Cerebral cortex

Question 1

What is the white matter of the brain and where is it found?

Answer 1

The inside - axons and connections

Question 2

What is the grey matter of the brain and where is it found?

Answer 2

Surface of the brain - has cell bodies

Question 3

What are the 3 types of fibres in the white matter?

Answer 3

• association fibres
• commisural fibres
• projection fibres

Question 4

What are association, commissural and projection fibres?

Answer 4

1. Association fibres: connect areas within the same hemisphere – local circuitry e.g. joining gyri next to eachother
2. Commissural fibres: connect left hemisphere to right hemisphere and integrate info between different association areas
3. Projection fibres: connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord. They are long projection pathways e.g. motor pathways

Question 5

What is the neocortex and the archicortex and how many layers do they have?

Answer 5

Neocortex - most of cortex
Archicortex - around hippocampus

N - 6 layer structure
A - 3 cortical layers

Question 6

What are the different layers of the neocortex?

Answer 6

• Layer I contains mainly neurophils
• The generally smaller pyramidal neurons in layers II and III have primarily corticocortical connections - Cortical layer IV is typically rich in stellate neurons with locally ramifying axons; in the primary sensory cortices, these neurons receive input from the thalamus, the major sensory relay from the periphery
• Layer V, and to a lesser degree layer VI, contain pyramidal neurons whose axons typically leave the cortex (output)

Question 7

How does the neocortex vary between cortical areas, give an example?

Answer 7

• Varies slightly in its microscopic detail between different cortical areas
• For example, the primary visual cortex has an extra layer of wet matter inserted within the 6-layer structure
• This is why we call it the striate cortex (it has an extra layer of white matter)

Question 8

How else is the cortex arranged?

Answer 8

• Cortical columns
• They have dense vertical connections
• Neurones with similar properties are connected in the same column
• The columns are the basis for topographical organisation

Question 9

What is the neocortex arranged into?

Answer 9

Different lobes

Question 10

What are primary and association cortices?

Answer 10

Primary cortices: function is predictable, organised topographically, left-right symmetry

Association cortices: function less predictable, not organised topographically, left-right symmetry weak/absent

Question 11

What are the different lobes?

Answer 11

occipital, parietal, temporal and frontal

Question 12

What is the role of the primary visual cortex and which lobe is it in?

Answer 12

• occipital lobe

- processing vision

Question 13

What does the visual association cortex do?

Answer 13

Analyses different attributes of visual image in different places. The form & colour is analysed along the ventral pathway; spatial relationships & movement along dorsal pathway. Lesions affect specific aspects of visual perception.

Question 14

What is the role of the primary somatosensory cortex and where is it?

Answer 14

• Post-central gyrus in the parietal lobe

- Processes sensory information

Question 15

What does the posterior parietal association cortex do?

Injury of parietal lobe leads to?

Answer 15

Creates spatial map of body in surroundings, from multi-modality information. Injury may cause disorientation, inability to read map or understand spatial relationships, apraxia, hemispatial neglect.

Question 16

What is apraxia?

Answer 16

Motor disorder in which the individual has difficulty with the motor planning to perform tasks or movements

Question 17

Where is the primary auditory cortex do and what does the temporal lobe do?
Injury leads to?

Answer 17

• In the superior temporal gyrus in the temporal lobe
• Processes language, object recognition, memory, emotion
• Injury leads to agnosia, receptive aphasia (Wernicke’s)

Question 18

What is agnosia?

Answer 18

Inability to process sensory information. Often there is a loss of ability to recognize objects, sounds, shapes, or smells

Question 19

Where is the primary motor cortex?

Answer 19

Part of the pre-central gyrus in the frontal lobe

Question 20

What is the role of the frontal lobe?

Injury leads to?

Answer 20

Judgement, foresight, personality, appreciation of self in relation to world. Injury leads to deficits in planning and inappropriate behaviour

Question 21

Are Broca’s and Wernicke’s area on right and left side?

Answer 21

No, lateralised to the left

Question 22

Where are Broca’s and Wernicke’s area?

Answer 22

Broca’s area - inferior frontal lobe

Wernicke’s area - junction between parietal/temporal

Question 23

What are some ways of measuring brain function?

Answer 23

PET
fMRI
EEG
Light micrcoscopy

Question 24

What are the two main visual processing pathways in the primary visual cortex?

Answer 24

The dorsal steam WHERE – spatial relationship

The ventral stream WHAT – colour, form

Question 25

What are some visual association pathways?

Answer 25

They connect to other parts of the brain and pick out individual attributes of images. One part detects motion.

Question 26

What can lesions of the visual posterior association area lead to?

Answer 26

The inability to recognize familiar faces or learn new faces—a deficit called prosopagnosia (aka face blindness)

Question 27

What happens in the visual association cortex?

Answer 27

Image attributes are processed separately

Question 28

What are frontal cortex lesions characterised by?

Answer 28

A lack of planning, behaviour becomes disorganised, attention span and concentration diminish and self-control is hugely impaired (disinhibition

Question 29

What are parietal cortex lesions characterised by?

Answer 29

- Disorientation, inability to read maps or understand spatial relationships, apraxia and hemispatial neglect (when patient draws something, they only draw half of it) - Patients lose their visual-spatial integration

Question 30

What does the parietal lobe (primary parietal association cortex) do?

Answer 30

- Creates a spatial map of the body in surroundings, from multi-modality information - Integrates memory and where things are in space

Question 31

What is the role of the temporal lobe? | What do lesions result in?

Answer 31

- language, object recognition, memory and emotion | - agnosia and receptive aphasia (difficulty understanding written and spoken language)

Question 32

How can temporal cortex lesions be treated? | How is this different to what was done in the past?

Answer 32

- Removal of the damaged portion of the temporal lobe | - Before the solution was to do a bilateral temporalobectomy which resulted in dense anterograde amnesia

Question 33

What is a callosotomy?

Answer 33

corpus callosum is cut (for epilepsy)

Question 34

What are the role of the right and left hemispheres?

Answer 34

The left hemisphere is language dominant, the right hemisphere is largely spatial processing.

Question 35

Can people be born without corpus callosum's and how are they different to those who had a callosotomy?

Answer 35

- Someone born without a corpus callosum will have automatic compensatory mechanisms - However, they will still have subtle psychological deficits - In patients who have this due to surgical procedures, this is often more obvious as they have gone from normal to impaired

Question 36

What are some experiments done in split brain research?

Answer 36

- A word is flashed briefly to the right field – you ask the patient what they saw - They will be able to do this, because the left hemisphere is dominant for verbal processing - If you flash the word briefly to the left field, the patient doesn’t can't say what they see - However, they will be able to draw what the word say

Question 37

What is diffusion tensor imaging?

Answer 37

- A MR modality that looks for alignment of water molecules, and coincident activity - Coincident alignment is taken to mean fibre connectivity - This way, you can build up a fibre network of the brain - We can use DTI in brain tumour patients to show break down of such connections - DTI gives us more information about interruption to specific intracortical circuitry

Question 38

What is transcranial magnetic stimulation?

Answer 38

The magnetic field induces an electric current in the cortex, causing neurons to fire. This can be used to test whether a specific brain area is responsible for a function, e.g. speech.

Question 39

What is transcranial direct current stimulation?

Answer 39

- Changes the local excitability of neurons, increasing or decreasing the firing rate - This does not directly induce neuronal firing , however, it changes the threshold for decreasing/increasing the firing rate - Affects the resting voltage of the neuronal membrane to stimulate a neuron’s activity in a desired direction

Question 40

What are PET scans?

Answer 40

- Work by detecting the radiation given off by a radiotracer (similar to GLUCOSE) as it collects in different parts of your body - This can be used to identify any abnormalities - E.g a high conc can identify cancerous cells because cancer cells use glucose at a much faster rate than normal cells

Question 41

Why is PET mainly used in research?

Answer 41

expensive

Question 42

How do MEG and EEGs work?

Answer 42

MEG: measures magnetic fields – involved a big machine EEG: measures electric fields – involved lots of electrodes

Question 43

What are event-related potentials?

Answer 43

- brain activity related to a stimulus | - lots of background noise so repeated and layered to remove noise

Question 44

What is an fMRI?

Answer 44

- This is usually about monitoring blood flow and glucose metabolism - Glucose use is probably related to functional activity of the brain - Where there is more glucose and more blood flow, there is probably higher activity

Question 45

How can we measure optimism?

Answer 45

- Measure the brain response to imagining positive and negative events in the future or the past - When participants imagined positive events in the future or the past, the amygdala and Rostral anterior cingulate cortex were more active than when they imagined negative events