The Daily Mail
Fri, 09 Nov 2012 03:36 UTC
New research suggests timekeeping in the brain is decentralised, with different neural circuits having their own timing mechanisms for specific activities.
Not only does it raise the possibility of artificially manipulating time perceptions, but the finding could also explain why our sense of time changes in different conditions - such as when we are having fun or are under stress.
Two researchers from the University of Minnesota in Minneapolis trained to rhesus macaques to perform tasks requiring them to move their eyes between two dots in regular one-second intervals, New Scientist reported.
Despite having to external cues to help them keep track of time, after three months the monkeys had learned to move their eyes between the dots with average intervals of 1.003 and 0.0973 seconds respectively.
Using electrodes, the researchers then recorded brain activity across 100 neurons in the monkeys' lateral intraparietal cortex - the brain region associated with eye movement - as they performed the task.
They found that the activity of these neurons decreased between each eye movement in a regular way that allowed them to predict when the next movement would occur.
A slower rate of decrease in the activity of the neurons corresponded with a macaque overestimating the length of a second, while a faster rate of decrease meant they would move their eyes before the time was up.
The results of the experiment suggest that scientists may one day be able to manipulate the subjective experience of the passage of time by tinkering with the neural connections that indicate its passage in our brains.
And it also suggests an explanation as to why, under certain conditions, the subjective sense of how much time has passed feels different.
When an individual is under stress, for example, it affects that amount of chemicals such as adrenalin in the brain. Scientists know adrenalin affects the rate of activity of neuronal activity.
'And in our model, a change in the activity decay rate is all you need to have a different sense of "what time" it is,' lead researcher Geoffrey Ghose told New Scientist.
Dr Ghose and his colleague Blaine Schneider now plan to test whether the neurons they have identified are the ultimate mental clock for the dots task by interfering with their behaviour to see if that affects the monkey's timing.