by Ingrid Fadelli , Medical Xpress

When making decisions, people do not just compare their options, but also appraise how they feel about their options. These two processes should be reflected in distinct neural activity, with an appraisal process reflected in activity shortly after the options are shown in addition to a choice process leading up to the response. This was tested looking at neural activity measured with EEG synchronized to the time the options are shown as well as to the time the choices were made, and how activity at each time point was related to how much people liked the options and how difficult the choice was. Credit: Nature Human Behaviour (2024). DOI: 10.1038/s41562-024-01971-z

Past neuroscience research has identified patterns in neural activity typically observed when humans are engaged in value-based decision-making. This is the process through which humans choose between options that could be linked to different costs and rewards, weighing their options carefully based on their own preferences, goals and expectations.

Researchers at Brown University and University of Birmingham recently carried out a study aimed at further elucidating neural signatures of value-based decision-making uncovered in previous papers, which closely resemble those underpinning the accumulation of evidence believed to precede choice.

Their findings, published in Nature Human Behaviour, suggest that in this context these signatures are not actually linked to evidence accumulation, but instead reflect choice-independent processes.

"Our study was inspired by the intuition that when we make decisions, we often do not only compare our options, but we also feel certain ways about them," Dr. Romy Froemer, first author of the paper, told Medical Xpress.

"For instance, when we get to choose among some great options, like when I get to pick from tasty looking breakfast options at this amazing vegan place I discovered in Ghent earlier this summer, we don't just think about which one is better.

"We also think how great all these options are. This feels very different to the case when all the options are not that great, like when I consider the packaged sandwiches that they sell for lunch at our university cafés."

In his previous studies, one of the authors of this recent paper, Amitai Shenhav, showed that the extent to which people like the options available to them during value-based decision-making correlated with activity in specific areas of the brain, while how difficult humans found to pick an option correlated with activity in other brain regions.

Although his findings were insightful, they did not clarify at what point of decision-making these two different processes (appraisal and choice comparison) occurred.

"To study this, we needed a different technique that can tell us what is happening in the brain moment to moment at the level of milliseconds," said Froemer. "To see whether we could identify neural activity associated with how people feel about their options, we used EEG, a method that has this exact property of being able to tell us millisecond by millisecond, what neural activity looks like."

The people who participated in the team's study were asked to wear caps with electrodes mounted on them while they made various value-based decisions. The decisions they had to make varied both in terms of how good available options were and how difficult it was to pick the best one.

"We expected that these two properties of the data would correlate differently with neural activity in the EEG," explained Froemer. "We predicted that we would see neural activity associated with how people feel about their options early on, shortly after they get to see the options, and separate neural activity associated with how difficult the choice is leading up to the response, and crucially not vice versa.

"We tested these predictions by looking at the neural activity during choice in two ways, one synchronized to the time the options appeared and one synchronized to the time participants made their decisions."

Distinct neural activity was found associated with how much people liked the options (Appraisal) and how difficult the choice was (Choice). As expected, the former was reflected in neural activity shortly after the options were shown, whereas the latter was reflected in the activity leading up to the decision. Surprisingly, the choice related activity (posterior) did not look like the pattern that was expected based on prior findings (top) at all, indicating that it may not reflect activity associated with making the choice after all, either. Credit: Nature Human Behaviour (2024). DOI: 10.1038/s41562-024-01971-z

Subsequently, the researchers examined the neural activity at two different points in time: when the possible choice options appeared and when the participants made the decision. Their goal was to determine if the neural activity at these two stages varied based on how much the participants liked available options and how difficult it was for them to come to a decision.

"First, as expected, we found that neural activity tracked this appraisal process (indicating how much people like their options while people were making their choice) independently of how difficult that choice was and much earlier than we would expect activity associated with decision-making," said Froemer. "This means that when we make decisions, we don't only make decisions, and in turn, that neural activity during decision-making need not reflect decision-making per se or at all. Our brains and minds can do many things at the same time."

The second finding of this recent study came as a surprise to the researchers. Specifically, the team found that neural activity linked to how difficult deciding between options did not look like a signal they expected to observe during decision-making.

"Previous work that has combined mathematical models of decision-making with EEG had described what neural activity associated with decision-making should look like and our data looked nothing like that," explained Froemer.

"In fact, we found that maybe there is a completely different explanation for why previous studies had found data that did look like the neural activity of the brain making decisions. This means that we need to be really careful in concluding that neural activity that correlates with how difficult a choice is reflects that choice process per se."

The recent study by Froemer and her colleagues gathered interesting new insights about the neural activity patterns underlying value-based decision-making and its varying dimensions. While their findings suggest that neural signals linked to making a choice can artefactually emerge from choice-independent processes, this interesting occurrence remains poorly understood.

"We still don't know for certain what the activity we found associated with choice difficulty means," said Froemer. "We speculate that perhaps it's processes that evaluate and guide the ongoing decision-process, but more research is needed to understand that."

The results of this recent study could soon inspire additional research probing the neural signatures of value-based decision-making under different conditions. In their next papers, Froemer and her colleagues plan to continue investigating the complex processes that the human brain relies on to guide decision-making.

"For instance, we need to figure out how to explore each of our options, how long we should explore them before we make a decision, what type of decision we want to make, e.g., pick the best or avoid the worst, whether we should decide at all or go do something else, and how each of these processes are reflected in neural activity," added Froemer.

"If we understand these processes better, then maybe we can gain some new traction in understanding and helping people who struggle with decision-making, like people with depression, obsessive compulsive disorder or addiction."

More information: Romy Frömer et al, Common neural choice signals can emerge artefactually amid multiple distinct value signals, Nature Human Behaviour (2024). DOI: 10.1038/s41562-024-01971-z

Journal information: Nature Human Behaviour 

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