Tag Archives: neuroscience

Performing the Oldest Tricks in the Newest Ways

Katherine suffers from rheumatoid arthritis in her hands, and has found that wearing tight bracelets or wrapping fingers with tape often reduces the amount of pain she feels. My uncle used to wear a copper bracelet, presumably for the same reason. My mother wraps her legs with compression bandages when her varicose veins cause her legs to hurt. She would also similarly wrap our legs as kids when we had growing pains. Athletes have been known to compress injured areas with tape or support braces. In the Olympics, volleyball players were seen with taped fingers and shoulders. In the far east, acupuncture was developed to relieve pain. All of these treatments for pain have one thing in common. They involve touch stimulus of the area at or near where the pain exists.

The subject of pain relief was restimulated for me last fall when I was introduced to the gate control theory of pain in a neurobiology class. At the simplest level, the notion is that normal touch known as somatosensation can interfere with nociception, the sensation of pain. This made me rethink why Katherine found pain relief from wearing bracelets. This prompted me to think further on all of the similar methods of pain control I had encountered as well as the tendency for someone that is exerting themselves to not feel low level chronic pain. From an evolutionary perspective it seems reasonable that feeling pain is generally not good when demands are being placed on the body. People have been taking advantage of this characteristic ever since.

The original theory was developed in the 60s when it was well accepted that pain was part of the somatosensory system. Now, the there are those that think nociception is exclusively part of the interoceptive system, also known as the visceral or autonomic nervous system. This is the system that helps us to maintain the environmental balance in our bodies. It tells us to eat and what to eat, drink, sleep, breathe, warm up by shivering and finding warmth, to cool down by sweating and seeking shade, and much more. It basically maintains our bodies. It does this in part by producing input into our higher thought through emotion and is affected by emotional feedback.

This leads me to an interesting experiment published in 1997. If 1/3 of the neurons leading into a section of the somatosensory cortex(SI) of a monkey were visceroreceptive, it is clear that there is some overlap. Considering that there isn’t extensive communication between the SI and emotion centers such as the insula, it seems likely that the inhibition of nociception by somatosensory probably occurs in the spinal cord as the gate theory suggests.

The next question of importance is what is the mechanism at work with Kerri Walsh’s Kinesio tape? They, like many before them, attribute their success to a special property of their proprietary method. In this case, they think it is from improved circulation. They even have a published study. From looking at the “sham” treatment on the third (390) page, it is evident that they aren’t differentiating their treatment from the gate control theory of pain. The “sham” isn’t producing tension, thus it isn’t significant stimulus to have gate control kick in.

I would go further and say that this is a poorly performed study for two reasons. First, their “sham” treatment is likely to not produce the placebo effect. A reasonable person might be inclined to laugh at such a crude tape job. Second, if I wanted to show a more significant improvement from one treatment over another, I would assign that treatment to more seriously injured individuals. If one looks at table 1 on the fifth (392) page, the KT group is the more injured group. My opinion of JOSPT is not high to say the least.

At the end of the day, the point is that Kinesio Tape is likely just a new incarnation of a trick that is probably thousands of years old. The difference is that maybe we are approaching the day where we will understanding the underlying mechanisms.

Realistic Portrayal Through Gender Tendencies

When Katherine and I work on book, we try to make sure that characters are distinctive and realistic. One of the most important ways we do this is to differentiate the way they look at the world, other people and the problems that arise. My approach is to have a model of these sorts of behaviors which is linked in a credible manner to people in the real world.

What I’ve learned from experience is well characterized by a specific encounter I had last fall in one of my classes. It was near the end of the semester and a fellow grad student was worried about an assignment to write up a mock grant proposal. Her concern was that she hadn’t been provided sufficient specific guidance to assure her that she would get a high grade on the assignment. I was less concerned for two reasons. First, I’m going to do what I’m going to do regardless of the instructions. Second, it had become clear to me that this instructor was more concerned with us showing original thought in our proposals than in our conforming to some standard. I tried to relate to her that her concerns weren’t warranted in this situation, but failed to satisfy her. To some degree, it seemed that she was more looking for an opportunity to vent her frustration rather than look for a solution. The differences between us were evident in more than just our approaches to the grant proposal assignment. Our behaviors were considerably different during the conversation. I have a tendency to not look at the face of the person I’m talking to because it is distracting. It takes considerable effort for me to translate my thoughts into words, and keeping track of the expression on someone’s face while doing so is too much multi-tasking for me. This may cause me to miss some part of what is going on with other people. However, I can still get and idea of what they are feeling and whether they are being genuine from the tone of their voice and my general assessment of them as a person. Meanwhile, she was intently studying my facial expression to the point of it being a bit uncomfortable.

My proposition is that myself and the aforementioned fellow student represent fairly polarized points on a continuum where there is a trade-off between two modes of thinking. She operates in a mode of mostly associating details directly with experience to make a conclusion. On the contrary, I look at the relationships between the details themselves to recognize a system from which to draw a conclusion. Her approach is more common amongst women while mine is more common amongst men. However, there is significant overlap between the genders with some hybridization of the two strategies going on in many people.

This model is supported by gender tendencies with respect to navigation. In humans, males tend to prefer a visual map when given instructions to find a destination while females tend to prefer explicit instructions. Similarly, female and feminized male rats tend to rely upon landmarks when navigating mazes while males and masculinized females tend to rely upon room geometry. Instructions and landmarks are essentially directly related to the goal. In this case, getting to the next landmark or step in the directions. This is similar to the previously proposed female tendency to identify direct relationships. The male tendencies also are similar to the aforementioned premise. Having a map in one’s head or depending upon the shape of a room is working from the association between multiple characteristics of the area being navigated.

This particular model best relates to writing in that it suggests what information is most important to a given character. It allows characters to be somewhat distinctive and internally consistent. When confronted by someone that is nervous, the more feminine character might be more inclined to notice specific behavioral abnormalities such as tense muscles that suggest something is amiss. Meanwhile, the more masculine character might be more focused on why the individual might be motivated to be deceitful and be watchful for behavior that confirms this. Depending upon the circumstances, one approach may be more effective than the other. In any case, they will not be paying attention to the same information and can’t be written the same way. This is difficult to do when one is writing from the perspective of a character that thinks differently than oneself.

MRI: the Particle Physics Laboratory for the Brain

Much like particle physics has particle accelerators such as the Large Hadron Collider at CERN and the Tevatron at Fermilab, neuroscience has MRI. All are high energy systems designed to induce and detect sub-atomic reactions. They also all require significantly complex mathematical tricks to discern useful information.

Increasingly more powerful magnets have enhanced the sensitivity of MRI and has called for new methods of analysis to learn about the structure of the brain. Voxel based morphemetry(VBM) is an analysis method which uses MRI to measure the volumes of gray and white matter structures in a living brain. I first encountered it while searching through the literature on the differences between typical male and female brain structure. It has also been used to recognize abnormalities for individuals with autistic spectrum disorders and should prove useful in determining the relationship between mental performance and structure of the brain.

On Monday, it was announced that a newer method, diffusion spectrum imaging (DSI), had been used to track white matter connections between different regions of gray matter in the cortex of the brain in five right handed male subjects. This finding supports work published two years ago in Brain and the theory of Antonio Damasio. A little studied region of the brain, the precuneus is implicated by Damasio as being a key player in consciousness and was the most widely connected part of the cortex in this latest DSI experiment. The notion is that an area key to consciousness would have to be connected to a wide swathe of cortex.

While these first looks at what DSI can reveal are exciting, it is only a glimpse. The study was done on a group of five right handed males who were instructed to stay alert with their eyes closed. The imaging was not functional in that results were averaged over a period of time where there might be considerable fluctuations. I look forward to the fruits of DSI analysis as MRI technology improves and more extensive studies are conducted. Not only does it have the potential to pinpoint important structures involved in consciousness, it also will be useful in understanding higher level reasoning by allowing us to correlate mental performance with the strength of the relationships between regions of the cortex.

Motivation vs Pleasure

Research that I’m currently doing for the Weordan project has revived thoughts about the nature of motivation and how physiology relates to behavior. What motivates people to spend long hours working or elite athletes to push through grueling training regimens? Most are clearly motivated beyond the potential return. They aren’t just fixated on the benefits of success. They have to be attracted to the idea of accomplishment itself. They want it more than they will enjoy it when it occurs.

The foundation of motivation comes from the interoceptive system. This is the system in the body that communicates the body’s status to its higher order systems in the brain. This is accomplished through chemical and stretch sensitive neurons as well as hormone signaling through the circulatory system. Satisfying the internal needs of the body can be accomplished by physiological means such as shivering when one is cold or by behavioral means such as acquiring and putting on a coat.

Behaviorally, there are two distinctive aspects of motivation. There is “liking”, which is the derivation of pleasure from partaking in a particular activity. The experience of “liking” leads to future pursuit of the experience, which can in turn be defined as “wanting”. Motivation is essentially “wanting” rather than “liking”. Further, especially in the case of addictive drugs, there doesn’t have to be much “liking” for a strong “wanting” to occur. This is because the chemicals contained in the drug act directly upon the “wanting” system rather than through “liking”.

Physiologically, “liking” and “wanting” are somewhat interdependent. However, they are modulated by different neuromodulators. This coincides with a difference in how “liking” and “wanting” wax and wane.

“Liking” is generally modulated by the neurotransmitter serotonin. Serotonin doesn’t perform the actual signaling between neurons. Instead, it acts to enhance or dampen the excitability of neurons in the region it is deposited and is supplied by neurons that originate in central regulating bodies. “Liking” is also homeostatic, meaning there is negative feedback. When a normally functioning individual engages in a behavior that is governed by a homeostatic system, they become sated to the point that they avoid the behavior.

“Wanting” is generally modulated by the neurotransmitter dopamine, which operate similarly to serotonin in that it doesn’t perform explicit signaling, but instead stimulates or depresses signaling globally within a region. “Wanting” is an allostatic system, meaning that it can’t turn itself off through normal signaling. It requires a homeostatic process to regulate it. This can happen if it is stimulated by a homeostatic system, such as those that are regulated by serotonin. It can also happen if over-stimulation causes post-synaptic neurons to desensitize. However, it seems that this desensitization isn’t as strong as a normal homeostatic response, as it doesn’t cause a negative response such as aversion, only desensitization.

This is a simplified view of the system. Many factors are at play in these systems. However, these are the strongest players, at least according to the best of my understanding. Further, the simplicity of the system is well supported by the distribution in the population. I would contend that extremely driven individuals aren’t all that uncommon. Neither are extremely unmotivated people. The distribution is flat compared to something like intelligence or athletic ability. This implies that a smaller number of factors govern innate drive to “want” than those more complex systems.

The differentiation between “wanting” and “liking” is nothing new in neuroscience. However, interesting behavioral consequences and world views present themselves when one considers these two drives as separate dimensions. One might expect someone with a strong “liking” system to spend more time enjoying the fruits of their accomplishments. Such a person would be inclined to accomplish less than another person who is otherwise identical but has a weaker “liking” system. Likewise, one might expect someone with a strong “wanting” system to spend more time in pursuit of accomplishments that are important to them. Such a person might be inclined to take on more challenging tasks and spend more effort on them than someone who had a weaker “wanting” system. This model suggests that a combination of strong “wanting” and weak “liking” would result in an extremely driven individual, the type of person that starts their own business and works long hours to make it successful. At the other end, someone with a strong “liking” and weak “wanting” would result in an extremely unambitious individual, the type of person who lives in their parents’ basement and spends all of their time on a hobby.

Serotonin and dopamine also happen to be associated with two other behavioral phenomena, depression and addiction. People that are depressed have a tendency to have a poorly functioning serotonin signaling system. This is treated pharmacologically with drugs called Selective Serotonin Re-uptake Inhibitors(SSRI). Prozac was the first such drug on the market. SSRIs increase activity of neurons affected by serotonin by blocking the systems that remove serotonin from the synapse. Dopamine is instead involved in addiction. Drugs like cocaine and methamphetamine have a similar affect on dopamine sensitive neurons that SSRIs have on serotonin sensitive neurons. Ritalin is a time-released low dosage amphetamine pill that is used to treat ADHD. The definition of the attention deficit portion of ADHD is quite compatible with a lack of “wanting”. Presumably, someone with a well functioning system for “wanting” would be more vulnerable to addictive substances than someone that has less “wanting”.

If high achievers have a tendency toward high dopamine and low serotonin, it is likely they are more prone than average to depression and substance abuse. Professional athletes and actors work in an extremely competitive environment where talent is usually not enough to make it. By and large, they must be extremely driven. They have to really “want” it and can ill afford to be spending their time enjoying what they’ve accomplished to maintain their position. Anecdotally, this group of individuals has a high incidence of depression and substance abuse. It is likely that this is in some part due to the stresses of celebrity. However, it seems possible that they also are more prone to these conditions due to the physiology that helped them to succeed.