Lab Talk

DMN Hubs

Assertiveness in Your Brain Activity

The activity of your wandering mind is a window into how assertive you are. 

Take a moment to close your eyes and allow your mind to wander.

What did you think about? Were you planning your day, wondering if you left the coffee pot on or imagining conversations yet to be had with people close to your heart? Was your inner voice chastising, complimentary or silly?

A wandering mind is a mind without a specific task to complete. It is a natural, normal state. In fact, your mind is likely wandering more often than you think. Though frequently overlooked, the wandering mind is a wealth of information. It is a window into a person’s inner-most strategies and assumptions when interacting with the world around us. Dr. Gennady Knyazev’s research peers into this window to understand what determines our individual styles of interacting with the world.

Human Neuroscience in Siberia

For over 20 years, Dr. Knyazev and his team have been studying the physiological correlates of various aspects of human behavior from his lab at the Institute of Basic Physiology and Medicine in Novosibirsk, Siberia. To many people, the thought of Siberia brings to mind images of a snow-covered tundra: beautiful, rugged and isolated. You might therefore be surprised to learn that Novosibirsk is the third most populated city in Russia. Though it does boast winters that would shock most people, this bustling metropolis also sports a well-established science and tech community with active human neuroscience research. Nestled 30 km South of the city center is Akademgorodok, or academic town that is home to Novosibirsk State University and 35 research institutes.

Dr. Knyazev in his lab

Knyazev’s work seeks out systematic relationship between the patterns of brain activity and individual personality using two important technologies:  The electroencephalogram (EEG) and more recently Functional Magnetic Resonance Imaging (fMRI) and (read 7 ways to peer into the living human brain for summary descriptions).  EEG readings measure electrical activity from the brain through a set of scalp electrodes (read What Does the EEG Signal Measure? for more details). In contrast, fMRI identifies brain activity using changes in blood flow and can probe into deep tissue.

EEG, fMRI and the Default Mode Network

One of the key ideas that has come out of fMRI research is that of the Default Mode Network or DMN. The DMN refers to a set of brain areas that are relatively more active when no particular task is at hand. Essentially these regions are anticorrelated with goal-driven and attention-heavy tasks and become dominant when the mind wanders (Raichle and Snyder, 2007). The DMN is your inner-world.  It is comprised of your thoughts and often those thoughts are self-referential – focused on oneself in reference to the world.

While the EEG is a very different measure from fMRI, it does measure signals from some regions involved in the DMN, providing an overlapping albeit distinct view of brain activity. These include the anterior and posterior DMN hubs in the cortex (shown as axial sections in the image above). Particularly it is the alpha band activity of the EEG (activity in one frequency range of the electrical siganl) that is most correlated to DMN activity (Knyazev GG et al, 2011 ). To the extent that the EEG can read aspects of DMN activity, it makes access less expensive, easier to use and very nearly consumer-friendly.

A Theory of Extraversion and the DMN

We’ve all known people that light up in big groups. They thrive on human interaction. Alternatively, others need space to recharge, garnering their internal energy from solitude. This distinction is a dimension of personality defined on a spectrum from introversion to extroversion.  A number of groups including Knyazev’s have found differences in the EEG spectral gradient from the frontal to posterior cortical regions between groups that perform differently on various sociability tasks that correlate with extraversion and  introversion.  However, while these differences were statistically different they were fairly broad, across multiple frequency bands and not very large.  Knyazev is advancing a theory that this dimension of personality may be most visible in the EEG as differences arising during self-referential mind wandering.

Specifically, he postulates that during self-referential thoughts there would be a greater spectral power in the alpha band in the posterior DMN hub in extraverted individuals, whereas in more introverted individuals there could be a relative increase of spectral power in the anterior DMN hub.

Why so? There are several reasons:

First, the correlations between extraversion and the EEG frontal to posterior spectrum have been observed predominantly in resting conditions, when the mind wanders, and overlap with the anterior and posterior DMN hubs.

Second, these areas, and their affiliated DMN, are functionally different. Specially, the anterior hub, which comprises the medial prefrontal cortex, is thought to be more involved in complex social relations and is often accompanied by negative emotions.  In contrast, the posterior hub is more involved in self-centered cognition (e.g., ongoing self-monitoring) and generally accompanied by positive emotions.

The anterior hub, or medial prefrontal cortex in particular, converges on deeper brain structures such as the nucleus accumbens to inhibit the release of dopamine, a neuromodulator that may be front and center in what we see as positive in the world. Moreover, studies by Jan Wacker and colleagues in Germany suggest that activity measured by EEG in the medial prefrontal cortex or anterior DMN hub relative to the posterior hub may serve as a proxy for dopamine inhibition that can be easily and non-invasively predicted (Wacker al, 2010, Wacker and Gatt, 2010).

From work that establishes the relationship between the EEG and DMN, to demonstrating the stability of these spectral gradients in individuals during specific tasks (Knyazev GG, 2009) and their relationship to extraversion (Knyazev GG et al, 2010), Knyazev has steadily been building evidence for his hypothesis.

Linking Self-Referential Thought with EEG Activity in the DMN

In one study, he assesses people on an assertiveness scale, generally thought to be one factor in introversion and extraversion (though admittedly it is not complete).  He looks at the alpha band activity in the anterior and posterior DMN during periods of self-referential thought.

Knyazev is the first to admit that the tools to measure self-referential thought and various aspects of personality are subjective and still need improvement. Nonetheless with the tools of the times, the results were surprisingly good. The figure below shows the behavior of those who scored in 0.5 standard deviations to the right of the mean of assertiveness scale (high assertiveness) compared to those 0.5 standard deviations to the left of the mean (low assertiveness). The measures he compares are the alpha band activity in the anterior and posterior DMN hubs and self-referential positive expectation (SRPE), a measure of how positive subjects reported feeling about their self-referential thoughts such as their rating of the statement that “expecting something positive that is going to happen to me”.



EEG and Assertiveness








Indeed the high assertiveness group had a fundamentally opposite pattern to the low assertiveness group.

In High Assertiveness scorers, SPRE scores significantly correlated with alpha band activity in the posterior DMN hub (r = 0.74, p = 0.001), but not the anterior DMN (r = 0.26, p = 0.313) whereas in Low Assertiveness scorers, SRPE scores significantly correlated with alpha band activity in the anterior DMN (r = 0.81, p < 0.001), but not with the posterior (r = −0.01, p = 0.969).  This suggests that how we perceive positive expectation in reference to ourselves, i.e which networks get involved, determine how we act in social situations.

This is a post hoc analysis but given the high regression coefficients, this looks like it is moving in the right direction.

Looking into the Future

How might this research be used? The answers are as varied as the imagination allows. Most obviously, an understanding of how people interact with the world can help doctors to diagnose and treat behavioral disorders. A person so anxious about social situations that they can’t leave the house may be trained to refocus his or her self-referential thought patterns. Given the relatively inexpensive costs of an EEG, people may even be able to monitor their progress from home. Though more research is needed to identify the many pathways of personality that the brain can produce, work from scientists like Knyazav is paving the way.

The ability to not just predict but understand the physiology of assertiveness and the broader characteristics of extraversion using EEG may not be far away.






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