I am going to start off gently by just pointing you to an interesting article I read in New Scientist this week about how in a scary situation it can feel like time slows down and the agony suffered seems to last for much longer [than it actually does]. Can it be that, in a scary situation, our brain works faster as a result of flight or fight? Or do we create memories about such events that are much more precise and therefore seem longer?
David Eagleman, a neuroscientist at Baylor College of Medicine in Houston, Texas, looked into the issue of the slowing of time by letting his colleagues experience a thirty meter free fall - a scary event over which you have no control. Afterwards he asked them to indicate how long they felt the fall had lasted for. All estimated times were about twice as long as the actual duration of the fall. I have uploaded a video to give you a sense of the experiment. Proving that we perceive time slowing down in such scary situations is one thing, finding out its cause is a wholly different issue, one that is discussed in the New Scientist article 'Timewarp: How the brain creates the fourth dimension'. The mechanism that keeps track of time may well be important for the understanding of diseases where people experience delusion, such as schizophrenia.
David Eagleman's interest in time does not stop in the past and present. In his recent book SUM ('I am' in Latin) he deals with the more existential issues of the afterlive.
