You wake up. You were dreaming, but in the haze of morning, you
cannot quite remember what ran through your head. Childhood
acquaintances were there. You were in Australia. One guy was a
pirate. There was something about a cow. Perhaps. We have all
had similarly murky memories of an earlier night’s dream. But
what if you could actually record your dreaming brain? Could you
reconstruct the stories that play out in your head? It appears
to be plausible. Science fiction is full of machines that can
peer inside our heads and decipher our thoughts, and science, it
seems, is catching up. The news abounds with tales of scientists
who have created “mind-reading” machines that can convert our
thoughts into images, most of these stories including a
throwaway line about one day recording our dreams. But
visualising our everyday thoughts is no easy matter, and dream-
reading is more difficult still. The task of decoding dreams
comes down to interpreting the activity of the brain’s 100
billion or so neurons, or nerve cells