Archive for November, 2012

Pseudobulbar Affect

So, here we are, at the last blog entry of the semester.  What a long, strange trip it’s been. 

I began this series of blogs with a description of an interesting, yet troubling behavior I saw in my mother while visiting her over the summer.  In addition to the Alzheimer’s Disease, which is progressing, she has a movement disorder, and she laughs all the time.  I used this as a springboard to examine laughter (and by extension positive affect) in this series of entries, so I would like to return to that behavior.

While researching the brain mechanisms that contribute to laughter, and discovering that there was no single area of the brain that controls laughter, I cam across a paragraph in Meyer et al (2007) discussing the source of “pathological laughter.”  This is involuntary, mood-independent laughter that often occurs without any external or internal trigger.  Poeck (1985) and Hartje (2006) (as cited by Meyers et al, 2007) suggest that this behavior is not caused by any true affect or emotional state, but is, instead, the result of disinhibition of the motor pathways that control laughter.  It’s seen in a number of neurological disorders, particularly those that are degenerative.

So, it’s somewhat common to see pathological laughter, sometimes termed “pseudobulbar affect” in Alzheimer’s Disease, and as I correctly surmised before doing any research on the matter, it was likely due to some disinhibition.  The frontal lobes are the main sources of this inhibition.  It’s the area of the brain that keeps the expression of inappropriate behaviors at bay in social situations, even though we may be thinking about it.  For people suffering from a neurologically degenerative disease, such as Alzheimer’s Disease, the destruction of neural tissue in the frontal lobe removes that inhibition and produces this behavior.  Anyone who has ever suffered from a mortifying bout of inappropriate laughter probably understands the issue of disinhibition all too well as they desperately attempt to stifle the giggles emanating from them.  I know I certainly have.

It is possible that on top of the Alzheimer’s Disease, my mother is suffering from some other disorder, such as multiple sclerosis, and her doctors are investigating that possibility as well.  I’m sure I will post here about it if we discover something new.  For now, I’m satisfied that there is a reasonable explanation for the behavior, and as I said in my original post, I am glad it is laughter and not some other type of emotion.  Even though the laughter may not have an underlying cause for my mother, it does evoke positive responses from the people around her, including us.  My sister found it very comforting, for example.

So, as always, this journey into a particular behavior has been enlightening and informative, particularly since I have such a personal connection to it.  Like yawning, laughter is a phylogenetically old, and stereotypical behavior.  Like the expression of all emotion, it is designed to communicate something.  Since evolution is conservative, and tends to find new uses for old things, this behavior eventually became a powerful mechanism for social bonding, and an important part of all social interactions.  Its importance in the brain is, I think, highlighted, ironically, by disorders such as those that cause pseudobulbar affect.  It makes me envision laughter as this effervescent substance inside a brain-shaped cauldron.  Its surface is calm, but the laughter is bubbling beneath, always waiting for the chance to escape.  And, in the end, I think that’s a good thing, because the world probably does need more laughter in it.

As this is the last blog of the semester, I’d like to again take this opportunity to thank my students in PSY229 Introduction to Biological Psychology, who have been blogging along with me as a class assignment.  Many of you approached this assignment with trepidation and hesitancy, yet have given it your best effort, which is greatly appreciated by me.  Critical thinking skills are among the most important things we strive to teach you in a college education, and continued, sustained writing is one way to help develop those skills.  For this assignment, you engaged your critical thinking skills to pick out a series of topics of interest to you.  Then, and even more importantly, you used those skills to sift through the enormous amount of information, good and bad, on the web.  While there were a few missteps with respect to that along the way, I think you all learned from it.  I hope this assignment has empowered you to continue investigating and researching those topics that interest you.

And to keep writing about them, too!


Meyer, M., Baumanne, S., Wildgruber, D., & Alter, K. (2007). How the brain laughs: Comparative evidence from behavioral, electrophysiological and neuroimaging studies in human and monkey. Behavioral Brain Research, 182, 245-260.


This week in class we’re going to be discussing emotion. The interesting thing is, when I prepared this course years ago, most of the resources I used focused on so-called negative emotions, such as fear, and anger and aggression. As we all know, Yoda felt that fear and anger were paths to the dark side of the force.

I used the term “so-called” because I don’t believe fear and anger or aggression, in and of themselves, are negative.  All our emotional responses, including fear and anger, evolved for a reason, and when you think about it, they evolved for very good reasons. Fear protects us from danger. Imagine not feeling afraid of that fire racing through the forest threatening your life, or that saber-toothed tiger bearing down on you. Anger, and perhaps aggression, are emotions of possession; we experience them when we perceive that something that we value has been taken from us. In an evolutionary framework, this is also a good thing. So much about survival and reproduction centers on resources. Access to food, access to suitable mates, both of these are vitally important things that must be protected, defended, and yes, reclaimed when lost, because they improve our reproductive success. A species that just let’s others take all their important resources is one that won’t be around very long.

So, in my opinion, Yoda was wrong about a great many things.  (And I really wanted to put that clip from “Return of the Jedi” here, but I couldn’t find it on YouTube).

It isn’t much of a stretch to understand why these emotions evolved in the first place, and the value they actually have in the grand scheme of things. But this blog series is about laughter, so lets focus on that for a bit. I’ve already talked about the social bonding function that laughter plays, which is why it’s important. We’re also not entirely sure what parts of the brain are involved in laughter, but we are beginning to image brains in such a way that we can tell if a person is generally happy or generally sad.

It seems to me that the dopaminergic system is probably a major player. Laughter is accompanied by (or produced by?) positive affect. I think it’s pretty safe to say that other people are most often the cause of our laughter. So a release of dopamine is our reward for sharing a laugh, or engaging in some kind of socially-mediated laughter, like those found in conversation. Mirror neurons, too, probably play a huge role. Most of the time, if someone smiles or laughs, you laugh along.  How many times have you laughed at something you didn’t quite hear because everyone around you laughed?  I do that all the time, and invariably someone turns to me and says “What did they say?” and I have to sit there and feel like a dork because I don’t actually know.

There’s a trend in psychology now, called positive psychology.  One of the important things it brings to the discipline is that it helps get us away from this obsession with abnormal behavior and dysfunction that has taken over psychology.  I talk often of the importance of understanding everyday behavior in class; it becomes depressing to contextualize all behavior in terms of how it goes wrong or is maladaptive, in my opinion.  I think that’s what takes us to the dark side, rather than certain emotions themselves.  People end up getting so caught up in their bad behavior that they downplay or overlook the good behavior, and that’s a shame.  With the rise of positive psychology comes an increased emphasis on understanding happiness and laughter, in figuring out how our nervous system mediates those emotions.  The potentially life-saving advantages of social bonding, which is in part mediated by happiness and laughter, are no less important than the direct benefits of fear and anger.  Social behavior evolved because it conferred an advantage to the individuals who engaged in it; anything that helps us get along in a social group, including mirroring the positive behavior and affect of others, is probably a good and beneficial thing in a broad context.  This is, after all, a major factor in how children learn what to do and how to be.

One goal I have for myself this summer is to revise my emotion lecture.  I think it’s pretty good, but I want to add a section on happiness and positive affect.  Understanding laughter in the nervous system is not only cutting edge in psychology, it has direct benefits for individuals and for my beloved discipline.  And I’m all for that.