Errors, or 'noise', in the information coming into the brain rather than faults in how the brain accumulates information is to blame for people making bad decisions, a new study has claimed.
The findings by Princeton University researchers address a fundamental question among neuroscientists about whether bad decisions result from noise in the external information - or sensory input - or because the brain made mistakes when tallying that information.
Previous measurements of brain neurons have indicated that brain functions are inherently noisy.
"The Princeton research, however, separated sensory inputs from the internal mental process to show that the former can be noisy while the latter is remarkably reliable," said senior investigator Carlos Brody, a Princeton associate professor of molecular biology and the Princeton Neuroscience Institute (PNI), and a Howard Hughes Medical Institute Investigator.
"To our great surprise, the internal mental process was perfectly noiseless. All of the imperfections came from noise in the sensory processes," Brody said.
The research subjects - four college-age volunteers and 19 laboratory rats - listened to streams of randomly timed clicks coming into both the left ear and the right ear.
After listening to a stream, the subjects had to choose the side from which more clicks originated. The rats had been trained to turn their noses in the direction from which more clicks originated.
The test subjects mostly chose the correct side but occasionally made errors. By comparing various patterns of clicks with the volunteers' responses, researchers found that all of the errors arose when two clicks overlapped, and not from any observable noise in the brain system that tallied the clicks.
This was true in experiment after experiment utilising different click patterns, in humans and rats.
The researchers used the timing of the clicks and the decision-making behaviour of the test subjects to create computer models that can be used to indicate what happens in the brain during decision-making.
The models provide a clear window into the brain during the "mulling over" period of decision-making, the time when a person is accumulating information but has yet to choose, Brody said.
The study suggested that information represented and processed in the brain's neurons must be robust to noise, Brody said.
"In other words, the 'neural code' may have a mechanism for inherent error correction," he said.
The study was published in the journal Science.
