The brain is much on our minds at the moment. Researchers are close to developing a blood test to detect which people will suffer from Alzheimer’s disease; brain-computer interfaces promise new solutions to paralysis; and the ongoing plight of Michael Schumacher has reminded us of the terrifying consequences of traumatic brain injury. And in the media we have magical images of the living brain to illuminate these stories, often showing the main “highways” along which brain connections are organised. Yet when asked, most neuroscientists will say we still know very little about how the brain works or how to fix it when it goes wrong.
The €1.2bn (£950m) Human Brain Project (HBP) is supposed to change all this. Funded by the European research commission, the project brings together more than 80 research institutes in a 10-year endeavour to unravel the mysteries of the brain and to emulate its powers in new technologies. Following examples like the Human Genome Project and the Large Hadron Collider (where Higgs’ elusive boson was finally discovered), the idea is that a large investment will deliver significant results. But now a big contingent of prominent European neuroscientists are rebelling against the HBP, claiming that its approach is doomed to fail.
Stepping back from the fuss, it is worth thinking about whether the project’s aims make sense. Sequencing the genome and looking for Higgs were both major challenges, but in these cases it was clear what would constitute success. There is no similar consensus among neuroscientists.
It is often said that the adult human brain is the most complex object in the universe. It contains about 90bn neurons and a thousand times more connections, so if you counted one connection each second it would take about three million years to finish. The challenge for neuroscience is to understand how this vast, complex and always changing network gives rise to our sensations, perceptions, thoughts, actions, beliefs and desires; our sense of self and of others; our emotions and moods; and all else that guides our behaviour and populates our mental life in health and in disease. No single breakthrough could ever mark success across such a wide range of issues.
The HBP approach is to build computational simulations of the brain. Befitting the huge investment, these simulations would be of unprecedented size and detail, and would allow brain scientists to integrate their individual findings into a collective resource. What distinguishes this project, besides the money, is its aggressively “bottom-up” approach. The vision is that by taking care of the neurons, the big things – thoughts, perceptions, beliefs and the like – will take care of themselves. The HBP does not set out to test any specific hypothesis or collection of hypotheses.
Could this work? Certainly, modern neuroscience is generating an accelerating data deluge demanding new technologies for visualisation and analysis. This is the “big data” challenge now common in many settings. It is also clear that better pictures of the brain’s wiring diagram – the “connectome” – will be essential as we move ahead. On the other hand, more detailed simulations don’t inevitably lead to better understanding. Strikingly, we don’t fully understand the brain of the tiny worm Caenorhabditis elegans even though it has only 302 neurons and the wiring diagram is known exactly.
A perfectly accurate model of the brain may become as difficult to understand as the brain itself, as Jorge Luis Borges long ago noted when describing the tragic uselessness of the perfectly detailed map.
Understanding the brain does not reduce to simulating the collective behaviour of all its minuscule parts, however interesting a part of the final story this might become. Understanding the brain means grasping complex interactions cross-linking many different levels of description, from neurons to brain regions to individuals to societies. It means complementing bottom-up simulations with new theories describing what the brain is actually doing when its neurons are buzzing merrily away. It means designing elegant experiments that reveal how the mind constructs its reality, without always worrying about the neuronal hardware underneath. Sometimes, it means aiming directly for new treatments for devastating neurological and psychiatric conditions like coma, paralysis, dementia and depression.
Put this way, neuroscience has enormous potential to benefit society, well deserving of high profile and large-scale support. It would be a shame if the HBP became a lightning rod for dissatisfaction with “big science” rather than creating a new and powerfully productive picture of the biological basis of the mind.