Cerebral cortex

Question 1

What is the cerebrum?

Answer 1

The cerebrum is the largest part of the brain (80% of the weight of the brain) and consists of two hemispheres. It consists of an outer coating of grey matter (cerebral cortex) which contains an inner mass of white matter.

Question 2

What is the cerebral cortex?

Answer 2

The cerebral cortex (also known as the cerebral mantle) is comprised of grey matter that covers the cerebral hemispheres. It has an intestinal like appearance with folds containing peaks (gyri) and grooves (sulci). The major peaks and grooves create divisions between the four major lobes of the brain.

Question 3

What does grey matter consists of?

Answer 3

Cell bodes
Neurons
Dendrites
Glial cells

Question 4

What does white matter consist of?

Answer 4

Axons specifically myelinated axon tracts. It is the myelination of these axons which cause this white colour.

Question 5

Why is the cerebral cortex highly convoluted?

Answer 5

Firstly the extent of convolution is proportional to the complexity of the animal as the cerebral cortex is the largest site of neural integration, where processing occurs.
With more convolution, this increases the surface area of grey matter and the amount of processing that can occur.

Question 6

Which side of the brain controls movement?

Answer 6

The hemispheres control movement on opposite sides of the body. For example the left hemisphere controls movement on the right hand side of the body.

Question 7

How are the two hemispheres able to interact?

Answer 7

The two hemispheres are able to crosstalk by the corpus callosum which is a fibre tract made of 300 million axons that runs between the centre of the two hemispheres.

Question 8

Why is it important that the two hemispheres are able to crosstalk?

Answer 8

The two hemispheres are not symmetrical in structure or function.
For example language centres are on the left hand side of the brain and therefore need to communicate through the corpus callosum to the right.

Question 9

Which higher functions are associated with the cerebral cortex (or cerebrum)?

Answer 9

Evolutionary this is the newest part of the brain and its function includes:
Language
Intellect
Conscious thought
Sensory analysis
Motor initiation

Question 10

What are the four lobes of the cerebral cortex?

Answer 10

Frontal (front)
Parietal (middle, behind frontal)
Occipital (back)
Temporal (below at the side of the brain)

Question 11

What are the functions of the occipital lobe and what is contained there to aid this function?

Answer 11

It is important in vision and contains the primary and secondary visual cortex (also called association area).
The primary visual cortex is where information directly from the retina is taken to the brain and visual processing occurs.
Adjacent to the primary visual cortex is the secondary visual cortex where further processing occurs.

Question 12

What is present within the temporal lobe?

Answer 12

Contains the primary auditory cortex which is the first relay centre for auditory information in the cortex. It is then surrounded by the secondary auditory cortex (also called association area) where further processing occurs.

Question 13

What is the primary function of the parietal lobe?

Answer 13

It is the location where all sensory information processing from the body occurs. Again contained within the temporal lobe is the primary somatic sensory cortex and the somatic sensory association area.

Question 14

Which inputs does the somatosensory area/cortex receive?

Answer 14

The somatosensory cortex is responsible for processing all sensory information from the body.
This involves analysis from inputs such as:
-Mechanoreceptors (touch and stretch)
-Thermoreceptors
-Nociceptors (skin, muscle, joints and internal organs.

This information travels via the brainstem and then the thalamus to the somatosensory centre.

Question 15

Where does the parietal lobe receive information from?

Answer 15

From the opposite side of the body

Question 16

Explain the concept of somatotrophic organisation.

Answer 16

Sensory information from areas of the brain is allocated to areas of the somatosensory cortex. The area of the cortex devoted to each area of the body is proportional to the amount of information received from that area. For example, a big proportion of the cortex is allocated to the lips and therefore is more sensitive. Areas of the cortex devoted to each part of the body can be mapped on to the sensory homunculus.

Question 17

Define neuroplasticity.

Answer 17

It is the ability of neural networks in the brain to change through growth and reorganization.

Question 18

Apply the concept of neuroplasticity to the concept of somatosensory organisation.

Answer 18

The area occupied by parts of the body in the somatosensory cortex, whilst is proportional to input is also use-dependent. This means that if one area of the body experiences an increased or decreased stimulation the size of the devoted area occupied in the brain will change accordingly and therefore is use-dependent. If someone was therefore to experience a limb loss for example of the thumb, neuroplasticity would occur in with a loss of area occupied in the cortex by the thumb whilst area occupied by other parts specifically other fingers would increase, becoming more sensitive.

Question 19

What happens after information is processed in the primary somatosensory cortex?

Answer 19

The information is then passed on to the association areas where further processing occurs and then to another association area where it is integrated with other sensory inputs and then information from past experiences is considered to build an idea of perception. This decides what the appropriate response shall be.

Question 20

What is the function of the frontal lobe?

Answer 20

This is mainly associated with motor function with the primary motor cortex which is adjacent to the pre-motor area which is involved in planning and initiation of movement.

Question 21

What is the function of the motor cortex?

Answer 21

It is responsible for voluntary movement which is located at the back of the frontal lobe adjacent to the central sulcus.

Question 22

Describe Penfield’s studies relating to the development of the motor homunculus.

Answer 22

Penfield, a neurosurgeon treated patients with severe epilepsy and developed the Montreal procedure in which he destroyed nerve cells within the brain in which the seizure originated. He did this by stimulating the areas of the cortex with electrical probes and observing their reactions. This lead to the development of the motor homunculus where it was mapped, as the somatosensory cortex, which parts of the body occupied which areas of the brain, with large areas allocated to the faces and hands.
Again stimulation on one side of the brain, stimulated the other side of the body.

Question 23

Was the motor cortex also use-dependent?

Answer 23

Yes again allocation within the cortical space of the motor cortex is also muscle use dependent and again there is neuroplasticity.

Question 24

What is the remainder of the pre-frontal* cortex allocated to?

Answer 24

Involved in processing motor information

Question 25

What is the function of the premotor cortex and supplementary motor area in application to the motor cortex?

Answer 25

The primary motor cortex is responsible for sending out signals to the alpha motor neurons, however both the premotor cortex and supplementary motor area are responsible for signalling to the primary motor cortex to co-ordinate these movements.

Question 26

Aside from the pre-frontal cortex and supplementary area which others input to the motor cortex?

Answer 26

Posterior parietal cortex
Basal ganglia
Thalamus
Cerebellum involved in fine motor control

These are involved in the planning, programming and co-ordination of complex movement

Question 27

What functions are associated with the pre-frontal area?

Answer 27

Thinking
Decision making
Intellect
Personality resides, damage to this area can cause changes in our personality

Question 28

What is Broca’s area?

Answer 28

Contained within the frontal area it is responsible for the formation of words.

Question 29

What is our highest mental function?

Answer 29

Language

Question 30

Which hemisphere is used in relation to language?

Answer 30

In 90% of the population the left hemisphere is used

Question 31

How is it usually distinguished the function of each part of the brain?

Answer 31

When damage occurs to a part of the brain, the clinical presentation can be observed in a patient and then you can develop an understanding which part of the brain was responsible to carry out a particular function.

Question 32

Define aphasias.

Answer 32

Language deficits arising due to brain damage which enabled language centres to be identified which was:
Broca’s area
Wernicke’s area

Question 33

What is the function of Broca’s area?

Answer 33

Located within the motor cortex, this area is responsible for the control of muscles to enable the articulation of speech.

Question 34

How would a patient present if damage occurred to Broca’s area?

Answer 34

The patient would be able to understand language however couldn’t articulate a response due to the inability to control the muscles in the correct way.

Question 35

What is the function of Wernicke’s area?

Answer 35

Located within the parietal cortex, this area is responsible for the comprehension, planning and coherence of language.

Question 36

How would a patient present if damage occurred to Wernicke’s area?

Answer 36

Would be unable to understand language and although could respond by controlling muscles the response would be incoherent.
Input to Wernicke’s area also includes from the auditory and visual cortex for hearing and reading language and additionally from the somatosensory cortex in the interpretation of brail.