Ever since I can remember, I've had a mind that refuses to switch off for more than a few seconds and a body that refuses to keep still for more than a couple of minutes. So, when a researcher for BBC's Horizon asked me to volunteer for an experiment to test the reactions of people living in solitary confinement in a nuclear bunker, I jumped at the challenge.

I later found out that only one person had ever taken part in an experiment of this kind and that was back in the 1960s. The deal was that I'd be in a cell for 48 hours, completely alone in pitch black with nothing but a bed, a desk and chair – with two microphones and several infrared cameras pointing at me. The director and one of the psychologists working on the experiment would be monitoring all six cells at all times, looking and listening out for anything unusual. I'd have meals brought to me, which I'd eat in very low light (the tomatoes looked green. I'll never know if they actually were green) and I'd have allocated bathroom breaks that would involve a member of the production crew unlocking my cell door, handing me a pair of RAF earmuffs and a blacked-out ski mask and guiding me to the bathroom, where I'd be left alone in the light for a few minutes, the only real light I'd see during the 48 hours. If any of us wanted to leave early, all we had to do was put our hands up, and we would be taken home.

Before we went to our cells, each volunteer was screened to ensure that we were mentally strong enough to take part in the test. The process included filling out a written series of personality tests and interviews, as well as continual monitoring by psychologists during the research and following the completion of the 48 hours in isolation.

Leading the experiments were Professor Ian Robbins, the head of trauma psychology at St George's Hospital, Tooting, and the University of Surrey, who treated some of the British Guantanamo Bay detainees after their release, and Tim Green, an independent forensic psychologist employed by the NHS to assess the mental states of people who have been charged with criminal offences.

First I was shown several pictures and read a few stories, which I had to memorise and then duplicate or recite back to the professor with only my memory to guide me. I think I did quite well, but obviously cannot really know. I was then taken to my cell and the door was shut behind me. Within minutes, I was already a bit bored and slightly frustrated by the lack of things to do. I accepted that I'd have to entertain myself and got on with talking to myself (and the crew, who I knew could see me and sometimes hear me).

In my time alone in the dark, I experienced several things. I laughed, cried, sang, joked, went over recent conversations in my head, hallucinated (I clearly saw a huge pile of oyster shells – maybe 1,000 – on the floor next to my bed), ate and slept.

Despite the hallucinations, the strangest of these experiences was sleep, as I'd wake up with no idea of how long I'd been asleep. I'd fall asleep in pitch black and wake up in pitch black. With no sunlight or watch, there was no way of guessing how long I'd been asleep. It was a vulnerable, slightly magical feeling. I understand from the programme producers, that left alone in a dark room, the average people will wake and sleep on a 25-hour cycle. It is only the access to the light of day which reboots our body clock and makes sure that we wake and sleep on a 24-hour cycle. Blind people often have trouble with sleep, and experience a feeling similar to jet lag, because they can't see daylight. Scientists believe that these strange cycles could have something to do with helping our bodies deal with the seasonal changes in the length of day.

After about a day, I started to use the length of my stubble to gauge how long I'd been in the bunker. My face had become a slightly incorrect, massive braille watch. After what felt like about 30 hours, I remember thinking that there was no way I'd make the full 48 without losing my mind or at least becoming so bored of looking forward to my next green tomato that I'd have to leave. Somehow I managed to get through the middle 24 hours and, once I realised that I was probably close to doing my time, it became fun trying to work out how long I had before the 48 hours was up. I actually guessed it within about two hours and I can't describe the feeling I had when a voice told me that it was all over and that I was about to be released. It was as intense as being a child again, doing a countdown to Christmas and finally getting to open my presents. I jumped for joy.

I was instantly whisked to a room to take my second set of memory tests. I later discovered that these tested the changes in the functioning of my brain, such as suggestibility, disruption to memory and verbal fluency, as a result of the lack of stimulation. Scientists are aware that stimulation helps increase connections within the brain, which aids information flow. However, apparently there have been very few scientific studies about how reduced stimulation affects the brain.

Some of the tests I did included the Gudjonsson suggestibility scale, which looked at my ability to recall a story and resist persuasive questioning. I also did the Stroop test, which investigates my brain's ability to absorb and process information, and the visual memory test, which investigated the change in my memory's capacity.

Not only was it hard to recite a story that I'd only just been told, I could barely listen when I was being told it. My mind drifted, even though my sole intention was to listen to what the psychologist was saying to me.

After the final tests were over, I went outside, which was as beautiful an experience as being told I was being let out in the first place. Suddenly I was seeing trees, flowers, the sun, the sky, hearing birds and feeling the breeze. For once, I wasn't taking these things for granted. I was stunned by the sights, sounds and smells as my senses had a reunion party.

Although I'd never do it again, it was an incredible experience. It taught me to appreciate my senses and all forms of interaction but, above all, to appreciate being able to go to the loo whenever I want to.

Horizon: Total Isolation is on BBC2 tonight at 9pm

Brain drain: deprivation and the mind

* Many psychologists believe that sensory deprivation can affect a crucial function of the brain called the "central executive", which is a component of the memory associated with co-ordinating cognitive functions.

* Sensory deprivation may lead to the sub functioning of the brain, but in short doses many people find reduced sensory activity very relaxing. Flotation tanks have become increasingly popular in the UK. Being both soundproof and often dark, the senses take time out from the over stimulation endured through a busy modern life.

* The earliest investigation into the effects of sensory deprivation was undertaken by psychologist Dr Hebb in the early 1950s at McGill University. Students were subjected to a number of gruesome sensory experiments, including being submerged in water for 12 hours.

* In 1978 the British Army were investigated over allegations they had used sensory deprivation techniques to interrogate suspected IRA members. Methods such as sleep deprivation and subjection to white noise were found to be in breach of the European Convention on Human Rights.

Kate Proctor

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