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It looks like my goal of world domination have gotten a few steps closer, if two of the popular press articles I posted in the webliography are any indication.

The two articles form a theme of sorts about control.  One of the articles talks about how scientists hacked into a monkey’s brain to control its movements.  There have been reports in the literature describing procedures by which monkeys can control objects in the real world with their brains.  This is usually achieved by an implant of some sort that can be affected by certain patterns of electrical activity in the surrounding brain tissue that then sends a signal to a device in the real world.  This research seems promising for a variety of things, particularly people with paralysis or prosthetic limbs,   Imagine being able to control the prosthetic not only with the muscles near it, but also with your brain to some extent.

Schematic of brain showing the ventral tegmental area (VTA).

Schematic of the brain showing the ventral tegmental area.

Researchers have figured out an elegant way to influence the decision making process of monkeys.  They implanted electrodes into the ventral tegmental area (VTA) of the brain, which is one of the places (as you will learn more about in the coming weeks) that produces dopamine and is involved in reward circuitry of the brain.  Then, they conducted a simple preference test by showing monkeys two pictures of random objects and had them indicate which one they liked better.  This initial preference test was their control procedure since they were interested in what choices the monkeys made without any interference from the experimenters.  Once this was done, they demonstrated that by sending brief electrical bursts through the electrodes implanted in the monkeys brains the researchers could get the monkeys to reliably switch their preferences for pictures.  Now, this doesn’t mean an evil mustache-twirling mastermind, or the government, or the NSA are going to take over your mind or anything like that, though that possibility is certainly there.  But this does build on some fascinating research from the 1950s that helped to further our understanding of the role the brain plays in motivating our specific choices.  The fact that this can be manipulated artificially is an interesting finding.

Long-term potentiation

A schematic of a regular synapse and one that has undergone stimulation to produce a long-term potentiation (LTP).

In the other interesting article, researchers were able to turn memories off and on.  This was done in genetically engineered rats using light pulses that strengthened or weakened synapses in the hippocampus.  This is another thing you’ll be learning about (in Week 5 I think).  One of the amazing things about our nervous system is that it is dynamic and is constantly changing due to our experiences.  It’s why we can learn new things.  One of the ways memories are formed is through strengthening and weakening of synapses, or long-term potentiation (LTP) and long-term depression (LTD).  This strengthening and weakening can be achieved through everyday use, such as when you memorize information for this class, or become classically or operantly conditioned to perform a response to a specific stimulus.  It can also be artificially induced, using different frequencies of light pulses that stimulate the synapse.  If you can find the right frequency of pulses (high or low) you can make the synapse stronger or weaker.  This is the mechanism by which the researchers in this particular study were able to manipulate memory in the rats. They were able to turn a conditioned fear off and on using light pulses to the hippocampus.

Both of these studies are interesting for a couple of reasons.  First, they tie together a lot of the information you’ve already learned in the course, particularly how synapses and neurotransmitters work, as well as brain structure (VTA and hippocampus) and shows how they all work together to produce complex behavior.  The added layer that makes this particularly fascinating to me is the fact that researchers can control behavior through selective brain stimulation, an idea that is exciting and a little terrifying.  I will admit it does conjure up images of a MatrixThe Matrix-like culture where people’s thoughts and behaviors are controlled by others by directly accessing their brains.  It’s easy to see how something like that could be abused at some future point, though we’re a long way from that.

I can see some tremendous potential for good, here, too.  In particular, imagine what the treatment of extreme phobias, Alzheimer’s disease, PTSD, and other types of problems related to memories would look like if we had the ability to either enhance memories or take some memories away at will.  It’s tempting to shrink from an idea like that, because our memories are what make us who we are, and common sense tells us we might be better off learning to just cope with them.  But imagine memories so awful, so debilitating and disturbing, that it becomes difficult or impossible to cope with them, and they begin to affect every aspect of your life.  I’ve never suffered from PTSD, but I imagine it can be quite horrible, and if conventional treatment doesn’t help then perhaps being able to suppress the memories, at least for a little while so that other coping mechanisms can be acquired and strengthened might offer some people a desperately needed reprieve.  And being able to counter the synapse weakening amyloid beta proteins in the brains of people with Alzheimer’s Disease seems like a promising idea worth investigating.

It’s a little harder to see the benefits of influencing choice.  One can easily envision unscrupulous advertisers using something like this to force people to choose their products, but again, I doubt that would ever happen.  I think the significance of this centers on the issue of motivation.  They were able to manipulate motivation, and got monkeys to choose things they might not otherwise choose.  Though it’s a stretch, this might be something beneficial to people suffering from depression or inactivity of one sort or another.  The idea is interesting, anyway. I wouldn’t mind being able to give my brain a little zap to get me motivated.

References

Arsenault, J.T., Rima, S., Stemmann, H., Vanduffel, W. (2014). Role of the primate ventral tegmental area in reinforcement and motivation.  Current Biology, 24(12), 1347–1353 DOI: http://dx.doi.org/10.1016/j.cub.2014.04.044

Nabavi, S., Fox, R., Proulx, C.D., Lin, J.Y., Tsien, R.Y., and Malinow, R. (2014). Engineering a memory with LTD and LTP.  Nature, doi:10.1038/nature13294

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!

References

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.