Cerebral Cortex

Question 1

Describe the organisation of grey matter and white matter

Answer 1

Grey matter is on outside and white matter is within the brain.
Grey matter contains cell bodies and white matter and white matter contain neuronal tracts.

Question 2

What are the three types of fibres and what are their connection?

Answer 2

Association fibres: connect areas within the same hemisphere

Commissural fibres: connect left hemisphere to the right hemisphere (e.g. corpus callosum)

Projection fibres: connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord (e.g. corticospinal tract all the way down to alpha motor neurons)

Question 3

Define the dorsal and ventral surface of the brain?

Answer 3

The dorsal is the outer surface

The ventral is the inner surface

Question 4

How many layers of grey matter are there?

Answer 4

There are 3 to 6 layers

Question 5

What is the neocortex?

Answer 5

Part of the cerebral cortex concerned with sight and hearing in mammals most recently evolved part of the cortex

Question 6

Describe layer 1

Answer 6

Most dorsal, very few neurons, glial cells are present, largely association fibres

Neutropil – an area composed mostly of unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies

Question 7

Which layer receives input from the thalamus?

Answer 7

Layer 4

Layer 4 is also rich is stellate neruons which are star shape and GABAergic

Question 8

Summarise the connections of the layers

Answer 8

Layers 1-3 = mainly cortico-cortical connections
Layer 4 = input from the thalamus
Layer 5-6 = connections with subcortical, brainstem and spinal cord

Question 9

What type of neurons are found in layer 5?

Answer 9

pyramidal neurons

Betz cells - large motor neurons that project all the way down the spinal cord

Question 10

How is neocortex arranged?

Answer 10

Lamina (layers) and columns
More dense vertical connections - topical organisation
neurons with similar properties are found in the same column

Question 11

What are the different lobes of the neocortex?

Answer 11

Frontal
Parietal
Occipital
Temporal

Question 12

Which corticies are involved in skeletal muscle movement?

Answer 12

Primary motor cortex

Motor association cortex

Question 13

What are the two parts of the visual association cortex and what are they responsible for?

Answer 13

Dorsal Pathway – responsible for interpretation of spatial relationships and movements WHERE pathway
Ventral Pathway – responsible for form and colour WHAT pathway

Question 14

What is APRAXIA?

Answer 14

Inability to perform skilled movements with accuracy

Question 15

What is AGNOSIA?

Answer 15

Disorder of the brain whereby patient can’t interpret sensations correctly despite sense organs and nerves conducting sensation to brain correctly.
auditory agnosia
tactile agnosia
visual agnosia

Question 16

What is RECEPTIVE APHASIA?

Answer 16

The patient is unable to understand language in its spoken or written form

Question 17

Compare primary cortices and association cortices?

Answer 17

Primary - function predictable, topographical, left-right symmetry

Association - less predictable function, not organised topographical, left-right symmetry is weak

Question 18

Discuss use of functional MRI

Answer 18

Decent spatial awareness
Long time to measure response
Blood flow response will take about 5-7 seconds after onset of a stimulus

Question 19

Lesion of visual association cortex effects?

Answer 19

Lesions of visual posterior association area can result in inability to recognise faces/learn faces
PROSOPAGNOSIA

Question 20

What is the role of the posterior parietal association cortex?

Answer 20

It creates a SPATIAL MAP of the body in its surroundings from multi-modality information

Question 21

What could injury of this part of the association cortex lead to?

Answer 21

Disorientation
Inability to read a map or understand spatial relationships
Apraxia
Hemispatial Neglect

Question 22

What are the consequences of a prefrontal lobotomy?

Answer 22

Change in personality
Inappropriate behaviour
Lack of ability to remember and relate things over time
Attention span and ability to concentrate are diminished

Question 23

What two areas does the prefrontal cortex receive massive inputs from?

Answer 23

Sensory association cortex (somatosensory, visual and auditory)
Dorsomedial Nucleus of the thalamus
NOTE: lesion of the dorsomedial nucleus will have similar consequences to prefrontal lobotomy

Question 24

If you give someone with a unilateral parietal lobe lesion something to draw, what will you expect him or her to do?

Answer 24

Hemispatial neglect – they will only draw half of it

Question 25

What effect do temporal cortex lesions have on memory?

Answer 25

Impaired short-term memory

They are effectively trapped in a 30 second window of memory

Question 26

Describe hemispheric specialisation.

Answer 26

Right hemisphere = creative + artistic

Left hemisphere = logical + scientific

Question 27

What is a callosotomy?

Answer 27

A palliative procedure used for the treatment of seizures

The corpus callosum is key for the interhemispheric spread of epileptic activity

Question 28

Hemispheric specialization test?

Answer 28

A word FACE is flashed to the right and the patient is asked to say what he saw
Left hemisphere is dominant for verbal processing, the patient’s answer matches the word

Word FACE flashed to the left of field of view and patient is asked what he saw
Right hemi cannot share info with left so patient can’t say it but he can draw a face

Question 29

What is diffusion tensor imaging?

Answer 29

Tractography
Movement of water can infer the integrity of functional pathways, used to estimate pathway of white matter tracts, any occlusion connection is disrupted in the imaging

Question 30

State two types of brain stimulation testing and what it can be used for.

Answer 30

Transcranial Magnetic Stimulation (TMS)
•Magnetic field induces a current in the cortex causing neurons to fire
•This is method of focally stimulating different areas of the cortex and testing what each area is responsible for
Used therapeutically for severe clinical depression

Transcranial Direct Current Stimulation (TDCS)
•This changes the excitability of neurones but does NOT directly induce neuronal firing
•Anode = increases neuronal excitability
•Cathode = decreases neuronal excitability
•TDCS could be used to reduce motion sickness by suppressing the area of the cortex associated with perceiving vestibular information

Question 31

Describe and explain how PET (positron emission tomography) scans work. What can it be used for?

Answer 31

A radioactive tracer is attached to a molecule to locate areas of the brain where that molecule is being absorbed
The tracer emits positrons, which are then detected by the receptors
It can be used in Parkinson’s disease to see the uptake of dopamine precursors by dopaminergic neurones

Lower uptake of dopamine in posterolateral putamen in PD patients and can be seen by less light, in Parkinson’s there is a loss in posterolateral putamen wit relative preservation of caudate

Question 32

What is the difference between MEGs and EEGs ?

Answer 32

MEGs = magnetoencephalography – measures magnetic fields
records magnetic field generated by electrical currents naturally occuring in brain

EEGs = electroencephalography – measures electric fields
non-invasive, electrodes on scalp, voltage fluctuates from ionic current with neurons of brain, less elaborate than MEG

Question 33

What is a major problem with MEGs and EEGs and how is this resolved?

Answer 33

It is quite noisy – there is a lot of background activity
This is resolved by doing a trial of a large number of participants so that an average can be found
Once the average has been found, it can be deducted from the captured signal to see the underlying activity

Question 34

What is a fMRI?

Answer 34

Function MRI
It detects changes in blood flow in the brain
It relies on the fact that blood flow in the brain and neuronal activity are coupled – more active parts of the brain require increased blood flow

Question 35

Which areas of the brain become more active when participants imagine positive events?

Answer 35

Amygdala (almond shape set of neurons located in brain’s deep medial temporal lobe)
Rostral anterior cingulate cortex

Question 36

What is function of occipital cortex and consequence of a lesion?

Answer 36

visual association cortex analyses different attributes of visual image in different places
form & colour analyzed along ventral pathway; spatial relationships & movement along dorsal pathway
lesions affect specific aspects of visual perception

Question 37

What is function of temporal cortex and consequence of a lesion?

Answer 37

language, object recognition, memory, emotion

injury leads to AGNOSIA AND RECEPTIVE APHASIA

Question 38

what is function of parietal cortex and consequence of a lesion?

Answer 38

posterior parietal association cortex 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 39

what is function of frontal cortex and consequence of a lesion?

Answer 39

• executive function
  judgement, foresight, personality, appreciation of self in relation to world
  injury leads to deficits in planning and inappropriate behaviour