Credit: Markku Lahdesmaki/Corbis

If only death were the end of consciousness. But Einstein was right, damn him. I am imprisoned within an Iron Maiden of flesh and bone. My own body is the torture device, reducing me to a blubbering imbecile.

Unable to speak, unable to move properly, unable to understand those around me. Not much better than a cabbage, except for the spark of consciousness within. My mind is intact! I'm still here!

I clench and unclench my fists again, heartbeat pattering in my chest. Looking down causes my head to flop about like a rag doll. My hands are useless – barely controllable.

The hands that once dissected human neural tissue in the finest research laboratory in the world now can't even hold a hammer straight. If this is the natural course of life, then I wish I'd never been born.

The summer sunshine warms my bald head. I breathe in and out, trying for the thousandth time to regain what control I once had. At least my lungs feel clean again.

The smell of the lush green grass I sit on fills my nose. A transitory buzz of a bee makes me forget the hammer and look around in surprise. The noisy insect is gone before I ever see it. Not that I can see properly anyway. Everything more than a metre away seems to blur into double vision. But I have no glasses any more.

My mother is kneeling nearby, looking impossibly young and pretty as she looks after my twin sister and me. How could it be fair that she should look like that?

She smiles at me and picks up the hammer, giving me a demonstration, using it on the piece of wood in a way my hands cannot. Was this supposed to be a lesson from her? Doesn't she realise I am one of the most dexterous neuroscientists who ever lived? No, of course she doesn't.

A bird twitters in the trees behind us. Turning to look makes the world spin as I fall over backwards. Like a turtle on its back, I can do nothing but wave my arms and legs. The grass does smell nice, though. It's cool and fresh against my face. My skin feels so smooth and sensitive to every experience. A tickle in my nose makes me sneeze.

I hear my twin sister giggle. She finds my predicament funny. Yet I know that behind the mask of young flesh she shares my frustration. Neither of us can concentrate on anything for more than a minute or two. Yet we both know we must try before we lose what remains of our sense of selves.

I can see it in her eyes: the sense of loss as more of us slips away each day, making us less and less who we are … were… will be. I know she remembers. Surely she must.

Every day I try to speak, to explain what I know about the nature of consciousness. This is my chance to achieve what my three decades of neuroscience research was unable to. So far my words have all been incomprehensible.

When I finally relearn how to shape my mouth and tongue properly and speak the words I long to say, it will be the biggest scientific breakthrough of all time. From the mouths of babes, they say … well, this time they will be right.

My mother sits me back up again and wipes my nose, which is dribbling. She finds the juice beaker and puts the little spout in my mouth. She finds another for my sister. We both suck noisily. The tart flavour makes us smile together in pleasure. All too soon, my beaker is empty.

Platitudes are burbled to me, which I ignore, grabbing my plastic hammer again before my sister can take it. My mother sits back and finds her place in her cloth-eared book.

As I clumsily hold the toy hammer in my right hand, I look down at it. How much longer will I know the truth? How long can I hold on to my precious memories before they are lost and I become an empty vessel like my beaker, only to be refilled with the same contents? I must try to hold on to my past, my life.

There is one memory above all that I still cling to. More than the memories of my work, my beautiful wife, my three children and five grandchildren. Oh Lord. I can't even remember their names. One was John. Or Jonny. Or was that my younger brother? He had fair hair … or was that my daughter? An involuntary whimper escapes from my mouth.

My mother looks up briefly from her book. I try to calm myself, but it is not easy. Where memories should stand there are only holes. How frightening, to know that your life is being stolen from you and there is nothing you can do to hold on to it.

But I'm getting distracted again. One memory remains imprinted in my mind as though burnt with a branding iron. This memory is too strong to be rubbed out like a mistake. Perhaps the trauma of it has reached too deeply into my brain: the memory of my death, 18 months ago.

The familiar antiseptic odour of the large room. Frustrated, I swivelled on the lab stool that squeaked. The latest results weren't right. The GFAP stains had failed and the whole batch of biopsies was barely readable. I readjusted the microscope, suppressing a yawn.

This should have been an ideal candidate for the double-blind trial – a patient who had developed epilepsy due to trauma five years before his death. The trial was my latest attempt to track down consciousness within the brain.

We were examining patients whose brains were measurably impaired, preventing them from being consciously aware of such ordinary actions as seeing movement, yet still able to carry out those actions unconsciously.

Rather than study living patients, my research group studied the neural structures after their deaths. Large-scale biopsies of key regions of the brains were prepared, sliced into layers less than the thickness of a single cell, stained, scanned into the computer, then image processing and extrapolation software derived their original three-dimensional neural connectivity.

This patient had been especially interesting. Apparently, in addition to blind-sight, his symptoms during each fit resembled a near-death experience: the classic tunnel with white light at the end, a feeling of weightlessness and calm. He maintained consciousness each time while experiencing this effect.

The biopsy of his parietal lobes should have been an excellent additional sample for the trial. Now it was ruined, damn it, all because of a faulty batch of stain.

Sighing, I released the slide and walked to the medical waste disposal, threw it away. My watch said 19:22 - already over an hour later than I'd promised my wife. I took off the old lab coat, grabbed my jacket. Locking the lab doors, I took the stairs two at a time as usual, palmed my swipe card on the security door and left the building.

It had been raining. Streetlights reflected their orange glows from the wet tarmac. My car flashed its lights at me as I disarmed it. Then the reassuring clunk of the door as I pulled it shut.

I barely remember the first part of the drive home. My mind was still on the failed biopsies. How many weeks behind were we now? Twin dazzling lights directly in front of my face. Maybe my airbag deployed. A horrible, deafening noise that seemed to come from inside my body. An instant of excruciating pain.

After that, my memories are patchy. Opening my eyes briefly: darkness. No pain, but my head felt wrong, as if it had ... changed shape. And I couldn't think properly. Like being drugged, nothing quite made sense. I couldn't understand what was happening…

Blackness.

An unknown amount of time later, a woman's voice, talking to someone. Her voice seemed to echo as though she were in a large room. She sounded calm and … familiar. Much closer to me there was a click-hiss, click-hiss noise that seemed to be making my chest rise and fall.

Blackness.

I felt a hand squeeze mine. I think I might have squeezed it back. Odour of plastic.

Blackness.

Raised voices. Some pressure, like a distant pounding on my chest. It seemed so far away.

Blackness.

A woman's voice, muffled as though speaking through a wall. The voice was somehow comforting.

Blackness.

My eyes seemed glued shut, but I could feel movement. I was being carried somewhere. I tried to shift my position, but was somehow being restrained.

Blackness.

I began to wake up more and more. Each time, I couldn't see anything, but often heard the same muffled woman's voice, and occasionally a man's voice in the distance. I began to try to move, weakly twitching my arms and legs. Sometimes I felt movement as something soft bumped into me. I vaguely realised that I was not breathing, yet this seemed to cause me no alarm.

Abruptly, everything around me changed. The woman's voice was louder. Other voices. Things pushed at me from all sides. I was being squeezed out of my bed like toothpaste from a tube. My head seemed as malleable as a balloon – I could feel it deform as I was pushed through a hole that seemed far too small. My whole body was squashed and stretched like a rubbery superhero and then … everything was bright and shockingly cold.

I couldn't see anything except brightness. Somehow, I was turned upside down and slapped vigorously on the back. Warm fluid came from my lungs and I took a breath of freezing cold air. With it came a world of strange smells as foreign as a Martian landscape. It was horrible. I screwed up my eyes and yelled. And stopped in surprise – the noise I'd made was a baby's scream.

Before I knew what was happening, I'd been wrapped in cloth and was being held tight. Not being able to move was surprisingly comforting. A second baby was crying in the room; I wondered who it was. I was passed to someone. Warmth through the cloth. The voice of the woman holding me.

My eyes still didn't let me see her, but I knew this woman. I'd last seen her, aged 79, in a hospital bed, drawing her last breath as cancer took her from me. It was my mother, young again. I cried.

My life had begun anew and fresh, bright days rolled by as though each were eons long. Every day was a new discovery of my limitations and losses. Of course I was overjoyed to see my parents and sister alive and well again.

But as the days turned to weeks, I felt more and more awake and alive, and I remembered more and more of my previous life. I heard the voices of my parents, and knew they must be speaking English, although I couldn't understand them.

But I could remember being an active human being who used to run a daily five kilometres, and now I couldn't even turn my own head. So every day I had to relearn these skills. Figure out how to think about the world around me. Re-learn the colours, sounds and smells of everything.

Learning was laborious but fast, for I was doing nothing but unlocking existing memories. Every smell reminded me of another universe of memories. The scent of cherry blossom was the time I met my college sweetheart Sarah, the smell of the sea was my 30th birthday party in Hawaii, the stink of oil was the tragic death of my sister when she was hit by a drunk driver, when she was just 13 years old.

I spent hours with my twin, playing with her, but mainly studying her, looking for signs that she recalled her all-too-short life. I was sure she also had such memories. But with no way to communicate with her, I could do nothing but stare.

Did her smile mean she understood my thoughts? Were those tears of hunger, or of anger at the prospect of her death, just a few years from now? Was her selfishness with my toys a way of compensating for the brevity of her ill-fated life?

As weeks turned to months, frustration made my moods turbulent and full of tantrums; new experiences released too many old memories and reminded me of what I had lost, yet I could talk to no one.

More recently, things have begun to change. My previous memories lose their urgency, fade. The older I become, the more my new experiences seem to replace that lost future. I struggle to recall how I'd nursed my father in the long decline of Alzheimer's, but mainly remember the young father who plays roll-the-ball with me.

The memories of yesterday's playtime now seem so much more real and vibrant than the memories of who I am to become.

So here I am this morning, less than two years old but with the fragmented, disintegrating memories of a 57-year-old 21st century neuroscientist. Sitting on the grass in my parents' back garden. Playing with a toy hammer that I can't hold properly. Thinking thoughts that should be beyond my capacity.

Again I glance over at my sister. If she could talk, what would she say? Is she running the same race as me?

Trying to relearn to speak before her memories of her past – or future – life desert her? Already I'm finding it desperately hard to remember what I want to say to the world. Was it something to do with consciousness, or was it that I can kick a football?

When each day lasts forever, the deep meaningful questions seem less important than finding out what a leaf tastes like.

I pull myself together again. I must remember. I must try. Remember what? Something about water? I frown as I try to make my young brain think more clearly.

Yesterday I watched ripples in my bath spread outwards and reflect back from the sides, merging together. As I watched, I thought: This is me. My life is a sequence of ripple-like events that spread out and reflect back, again and again forever. These events shape our brains from the beginning, I now realise.

My baby brain, like every infant's, is packed full of neurons and connections – far more than I will retain as an adult.

But if the events of my whole life are already in my brain, does this mean I've lived this same life an infinite number of times, and will continue to do so for all infinity? Nobody could live a normal adult life with such infinitely accumulating memories.

And so, I allow myself at last to understand, I am programmed like everyone to forget these earliest years – and because of this amnesia, forget that I've experienced every second of every minute before. To cope with my eternal life I must believe it is the first time, every time.

In shock, I drop my plastic hammer on the grass. I'm a fool. I will never change the world with some ridiculous childhood announcement.

I know this because I can still remember the sweep of my life even as the details slide away from my clutching hands. I do remember being driven throughout my life to understand the brain and consciousness.

I am going to forget the truth but retain some unconscious drive to tell that truth. I'll become a neuroscientist and dedicate my career to solving a problem that I knew the answer to when I was 18 months old.

Another bee buzzes past my head, distracting me. What was I thinking again? Oh, yes. I pick up my plastic hammer. Daddy will be impressed if I can hammer the blue peg in. Next to me, my sister plays with some wooden blocks with letters on them, clumsily arranging them in a row. Neither of us can read the word she has made.

As I pound ineptly with my hammer, I have a hazy awareness that my brain is continuing its natural growth, pruning away more of my neurons, losing more connections. A memory of something Einstein had once written in a letter stirs in my mind:

Nobody is ever lost. Each of us will always exist in a given region of space-time, perfectly preserved as though trapped in amber.

What the famous physicist hadn't remembered, when he wrote those words to comfort a grieving relative ... what was the physicist's name again? ... was that his consciousness is also trapped in his own space-time amber, destined to loop forever.

The fragment of memory fades away.