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at the way we assess durations of a few seconds or more, an amount of time that would seem like nothing to Michel, but which surprisingly counts aslong in time-perception research. Warren Meck is a neuroscientist at Duke University in the USA who studies people with a skewed sense of time. By examining the cognitive processes involved in processing durations ranging from seconds to hours, he has localised the perception of time-frames of more than a few seconds to an area at the centre of the brain called the basal ganglia. Until 2001 no one had any idea that these areas housing a mass of neurons could be involved in the perception of time. The basal ganglia, one in each hemisphere of the brain, are deep inside the middle of your head and they loop around in a curve a bit like the older kinds of hearing aid which curl around over the top of the ear. The basal ganglia help control movement using the neurotransmitter dopamine to put brakes on your muscles. If you want to sit down you need to stop the activity in all your muscles, apart from those needed to maintain your sitting position. Then when you want to get up the basal ganglia release the brake on the muscles and that helps you to move off smoothly. Meanwhile a brake is put on those postural movements that were keeping you still. Without enough dopamine to power this brake you would experience both the tremors and jerky movements associated with Parkinson’s disease. You would find it difficult to initiate movement, rather like trying to drive with the handbrake on. But the basal ganglia are also implicated in timing events which last longer than two seconds. This is also something people with Parkinson’s disease find difficult. This condition destroys the cells producing dopamine and the greater the number of cells a person has lost, the harder they find it to estimate time.
    The whole dopamine system appears to be crucial in the perception of time. If you give someone the drug haloperidol, often prescribed for schizophrenia, it blocks the receptors for dopamine and causes people to under estimate the amount of time that’s passed, while the recreational drugs methamphetamines (or speed) do the opposite; they increase the levels of dopamine circulating in the brain, which causes the brain’s clock to speed up with the result that people then over estimate the amount of time that has passed. This might seem somewhat counter-intuitive, but it echoes the process that has been hypothesised to occur when people are in fear for their lives.
    EMOTIONAL MOMENTS
    The basal ganglia, along with the cerebellum and the frontal lobe, bring to three the areas of the brain we’ve looked at so far. When you consider their other functions, it makes sense that these areas of the brain also relate to time. But the involvement of a fourth area is more mysterious. A psychologist called Bud Craig noticed that whenever people carried out time estimation tasks in a brain scanner, another area kept showing up yet appeared to go unremarked – an area that processes sensations from the rest of the body. He realised that parts of the body outside the brain might have a part to play in time perception. 23
    If it’s very quiet and you lie very still in bed at night, you can sometimes detect your heartbeat, without putting a hand up to your chest. Ten per cent of people can feel their heartbeat at any time, particularly if they’re lean, youngmen – it helps to have as little flesh as possible getting in the way. This ability to detect changes in our physiology is known as interoceptive awareness. When I was making a programme about it, I canvassed lots of people to see whether they could do it. None could. As I climbed the many stairs up to my flat I passed the door of the lean young man called Hadley who lives in the flat below. He’s used to my asking strange questions for programmes and when I knocked on his door and asked whether he could hear his own heart beating, he instantly tapped