The parietal and frontal lobes

Question 1

Where is the parietal lobe?

Answer 1

Sort of in the middle of the brain, with boundaries on the frontal lobe (central sulcus/rolandic fissure), temporal lobe (lateral sulcus/sylvian fissure) and occipital lobe (parieto-occipital fissure).

Question 2

What are the three main parts of the parietal lobe?

Answer 2

• Somatosensory cortex
• Superior parietal lobule
• Inferior parietal lobule
  (The lobules together form the posterior parietal cortex).

Question 3

Where is the somatosensory cortex?

Answer 3

Between the central and postcentral sulci.

Question 4

What is the main function of the somatosensory cortex?

Answer 4

Processing information about somatic sensations (e.g. pressure, temperature, pain, proprioception and visceral sensations).

Question 5

What is proprioception?

Answer 5

The sensation of muscle movement and position.

Question 6

What are visceral sensations?

Answer 6

Sensations related to our internal organs (viscera).

Question 7

What is somatotopy?

Answer 7

The mapping/localisation of sensation from different body areas.

Question 8

What did Dr Wilder Penfield do in the 1930s-1950s?

Answer 8

Created a somatotopic map by stimulating epileptic patients’ brains (before surgery under local anaesthesia) and recording their reported sensations.

Question 9

What does the homunculus represent?

Answer 9

The body parts’ dedicated area sizes.

Question 10

Where does the input into the somatosensory cortex come from?

Answer 10

Spinal cord –> thalamus –> ss cortex

Question 11

Where does somatosensory cortex output go?

Answer 11

• Motor cortex (frontal lobe)

- Posterior parietal areas (for higher-level sensory processing and integration).

Question 12

What can somatosensory cortex reorganisation in amputees result in?

Answer 12

Phantom limbs

Question 13

How does somatosensory cortex reorganisation in amputees occur?

Answer 13

Cells in the arm region don’t receive input and so the neighbouring face cells expand and activation spreads from the arm region to the face region, which the brain then interprets as signals from the missing arm.

Question 14

What are the main roles of the superior parietal lobule?

Answer 14

• Elaboration and integration of sensory information from the somatosensory cortex.
• Maintenance of a representation of the body state used in voluntary and involuntary limb movement.
• Also attention control.

Question 15

What are the main roles of the inferior parietal lobule?

Answer 15

• Multimodal sensory integration (somatic, visual and auditory).
• Calculation
• (Left side) language, e.g. name retrieval, reading.
• Sense of self (self/other distinction, agency)
• Direction of attention to objects
• Visuo-motor coordination.

Question 16

What can damage to the left side of the inferior parietal lobule cause?

Answer 16

• Expressive aphasia (production deficit, non-fluent)

- Receptive aphasia (comprehension deficit, fluent but wrong words)

Question 17

What can unilateral damage to the posterior parietal cortex cause?

Answer 17

Hemispatial neglect - can only see part of images. Due to problems with direction of attention to objects.

Question 18

What can bilateral damage to the posterior parietal cortex cause?

Answer 18

Balint’s syndrome:

• Optic ataxia (difficulties looking/reaching)
• Ocular apraxia (visuo-motor disturbance, gaze)
• Simultanagnosia (difficulties seeing more than one object at once)

Question 19

What structures are part of the frontal lobe?

Answer 19

Prefrontal cortex and motor cortex (Premotor area, supplementary motor area and the Primary motor cortex).

Question 20

Where is the frontal lobe situated?

Answer 20

Boundary with parietal lobe on the Central sulcus (Rolandic fissure) and the temporal lobe with the lateral sulcus (Sylvius fissure).

Question 21

What is the role of the primary motor cortex?

Answer 21

Control of voluntary movement - organisation into a somatotopic map similar to the one in the somatosensory cortex. Discovered by Penfield, too - stimulation induced movements.

Question 22

What are the inputs of the primary motor cortex?

Answer 22

• From somatosensory cortex (sensations info)

- from the premotor and supplementary motor areas (motor planning)

Question 23

What are the outputs of the primary motor cortex?

Answer 23

• To somatosensory cortex

- To spinal cord (via cortico-spinal tract or brainstem = muscle execution).

Question 24

What are the main roles of the premotor and supplementary motor areas?

Answer 24

• Planning of complex movement sequences

- Selection of appropriate actions (intention to act)

Question 25

What does the prefrontal cortex do?

Answer 25

• Attention, decision making and coordination - controls other brain areas, so that our behaviour fits our goals.
• Well placed to control other areas (connected to all sensory and motor areas and to subcortical areas, exerts a top down influence).

Question 26

What are the main roles of the prefrontal cortex?

Answer 26

• Executive function
• Controlled attention
• Working memory
• Problem solving
• Emotion and decision-making (Phineas Gage, Iowa task)
• Language.

Question 27

What can damage to the prefrontal cortex cause?

Answer 27

Effective and receptive aphasia.

Question 28

So, in essence, what do the frontal and parietal lobes do?

Answer 28

Movement control:
- Simple action = somatosensory and motor cortices
- Slightly complex action = premotor and posterior parietal lobe
- Complex action = all areas, integration.
Attention (goal setting and attention bias