Subjectivity and the neural basis of opinions

 Subjective decisions are necessary component of human behavior.  Every day, we navigate life through our perspective by making subjective judgements and forming opinions about our environment. Recent research has identified cells in the dorsolateral pre-frontal cortex (dlPFC) that are active in humans while making subjective decisions during an opinion-based task1. All participants were asked to judge situations on whether they were safe or unsafe. The activity of these neurons varied gradually as the participants transitioned between choices. In short, they found that variability in decision making is mediated by these neurons, an essential component of subjective decision-making because it is based in opinion. To make these judgements, a person must rely on their prior knowledge and experience to decide what they believe to be the truth.

The dorsolateral pre-frontal cortex (the purple region)

The results of this study are incredible. Using single-cell recording, the researchers were able to see the pattern of activity while the participants were making subjective decisions. The researchers also looked at subjective decision-making in participants that had lesions removed from their dlPFC. Compared to control participants, the pattern of activation for these people while making subjective judgements was more dichotomous, at a neural level, there was less variability in their decision. The pattern of activity in the dlPFC of healthy controls depicts more of a continuum on which the choice is just one point and many potential decisions are considered.

It is important to keep in mind that although the findings of this study are compelling, there are a number of other factors that contribute to subjective decision making. Findings like these are often misinterpreted as purely causative, when the actual “cause” of a particular behavior must include all relevant genetic, endocrine (hormones) factors and life experiences.

An illustration of the basic “trolley problem”, a classic moral reasoning problem.

In his book, Behave, Robert Sapolsky discusses the neurobiological underpinnings of moral decision making. Although these decisions are often rooted in objective facts and experiences, there is definitely a subjective component involved. The pattern of activation in the brain during moral decision making is very interesting in the context of this current research. Sapolsky concludes, in short, that moral decision making is a product of context and has been related to activation in a number of brain regions. The primary areas active while making moral decisions are the ventromedial (vm) PFC, amygdala, insula and the dlPFC. In these situations, vmPFC, amygdala and insula activation precede dlPFC activation2. I would like to see the result of research looking at single-cell activation of the dlPFC during moral decision making specifically. To begin, the researchers would have to implement some type of survey beforehand so they would have a morality measure to compare these decisions to. Then, the researchers would be able to determine whether the activation of these dlPFC neurons reflected a gradual subjective shift in their moral decision given the situation. If it could be demonstrated that dlPFC activation reflects the cognitive component of situations that are subjective, this could have exciting/terrifying implications. Could humans eventually be programmed to make the right decision or at least to help themselves make the right decision? What could this mean for people suffering from frontal cortex damage, whether this is from TBI, epilepsy, stroke, etc.? Could their decision-making be improved or mediated?

References

[1] Jamali, M, Grannan, B, Haroush, K, Moses, ZB, Eskandar, EN, Herrington, T, Patel, S & Williams, ZM, Dorsolateral prefrontal neurons mediate subjective decisions and their variation in humans, Nature Neurosci. (2019).

[2] Sapolsky, R, Behave, New York (2017) Penguin Press.

One thought on “Subjectivity and the neural basis of opinions

  1. I really enjoyed reading this article and found it very informative! I think that although it is interesting to discover a correlation between a particular behavior and a specific brain area, it is important that you noted other factors that could be involved because correlation does not always mean causation. I also think it would be interesting to see where subjective decision making is headed in the future, especially for people with damage to their PFC.

    Like

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