Psychopathic people are callous and deceitful, and they often break laws. Our new paper shows that psychopathic people’s brain networks interact differently than non-psychopathic people’s, adding to growing evidence.
Brain networks are collections of brain regions that tend to work together. We focused our analyses on three networks that appear to support core brain functions: the default mode network, frontoparietal network, and salience network.
Don’t be fooled by the names – these brain networks are involved in a variety of functions, including emotion and regulating the body’s resources. It’s important to note that the brain doesn’t have a “default mode.” Every brain seems to switch between a variety of states throughout the day in order to meet the demands of the moment and prepare for the next moment. I’ll still call the network in blue above – which includes parts of the medial prefrontal cortex and posterior cingulate cortex – the “default mode network,” since that’s the name that most scientists use.
Names aside, let’s talk about these networks in terms of their role in attention. Two of the networks, the default mode and frontoparietal network, seem to be involved in different types of attention.
The default mode network is involved in internally-focused attention, for example mind-wandering, daydreaming, or getting lost in your own thoughts. The default mode network tends to be less active when a person is focused on something outside their body. So if an experimenter tells a participant in a magnetic resonance imaging (MRI) scanner to pay attention to a task on a computer screen, the experimenter is likely to see a decrease in default mode network activity.
(In fact, this is how the default mode network got its misleading name. Experimenters kept seeing this over and over – when they told people to pay attention to a task on the screen, they saw decreased activity in the regions in blue above. They considered the brain state before and after an experimental task to be the brain’s “default mode,” which they were changing by directing participants’ attention elsewhere. That’s a big assumption to make, and I disagree with it. But that’s a story for another time.)
The frontoparietal network, on the other hand, is involved in externally-focused attention. The frontoparietal network tends to be more active when a person is focused on something outside their body, for example a problem-solving task.
As you may have guessed, when one of these networks is more active, the other is less active. For this reason, we say that these networks are “anticorrelated.”
What brain mechanism coordinates the see-sawing of activity between the two anticorrelated networks (default mode and frontoparietal network)? One mechanism is – yes, that’s correct – the salience network.
The salience network is involved in quickly detecting important pieces of information in the body and in the environment. It then activates other networks to focus on that information. Importantly, the salience network appears to play a role in switching between the two anticorrelated networks.
We hypothesized that, in psychopathic people’s brains, the salience network’s switching role would be reduced. We made this hypothesis because psychopathic people have: 1) less anticorrelated default mode and frontoparietal networks, and 2) difficulty attending to salient information (like the threat of punishment or another person’s distress).
To test this hypothesis, we studied 148 incarcerated men age 18-30.
47 people scored high, 53 intermediate, and 48 low in psychopathic traits. We used fMRI to measure spontaneous changes in brain network activity. Participants were not told what to focus on during the scan.
To measure the salience network’s switching role, we used methods called independent component analysis (ICA) and dynamic causal modeling (DCM). You can read more about these methods in the paper (linked at the end of this post). Basically, ICA helped us find the average activity within each person’s brain networks at each moment in the scanner. Then, DCM helped us model how the three networks were interacting.
The data supported our hypothesis. The salience network’s role in switching between default mode network and frontoparietal network activity was reduced among people who scored high in psychopathy.
You can see this in the bar graph below. The x-axis along the bottom shows the low, intermediate, and high psychopathy groups. The y-axis along the left side shows how much the salience network was switching between the other two networks.
Our paper is the first to study the salience network’s switching role in relation to psychopathy. This is exciting, because this could be a brain mechanism related to psychopathic people’s callousness and difficulty attending to salient info.
But it’s also a cause for caution. The study will need to replicated by other research groups using similar methods.
We’re also limited in what we can conclude from the study. In our main analyses, we did not show participants salient info. We did not tell them what to focus on at all. To really support our hypothesis about reduce salience network switching, we would want to tell participants what to focus on and change the information they’re seeing or hearing throughout the scan.
We did try this, although we’re considering these analyses to be preliminary. We had participants perform an externally-focused task with changing information throughout the scan. Results were similar to our main analyses – again, the salience network’s switching role was reduced among people who scored high in psychopathy. However, these results did not quite reach statistical significance. You can read more about this in our paper’s supplemental materials.
To summarize, we found evidence that people with psychopathy, who have trouble detecting salient information and changing their behavior to address this information, show altered interactions between three large-scale brain networks that play crucial roles in core functions like attention, emotion, and regulating the body’s resources.
Our hypothesis was first made by the Impaired Integration theory. The theory is worth a read if you want to learn more about how impaired interactions between brain networks may cause cognitive deficits in psychopathy. You can read it here.
In my opinion, if we want to uncover the brain basis of psychopathy, we need to continue studying dynamic interactions between large-scale brain networks, rather than activity in individual brain regions. Doing so could lead to the development of much-needed, brain-based treatments for psychopathy.
Read the full paper here.
Deming, P., Cook, C.J., Meyerand, M.E., Kiehl, K.A., Kosson, D.S., & Koenigs, M. (2023). Impaired salience network switching in psychopathy. Behavioural Brain Research, 452, 114570.