Biology 202
1999 First Web Reports
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Social Affects on Neurobehavior


Jessica Zaldivar

"The brain does not exist in isolation but rather is a fundamental, interacting component of a developing, aging individual who is a single actor in the larger theater of life. This theater is undeniably social. . ." (1)

For the past few weeks our class discussions have largely hinged on brain and neuron function and how this relates to behavior. Some students in the class have expressed a difficulty with the concept that brain equals behavior because they feel like this limits their individuality and choice if they are only a combination of inputs and outputs. As a student of the social sciences I question this thinking because behavior is not just limited by brain function but also by social constraints. People's actions are limited by values, norms and mores found in their respective environment.

In my web research, and with help from Dr. Grobstein, I found a few sites dedicated to what is called 'Social Neuroscience' and some studies that have been done to show that in animals and humans social influences can have a direct effect on biological function from the release of certain chemicals to actual changes in receptors. The first site is run by Ohio State and tells the history of social neuroscience and looks at social factors and the immune system. The second is run by a professor in the United Kingdom looking at diet and criminality and the last is from Georgia State and looks at social status and defense mechanisms in crayfish.

William James an American psychologist of the 19th century was one of the first people to state that there is a connection between neurophysiological processes and psychological phenomena (1). In 1992 John Cacioppo and Gary Bernstein determined that there is a relationship between mental and social processes. The Ohio State Social Neuroscience page is largely dedicated to the connection between social environment, the immune system and reactions to hostile and hospitable environments.

All organisms have rudimentary, biological mechanisms for approaching, acquiring, or ingesting certain classes of stimuli, and withdrawing from, avoiding, or rejecting others." (1). All animals have these mechanisms for differentiating between hostile or hospitable environments and this process of differentiation is both social and biological. The social environment shapes neural structures and processes. The example of infant rats is given to illustrate this. Depending on how they are handled, it changes the mother child relationship and this affects the structure and reactivity of the hypothalamic pituitary adrenocortical system which in turn affects future processing of environmental stresses and immune system function (1). The same sort of reaction is noted in human infants. When they are denied physical and emotional comforts such as being held or calmed, they can become retarded and are less likely to be able to fight off illness. This idea was brought up in the second site.

Derek Bryce-Smith of the University of Reading in the UK discusses how diet and social influences affects criminality (2). Although, I do not find his argument very convincing or well presented, he does make a few good points. He states that diet can often be the cause of chemical imbalances in the brain which can in turn cause listless or violent behavior. He also talks a bit about lead and its effect on the immune systems of children, making the connection that children who are exposed to led are more likely to become ill if they have a poor mother child relationship (2). I think this is a bit of a stretch, but does point to the fact that people, especially children who are more likely to have poor diets or be exposed to large amounts of lead and other chemicals are people who are likely to have a low socioeconomic status and live in poor conditions.

Another interesting site that looked at a very specific example of social factors having a direct influence on neural behavior examined the effect of social status on seratonin levels in crayfish (3). Dr. Glanzman and Krasne at Georgia State found that seratonin can either inhibit or increase the responsiveness of the Lateral Giant (LG) neuron in the crayfish depending on its status. The LG neuron is responsible for the tail flip response to stimuli that could precede an attack. They found that in isolated crayfish seratonin increases the responsiveness but when crayfish are paired, in the socially subordinate one (usually the smaller) seratonin decreases the responsiveness (3). It takes only an hour to establish dominance but weeks for the difference in seratonin to take effect. Even more interesting is that if the subordinate one in one pair is repaired and becomes dominant, seratonin will then increase its responsiveness (3). Also, once a crayfish has been dominant seratonin will continue to increase the responsiveness even when the crayfish becomes the subordinate. So a change in the social status of the crayfish causes changes in the receptors for seratonin in the nervous system of the crayfish. This is a striking example of the social environment causing direct changes in the nervous system. As more and more research in this area develops, I am sure we will see an even stronger connection between social environment and the development and functioning of the nervous system and maybe gain more insight into why people behave the way they do.

WWW Sources

1)Ohio State Social Neuroscience Laboratory

2)Crime and Nourishment

3)Research: The Neural Bases of Behavior, (very interesting picture of the LG neuron)




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This paper reflects the research and thoughts of a student at the time the paper was written for a course at Bryn Mawr College. Like other materials on Serendip, it is not intended to be "authoritative" but rather to help others further develop their own explorations. Web links were active as of the time the paper was posted but are not updated.

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