Previous studies of the brain have depicted the cortex as a patchwork of function-specific regions. Parts of the visual cortex at the back of the brain, for instance, encode color and motion, while specific frontal and middle regions control more complex functions, such as decision-making. Neuroscientists have long criticized this view as too compartmentalized. In this new study, the researchers built an array of 108 electrodes that measured neural spikes in 2,694 sites across six cortical regions that are thought to control specific functions.
Multiple cortical regions work together simultaneously to process sensorimotor information — sensory input coupled with related actions — despite their predetermined specialized roles. “Some areas may process motion more than color, some may process color more than motion, and sometimes you can see the information rising up in one area before the other,” Miller says. “But generally information is distributed all over the cortex.”
Of particular note, Miller adds, was how widely the executive “choice” signals — deciding which direction to move their eyes — were distributed across the cortex. Previously, it was thought that decisions rise solely in specific cortical areas. “But you see the decision percolating up all over many parts of the cortex simultaneously, so even decision-making is more of an emerging property of many cortical areas,” he says.
In providing a better understanding of the cortex’s sensorimotor processing, Miller says, the study may open doors for broader use of noninvasive treatments for stroke recovery, which deliver electrical pulses to increase brain waves in damaged cortical areas to restore sensory or motor functions.