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IB SL/HL Psychology (biological approaches to behaviour): Discuss effects of neurotransmission on behaviour
A level 7 essay discussing the effects of neurotransmission on behaviour.
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Discuss the effects of one or more hormones on human behaviour [22] SWEDISH AND BRITISH SCIENTISTS- Oxytocin spray inhibits anxiety (electric shock and faces) [2008]
NEWCOMER ET AL- Cortisol affecting verbal declarative memory [1999]
One of the principles of the biological level of analysis states that there are biological correlates to
behaviour. Therefore much research has been done to try and correlate the blood concentrations of
certain hormones with specific human behaviours. Hormones are protein molecules secreted by the glands
making up the endocrine system within the body. These molecules are highly specific, and hence each
plays a specific function in the maintenance of normal bodily function and conditions, called homeostasis.
These molecules are similar to the chemical messengers called neurotransmitters, which control the
nervous system, however they tend to produce a longer lasting effect. The two neurotransmitters I will
explore within this essay are oxytocin and cortisol.
Oxytocin is synthesized in the hypothalamus, then stored and released by the pituitary gland in the brain.
The hormone induces a feeling of love and satisfaction when it is released and binds to receptor molecules,
and causes the mother-child attachment to develop after childbirth. Oxytocin plays an important role in
processing emotional stimuli, perhaps by affecting the firing of neurons in the amygdala (the part of the
brain that processes emotion). When oxytocin levels are increased in a healthy individual, it affects the
brain circuits relating to fear regulation and makes an individual more trusting, and therefore it may
benefit individuals suffering from anxiety. A study by Petrovic [2008] investigated the role of oxytocin on
trust. Participants were shown pictures of four different unknown faces. Two of these were delivered with
a small, harmless yet unpleasant electric shock. Half of the participants were then given an oxytocin nose
spray, while the other half received a placebos pray as the control group. The faces were then shown the
the partcipants again, and fMRI scans were taken to identify the active regions of the brain. It was found
tha the participants given the oxytocin spray found all the faces agreeable, while those given the placebo
spray had found only faces shown without a shock agreeable, and the other two disagreeable. The fMRI
scans also showed that participants who had developed shock-induced feelings of anxiety for certain faces
had higher levels of activity in the amygdala and fusiform face area when shown those faces. These brain
areas process unpleasant and threatening faces. The study concluded that oxytocin can reduce anxiety and
block feelings of fear within the brain, and hence shows the hormone plays a role in increased trust levels
in humans.
Cortisol is a steroidal hormone produced by the adrenal cortex and released by the adrenal gland for
blood-glucose regulation, immune functions and anti-stress responses. Cortisol plays a role in the ‘fight or
flight’ response, triggered by threatening or stressful situations. During prolonged exposure, cortisol can
negatively affect memory, causing atrophy of the hippocampus, and have other adverse health effects.
Newcomer’s study [1999] aimed to investigate the function of cortisol in verbal declarative memory. A self-
selected sample (recruited through advertisement) of 51 normal and healthy people aged 18–30 was used .
One group received a 40mg dose of cortisol (similar to blood cortisol levels during mild psychological
stress) and the other 160mg (comparable to a major psychological stress response). A control group
received a placebo. Paragraph recall used as test of verbal declarative memory, as this action is dependent
on cognitive abilities such as encoding, retrieval and organizational and learning strategies. The study
found that cortisol treatment produced reversible decreases in verbal declarative memory. The high-level
group performed worse on the verbal declarative memory test than the low-level group. They performed
below placebo levels after day 1. The low-level group (mild stress) showed no memory decrease. This was a
controlled randomized experiment so it was possible to establish a cause-effect relationship between
levels of cortisol and scores on a verbal declarative memory test. Therefore this study suggests that
excessive levels of cortisol can negatively impact memory formation and retrieval.
These studies are useful in correlating hormone concentrations with specific behaviours to uncover the
biological correlates to human behaviour.
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