Biopsychology Flashcards
What is brain localisation?
Theory that different parts of the brain are responsible for different functions. It was put about by Broca and Weirnicke
What are the parts of the brain? (Cortexes, etc.)
In each cortex their are four lobes; the frontal lobe; the parietal lobe; the occipital lobe and the temporal lobe. The cerebral cortex is 3mm thick and covers the whole brain, acting like a tea cosy. Each lobe is responsible for a different function.
The frontal is responsible for Motor functions - controlling voluntary movement in the other side of the body (due the hemisphere stuff).Damage to this could result in a loss of control over fine movements.
In the front of the parietal lobes in the somatosensory area which in responsible for sensory information from the skin. The amount of the somatosensory area dedicated to one body part denotes it’s sensitivity -for example over half of the somatosensory area is dedicated to the face and hands.
The visual area is at the back of occipital lobe. each eye sends visual information from the left visual field to the right hemisphere and information from the right visual field to the left hemisphere. This means the damage to the left hemisphere will result in blindness in the right visual field of both eyes.
The temporal lobes house the auditory area which analyses speech information. Damage may produce deafness - the more significant the damage the greater the loss. Damage to Wernicke’s area may also result in loss of the ability to comprehend language. In some patients with Wernicke’s aphasia language is fluent but makes no sense (neologisms)
Speech is produced in the left hemisphere in Broca’s area - a small area in the left frontal lobe. Damage can result in Broca’s aphasia which is speech that slow, laborious and lacks fluency (one patient could only say “tan”).
Evaluate brain localisation
Brain scans provide evidence to support the theory of brain localisation. Petersen et al (1988) showed that different areas are during different tasks - suggesting the have different functions. Tulving et al (1994) also found that different types of memory reside in different areas of the prefrontal cortex. There are also many ways of researching activity in the brain.
Neurosurgery is sometimes used in extreme cases of OCD or depression. Dougherty (2002) reported on 44 patients that had undergone a cingulotomy - after 32 weeks a third had met criteria for success and 14% for a partial success. This suggests that behaviours and symptoms for serious mental illnesses are localised.
The case of Phineas Gage also supports this theory.
The theory of brain plasticity however contradicts this theory.
What is the theory of brain plasticity?
Brain plasticity is the theory that the brain has the ability to change throughout it’s lifetime. During infancy the brain has a rapid increase in the amount of synaptic transmissions it can make; peaking at around 15,000 at age 2-3 (around double the amount in an adult brain). As we age rarely used synaptic connections are removed and ones used often are strengthened (synaptic pruning).
It was thought that after childhood the brain remained fixed - it is however thought that anytime neural connections can change and be made due to new learning.
Outline research into brain plasticity.
Maguire et al (2002) found that london taxi drivers and found that there was significantly more grey matter (the area associated with spatial and navigational skills) in their brains that that of bus drivers. This is because taxi drivers have to take a text called “the knowledge” which assess their knowledge of london’s streets and possible routes - it is thought that this alters the structure of their brains. It was also found that the longer they had been in the job the more pronounced the difference was.
What is functional recovery?
After a trauma, such as a stroke, unaffected areas of the brain are able to compensate for damaged areas. This functional recovery is an example of brain plasticity. The areas will take over for areas that are damaged, missing or destroyed. Neuroscientists suggest that initially it occurs quickly but slows down after several weeks or months.
During recovery the brain is able to create new synaptic transmissions close to area of damage. Secondary neural pathways are also created or “unmasked”. A number of structural changes also occur.
Axonal Sprouting: The growth of new nerve endings which connect with undamaged nerve endings.
Reformation of blood vessels
Recruitment of similar areas on the other side of the brain to carry out functions. After a while functions may shift back to the other side of the brain.
Evaluate plasticity.
Understanding has contributed to the field of neurorehabilitation. Following illness functional recovery slows down so therapy is needed to help encourage this.
Plasticity can also work backwards. Prolonged drug use has shown reduced cognitive ability as well as an increased risk of dementia in later life. 60-70% of amputees have also shown phantom limb syndrome. This is unpleasant, painful and thought to be down to the cortical reorganisation of the somatosensory area.
Functional plasticity tends to reduce with age. One study gave people aged 40-60 40 hours of golf training and using fMRI scans found reduced motor cortex movements compared to a control group - suggesting that neural plasticity continues throughout life.
One study found that educational attainment may influence how well the brain recovers after injury. The more time patients spent in education the greater the chance of disability-free recovery (DFR). 2/5 of those who achieved DFR had 16 years of education - compared to 10% who had had 12 years of education
What is hemispheric lateralisation?
The idea that certain functions or abilities are found in one hemisphere of the brain. As such the two hemispheres are functionally different
Outline split-brain research.
Sperry (1968)
Aim: To see if brain hemispheres are functionally different.
Procedure: Participants were patients who had had a commissurotomy - breaking the connection between the two hemispheres. Sperry projected one word in the left visual field and another in the right; this was done quickly so that only the intended eye could see the word.
Findings: Participants could identify words in the right visual field, but not in the left - this is because there is no language in the right hemisphere.
Participants were able to select objects matching words with their left hand - but could not attach verbal labels to objects in the left visual field. They were also able to select objects associated with words in the left field (i.e Ashtray/cigarette). If two words were presented (one in each field) the participant would write the word in the left field and say the word in the right field.
Conclusions: The brain is subject to hemispheric lateralisation as participants behaved differently to how those with a “normal” brain would.
Evaluate split brain research
Most research suggests that the brain is under hemispheric lateralisation. It suggests that the left hemisphere is the language center and the right hemisphere is better at spatial tasks and music. The left hemisphere is the analyser and the right is the synthesiser.
Sperry used highly standardised procedures that allowed him to control and vary parts of it. This allowed him to develop a useful procedure and thus increased the validity of the study.
Sperry’s research had prompted a theoretical debate about the level of integration within the brain. Some researchers have suggested that the brain is actually two minds inside one, whilst others suggested that it is a highly integrated process.
Sperry’s research used 11 severely epileptic patients so their brain’s may have been damaged by the epilepsy - resulting in their brains operating differently.
What is an fMRI scan?
A Functional Magnetic Resonance Imaging (fMRI) scan. detects changes in blood oxygenation in the brain and visualise this as an image. Blood oxygenation occurs as a result of activity in the brain (haemodynamic response) and so this shows up on the scan. fMRI’s can produce 3D images that show which areas are the most active (activation maps). it is good for showing localisation of function in the brain.
Evaluate fMRI scans
Positives:
It does not involve using radiation - unlike other scanning techniques (such as PET). If used correctly it is virtually risk free, non invasive and straightforward to use.
The images it produces also have high spatial resolution - meaning that it very clear which parts of the brain are being used.
Weakness:
It is expensive and is only clear if the participant stays completely still.
It has poor temporal resolution as there is a 5 second lag between activity and it appearing on screen. It can also only show blood activity and not individual neurons - meaning that it does not show what activity is taking place.
What is a Electroencephalogram (EEG)?
Measures brain activity using electrodes that are fitted to a participant’s brain using a skull cap. The scan provides information from millions of neurons - thereby giving an overall representation of brain activity. Clinicians often use EEG’s to diagnose conditions with arrhythmic patterns - such epilepsy, tumors or sleep abnormality.
Evaluate EEG’s
Strengths:
EEG’s have been useful in diagnosing epilepsy (this is because it is characterised by random bursts of activity - which can be seen on screen). It has also helped with our understanding of sleep patterns.
It also has a high temporal resolution and so can detect activity to within a millisecond.
Weaknesses:
The information received is very generalised and the EEG cannot pinpoint where the signal is coming from. This means researchers cannot differentiate between different, but adjoining, areas of the brain.
What are Event-Related Potentials (ERPs)?
EEGs provide a crude overview of brain activity but do contain all the information that is related to sensory, cognitive and motor actions. This means that researchers can isolate this responses using a statistical averaging technique; leaving only actions that relate to a specific event. These are ERPs - neural responses triggered by a specific event or stimuli. Research has found many ERPs related to processes such as attention or perception.
