Simulation as a tool for us humans to identify others' actions and thoughts has been a point of conversation for a while between psychologists and philosophers. However, up until now, the neural basis of this process had yet to be identified.
A recent study published on 14 April in Cell, one of the journals with the highest impact factor. It is led by Wolfram Schultz, a scientist at the University of Cambridge in the UK; along with Gustavo Deco, ICREA research professor with the Department of Information and Communication Technologies and Director of the Center for Brain and Cognition at the Universitat Pompeu Fabra in Barcelona.
What they have been working on is discovering how the amygdala in our brain is closely related to our social behavior and in autism. However, it was not yet known whether or not the amygdala neurons contributed to advanced social knowledge, in this case, simulating the decisions of other individuals.
Recognizing others' decisions
In this study, a type of neuron is newly identified which actively and spontaneously learns from decision-making by other individuals and simulates their mental processes.
One speculation made by the authors of the study is that when a dysfunction occurs in the simulation of these neurons, this could lead to a restriction in societal norms, such as seen in autism, which may end up providing an exaggerated version of others and their decisions, leading to social anxiety.
Furthermore, the authors also speculate that these 'simulation neurons', found in the amygdala, which is a collection of nerve cells in our brain's temporal lobe, permits animals (and potentially humans) to predict the intentions of their social partners.
Food for thought
Gustavo Deco, co-author of the study, states that the simulation of the decisions of others is a sophisticated cognitive process within social learning. "By observing the foraging choices of another individual, we can learn what food is worth choosing. This knowledge is not only to do with our own decisions, but also to help us predict the future decisions of others".
Recorded activity from amygdala neurons in monkeys helped further the study, as they were watched during observational learning tasks. Pairs of monkeys were given the choice whether or not they wished to receive a reward (juice, in this case study).
What did the monkeys' brains predict?
The animals were allowed to observe the choices taken by their counterpart and learn the reward values of each image. What the researchers noticed was that once the images were switched, the observing animal could make use of this knowledge when it was the next monkey's turn to choose.
Astonishingly, it was seen that when an animal observed its partner, the neurons in the amygdala of the observer seemed to make a decision computation. They were able to make a prediction as to what the other monkey would pick.
Based on the results, the scientists created the first computational model of the neural circuits of the amygdala involved in social cognition. As Deco says, "when observing how the specific types of neurons influence each other, this model suggests that the amygdala contains a "decision circuit" that identifies the animal's own choices and a separate "simulation circuit" that calculates the prediction of the choice of the social partner".
What does this mean in relation to social anxiety and autism?
The researchers point out that an alteration in the functionality of simulation neurons may minimize social cognition.
As Fabian Grabenhorst, the first author of the study explains: "If simulation neurons do not work properly, a person may not interact effectively with the mental states of others. We know very little about how specific types of neurons contribute to social cognition and the social challenges faced by individuals with autism.
By identifying the neurons and mechanisms of specific circuits for mental simulation, our study may provide new ideas on these conditions".