L6 - Localisation Of Function

Question 1

3 main sections of the brain

Answer 1

• forebrain - front part of the brain
• midbrain - middle part of the brain
• hindbrain - back part of brain

Question 2

4 main regions of brain

Answer 2

• cerebrum
• Diencephalon
• brain stem
• cerebellum

Question 3

Cerebrum

Answer 3

• largest part of the brain and is split in the middle into two halves – known as hemispheres
• two hemispheres communicate to each other via the corpus collusum - cerebrum also has four lobes
  The frontal lobe – this is involved in thought and production of speech.
  The Occipital lobe – this is involved in the processing of images.
  The temporal lobe – this is involved in dealing with the cognitive skills.
  The parietal lobe – is involved in dealing with sensory information

Question 4

Diencephalon

Answer 4

• located just inside the cerebrum just above the brain stem – this is responsible for sensory function, food intake and the body’s sleep cycle
• It is divided into sections: thalamus, hypothalamus and epithalamus

Question 5

Cerebellum

Answer 5

• this is below and behind the cerebrum and attached to the brainstem.
• It controls motor function, the body’s ability to balance, ability to interpret information sent to the brain by senses

Question 6

Brain stem

Answer 6

• this governs blood pressure, some reflexes, ‘fight & flight’, breathing, heartbeat.
• Motor and sensory neurons travel through the brainstem, allowing impulses to pass between the brain and the spinal cord.

Question 7

Localisation of Function in the brain

Answer 7

• refers to the principle that specific functions such as language, memory etc. have specific locations in the brain
• By the end of the 19th century, researchers had shown in cats, dogs and monkeys that small lesions could have highly specific effects on movement and perception.
• these studies seem to show conclusively that the brain is organised in a highly systematic way, with functions localised to specific areas.

Question 8

The somatosensory cortex

Answer 8

• receives sensory input from receptors in the skin, including touch, pain, pressure, and temperature from all areas of the body surface.
• It is located in the parietal lobe of the brain
• the body surface is represented systematically in the somatosensory cortex.
• The amount of somatosensory area dedicated to a body part reflects its sensitivity
• Our face and hand take up over half of the somatosensory area - as where most senses are

Question 9

Motor cortex

Answer 9

• motor cortex is responsible for the generation of voluntary movements.
• is located in the back of the frontal lobe.
• Both hemispheres of the brain have a motor cortex, with the motor cortex on one side of the brain controlling the muscles on the opposite side of the body.
• Different parts of the motor cortex show control over different parts of the body.
• These regions are arranged logically next to each other e.g. the region that controls the foot is next to the region that controls the leg etc.

Question 10

Visual centre

Answer 10

• The primary visual centre is located in the occipital lobe of the brain.
• With visual perception – this requires additional processing in neighbouring cortical areas (secondary visual areas).
• It is in these areas that sensation is converted into perception.
• We know this because damage to these secondary visual areas does not lead to blindness but can lead to a loss of specific aspects of visual perception
  E.g. prosopagnosia (loss of ability to recognise and identify faces) and/or Achromatoposia (loss of the ability to see in colour – the world perceived in black and white)

Question 11

Brocas area

Answer 11

• is named after Paul Broca who in the 1880s, treated a patient named ‘Tan’ who could understand spoken language but could not speak(except repeat his name) or put his thoughts down in writing
• Broca studied 8 other patients similar to Tan who also had similar language problems along with lesions in their left frontal hemisphere.
• patients who had these areas damaged in the right hemisphere did not have these problems - ‘language centre’ is in the posterior portion of the frontal lobe of the left hemisphere (Brocas area) this area is believed to be important for speech production.
• If an individual has damage to Brocas’s area, this is known as Broca’s/expressive aphasia

Question 12

New research about Broca’s area

Answer 12

More recently, there has been activity found in the Broca’s area for other tasks that have nothing to do with speech production such as cognitive tasks. For example, Fedorenko et al (2012) discovered two regions of the Broca’s area – one for language and the other for cognitive tasks.

Question 13

Wernicke’s area

Answer 13

• Karl Wernicke (1874) discovered another area in the brain that was involved in understanding language - Wernicke’s area – in the posterior portion of the left temporal lobe – this explains why Broca’s patient Tan was able to understand language but not speak it
• damage to Wernicke’s area, is known as Wernicke’s/receptive aphasia.
• Wernicke proposed that language involves separate motor and sensory regions located in different cortical regions.
• The motor region – located in Broca’s area is close to the area that controls the mouth, tongue and vocal cords (all necessary to speak)
• The sensory region, located in Wernicke’s area, is close to regions of the brain responsible for auditory and visual input
• There is a neural loop known as the arcuate fasciculus running between Broca’s area and Wernicke’s area.

Question 14

Evaluation of localisation of function

Answer 14

strengths
- brain scan evidence of localisation
- neurological evidence
- case study evidence
- support from aphasia studies
weaknesses
- reductionist
- plasticity
- individual differences

Question 15

Brain scan evidence of localisation

Answer 15

• evidence to suggest that neurological functions are localised particularly in relation to language and memory.
  E.g. Peterson et al., (1988) used brain scans to show how Wernicke’s area was active during a listening task (understanding of speech) and Broca’s area was active during a reading task (production of speech).
• This suggests that language is localised to these two areas.
• as it can be shown through brain scans – this further increases the validity of brain localisation through scientific evidence.

Question 16

Neurological evidence

Answer 16

• brain localisation can further be supported through neurosurgical evidence.
• Neurosurgery requires specific areas of the brain to be deliberately damaged to help patients with mental illness.
  E.g. Dougherty et al (2002) reported on 44 OCD who had undergone brain surgery (which involved removing area of the brain seen responsible for OCD)
• After 32 weeks of surgery, it was found that 1/3 had recovered from the symptoms of OCD whilst 14% had some recovery of the symptoms.
• This study shows how certain mental disorders are localised to specific areas of the brain through neurosurgical evidence.

Question 17

Case study evidence

Answer 17

• case studies provide psychologists the opportunity to study brain localisation in detail through an individual who has unique circumstances.
• The important landmark study on Phineas Gage who after a traumatic accident on the railway tracks in 1848

Question 18

Phineas Gage

Answer 18

• was working on the railroad in 1848 & preparing to blast a section of rock with explosives but a mishap meant the explosion hurled a metre length pole through Gage’s left cheek, passing behind his left eye and exiting his skull from the top of his head taking a significant proportion of his frontal lobe with it.
• Gage survived but the damage to his brain made a permanent mark on his personality – he had turned from someone who was calm and reserved to a quick-tempered, rude and ‘no longer Gage’
• Gage is seen as an extremely strong case in supporting localisation of function and indeed science as it has been shown that the frontal lobe may be responsible for regulating mood.

Question 19

Support from aphasia studies

Answer 19

• brain localisation can also be supported through aphasia studies.
• Aphasia means the inability to produce or understand speech.
• Studies have shown that people who suffer damage to the Broca’s area suffer ‘expressive aphasia’ (inability to produce speech).
• Studies have also shown that people who suffer damage to Wernickes area suffer ‘receptive aphasia’ (problems with understanding of speech).
• Aphasia studies therefore support brain localisation.

Question 20

Seen as reductionist method

Answer 20

• Karl Lashley (1950) found that higher cognitive functions such as learning are not localised to specific brain areas.
• Lashley removed areas of the cortex (between 10 and 50%) in rat’s brains and found that no area was more important in terms of the rat’s ability to run the maze.
• In other words the learning to run the maze was not localised to any specific area of the cortex
• this suggests that the study of brain localisation is reductionist as it is simplifying our behaviour to specific brain areas and therefore losing the working of the brain as a whole.

Question 21

Plasticity

Answer 21

• notion of cortical remapping or plasticity argues against localisation.
• When the brain is damaged, and a particular function is lost, the rest of the brain appears to re organise itself in an attempt compensate for the lost function.
• This suggests that other brain areas can compensate for the loss of function of a particular area of the brain
  E.g. if the Wernicke’s area is damaged, another area could compensate which means that an individual could still understand speech.
• Thus brain plasticity can compensate for damage of brain localisation.

Question 22

Individual differences in brain localisation

Answer 22

• evidence to show individual differences in response to various activities and localisation of function. E.g. Bavelier et al. (1997) found a large variability in individual patterns of activation across individuals
  E.g. they observed activation in the right and left temporal lobes.
• Harasty et al. (1997) found gender differences in the size of the Broca’s and Wernicke’s area of the brain with women having proportionally larger Broca’s and Wernicke’s areas than men.
• This may be because of women’s greater use of language.
• This suggests that localisation of function may not be generalisable to all humans as there are vast individual differences.