Localisation Of Function

Question 1

What are the 3 main sections of the brain

Answer 1

the forebrain (front part of the brain), midbrain (middle part of the brain) and hindbrain (back part).

Question 2

Regions of the brain

Answer 2

Cerebrum or cerebral hemisphere
Dicephalon
Brain stem
Cerebellum

Question 3

What is the cerebrum

Answer 3

1. Cerebrum (cerebral hemispheres)-(in the forebrain) this is the largest of the brain and is split in the middle into two halves – known as hemispheres. The two hemispheres communicate to each other via the corpus collusum. The cerebrum also has four lobes. The frontal lobe – this is involved in though 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 (see image below)

Question 4

What is the dicephalon

Answer 4

2. Diencephalon – (in the forebrain) this is 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

3. Cerebellum – (in the hindbrain) – 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

4. Brainstem – (midbrain and hindbrain) – 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

What is localisation of function

Answer 7

Localisation of function refers to the principle that specific functions such as language, memory etc. have specific locations in the brain.

Question 8

Who developed the idea of localisation of function

Answer 8

Franz Gall a German physician began the debate over localisation of function in the human brain in the early 1800s. He proposed that a person’s personality was reflected in bumps on the skull that in turn reflected functions of the brain lying underneath the bump; this theory was called phrenology. Gall’s ideas that functions were localised to specific regions of the brain eventually became extremely influential. The opposing view was that the brain functions in a more holistic manner, with all or large parts of the brain involved in all behaviours.

Question 9

Who identified the Borcas area

Answer 9

In 1865- Paul Broca on the basis of his case studies of brain-damaged patients had concluded that speech production was localised to an area in the frontal lobe – now known as ‘Broca’s area’.

Question 10

Localisation of function research development near the end

Answer 10

By the end of the 19th century, other researchers had shown in cats, dogs and monkeys that small lesions (damage) could have highly specific effects on movement and perception. Overall, these studies seem to show conclusively that the brain is organised in a highly systematic way, with functions localised to specific areas. In fact, by the middle of the 20th century, we could map out a number of functions localized in the cortex of the brain.

Question 11

What are the functional areas of the cerebral cortex

Answer 11

Primary motor cortex
Primary sensory cortex
Multimodal association cortex
Motor association cortex
Sensory association cortex

Question 12

Motor, somatosensory, visual and auditory areas of the cortex

Answer 12

This image of the brain shows the key visual, auditory, somatosensory and motor areas of the cortex. Electrical stimulation of these areas can produce the appropriate sensation.

Question 13

somatosensory cortex

Answer 13

The somatosensory cortex 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. Interestingly, the body surface is represented systematically in the somatosensory cortex. Head areas are represented at the bottom and legs and feet at the top. 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.

Question 14

Motor cortex

Answer 14

The motor cortex is responsible for the generation of voluntary movements. It 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 15

Visual and auditory centres

Answer 15

The visual and auditory cortical areas ‘seen in the image above (on p30)’ receives input directly from the eyes and the ears. Damage to them can lead to blindness and deafness.

Question 16

Visual centre

Answer 16

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 such as 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 17

Auditory centre

Answer 17

This is concerned with hearing. Most of this area lies within the temporal lobes in both the left and right hemispheres, where we find the auditory cortex. The auditory pathways begin in the inner ear, where sound waves are concerted to nerve impulses, which travel via auditory nerve to the auditory cortex in the brain.

Question 18

What are the language centres

Answer 18

Brocas area
Wernickes area

Question 19

Broca’s area

Answer 19

This area is named after Paul Broca who in the 1880s, treated a patient named ‘Tan’ who could understand spoken language but could not speak or put his thoughts down in writing
Broca studied 8 other patients similar to Tan who also had similar language problems along with lesions (cuts) in their left frontal hemisphere. Interestingly, patients who had these areas damaged in the right hemisphere did not have these problems.
Therefore the ‘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.
Thus if an individual has damage to Brocas’s area, this is known as Broca’s aphasia or expressive aphasia
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 20

Wernickes area

Answer 20

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.
Thus if an individual has damage to Wernicke’s area, this is known as Wernicke’s aphasia or 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 21

Strengths of localisation of function

Answer 21

Brain scan evidence of localisation – there is a lot of evidence to suggest that neurological functions are localised particularly in relation to language and memory. For example, 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. And because it can be shown through brain scans – this further increases the validity of brain localisation through scientific evidence.
Neurosurgical evidence – 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. For example, Dougherty et al (2002) reported on 44 OCD patients who had undergone brain surgery (which involved lesioning a certain 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.
Case Study evidence – 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 suffered brain damage with a pole which forced his temporal lobe out of his brain. Gage suffered a complete change of personality after this accident suggesting that our personality may be localised to the temporal lobe (see below on Phineas Gage)

Phineas Gage
‘Phineas Gage whilst working on the railroad in 1848, Mr Gage was preparing to blast a section of rock with explosives to create a new railway line. In a mishap, causing the explosive to ignite, this 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. Interestingly, Gage survived but the damage to his brain made a permanent mark on his personality – by all accounts 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.
Support from aphasia studies – 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 22

Weaknesses of localisation of function

Answer 22

Challenges to localisation – it is seen as a reductionist method - 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.
Plasticity – The 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 – for example, 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.
Individual differences in brain localisation – There is evidence to show individual differences in response to various activities and localisation of function. For example, Bavelier et al. (1997) found a large variability in individual patterns of activation across individuals. For example, 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.