Biological Approach Flashcards
Localization of a function
Theory that certain parts of the brain correspond to certain functions and reflect that behaviour, emotion, and thoughts originate in specific regions of the brain
Weak localization
The idea that several parts of the brain are responsible for the same function, but only one of these areas is dominant
Role of amygdala
Triggers fear. When perceiving things that are threatening, the amygdala helps activate a process that results in the release of stress hormones.
Role of prefrontal cortex in decision making
Is located in the frontal lobe and is responsible for executive functions such as decision making, planning, self-regulation, and social behaviour
Grafman et al. (1996)
Aim: impact of brain injuries on behaviour/aggression
Procedure:
- viet war veterans who had suffered head injuries that resulted in damage to areas of the brain, which included the prefrontal cortex
- was compared to a control group
- participants measured aggression on self-reported scales and questionnaires
Findings:
- veterans who had damage to the PFC had higher levels of reported violence and aggressions than the controls or veterans with damage to other parts of the brain
Conclusion:
- damage to the PFC lessens decision making and self-regulation, and increases aggressive behaviour that no damage or damage to other areas of the brain
Neuroplasticity
The brains ability to adapt by forming new connections as a result of genetics, experience, learning, or following an injury.
Neural networks
Created when activity is repeated, causing the brain to stimulate and neurone to connect to one another as new things are learned.
Grey matter
The branching of neutrons in the brain and can result in changes to brain structure
Neural pruning
The activity is not practiced, leads to a decrease in number of neural connections
Maguire et al. (2000)
Aim: investigate whether neuroplasticity occurs in London cab drivers, who must memorize thousands of street names, landmarks, restaurants, and hotels to earn a cab license
Procedure:
- right handed male taxi drivers
- a control group: healthy right handed male subjects who did not drive a taxi
- MRI was used to measure the variables and then compared between the 2 groups
Findings:
- taxi drivers had increased grey matter volume in the posterior hippocampus, compared to the control group. On the other hand, the controls subjects had increased grey matter in the anterior hippocampus.
Conclusion:
- the hippocampus is the region of the brain associated with memory, and the posterior is believed to be related to spacial memory and navigation. experienced cap drivers develop a “mental map” of London and this causes an increase in the posterior of the hippocampus and the development of neural networks.
Draganski et al. (2004)
Aim: to investigate whether structural changes in the brain would occur in response to practicing a simple juggling routine
Procedure:
- sample was randomly divided into 2 groups: jugglers and non-jugglers
- jugglers spent 3 months learning to juggle with 3 balls followed by 3 months in which they stopped practicing
- participants in the control group never practiced juggling for the 6 months
- 3 brain scans (MRI) were performed in both groups before the experiment, 3 months in, and after 6 months
Findings:
- after 3 months, jugglers had significantly more grey matter in the mid-temporal area of the cortex, which is responsible for the coordination of movement
- after 6 months, the group that stopped practicing saw a decrease in the grey matter but they still had more than non-jugglers
Conclusion:
- grey matter grows in the brain in response to environmental demands in the absence of stimulation (neural pruning). This shows the cause-and-effect relationship between learning and brain structure.
Brain imaging techniques
Allows for non-invasive methods to study the brain (classified at tools to measure variables)
MRI - principal of work
When placed in external magnetic field, some atomic nuclei (hydrogen) can emit energy. these pulses of energy can be detected and be used to produce a 3D image of brain structure. Can also be used to investigate which parts of the brain are involved in specific thoughts and behaviour.
Strengths:
- allows for research triangulation
Limitations:
- produce a static image and is therefore correlational
Neurotransmitters
Chemical messengers that send messages along neural pathways. the nervous system is a system of neutrons.
1. When the axon of 1 neuron approaches another neuron, a synapse is formed. neurotransmitters are released into the synaptic gap connecting the 2 neurons.
2. They then bind to a specific receptor sites of the postsynaptic neutron, creating an electrical signal called the action potential, which passes the signal further.
3. The signal continues to spread until reuptake - the neurotransmitters are pulled back into the axon that released it - occurs
Neurotransmitter associations
Low levels of serotonin and dysfunction in this part of the brain could help explain violence and impulsive behaviour. High levels have been associated with prosocial behaviour.
Passamonti et al. (2012)
Aim: test the effects of reduced levels of serotonin within the prefrontal cortex
Procedure:
- randomized, double blind study
- healthy participants consumed a drink that lacked tryptophan (an amino acid that helps build serotonin in the brain) or a placebo that would not alter tryptophan levels.
- participants were then put in a fMRI and their brain activity was measured while they were seeing images of happy, angry, or neutral faces.
Findings:
- the group low in serotonin had reduced PFC activity when viewing angry faces (but not others)
- they also showed weaker communication between the amygdala and PFC
Conclusion:
- low serotonin levels disrupt the function of PFC and its ability to regulate stress/fear triggered by the amygdala
- this might increase emotional levels and increase the chances of a highly emotional reaction to the threat.
Inhibitory neurotransmitters
Stop the impulse, preventing it from crossing, producing a calming effect on the brain, decreasing the likelihood that the postsynaptic neuron will fire an action potential.
Example of inhibitory neurotransmitter
Serotonin. Low levels have been correlated with impulsive behaviour and violence, high levels have been associated with promoting prosocial behaviour. Adequate amounts of serotonin are necessary for a stable mood and to balance excessive excitatory (stimulating) neurotransmitters, such as dopamine from firing in the brain.
Agonist
Act by enhancing the action of neurotransmitters, by producing the same effect as whatever molecule normally binds to a receptor.
- neurotransmitters are endogenous agonists: the brains natural chemical that binds to receptor sites, leading to an action potential.
- drugs can also play the same role and are called exogenous agonists: they bind to receptors, causing the neuron to fire, or they inhibit reuptake, thus increasing its concentration in the synapse.
- citalopram is an example of an SSI (selective serotonin reuptake inhibitor) and an indirect agonist for serotonin. by inhibiting reuptake of serotonin, this increases the levels of serotonin in the synapse.
