Incognito: The Secret Lives of the Brain

by David Eagleman

Although we know that there is a strong relationship between brain and behavior, neuroimaging remains a crude technology, unable to meaningfully weigh in on assessments of guilt or innocence, especially on an individual basis. Imaging methods make use of highly processed blood-flow signals, which cover tens of cubic millimeters of brain tissue. In a single cubic millimeter of brain tissue, there are some one hundred million synaptic connections between neurons. So modern neuroimaging is like asking an astronaut in the space shuttle to look out the window and judge how America is doing. He can spot giant forest fires, or a plume of volcanic activity billowing from Mount Rainier, or the consequences of broken New Orleans levies—but from his vantage point he is unable to detect whether a crash of the stock market has led to widespread depression and suicide, whether racial tensions have sparked rioting, or whether the population has been stricken with influenza. The astronaut doesn’t have the resolution to discern those details, and neither does the modern neuroscientist have the resolution to make detailed statements about the health of the brain. He can say nothing about the minutiae of the microcircuitry, nor the algorithms that run on the vast seas of millisecond-scale electrical and chemical signaling.