Since the advent of neuroimaging in the 1980s with positron emission tomography (PET), the sight of a living human brain in action has captivated scientists and the public. The emergence of functional magnetic resonance imaging (fMRI) in the early 1990s was a watershed. MRI scanners were already common in hospitals and, unlike PET, fMRI does not expose people to radioactivity. By measuring activity in the brain at the scale of a few millimetres, these scans seem to promise profound insight into the workings of the brain. That has led to wild claims that the technique could enable mind reading — actually knowing a person’s precise thoughts.
Russell Poldrack tackles these claims head on in The New Mind Readers. The experimental psychologist and neuroimaging pioneer takes readers through three decades of fMRI, its promise and limitations. From the race between groups in Minnesota, Massachusetts and Wisconsin in 1991 to show that MRI measures of blood oxygenation can reflect functional brain activity, to the development of techniques for decoding what someone is looking at, Poldrack surveys the history and biological basis of the technique and its potential application in areas as diverse as law and psychiatry.
Poldrack is an ideal guide. As director of the Stanford Center for Reproducible Neuroscience in California, he actively advances fMRI methods. His enthusiasm for them is clear, as is his frustration at how their data have been misinterpreted and abused.
The technique has revolutionized neuroscience. Thousands of fMRI studies are published each year on topics ranging from perception to decision-making. For example, we now know that the pattern of blood flow to the fusiform face area in the temporal lobe can indicate that a person is looking at a face instead of a ball; and that imagining playing tennis or walking around your house, say, elicits activations in different brain regions. That is a major advance for neuroscientists and physicians who work with people in apparently non-responsive states after brain injury. It means they can identify patients with conscious awareness simply by asking them to engage their imaginations.