Emotions and the insula

I've been meaning for some time to write more about a brain region known as the insula. Looks like now is as good a time as any.

This is a big topic. We had one previous, tentative discussion here. It dealt with involvement of the insula in the "feeling" of fairness and how moral/ethical decisions are made.

Let's start with a review of what the insula actually is, anatomically. It is a part of the brain's cerebral cortex, the outermost layer of the brain, which in humans ranges from 2 to 4 mm in thickness. Although part of the cortex, the insula is located fairly deep within the brain, in an especially deep fold (or "sulcus") of the cortex, between the temporal lobe and the inferior parietal cortex.

Since the insula is adjacent to the temporal lobe on each side of the brain, it is made up of two separate parts, on the right and left sides of the brain. It is found that one side or the other, often the part on the right side, may be more important than the other in particular circumstances. Sometimes the critical area is even smaller, such as the anterior or posterior region of the insula on one side.

A good reason for considering the insula is that it seems to be deeply involved in mediating various emotions in humans. However, the evidence is somewhat indirect.

One important clue is that when a part of the brain including the insula is damaged due to disease or trauma, significant changes in emotions of the affected individual are observed. For example, smokers who experience damage to the insula suddenly cease to feel pleasure from smoking, and they are able to quickly give up the habit. (See here.)

Another clue is that fMRI brain scans show significantly increased activity in the insula when experimental subjects feel strong emotions. There are many example of this. In fact, the relationship seems so predictable that activity in the insula as revealed in fMRI scans is taken to be a marker for emotional experience.

However, there's a lot more we would like to know about exactly how the insula is involved with emotion. For instance, is there anything special about neurons found in the insula, some genes expressed in those neurons more than in neurons elsewhere? Or is the insula's role simply a matter of how it is connected to other parts of the brain? Are there particular hormones or neurotransmitters that are important for processing of emotions in the insula?

In order to even think about such questions, we need to look more closely at what is known about emotions themselves, from classical psychological studies.

To begin with, psychologists distinguish between different "levels" of emotion, not in the sense of intensity, but in the degree to which a particular emotion is more or less "fundamental" and related to basic instinctual needs or aversions. Fundametal emotions are such things as hunger, lust, craving, and fear. It is easily imagined that most animals with a developed central nervous system have such emotions.

Other emotions are a little more abstract, such as happiness, sadness, anger, disgust, anxiety, joy, surprise, delight, pleasure, and amusement. One supposes that substantially fewer animal species experience such "higher" emotions.

And then there are emotions which are pretty much limited to complex social animals that have a rich social life – for example, group loyalty, a sense of fairness or unfairness, altruism, trust, pride, shame, envy, jealousy, greed, grief, etc.

A whole lot more could be (and has been) said about such a categorization of emotions or alternative categorizations, but this will serve to provide an idea of what is meant by "emotion".

There are very good reasons for studying emotions per se. Here are some of them:

• Emotions play a large role in making moral and ethical judgments. The sense of "fairness" and empathy, as well as various other emotions (especially social ones), come in here. This was discussed here.
  
• Another special case of emotional involvement with decision making is found in politics. For instance, our attitudes towards particular candidates have a lot to do with our emotional reactions to the candidates as people – e. g., whether or not they give us a feeling of trust or security or empathy. (Some discussion here.)
  
• Emotions play a significant role in economics. For instance, choices made about investments depend a lot on whether one has emotions of fear (in troubled times) or greed (when the economy seems to be doing well).
  
• Emotions play a large role in decision making in general. Everyone understands the importance of "gut feelings" here. The emotions a person typically has in certain situations have a large effect on the decisions the person makes in such situations.
  
• Critiques of artificial intelligence and certain forms of cognitive psychology assert that intelligent behavior is not simply a matter of algorithmically applying rules and heuristics to known facts. The idea is that computers in their present form are not capable of fully human intelligent behavior because they are not embodied in the way humans are, and in particular they lack emotions. Such critiques have been posed by many philosophers and cognitive scientists, such as Hubert Dreyfus, and George Lakoff. The latter is a representative of the viewpoint known as "embodied philosophy".
  

We're not going to address all those issues right away. They just serve to remind us of things where more knowledge of the insula and emotions might help our understanding.

As an example of very recently reported research on the insula and emotions, we have this:

Why An Exciting Book Is Just As Thrilling As A Hair-raising Movie (8/12/08)

We all know, however, that reading a book describing the same scene can be similarly gripping. This week, in a paper published in the online, open-access journal PLoS ONE, Mbemba Jabbi, Jojanneke Bastiaansen and Christian Keysers show us why.

At the NeuroImaging Center of the University Medical Center Groningen of the University of Groningen (the Netherlands), Jabbi and colleagues compared what happens in our brains when we view the facial expressions of other people with the brain activity as we read about emotional experiences. ...

"Our striking result," said Keysers, "is that in all three cases, the same location of the anterior insula lit up. The anterior insula is the part of the brain that is the heart of our feeling of disgust. Patients who have damage to the insula, because of a brain infection for instance, lose this capacity to feel disgusted. If you give them sour milk, they would drink it happily and say it tastes like soda."

Prof. Keysers continued, "What this means is that whether we see a movie or read a story, the same thing happens: we activate our bodily representations of what it feels like to be disgusted– and that is why reading a book and viewing a movie can both make us feel as if we literally feel what the protagonist is going through."

To summarize: the question was about similarities (and differences) in brain response to the emotion of disgust, which may be stimulated in three different ways: actual experience (tasting something very unpleasant), observation of facial expressions of others experiencing disgust, and subjective imagination of disgust.

It was already known that fMRI scans showed activity in the insula and an adjacent region (the frontal operculum) – collectively termed the IFO – as a result of experiencing or observing the emotion of disgust. The research showed that very similar activity occurred as a result of imagining disgust.

Further reading:

Why real and imagined disgust have the same effect (8/13/08) – New Scientist article about the research

Emotional Thrills From A Movie (or a Book) – blog post on this research

A Common Anterior Insula Representation of Disgust Observation, Experience and Imagination Shows Divergent Functional Connectivity Pathways – August 2008 research article in PLoS ONE

Tags: insula, insular cortex, emotion

Moral choice: fairness, utility, and the insula

We continue to learn more about the neuropsychological basis of moral thinking and moral emotions in humans:

Justice In The Brain: Equity And Efficiency Are Encoded Differently (5/8/08)

Which is better, giving more food to a few hungry people or letting some food go to waste so that everyone gets a share" A study appearing in Science finds that most people choose the latter, and that the brain responds in unique ways to inefficiency and inequity.

The study, by researchers at the University of Illinois and the California Institute of Technology, used functional magnetic resonance imaging (fMRI) to scan the brains of people making a series of tough decisions about how to allocate donations to children in a Ugandan orphanage.

There are two main issues regarding moral decision making here.

The first involves two separate principles often used in analyzing moral/ethical problems related to the distribution of goods within a group of people. (The group might be children in a family or different classes of people in a society, among many possibilities.) On one hand, it is generally regarded as "good" to maximize "equity" in moral decisions, so that some individuals are not favored over others without significant justification. (I prefer the term "fairness" for this.)

On the other hand, it is also regarded as "good" to maximize "efficiency", so that the greatest total amount of benefit accrues to a group as a whole. (I prefer the term "utility" for this.)

But these principles can come into conflict, and the research discussed here investigates a contrived, but sharp, example. Philosophers of ethics call such dilemmas the problem of "distributive justice".

The second issue concerns the style of thinking that a decision maker faced with this kind of dilemma does use, and also, perhaps, what style the decision maker "should" use. On one hand, the decider might try to systematically and logically apply some standard set of rules that are considered appropriate for the situation. But on the other hand, the decider might rely more on emotional factors that indicate what "feels right", the "gut feeling", about what seems "right" in a concrete situation.

Philosophers often describe these two alternatives as "cognitivist" vs. "sentimentalist". The former is sometimes associated with the philosopher Immanuel Kant, and the latter with David Hume.

What emerges from the research is (not surprisingly) that individual decision makers differ in the degree that they favor "equity" vs. "efficiency", and also whether they tend to rely more on logic or emotion to make their decisions.

More interestingly, most people normally process considerations of both equity and efficiency in order to reach a decision, but different parts of the brain are used for the two. Likewise, in making the decision, distinct parts of the brain which normally handle emotional or logical processing can become involved in processing the equity/efficiency trade-off.

One way to think of this is that there are separate calculations of both equity and efficiency that are made for each available choice. And then the result of those calculations are fed to separate subsystems to weigh the alternatives.

The different moral and ethical decisions that different people will arrive at can be attributed to individual differences as to how the various stages of the decision process are handled. For instance, an individual may favor equity over efficiency, and tend to use emotion rather than logic to reach the decision.

Here's what the study found:

In these trails, subjects overwhelmingly chose to preserve equity at the expense of efficiency, Hsu said. "They were all quite inequity averse." The findings support other studies that show that most people are fairly intolerant of inequity.

The animation, in conjunction with the fMRI, allowed the researchers to view activity in the brain at critical moments in the decision-making process. After analyzing the data, they found that different brain regions -- the insula, putamen and caudate -- were activated differently, and at different points in the process, Hsu said.

Activation of the insula varied from trial to trial in relation to changes in equity, while activity in the putamen corresponded to changes in efficiency, he said.

In contrast, the caudate appeared to integrate both equity and efficiency once a decision was made.

The role of the insula (or, more formally, insular cortex) is especially interesting, since this brain region has been associated with quite a few other types of social-emotional mental processing. We'll come back to that in a moment. But here are the conclusions of the researchers:

The involvement of the insula appears to support the notion that emotion plays a role in a person's attitude towards inequity, Hsu said.

The insula is known to play a key role in the awareness of bodily states and emotions. Studies have shown that it is activated in people experiencing hunger or drug-related cravings, and in those feeling intense emotions such as anger, fear, disgust or happiness. Other research has implicated the insula in mediating fairness. ...

Together, the results "show how the brain encodes two considerations central to the distributive justice calculus and shed light on the cognitivist/sentimentalist debate regarding the psychological underpinnings of distributive justice," the authors wrote.

Here's how another report about this research summed it up:

Your Brain on Ethics (5/8/08)

The fMRI scans contain hints of how these two factors might be encoded by the brain. The insula, a brain region linked to processing emotion, became more active when subjects considered more inequitable distributions of meals; it was also more active in subjects whose choices suggested a greater-than-average aversion to inequity. Activity in another region, the putamen, seemed to track the common good, rising in proportion to the total number of meals that could be donated in a given case.

Now let's have a quick overview of the insula. Turns out that it's involved in a lot more than just moral decision-making. Here's a general article from a bit over a year ago:

A Small Part of the Brain, and Its Profound Effects (2/6/07)

According to neuroscientists who study it, the insula is a long-neglected brain region that has emerged as crucial to understanding what it feels like to be human.

They say it is the wellspring of social emotions, things like lust and disgust, pride and humiliation, guilt and atonement. It helps give rise to moral intuition, empathy and the capacity to respond emotionally to music. ...

If it does everything, what exactly is it that it does?

For example, the insula “lights up” in brain scans when people crave drugs, feel pain, anticipate pain, empathize with others, listen to jokes, see disgust on someone’s face, are shunned in a social settings, listen to music, decide not to buy an item, see someone cheat and decide to punish them, and determine degrees of preference while eating chocolate.

Damage to the insula can lead to apathy, loss of libido and an inability to tell fresh food from rotten. ...

Of course, like every important brain structure, the insula — there are actually two, one on each side of the brain — does not act alone. It is part of multiple circuits.

The insula itself is a sort of receiving zone that reads the physiological state of the entire body and then generates subjective feelings that can bring about actions, like eating, that keep the body in a state of internal balance. Information from the insula is relayed to other brain structures that appear to be involved in decision making, especially the anterior cingulate and prefrontal cortices.

Stay tuned. We'll be discussing the insula quite a bit more here, I think.

Further reading:

The Right and the Good: Distributive Justice and Neural Encoding of Equity and Efficiency – Original research report published 5/8/08 at Science Express (sub. rqd. for full access)

Which Orphans Do You Want to Starve? – Blog article by Sharon Begley at Newsweek

How Fairness Is Wired In The Brain – 5/28/08 press release about the research dealing with fairness and the insula

Tags: morality, fairness, utility, neuroscience, neurobiology, insula, insular cortex