Lesson 6 - Localisation of Function

Question 1

Cerebrum

Answer 1

• Located in the forebrain
• Split into two hemispheres, they communicate via the corpus collusum

Split into:

• The frontal lobe: involved in thought and production of speech
• The occipital lobe: involved in processing images
• The temporal lobe: involved in cognitive skills
• The parietal lobe: involved in dealing with sensory information

Question 2

Diencephalon

Answer 2

• Located just above the brain stem in the forebrain
• Responsible for sensory function, food intake and the sleep cycle
• Divided into the thalamus, hypothalamus and epithalamus

Question 3

Cerebellum

Answer 3

• Located in the hindbrain, below and behind the cerebrum and attached to the brain stem
• It controls motor function, balance, interpreting sensory information

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Question 4

Brain stem

Answer 4

• Located in the mid/hindbrain
• governs blood pressure, fight or flight, breathing, heartbeat
• Motor and sensory neurons pass through the brain stem, and this allows impulses to pass between the brain and spinal cord

Question 5

History of localisation of function

Answer 5

• Franz Gall developed the idea of phrenology in the early 1800s. He believed that a person’s personality was dictated by the bumps on the skull that reflected the functions of the brain underneath
• In 1865, Paul Broca formed the conclusion based on case studies that speech production was localised to a part of the frontal lobe, now called ‘ Broca’s Area’
• Other studies found that in cats, dogs and monkeys, damage to some parts of the brain have very specific effects on movement and perception

Question 6

The somatosensory cortex

Answer 6

• Receives sensory input from receptors in the skin
• Located in the parietal lobe
• The part of the body that is receptive to stimuli is represented in its own part of the somatosensory cortex, for example, the hands and face take up most of the area of the region

Question 7

The motor cortex

Answer 7

• Located in the back of the frontal lobe
• Located in both hemispheres, controlling opposite sides of the body
• Different parts of the motor cortex control different parts of the body, and they are located logically next to each other

Question 8

Visual centre

Answer 8

• Located in the occipital lobe of the brain
• Processing images also requires the neighbouring secondary visual areas
• Damage to secondary areas does not directly lead to blindness, but the inability to recognise faces or see in colour for example

Question 9

The auditory centre

Answer 9

• Mostly located in the temporal lobe
• Sound waves in the inner ear are converted to nerve impulses and travel via the auditory nerve to the auditory cortex

Question 10

Broca’s area

Answer 10

• Paul Broca treated a patient named ‘Tan’
• He could understand spoken language but could not speak or convert to writing
• He studied 8 other similar patients who had similar difficulties and legions in their left frontal hemisphere. However, patients with damage to the right frontal hemisphere did not have the same issues
• Therefore the ‘language centre’ is in the posterior left frontal lobe (‘Broca’s Area’) which controls speech production
• Damage to this area is known as ‘Broca’s Aphasia’

Question 11

Wernicke’s area

Answer 11

• Karl Wernicke (1874) discovered another part of the brain involved in understanding language
• Located in the posterior left temporal lobe (Broca’s patient ‘Tan’ could therefore understand language but not speak it)
• Damage to this area is called ‘Wernicke’s aphasia’

He proposed that language involves separate motor and sensory regions located in different cortical regions

• The motor region: located in Broca’s area, close to the area that controls the mouth, tongue and vocal cords
• The sensory region: located in Wernicke’s area, and is close to the areas responsible for auditory and visual input

A neural loop called the arcuate fasciculus runs between Broca’s and Wernicke’s areas

Question 12

Strengths of localisation of function

Answer 12

• Brain scan evidence. Peterson et al (1988) used PET brain scans to show that Wernicke’s area was active during a listening task (understanding of speech) and that Broca’s area was active during a reading task (production of speech). Brain scans are also a very reliable source of evidence
• Neurological surgeries have shown that certain illnesses are localised to specific areas of the brain. Dougherty et al (2002) found that 44 OCD patients who underwent surgery which involved lesioning a part of the brain, 1/3 of them recovered from the symptoms of OCD, while 14% recovered from some symptoms
• Case study evidence also provides an insight into brain localisation. Phineas Gage who suffered a trauma to his temporal lobe leaving it damaged experienced changes in personality, suggesting that personality may be localised to the temporal lobe. It is a very strong case supporting this
• Aphasia studies also show us that damage to the Broca’s area results in expressive aphasia (inability to produce speech) and damage to the Wernicke’s area resulted in receptive aphasia (inability to understand speech)

Question 13

Weaknesses of localisation of function

Answer 13

• Localisation is seen as reductionist. Karl Lashley (1950) found that when you remove different parts of the cortex in the brain of a rat (10-50% of the area) no one area was more important than another in the rat’s ability to run a maze, showing that learning is not localised to a specific area of the brain
• Cortical remapping/plasticity shows us that the brain has the ability to remap itself when an area loses its function. So plasticity can compensate for trauma to the brain
• Harasty et al (1997) found gender differences in the size of the Broca’s area with women having proportionally larger Broca’s and Wernicke’s areas. Could be due to greater use of language? Thus it is not generalisable to all humans