Do microorganisms control our behaviour?

Smand, M. (2012) Do microorganisms control our behaviour? Bachelor's Thesis, Biology.

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Abstract

Can microorganisms infect particular parts of the brain and do they control our behaviour? Toxoplasma gondii can only reproduce sexually in cats’ intestines. Asexual reproduction can take place in humans, rodents, cats, and birds. In humans the brain and muscle cells are mostly infected. Chronic infection is thought to cause behavioural changes. Rats with the T. gondii infection are way more active, more novelty seeking, and have higher interest in cat-smelling areas than the control group of non-infected rats. One may conclude that T. gondii does influence the behaviour of their host. According to the researchers this may be because of the need of the parasite to be transmitted to the cat’s intestines to fulfil their life cycle. The success of the parasite through manipulation by the parasite is called the behavioural manipulation hypothesis. Data shows that T. gondii is located primary in the amygdala. This is remarkably, because it indicates that the parasite can determine very specifically which part of the brain it will infect. This specificity indicates that the behavioural manipulation hypothesis is plausible. Does the parasite have similar effects on human behaviour? One way of investigating the human behaviour is via personality questionnaires. Infected persons showed higher anxiousness, and a decrease in novelty seeking. Infected men showed lower rule consciousness, higher cautiousness, jealousy, suspiciousness, and expedience. Women who are infected showed higher warmth and, unlike men, higher rule consciousness. Humans infected with T. gondii rated the pleasantness of cat urine different than non-infected humans, there is a gender-specific difference. A different way of investigating human behaviour is via behavioural testing. Men showed lower self-control and clothes tidiness, lower relationships/warmth, and higher mistrust in rural environment. Women showed a trend for higher self-control and clothes tidiness. After infection people have a slower reaction time and a lower ability to concentrate, which is problematic in daily life, since these things result in a higher change of (traffic) accidents. There is also a correlation with psychiatric disorders, which have dopamine dysfunction in common. So there might be a relation between toxoplasmosis and the dopamine pathway. There is a big chance that microorganisms do affect our behaviour. In rats the results are more convincing than in human beings. General medical investigations can be a good way investigating behavioural changes. Since mechanisms are unknown, medication can be antibiotics or dopamine inhibitors. When researchers investigate other microorganisms more, they may achieve more insight in the problems surrounding the question if and how microorganisms affect our behaviour.

Item Type:	Thesis (Bachelor's Thesis)
Degree programme:	Biology
Thesis type:	Bachelor's Thesis
Language:	English
Date Deposited:	15 Feb 2018 07:50
Last Modified:	15 Feb 2018 07:50
URI:	https://fse.studenttheses.ub.rug.nl/id/eprint/10485

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