Wednesday, 5 October 2011

Week 2 - How do we study our brain and it's cognitive functions?

Article for lecture two

In this article it is pointed out that neurological disorders cannot solely be explained by just medical neurology alone.
Mental Illness is generally approached by (a) chemical imbalances and changes in transmitters & receptors in the brain which is corrected by drugs, which has been very successful. And (b) The Freudian approach which suggests that mental illness is because of your up-bringing. A third approach has been proposed in this article which is evolutionary neuro-psychiatry, it explains why symptoms are different for different types of mental illness.
Hysteria is a medical term for paralysis in a part of the body, but when neurologically tested there is no evidence of deficits or lesions in the brain. Therefore this condition is often described as psychological. However PET & FMRI scans now show us what parts of the brain are active or inactive, so therefore shows when a patient makes a specific action or mental process. The parts of the brain that are active will light up when an action is performed.
An action such as wiggling a finger lights up two parts of the brain; the motor cortex which sends messages to execute the action and the pre-frontal cortex that prepares your finger to move. For a patient with hysteria the pre-motor area lights up which shows they are pre-paring to do the action however the anterior cingular and ventromedial frontal lobes (parts of the frontal cortex) show up which are inhibiting the attempt of moving the arm. This latter part of the brain mentioned that lights up are linked to the emotional centres of the brain which makes sense because hysteria is caused by an emotional trauma. This highlights the causation of hysteria and also the brain malfunctions that may maintain hysteria.

If there is damage to the limbic system and the amygdala this could cause major damage to a person’s emotion. A gut-level emotional reaction to a visual stimulus can be measured by the amount a person sweats. When shown something emotionally important or exciting we sweat more - this can be measured by the Galvanic skin response (involves two electrodes in your skin) The Galvanic skin response can be used to assess damage connected to the emotional centres of the brain.

Derealisation and Depersonalisation involve the limbic system. It is known as feeling like you are not real or feeling like a zombie. Here it is explained as an evolutionary adaptive mechanism. It is said that in dire emergencies such as soldiers in battle the anterior cingular in the brain becomes extremely active. This inhibits the amygdala and other emotional centres, therefore suppressing emotions and fear. It also makes you really alert for action. It is described as an adaption from evolution because it can keep you out of harm’s way, however chemical imbalances can cause this to happen frequently, therefore causing you to become depersonalised.

Overall an understanding of brain mechanisms helps make sense of different symptoms for different mental illnesses.

This shows that there are many tools we can use to study our brain and its cognitive functions; these include the different scans and tests that highlight brain functioning, and what parts of the brain are responsible for what cognitive functions such as emotion.

Important info from lecture:

Cognitive Psychology = the study of mental processes and is needed for everyday life.
Neuropsychology = focuses on brain structures & processes that cause behaviour - e.g. appetite & emotion.

It is beneficial to study brain damaged patients  because it may help understand the role of that particular brain region, however a criticism of this is that the previous levels of functioning may not be known so it would be hard to make comparisons before and after a brain lesion.

EEG - Electroencephalography

  • Non invasive, easy & cheap to operate, used on healthy humans
  • Not sure what EEG changes signify, mass neuronal activity, weak function localisation.
PET - Positron Emission Tomography
  • It is a gamma ray detector, Measures changes in local blood flow correlated with mental activity (Blood flow is the most reliable measurement)
  • However it is invasive & expensive.
MRI - Magnetic Resonance Imaging
  • Non-invasive, good spatial resolution, participants can still take part in cognitive testing whilst being scanned.
  • Downfalls include claustrophobia and it is reported to be noisy, radio frequencies must be shielded.
FMRI - Functional Magnetic Resonance Imaging
  • Measures blood oxygen level dependent responses (BOLD)
  • This is non-invasive and has good spatial resolution however analysis is complex, this too is claustrophobic and expensive and produces low temporal resolution.

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