The cerebral hemispheres

Question 1

Describe the landmarks of the 5 cortical lobes

Answer 1

• Frontal: In front of the central sulcus
  
  • Parietal: Behind the central sulcus and in front of the parieto-occipital sulcus
  • Temporal: inferior to the lateral sulcus
  • Occipital: posterior to the parieto-occipital sulcus
  • Insula: posterior to Herschel’s convolutions (part of the temporal lobe)

Question 2

Discuss to function topography of the Frontal lobe

Answer 2

• Area 4 (precentral gyrus): primary motor cortex
- Controls the contralateral half
- Motor homunculus
• Area 6 (prefrontal cortex): cognitive functions of a higher order such as intellect, judgment, prediction and planning
• Area 8 (anterior to prefrontal cortex): eyes
• Areas 44 and 45 (Inferior frontal gyrus): Broca’s area of motor speech
- Broca’s area is just in front of the muscles of speech in area 4 (primary motor cortex) and so Broca’s area decides how something will be said (which muscle to contract so it doesn’t sound like gibberish) and the primary motor cortex implements it

Question 3

Discuss the function topography of the parietal lobe

Answer 3

• Area 1,2 and 3 (postcentral gyrus): Primary sensory cortex
- Senses the contralateral half
- Sensory homunculus
• Superior parietal lobule: sensory association area and proprioception
• Inferior parietal lobe: Global association area
- Contributes to language functions

Question 4

Discuss the function topography of the temporal lobe

Answer 4

• Areas 41 and 42 (superior temporal gyrus): primary auditory cortex
- Herschel’s convolutions
• Wernicke’s area (posterior to 42 and 42 in dominant hemisphere): auditory association area
- Understands language

Question 5

Discuss the function topography of the occipital lobe

Answer 5

• Area 17 (either side of the cuculine fissure): Primary visual cortex
  
  • Areas 18 and 19: Visual association areas

Question 6

Discuss the function topography of the limbic lobe

Answer 6

Limbic lobe (Medial surface of cerebral hemispheres)
• Memory
• Emotions

Question 7

Explain the differences between sensory, motor and association areas

Answer 7

• Motor areas are for control of muscles
  
  • Sensory areas are for touch, pain and temperature
  • Association areas combine all of the senses and identify what is being touched e.g. feeling a coin in your pocket and identifying what it is without seeing it

Question 8

Identify the language centres of the forebrain

Answer 8

• Broca’s area: motor speech area (44 and 45)

* Werneck’s area: auditory association area (41 and 42)

Question 9

Describe the main fibre systems of the forebrain

Answer 9

• Commissural fibres: connects the two hemispheres (corpus collosum)
  
  • Association fibres: connects one part of the cortex with the other (they can be short or long)
  • Projections fibres: project either up or down from cortex (motor or sensory)

Question 10

What are the names of the components of the basal ganglia

Answer 10

• The caudate nucleus 
	• Lentiform nucleus
	- The putamen 
	- The Globus pallidus
	• The substantia nigra

Question 11

What are the connections of the basal ganglia

Answer 11

• The caudate nucleus and the putamen
- “input nucleus”
- Pre-motor cortex sends them information
- Motor cortex sends them information
- Thalamus sends them information
- These two ganglia need to communicate and so there are a lot of fibres between them and this is why the two of them are often referred to as the striated nucleus
• The Globus pallidus and the substantia nigra
- Receives information from the striated nucleus
- Sends information to the thalamus
• Thalamus
- Receives information from the from the Globus pallidus and the substantia nigra
- Sends signals to the striated nucleus
- Sends signals to the motor cortex

Question 12

What are the functions of the basal ganglia?

Answer 12

• Overcomes inertia (initiation and termination of movements)
  
  • “extrapyramidal system”
  • Pathology: Parkinson’s, chorea, athetotic etc.