A Constant Battle: Conscious and Subconscious Brain Areas – Blog #2

July 7, 2019 at 10:12 AM
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A Constant Battle: Conscious and Subconscious Brain Areas – Blog #2

Sarmin Akter, Branden Eggan, PhD, James Stellar, PhD

 

In our  first blog, we discussed the basic idea of what we called conscious vs. unconscious brain processes and the roles they play working together in Sarmin’s decision-making around the issue of diversity.  We equated conscious areas with logic and suggested they were cortical whereas the unconscious is subcortical and related to emotion or automatic processing.  In this blog, we want to dissect those two broad areas a bit and describe several regions in each and apply them to decisions as discussed in the 2007 paper “Should I stay or should I go?

The diagram below shows just a few brain areas we will mention.  Those labeled in red are from the subcortical, unconscious areas.  Those labeled in blue are from the prefrontal cortex (PFC), the most recently evolved, uniquely human of the cortical areas.  Those labeled in green are cortical but have a more emotional function to them. This entire system works together, so it is hard to make clear separations, but to get to Blog #3, we need to delve deeper in to these areas. References are provided for each area for those who want to follow up.

 

 

The PFC (blue) has been shown to be involved in high-level planning. Humans have significantly larger PFCs than in even our most evolutionarily similar neighbors, the primates hence why a chimpanzee does not stress about what college to attend. We want to talk about three areas within the PFC as an illustration of higher-level processing operations working in communication unconscious brain circuits. As an example, you may have heard of Phineas Gage, the man whose entire PFC (and other areas) of his left hemisphere was destroyed after his being impaled in his head by a lineman’s rod in a railroad accident. Prior to the accident he was described as “energetic and serious.” After the accident he had the maturity of a child, seemed to have lost his logical/emotional balance with this damage to the PFC. Luckily, some say he may have improved after years of recovery.

Ventromedial Prefrontal Cortex (vmPFC; reference link):  Located on the bottom inside of the PFC. From brainscan and other studies, this area and its network seems to represents reward and value-based decision-making. Damage to this region decreases one’s ability to make a decision when the outcome is ambiguous. Remember what I (SA) said in Blog #1 about choosing a college major? Without my vmPFC, I would not be able to choose biology or business, as they both come with much uncertainty.  This region also seems to control and regulate negative emotions in social situations as well as the feeling of empathy that results from the facial expressions of others. Emotions are important, think about those gut feelings, but they must be integrated with logic and that may be what the vmPFC does.

Orbital Prefrontal Cortex (OFC; reference link):  Also, located on the bottom of the PFC like the vmPFC and overlapping with many of its functions, the OFC area lies more to the outside on top of the eyes (the orbits).  It seems to take into consideration body processes that are related to what is good for you, like eating food, and tying this kind of input to cognitive or conscious decision-making. It may govern that feeling of rightness and working with aspects of memory, it  may help to make a decision in this area when there is insufficient factual information. For example, in one study, the OFC seemed to encoded a willingness to pay for food in hungry subjects. Maybe this is why I have a hard time deciding between Uber Eats (more expensive) and going to the campus center (a long walk from my dorm room).

Dorsolateral Prefrontal Cortex (dlPFC; reference link):  Located on the upper outside of the PFC, this area seems to be involved in regulation of learned emotional responses from a history of outcomes over time.  It also has a role situations that involve in temporal processing. This area, like the PFC, also shows heightened activity when making decisions with an uncertain outcome. Patients with damage to the dorsolateral PFC have “threat-induced anxiety” and lose the ability to make risky or moral decisions. When choosing between helping your friend who got a flat tire on the way to class and potentially being stuck with a zero on your exam that day, the  dlPFC helps to choose the most equitable option.

 

Two subcortical areas (red).  These structures are older evolutionary and more similar anatomically between humans and subhuman mammals.  They seem to underlie basic functions connected to emotions as part of the limbic system.  We picked two of them as representatives, one from the positive and one from the negative side.  Again, we oversimplify and this time, we leave out any interactions between them.

Accumbens (reference link):  Located nearly in the center of the brain, this area seems to mediate reward and pleasure.  It is part of a limbic circuit described in a set of three blogs written about the neurotransmitter dopamine, the reward neurotransmitter of the brain. This area has been implicated in addiction, motivation, and reinforcement learning. Feeling on top of the world because you earned that A on your calculus midterm that you’d been studying for every night for the last three weeks? That’s the accumbens. Being motivated to study just as hard to earn an A on that final exam? Also the accumbens and a phenomena scientists call positive reinforcement.

Amygdala (reference link):  Located in the temporal lobe on the lateral side of the brain, this structure seems to mediate fear and fear learning.  It is known to learn and warn us of coming bad situations that in the past have been hurtful or threatening. Walking across campus at 2:00am after a late night study session and hear a shriek coming from the woods 10 yards in front of you, what do you do? Drop everything and run in that direction to see if someone needs help? Turn around immediately in your tracks and head in the opposite direction? Regardless of your decision, that immediate fear you get that something’s wrong and you might be in danger, that’s the amygdala.

 

Finally, there are two intermediate structures (green)  that are both cortical but yet exist as deeper brain structures.

Anterior Cingulate Cortex (reference link):  Also located centrally but more forward than the accumbens, this structure seems to detect when things do not go as planned, such as when an expected reward does not occur.  In a sense, this is an error detector and errors are often lead to new learning. It also operates in impulse control, and with other structures mentioned above, in making moral decisions.  Back to Blog #1, I mentioned that when I arrived on campus I thought that I would be immersed in diversity. It didn’t take long for my ACC to become active as I realized that this was an error as my expectations were not met.

Insula Cortex (reference link):  Buried in the fold of the brain that divides the temporal lobe from the brain above, this structure seems to encode interoceptive and body self-awareness and, importantly, risk, as well as other emotions.  In a sense the risk balances out reward along with fear generated in the amygdala and other regions.  It is particularly sensitive to situations of prior risk and is active in learning and perceiving the feelings of others. Score an F on a term paper? You’re going to feel upset. Does that put you at the risk of failing the course? There you’ll see heightened activity in the insular cortex. What if on the next report you score an A but your best friend scores an F? That “I feel your pain response” comes straight from activity in the insular cortex.

 

Communication between these areas

Clearly communication between these brain areas is the most important topic of Blog #2, even if we spend the least blog-space on it.  Brain areas are never on their own.  They are always communicating and interacting.  But we have some divisions above, and broadly, those that are more associated with cognitive or conscious functions and control over emotion, we suggest are located in the prefrontal cortex.  Those that are located in the limbic system are more directly associated with emotion but make decisions too.  Look at the Dopamine Blog mentioned already and its role in reward prediction down at the dopamine release level.  Therefore both make decisions.  The amygdala learns what produces threat as well as generating fear when a threat occurs.  It may have overlearned in PTSD (Post Traumatic Stress Disorder). Yet the PFC  is also learning and regulating the amygdala emotion with the ventromedial PFC and other areas. Clearly it gets complicated, with all of these many “voices” (and with many more than we’ve included in this blog).  It looks like a constant battle to get the spotlight hence the title for this series. Decision-making ultimately occurs as these circuits reverberate their communication and the maybe the loudest voice wins, logical or not, moral or not, and it happens in a fraction of a second.

 

What does this have to do with diversity?

Implications for diversity is really the subject of blog #3 and the last in this series.  We will pick only two of the above structures to discuss, the PFC and the amygdala and we will discuss the role that communication between these two areas might play in challenges associated with in-group / out-group feelings and helping us to not fall prey to fear or social anxiety.

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