visual-Spatial Attention, Plos Biology