Early in the 20th century, Alois Alzheimer first described a disorder of progressive memory loss and confusion in a 50-year-old woman. After she died, he examined her brain and saw that it was full of unusual protein clumps, known as plaques. Over a century later, we know that these plaques are full of a protein called beta-amyloid and are a hallmark of the disease that bears Alzheimer’s name. While other features of Alzheimer’s disease have been discovered, the theory that beta-amyloid is the main cause of this incurable disease has dominated.
Say you meet an old friend at the train station. She is standing about a metre ahead of you, and on the tracks to your right a train has just pulled into the station. Behind your friend you see a bakery. We often remember such scenes in vivid detail. But exactly how we do that by forming mental images has long been a bit of a mystery.
To uncover how the brain keeps track of an animal’s experience, we started by asking how the brain records its electrical activity. Every experience you have, from chatting with a friend to smelling french fries, corresponds to its own unique pattern of electrical activity in the nervous system and brain. These activity patterns are defined by which neurons are active and in what way they’re active.
Most animals have brains in proportion to their body size – species with larger bodies often have larger brains. But the human brain is almost six times bigger than expected for our bodies. This is puzzling, as the brain is very costly – burning 20% of the body’s energy while accounting for only 4% of its mass.
In 47 CE, Scribonius Largus, court physician to the Roman emperor Claudius, described in his Compositiones a method for treating chronic migraines: place torpedo fish on the scalps of patients to ease their pain with electric shocks. Largus was on the right path; our brains are comprised of electrical signals that influence how brain cells communicate with each other and in turn affect cognitive processes such as memory, emotion and attention.
Just as ancient Greeks fantasized about soaring flight, today’s imaginations dream of melding minds and machines as a remedy to the pesky problem of human mortality. Can the mind connect directly with artificial intelligence, robots and other minds through brain-computer interface (BCI) technologies to transcend our human limitations?