Forebrain: Anatomical Organisation & Cortical Function

Question 1

Where is the cingulate gyrus?

Answer 1

Immediately above the corpus callosum

Question 2

Outline key features of the cerebral cortex.

Answer 2

• outer rind of grey matter
• 40% of brain weight

Question 3

What can the cerebral cortex be divided into?

Answer 3

1) Allocortex: comprises 3-5 layers –> divided into archicortex (most primitive) and paleocortex (includes olfactory areas such as uncus)

2) Neocortex/isocortex: consists of 6 layers that vary in thickness depending on functional localisation:
- pyramidal layers are thicker in motor areas
- granular layers are thicker in sensory areas

Question 4

What is the role of motor areas?

Answer 4

• give rise to descending motor tracts
• if electrically stimulated, result in movement

Question 5

What is the role of sensory areas?

Answer 5

• receive discrete inputs from sensory pathways via relays in the thalamus
• each contains a map of its sensory ‘world’

Question 6

What is the concept of ‘lateralization of function’?

Answer 6

The idea that control areas are not always symmetrical between the two hemispheres.

Question 7

Where is the primary motor area (M1)?

Answer 7

Precentral gyrus

Question 8

What is the role of the primary motor area?

Answer 8

Voluntary control of muscles to the opposite half of the body

Question 9

What is a lesion of the primary motor area?

Answer 9

• contralateral flaccid paralysis –> weakness/paralysis + reduced muscle tone) that becomes spastic (stiff) after several days

Question 10

What are the two motor association areas?

Answer 10

Premotor cortex + supplementary motor cortex
- located anterior to precentral gyrus on frontal lobe
- responsible for complex movements + influence the movement initiated in the primary motor cortex

Question 11

What is a lesion in the premotor cortex?

Answer 11

Form of apraxia, in which the patient is unable to perform complex movements that are guided by sensory cues e.g dressing oneself

Question 12

Outline the frontal eye field.

Answer 12

• located anterior to the PMA
• responsible for rapid eye movements

Question 13

Outline the prefrontal cortex

Answer 13

• governs personality, consciousness, emotional control
• located in most of the frontal love anterior to the motor areas
• responsible for problem solving, judgement, emotional/social behaviour

Question 14

What is a lesion of the prefrontal cortex?

Answer 14

Inappropriate social behaviour, emotionally labile, poor concentration, motivation and abstract reasoning

Question 15

Where is the primary somatosensory area?

Answer 15

Postcentral gyrus on the parietal lobe

Question 16

What does the primary somatosensory area receive?

Answer 16

Input (e.g touch, proprioception, pain) from the contralateral side of the body via the thalamus.

Question 17

What are the somatosensory association areas?

Answer 17

• Superior + anterior parietal lobule, separated by intraparietal sulcus
• located posterior to precentral gyrus on the parietal lobe
• responsible for integration of somatosensory information with other areas of cortex

Question 18

What does the superior parietal lobule control?

Answer 18

• attention + visuospatial perception including manipulation of objects
• interpretation of general sensory information, consciousness of contralateral body

Question 19

What does the inferior parietal lobe control?

Answer 19

• interpretation of emotions from facial stimuli
• interpretation of general sensory information
• language, maths, body image

Question 20

Where is the primary auditory area?

Answer 20

• transverse temporal gyri (temporal lobe)

Question 21

How is the primary auditory area tonotpically organised?

Answer 21

Low frequency sounds are most anterolateral and high frequency sounds are most posteromedial

Question 22

Outline auditory association areas

Answer 22

• located lateral to primary auditory area, overlaps with Wernicke’s area
• important for interpretation of sounds
• lesion: inability to understand language, both spoken and written

Question 23

Where is the primary olfactory cortex and olfactory association area?

Answer 23

Uncus (most anterior part of the parahippocampal gyrus which is the most inferomedial part of the temporal lobe)

Question 24

Where is the primary visual area?

Answer 24

• located on the area surrounding the walls of the calcarine sulcus (occipital lobe)

Question 25

Outline key features of the primary visual area.

Answer 25

• receives input from the opposite half of the visual field of both eyes via the LGN of the thalamus
• lesion of occipital lobe results in cortical blindness (a lack of conscious vision in the hemifield contralateral to the damaged hemisphere)

Question 26

Where is the visual association area?

Answer 26

• surrounding primary visual area in occipital lobe, extends into the inferolateral part of the temporal lobe

Question 27

What is the importance of the visual association area?

Answer 27

• important for recognition of form + colour + movement + attentional aspects of vision
• lesion –> various types of visual agnosis (ex. cant perceive colour/movement/recognise faces)

Question 28

What does the insula look after?

Answer 28

• gustation (taste)
• located in the inferior aspect of post central gyrus, lateral fissure

Question 29

What are the parts of the limbic system?

Answer 29

• cingulate gyrus
• parahippocampal gyrus
• hippocampus
• thalamus
• hypothalamus
• mamillary body
• amygdala

Question 30

What is the limbic system important for?

Answer 30

Control of innate behaviours associated with survival and particularly memory

Question 31

What is the uncus?

Answer 31

• primary olfactory cortex
• located on the anterior extremity of the parahippocampal gyrus