Psychology- Biopsych part 2 the brain, biological rhythmss

What does localisation of function mean?

The theory that different areas of the brain are responsible for different behaviours, processes or activities.

Where is the motor cortex found and what is its function?

Found in both hemispheres in the frontal lobe. Controls voluntary movement in the opposite side of the body.

Where is the somatosensory cortex found and what is its function?

Found in both hemispheres in the parietal lobe. Responsible for sensory information, production of sensations.

Where is the auditory cortex found and what is its function?

Found near the ears in both hemispheres in the temporal lobe. Responsible for analysing hearing and speech based information.

Where is the visual cortex found and what is its function?

Found in the occipital lobe in the back of the brain in both hemispheres. Responsible for processing and interpreting visual information.

Where is Broca’s area found, what is it responsible for and what are the effects of its damage?

Found in the left frontal lobe and responsible for speech production. Damage to Broca’s area causes Broca’s aphasia characterised by effortful speech made up of short sentences with a very simple grammatical structure. These patients understand language and so know what they want to say but have difficulty articulating it.

Where is Wernicke’s area found, what is it responsible for and what are the effects of its damage?

Found in the left temporal lobe and responsible for language comprehension. Damage to Wernicke’s area causes Wernicke’s aphasia whereby the patient speaks with normal grammar and rate but they leave out verb and tenses and so their speech does not make sense. Sentence length and intonation is normal but without meaning and they may talk excessively.

Brain scan evidence of localisation.

Peterson et al 1988 used brain scans to demonstrate how wernickes area is active during a listening task and Broca’s area during a reading task suggesting these areas of the brain have different functions.

Tulving et al 1994 in a study of LTM found that semantic and episodic memories reside in different parts of the prefrontal cortex.

This produces scientific evidence of localisation of function as the methods are objective and empirical.

Neurosurgical evidence of localisation.

Neurosurgery may sometimes be used for extreme cases of OCD and depression e.g. Dougherty et al 2002- 44 OCD patients underwent a cingulotomy and after 32 weeks a third had successfully responded to surgery.

This suggests that symptoms and behaviours associated with serious mental disorders are localised.

Case study evidence of localisation.

E.g. case study of Phineas Gage who had a drastic accident in which a piece of iron went through his skull and damaged a part of his frontal lobe. As a result of this accident, Gage experienced a change in personalty e.g. anger. This change provided evidence to support the theory of localisation as it was believed the area that was damaged was responsible for personality.

However, case studies can lack generalisability to other people, because a case study deals with only one person or small group e.g. Phineas Gage who experienced something very unusual. Therefore, we can never sure whether the conclusions drawn from this case applies elsewhere. Therefore, the results of the Phineas Gage case study are not generalisable because we can never know whether the case investigated is representative.

What is a weakness of localisation of function?

The notion of plasticity goes against the theory of localisation. if the brain becomes damaged e.g. during an accident which causes a person to lose a particular function, the rest of the brain appears to attempt to mend itself to recover lost neurological functioning e.g. cases of stroke victims recovering lost language abilities after a stroke - functional recovery. This is a problem for the localisation of function argument as plasticity like this supports the holistic theory of the brain

What is plasticity?

The brains tendency to change and adapt as a result of experience and new learning.

What is synaptic pruning?

During infancy the brain experiences a rapid growth in the number of synaptic connection- 15,000 by ages 2-3, nearly twice as many as there are in the adult brain. As we age, rarely used connections are deleted and frequently used connections are strengthened. 

Research into plasticity: Eleanor Maguire et al 2000.

Studied the brains of London taxi drivers using an MRI scanner. Found an increase in the volume of grey matter in the posterior hippocampus compared to a control group. This part of the brain is associated with spatial and navigational skills. There was also a positive correlation between how long they had been in the job and how pronounced the structural difference was.

What is functional recovery?

A form of plasticity where the brain is able to redistribute or transfer functions usually performed by damaged areas to other undamaged areas following trauma. This is most likely when the brain is still maturing.

What happens in the brain during functional recovery?

The brain can form new synaptic connections close to the area of damage. Secondary neural pathways that would not typically be used to carry out certain functions are unmasked to enable functioning to continue. This process is supported by a number of structural changes e.g.:

• axon sprouting- new nerve endings grow and connect with undamaged areas

• reformation of blood vessels

• recruitment of homologous areas on the opposite hemisphere

Research support for brain plasticity.

Kuhn et al 2014 found a significant increase in grey matter in various regions of the brain after ppts played video games for 30 minutes a day over a two month period. This highlights the idea of plasticity and the brains ability to adapt as a result of new experience.

Research support for functional recovery.

Taijiri et al 2013 found that stem cells provided to rats after brain trauma showed a clear deployment of neuron-like cells in the area of injury. This was accompanied by a solid stream of stem cells migrating to the brain site of injury. This demonstrates the ability of the brain to create new connections using neurons manufactured by stem cells.

What is a weakness of plasticity?

Plasticity can have negative behavioural consequences.

Evidence has shown the the brains adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as increased risk of dementia. Also 60-80% of apmutees develop phantom limb syndrome thought to be due to cortical reorganisation in the somatosensory cortex after limb loss.

This suggests that the brains ability to adapt to damage is not aways beneficial.

What is a strength of plasticity.

Led to practical applications i.e. the development of neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions.

For example, constraint induced movement therapy is used with stroke patients where they practice using the affected part of the body while the unaffected arm is restrained.

This demonstrates positive application of research to help improve cognitive functions of people suffering from injuries.

What is hemispheric lateralisation?

The idea that the two halves of the brain are functionally different and each hemisphere has functional specialisations e.g. left dominant for language, right dominant for visual motor tasks.

Split brain research- Sperry and Gazzaniga 1967.

Aim: to examine the extent of hemispheric lateralisation.

Method: used 11 epileptics who had already had their corpus callosums split (so split brain) to conduct a quasi experiment. When info is presented to one hemisphere in a split brain patient it is not transferred to the other hemisphere. So, projected an image/word to the patients left visual field (processed by right hemisphere) or the right visual field (processed by left hemisphere).

Findings: when picture presented to right visual field, patients could describe what they saw but when presented to left visual field patient could not describe what was shown and often reported there was nothing present. when object placed in right hand, patients could describe verbally what they felt but could not when object placed in left hand. when picture presented to right visual field, while the right hand would attempt to draw a picture, it was never as clear as the left hand. when picture presented to left visual field, the left hand would consistently draw clearer and better pictures than the right hand.

Conclusion: left hemisphere is dominant in terms of speech and language whilst right hemisphere is dominant in terms of visual motor tasks.

What is a weakness of lateralisation?

Language may not be restricted to the left hemisphere.

Turk et al 2002 discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere, eventually leading to the ability to speak about the information presented to either side of the brain.

This suggests that perhaps lateralisation is not fixed and that the brain can adapt following damage to certain areas e.g. functional recovery- recruitment of homologous areas.

How is age differences a weakness of lateralisation?

Lateralisation changes with age

Szaflarki et al 2006 found that language became more lateralised to the left hemisphere with increasing age in children and adolescents, but after the age of 25, lateralisation decreased with each decade of life.

This raises questions about lateralisation such as whether everyone has one hemisphere that is dominant over the other and whether this dominance changes with age.

Methodological evaluation of Sperry -split brain research

In real life the split brain patients can adjust their visual position so information goes to both hemispheres. this means that it was conducted in artificial setting as images are not normally seen for 1/10 of a second through just one visual field. In real life they would have time to compensate by moving their eyes so the material is received by both visual fields allowing them to correctly identify the material, Therefore, the study lacks ecological validity.

Sample was 11 patients- may not be large enough to generalise. May be inappropriate to make lateralisation generalisations about non-epileptic brain patterns from these patients. The epileptic seizures or even the medication they had previously taken for their epilepsy could have made changes to the brain that impacted the validity of the findings.

What are biological rhythms?

Cyclical patterns within biological systems that have evolved in response to environmental influences.

What are endogenous pacemakers and exogenous zeitgebers?

Endogenous pacemakers are internal biological clocks/mechanisms that govern biological rhythms

Exogenous Zeitgebers are external factors that influence biological rhythms.