Discuss Environmental and Physiological Effects on Cognition
In the past, people primarily related physiological processes to be influenced by genetics only and therefore it was largely believed that the brain was fixed. Now, it is said that certain effects of the environment can affect physiological processes. It can be induced that the there is a bidirectional relationship between both the environment and physiology as cognition can affect biology and vice versa. The two effects of the environment on physiological processes that will be discussed include the enrichment of certain environments on brain plasticity and that higher levels of melatonin contribute to seasonal affective disorder.
In Rosenthal’s experiment, he hypothesized that seasonal depression is due to high melatonin in the body was due to a lack of light. He therefore conducted light therapy to help patients suffering from seasonal affective disorder (SAD). There was a selected 29 patients of 2000 who reported suffering from depressions in fall and winter who contacted Rosenthal’s team to be a part of this treatment. During the winter of 1981, 11 patients were treated with bright white lights and all experienced some antidepressant effect. The results may be dramatic for such a small sample size as it shows that a brighter environment can counteract depression. Yet, there are lots of discrepancies relating to this experiment. First of all, the SAD article was written in a newspaper, which asked people to take apart. People knew in advance that light was supposed to be good for you after reading the article. What this indicates is that the people that participated in this experiment were under the “placebo effect”. This is when people get better just because they are being treated and not because of the treatment itself. Coupled with a small sample size, Rosenthal’s findings should be regarded as preliminary. What Rosenthal could do to verify his findings would be to conduct a blind study where patients don’t know which treatment is real or fake so that it would truly be objective.
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The second effect of an environment on physiological processes that will be discussed is brain plasticity. This is the brain’s ability to rearrange its connections with its neurons. This translates to the idea that the structure of the brain changing as a result of exposure to different environments. Two studies that support the idea that the brain is effected by the environment include: Maguire's study on spatial navigation and its effect on the hippocampus, and Rosenzweig and Bennett's study on deprivation versus enrichment and its effect on rat brains.
In Rosenzweigs and Bennets (1972) study, rats were placed in two different environments. The independent variable was the type of environment the rats were exposed to. One environment was stimulating which contained enrichment items such as toys and the other was deprived with no form of entertainment. These rats spent about 30-60 days in their respective environments and were killed at the end for a post-mortem study. This allowed researchers to dissect and measure the cortexes. The results were that rats that lived in the stimulating environment had a thicker cerebral cortex and heavier frontal lobe than the rats that lived in the deprived environment. This experiment, while demonstrating that a rat’s brain is literally shaped by the environment, is not 100% conclusive as it lacks ecological validity. Even though rats may be mammals, the findings cannot be wholly generalized to humans as the brain and environmental inputs differ between humans and animals such as rats. This doesn’t mean that the experiment isn’t useful - it only means that it has a limitation that needs to be developed upon with further studies that directly relate to the human brain.
Another experiment that fits the role of further studies would be Maguire et al. (2000). Maguire investigated whether or not the hippocampus played a role in human spatial memory such as memorizing and learning. This correlational study included London taxi drivers with a range of age/experience and MRI scanning to assess how their brains differed to the control group. The results demonstrated produced by the scans showed significantly more grey matter in both left and right hippocampi of the taxi drivers compared to the control group. For the control group, the pixel counting revealed a larger anterior right hippocampus than the left and larger body of the hippocampus on the right than the left than in taxi drivers, but the posterior hippocampus was larger in taxi drivers than in controls. Maguire’s experiment establishes a very strong correlation between the use of spatial memory and the hippocampus, as it is the first study that shows brain plasticity in humans. In essence, it adds to Rosenzweigs study.
That’s not to say this is a perfect experiment. It is important to recognize that this is a correlational study, which means there are no definite causations. A minor uncertainty that should be noted relates to the nature vs. nurture debate: did the driving influence the change in the hippocampus or did their larger than average hippocampus lead them to become taxi drivers? Correlation may not be causation in this bidirectional ambiguity problem. To fully confirm her findings, Maguire would theoretically have to take 40 guys and force 20 of them to learn “the Knowledge” test and measure the hippocampus before that. This form of longitudinal study would not be time efficient, as it would take an incredibly long time of 1 to 2 years. It is simply something that could be expanded upon in order to further develop Maguire’s original study. Despite this limitation, Maguire’s experiment is convincing as she also conducted other tests by looking at the brain scans of bus drivers and trainee taxi drivers to vary her subjects so that it wouldn’t be limited to only a certain group. In the end her study was groundbreaking as her finding showed that physiological processes do affect human brain plasticity.
In conclusion, the two discussed effects of the environment on physiological processes are enrichment on brain plasticity and climate effects on melatonin and behavior. With evidence provided by supporting studies and theories, it can be stated that there is a bidirectional relationship between the environment and physiological processes.