Perusing Psychology

The air was chilly in 19th Century Paris as a criminal was led to his fate. The man had committed a crime and was sentenced to pay. A crowd gathered to watch his punishment. There standing before him was the fateful Madame, the progeny of a French engineer. This Woman with the acerbic jaw was to seal the criminal’s fate. He faced the crowd wide-eyed and fearful, pleading for his life. His pleas seemed to fall on deaf ears as the frenzied crowd prepared for the spectacle. A German man stood waiting to play his part. Theodor Bischoff was not there to enjoy the public execution, he was there in the name of science. As the executioner led the criminal to the apparatus named after Joseph Guillotin (who by the way did not invent the guillotine), Bischoff approached. The blade fell and the criminal’s head dropped to the ground. Bischoff quickly rushed over to the head to perform his experiment.

Bischoff wanted to know whether or not consciousness was centered in the head – in the brain – and if any awareness resided after the beheading. He quickly thrust his fingers at the poor criminal’s eyes to see if there was any eye-blink. There was none. He placed smelling salts under the nose, with no reaction. Finally he spoke the word, “Pardon!” into an ear. Again, no response. He was satisfied with the results and concluded that consciousness did in fact reside in the brain and that it ended when the head was severed. His early neuroscience experiment was complete.

While this approach seems unorthodox at best today, early researchers had to resort sometimes to interesting techniques in order to investigate the influence of the brain on behavior, emotions, and consciousness. Their research methods were often seriously flawed but the work they did was important. Each new discovery led to our current understanding of the brain. So while we have much better methods to research the brain than antagonizing disembodied heads, our current research as neuropsychologists and neuroscientists is founded on the research of such creative men as Bischoff.

Note: I dramatized the story and as such, it is a bit of historical fiction. I don’t know if Bischoff was in Paris, he might have been in Germany when he did the experiment. However, Bischoff did perform this experiment.

Psychology is a field that traces its roots back thousands of years. In its earliest forms it was a subset of philosophy; Aristotle, Plato, and other Greek philosophers all posited psychological principles. Decartes is sometimes considered the founding father of modern philosophical psychology. He is possibly the most famous dualist; he believed that there was a split between mind and body. The mind influenced the brain through the pineal gland, a small structure in the middle of the brain. It is situated near the ventricles in the brain. Descartes believed that the pineal gland moved the “animal spirits” in the ventricles and sent them throughout the body, through the nerves, to control behavior and movement. This was not true but back in the day it seemed a very logical explanation, especially in light of the new discovery about how the heart worked like a pump for blood. The pineal gland was Descartes ideal structure where mind and body interacted because it was in the middle of the brain and was a singular brain structure (most structures in the brain are in both hemispheres. So for example, there are two hippocampi, two caudates, two frontal lobes, etc…). Even with Descartes advances, psychology remained a philosophy until the 1800s when Wundt and other empiricists created experimental psychological laboratories. From there, the field of psychology grew exponentially into the major field it is today.

Many other people influenced psychology over the years, people such as William James, Charles Darwin, B. F. Skinner, Sigmund Freud, and Jean Piaget but Descartes is the earliest of “modern psychologists,” even though he was involved in so much more than psychology. Contrary to conventional wisdom, Descartes was someone who came before the horse and led the way (pun intended; “Don’t put the cart {Descartes} before the horse.”).

A significant proportion of dopamine (DA) is produced in the substantia nigra pars compacta (SNpc) and is carried to the striatum via the nigrostriatal pathway. While this pathway has been traditionally linked with motor functioning, recent research has implicated striatal DA involvement in language (Crosson, 2003) and learning (Seger, 2006). One disease in which there is considerable DA disruption is Huntington’s Disease (HD). In HD the head of the caudate is typically the first brain structure affected by neuronal cell loss. This cell loss not only affects connections with the SNpc but also affects the connections between the striatum and the prefrontal cortex. In HD the disruption of these dopaminergic pathways leads to disruptions in motor and cognitive functioning.

How DA disruptions affect cognition has been explained by theories that are modifications of Mink’s model (1996) of center and surround (i.e., direct and indirect) basal ganglia regulation. Within the caudate there are two main families of DA receptors – D1 and D2. These receptors have been shown to have different functioning within the basal ganglia (Seger, 2006) – the D1 receptor is involved with the direct pathway and the D2 receptor is involved in the indirect pathway. The D1, or direct pathway, can be viewed as increasing the strength of the signal of the desired response while the D2, or indirect pathway, serves to reduce the noise of the competing undesired responses. Dopaminergic systemic disruption in HD should thus decrease the signal-to-noise ratio, which results in the person having a greater difficulty selecting the desired response (see model below).

*Model based on Mink (1996) and Frank, Seeberger, and O’Reilly (2004)

There is evidence that in early stages of Huntington’s disease, D2 receptors are the first to be affected, with less binding occurring at D2 receptors presumably due to receptor loss. As the disease progresses, the D1 receptors also start to become depleted, with the end result of widespread DA dysfunction (Glass, Dragunow, & Faull, 2000). This DA dysfunction possibly affects verbal learning and recall by impacting the indirect pathway in the early stages of HD and indiscriminately the whole direct and indirect system in later stages of the disease process.

References

Crosson (2003). Left and right basal ganglia and frontal activity during language generation: Contributions to lexical, semantic, and phonological processes. Journal of the International Neuropsychological Society, 9, 1061-1077.

Frank, M. J., Seeberger, L. C., & O’Reilly, R. C. (2004). By carrot or by stick: Cognitive reinforcement learning in Parkinsonism. Science, 306, 1940-1943.

Glass, M., Dragunow, M., & Faull, R. L. M. (2000). The pattern of neurodegeneration in Huntington’s disease: A comparative study of cannabinoid, dopamine, adenosine and GABAA receptor alterations in the human basal ganglia in Huntington’s disease. Neuroscience, 97(3), 505-19.

Seger, C. A. (2006). The basal ganglia in human learning. Neuroscientist, 12(4), 285-290.

Modern experimental psychology started in the 1800s with the research of Wilhelm Wundt. Psychology in the United States is generally traced back to the work of William James. There have been many different theoretical approaches to psychology since then. Probably the most famous psychologist is Sigmund Freud, whose work spawned the psychodynamic theories of human behavior. Somewhat in reaction to Freud’s work are the behavioral approaches to behavior (with Ivan Pavlov, John Watson, B. F. Skinner, and Edward Thorndike as some of the major theorists behind behaviorism). The cognitive theories came next. All in all, there are many different theoretical approaches to the psychology of behavior and most psychologists today are influenced by each approach. For a slightly more in-depth outline of the history of psychology, please view the pdf slides below.

History of Psychology Slides

Note: I’ve included links to Wikipedia for all of the above researchers because I believe the information on Wikipedia is mostly accurate and fair. The site also allows the information to be easily modified if any of it is inaccurate.