New research from Cedars-Sinai investigators has contributed to the scientific understanding of how the brain processes decisions related to personal preferences, such as selecting a book to read, choosing a restaurant for lunch, or even deciding which slot machine to play in a casino. The study, published in the peer-reviewed journal Nature Human Behaviour, involved monitoring the activity of individual human neurons.
This research focused on value-based choices, where there is no definitive right or wrong option, explained Ueli Rutishauser, PhD, the study’s senior author, director of the Center for Neural Science and Medicine, and professor of Neurology, Neurosurgery, and Biomedical Sciences at Cedars-Sinai.
“Learning how the brain makes these kinds of choices could help us better understand neurological disorders including addiction and obsessive-compulsive disorder because all of these conditions can involve a person making the same choice over and over to their detriment,” said Rutishauser.
The study involved 20 volunteer participants, all of whom were epilepsy patients hospitalised for monitoring their brain activity to identify the origins of their seizures. This setup allowed researchers to record the activity of individual neurons in the participants’ brains as they engaged in a computerised slot-machine game.
The game, known as “two-armed bandit”, required participants to choose between two simulated slot machines in each round. They would press a button to select their preferred “bandit”, which then either paid out or did not. Each bandit featured distinct markings, enabling participants to recognise if they had played it before. The game consisted of several rounds played over a 30-minute period.
Rutishauser identified several factors influencing value-based choices in the study. Familiar options referred to instances where participants had chosen a specific bandit multiple times, giving them a relatively accurate idea of its winning frequency. Uncertain options arose when participants had played a bandit only a few times and were less confident about its winning prospects. Lastly, new options emerged when participants encountered a new bandit and had to decide between opting for a familiar one or taking a chance with the new option. In some cases, the appeal of novelty itself held intrinsic value, influencing their decision-making.
Previous research primarily utilised functional magnetic resonance imaging (MRI) to observe brain activity and suggested that the ventromedial prefrontal cortex (vmPFC) played a key role in evaluating these factors. But in this recent study, Cedars-Sinai researchers discovered that the pre-supplementary motor area (pre-SMA) actually took the lead.
Using single-neuron recording, the investigators observed that while the vmPFC signalled the “novelty” value of newly appearing bandits, it was the pre-SMA that assessed which option had the best likelihood of providing the highest reward. Participants ultimately based their choices on this signal.
“Previous studies weren’t giving us a complete picture and couldn’t draw the distinction we could here,” explained Tomas Aquino, PhD, a postdoctoral fellow in the Rutishauser Lab and first author of the study. “Since our single-neuron recordings are more sensitive than other, more common methods, we could measure directly how preSMA neurons compute the value of each option and determine participants’ choices.”
Both the vmPFC and the pre-SMA are located in the brain’s frontal lobe and have been linked to planning and decision-making processes. However, this study, for the first time, enabled researchers to distinguish their separate roles. This new finding adds to a growing body of recent evidence highlighting the critical importance of the pre-SMA in human decision-making.
“The unique window into the human brain that is opened by these single-neuron recordings continues to deepen our understanding of the precise mechanisms behind cognitive processes,” noted Adam Mamelak, MD, director of the Functional Neurosurgery Program at Cedars-Sinai and a co-author of the study. “These continued gains in understanding are the key to finding new treatments for complex neurological disorders and improving the lives of patients.”
This research represents an ongoing collaboration between Cedars-Sinai and co-senior author John O’Doherty, the Fletcher Jones Professor of Decision Neuroscience at the California Institute of Technology. The partnership aims to advance the understanding of decision-making processes in the human brain.