Summary: Neuroimaging and computational neuroscience studies reveal different ways and brain areas implicated in decision making.
Source: University of Plymouth
Research carried out by a University academic has shed new light on the fundamentals of how, and why, we make the decisions we do.
In two separate studies, UKRI Future Leader Fellow and Lecturer in Psychology, Dr Elsa Fouragnan has used her expertise in functional magnetic resonance imaging (fMRI) and computational analysis to discover exactly what happens in the brains of human and non-human primates when certain kinds of decisions are made in different contexts. Both pieces of work were carried out in collaboration with researchers at the University of Oxford’s Department of Experimental Psychology.
The first, published in Nature Communications, explores how and where the brain encodes a memory of the general reward rate in an environment, what the team describes as the ‘richness’ of the context in which decisions are made.
The decisions we make are influenced by the context in which they take place, and our perceptions of their outcomes are also seen through the same lens.
Dr Fouragnan explained:
“To give a simple example, in a context where punishment is regularly experienced, if nothing happens that might be seen as a good thing. On the other hand, in a context where normally many good things occur, nothing happening would be viewed as negative.
“This richness of context we named the global reward state of an environment, and in this study we identified where in the brain this global reward signal is encoded.”
In the research, the team found that the global reward state had a striking impact on behaviour. Subjects were more likely to repeat rewarded choices in environments with high global reward state, and to abandon poor choices more readily when encountered in low global reward states.
They were also able to identify the areas of the brain – the anterior agranular insular cortex and the dorsal raphe nucleus – where activity was associated with decision-making being influenced by the global reward state.
The second paper, published this week in Nature Human Behaviour, explored how decisions are made when we are faced with uncertainty about choices that could lead to different outcomes. It focused on the exploration/exploitation dilemma: the choice between exploiting a familiar option with known value, and exploring an option with uncertain value, but which might turn out to be better. Do you just go for what you know, or do you decide to try something you’ve never had before?
Again using fMRI and computational modelling, the study found that another key area of the brain involved in decision-making, the ventromedial prefrontal cortex, not only played a role in calculating the values of the options being considered, but also displayed different activity depending on whether the subject was in explorative or exploitative mode. This showed, according to the researchers, that this part of the brain has a unique role in representing the beliefs that guide choices.
Dr Fouragnan added:
“These studies have added a bit more to our growing knowledge of how decisions are made: how they are influenced by context, and how our beliefs about the decisions we make are shaped by uncertainty. The really exciting part, however, is that we have now found the neural processes that underlie these different kinds of decisions.
“Ultimately, these studies can be translated into benefits for patients with mental illness, particularly those for which decisions are pathological, for example in addiction.”
About this neuroscience research article
Source: University of Plymouth Contacts: Press Office – University of Plymouth Image Source: The image is in the public domain.
Global reward state affects learning and activity in raphe nucleus and anterior insula in monkeys
People and other animals learn the values of choices by observing the contingencies between them and their outcomes. However, decisions are not guided by choice-linked reward associations alone; macaques also maintain a memory of the general, average reward rate – the global reward state – in an environment. Remarkably, global reward state affects the way that each choice outcome is valued and influences future decisions so that the impact of both choice success and failure is different in rich and poor environments. Successful choices are more likely to be repeated but this is especially the case in rich environments. Unsuccessful choices are more likely to be abandoned but this is especially likely in poor environments. Functional magnetic resonance imaging (fMRI) revealed two distinct patterns of activity, one in anterior insula and one in the dorsal raphe nucleus, that track global reward state as well as specific outcome events.
Polarity of uncertainty representation during exploration and exploitation in ventromedial prefrontal cortex
Environments furnish multiple information sources for making predictions about future events. Here we use behavioural modelling and functional magnetic resonance imaging to describe how humans select predictors that might be most relevant. First, during early encounters with potential predictors, participants’ selections were explorative and directed towards subjectively uncertain predictors (positive uncertainty effect). This was particularly the case when many future opportunities remained to exploit knowledge gained. Then, preferences for accurate predictors increased over time, while uncertain predictors were avoided (negative uncertainty effect). The behavioural transition from positive to negative uncertainty-driven selections was accompanied by changes in the representations of belief uncertainty in ventromedial prefrontal cortex (vmPFC). The polarity of uncertainty representations (positive or negative encoding of uncertainty) changed between exploration and exploitation periods. Moreover, the two periods were separated by a third transitional period in which beliefs about predictors’ accuracy predominated. The vmPFC signals a multiplicity of decision variables, the strength and polarity of which vary with behavioural context.