Scientists and philosophers alike have long pondered how time can either evaporate in a flash or drag out into time, depending on the event.
A new study has revealed one part of the brain where that perception occurs – in rodents, at least.
In tests on rats, researchers from the University of Oxford and University College London in the United Kingdom, as well as the Champalimaud Foundation in Portugal, found that a delay or acceleration of activity in this brain region changed the way the animals were able to judge time.
The experiments were focused on a deep part of the brain called the striatum, which is linked to motor and action planning, and decision making. SmAll temperature changes were used to tweak the neural activity of the striatum.
“Temperature has been used in previous studies to manipulate the temporal dynamics of behaviour, such as birdsong. Cooling a specific brain region slows down the song, while heating speeds it up, without changing its structure,” say behavioral ecologist Tiago Monteiro from the University of Oxford.
“We thought that temperature might be suitable because it would allow us to change the speed of neural dynamics without affecting its pattern.”
The researchers used implants to heat or cool the rats’ brains. Analysis about anesthesia showed striatum brain activity speeding up as the temperature rose, and slowing down as the temperature fell.
When the rats were conscious, these same changes in temperature and brain activity were mapped to time-varying perception in laboratory experiments. A hotter and faster striatum made time pass so quickly; with a cooler, slower one, time had gone faster.
However, the temperature changes (and subsequent brain pattern changes) did not affect the speed at which the rats moved – only the speed at which they decided to initiate movements. It seems that two different parts of the brain handle the perception of how fast time passes, and how fast to move.
In other words, the striatum handles when to swing a tennis racket, while another brain area handles the speed of the actual swing. That other area could be the cerebellumthe researchers saya region associated with motor control and coordination.
Previous MRI data have suggested that the basal ganglia is also involved in timing behavior in humans, but much more research will be needed to see exactly how this translates across species.
We use time all the time, and when our understanding of it is impaired – for example with Parkinson’s – movement and perception are affected. The study sheds more light on the inner brain mechanisms of mammals.
“There are many more mysteries to be solved,” say Monteiro.
“What brain circuits create these time-of-action leaks in the first place? What computations, other than time-keeping, might make such leaks? How do they help us adapt to our environment and respond intelligently?”
The research is published in Nature Neuroscience.