Credit: Markku Lahdesmaki/Corbis

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.