Time may sometimes seem slower than it is because part of our brain becomes fatigued.
鈥淥ne might have experienced this manipulation after hearing music with fast tempo,鈥� says Masamichi Hayashi at Osaka University in Japan. 鈥淭he next song with a slightly slower tempo will feel even slower.鈥�
Using a similar method of manipulation, Hayashi and his colleagues wanted to determine if there was a neural basis for our subjective sense of time. They focused their efforts on the brain鈥檚 supramarginal gyrus (SMG) after reading reports on how people with damage in that part of the brain had an impaired sense of time.
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The researchers scanned the brains of 20 people, with an average age of 21, as they were shown a quick succession of grey circles on a screen. The circles were used to manipulate the participants鈥� sense of time. Some participants only saw each circle for 250 milliseconds, whereas others saw them for 750ms.
After this, each person was shown another grey circle, followed by a loud beep for 500 ms. These circles appeared for either 350, 450, 550 or 650ms and the participants were asked to judge whether this time period was shorter or longer than the beep.
Participants who initially saw the grey circles聽 for 250ms overestimated how long the new circle was on screen, while the other group underestimated.
These findings were reflected in the brain scans, which showed that the participants who reported bigger time distortions had a greater reduction in the activity of the SMG. Hayashi speculates that this is because the first phase of the experiment fatigued the time-sensitive neurons in the SMG, making them less likely to fire as they became tuned to repeated stimuli.
Hayashi says he is unsure why some people reported greater time distortions than others. 鈥淏ut I guess it makes sense when you think that some people are very good at timing, and other are not,鈥� he says.
鈥淭his study provides some of the best evidence to date of a specific brain area that is involved in the subjective perception of time,鈥� says Dean Buonomano at the University of California.
Journal of Neuroscience
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