It was an expedition seeking something never caught before: a single human neuron lighting up to create an urge, albeit for the minor task of moving an index finger, before the subject was even aware of feeling anything…Probes in place, the patients—who were conscious—were given instructions to press a button at any time of their choosing, but also to report when they’d first felt the urge to do so.
…he found telltale flashes of individual neurons in the pre-supplementary motor area (associated with movement) and the anterior cingulate (associated with motivation and attention), preceding the reported urges by anywhere from hundreds of milliseconds to several seconds. It was a direct neural measurement of the unconscious brain at work—caught in the act of formulating a volitional, or freely willed, decision…
A variety of imaging studies in humans have revealed that brain activity related to decision-making tends to precede conscious action. Implants in macaques and other animals have examined brain circuits involved in perception and action. But Kreiman broke ground by directly measuring a preconscious decision in humans at the level of single neurons…ultimately, those neurons fired only in response to a chain of even earlier events.
But as more such experiments peer deeper into the labyrinth of neural activity behind decisions—whether they involve moving a finger or opting to buy, eat, or kill something—science could eventually tease out the full circuitry of decision-making and perhaps point to behavioral therapies or treatments. “We need to understand the neuronal basis of voluntary decision-making—or ‘freely willed’ decision-making—and its pathological counterparts if we want to help people such as drug, sex, food, and gambling addicts, or patients with obsessive-compulsive disorder…Many of these people perfectly well know that what they are doing is dysfunctional but feel powerless to prevent themselves from engaging in these behaviors.”
“There is no “god in the machine”—only neurons that are firing”
…there is nothing really free about free will. Ultimately, there are neurons that obey the laws of physics and mathematics. It’s fine if you say ‘I decided’—that’s the language we use. But there is no god in the machine—only neurons that are firing…The rules that govern our decisions are similar to the rules that govern whether a coin will land one way or the other. Ultimately there is physics; it is chaotic in both cases, but at the end of the day, nobody will argue the coin ‘wanted’ to land heads or tails. There is no real volition to the coin.”
It’s only in the past three to four decades that imaging tools and probes have been able to measure what actually happens in the brain. A key research milestone was reached in the early 1980s when Benjamin Libet, a researcher in the physiology department at the University of California, San Francisco, made a remarkable study that tested the idea of conscious free will with actual data.
Libet fitted subjects with EEGs—gadgets that measure aggregate electrical brain activity through the scalp—and had them look at a clock dial that spun around every 2.8 seconds. The subjects were asked to press a button whenever they chose to do so—but told they should also take note of where the time hand was when they first felt the “wish or urge.” It turns out that the actual brain activity involved in the action began 300 milliseconds, on average, before the subject was conscious of wanting to press the button…Since then, functional magnetic resonance imaging (fMRI) has been used to map brain activity by measuring blood flow, and other studies have also measured brain activity processes that take place before decisions are made…Kreiman’s own study design was the same as Libet’s, with the important addition of the direct single-neuron measurement…