Organisation of cerebral cortex

Question 1

What are the three types of fibre of the cerebral white matter?

Answer 1

Association fibres= connect with areas in same hemisphere
Commisural fibres= connect with two hemispheres-corpus callosum, anterior and posterioir
Projection fibres= connect the cortex with lower brain structures (e.g. thalamus), brainstem and spinal cord - cortical spinal tract

Question 2

Grey matter consists of?

How is the grey matter organised?

Answer 2

Cell bodies

It is organised into layers (laminar structure) with 3-6 cortical layers which are designated by roman numerals with letters for laminar subdivisions (layer 1 most dorsal, layer 6 most ventral–nearest to white matter)

Layer 1-3-Mainly cortico-cortical connections
layer 1) largely acellular–some glial few neurones-mostly association fibres local connectivity

Layer 4 -Input from thalamus

Layer 5-6- Connections with subcortical, brain stem and spinal cord

5- bett cells large upper motor neurones with long projection of spinal cord and brainstem

Question 3

From this slide onwards grey matter

Neocortex arrangement?

How are the neurones with similar properties locally organised into?

Answer 3

Layers (lamina structure) and columns

Columns

Question 4

More dense vertical connections in columns are the basis for

Answer 4

Topographical organisation

Question 5

What is the occipital cortex involved with?

Temporal lobe

Frontal lobe

Answer 5

Vision:
Visual cortex and Visual association cortex

Auditory cortex, auditory association area

Prefrontal association area
-Coordinates info from other association areas, controls some behaviours

Question 6

What is the parietal lobe involved with?

Answer 6

Primary somatic sensory cortex and sensory association area

Sensory information from skin, musculoskeletal system, viscera and taste buds:

Question 7

What does the posterior parietal association cortex do?

Answer 7

It creates a spatial map of body in its surroundings from multi-modality information

Question 8

What does injury to the posterior parietal association cortex lead to?

Answer 8

It may cause disorientation, inability to read a map or understand spatial relationships, apraxia, hemispatial neglect

Question 9

What is apraxia?

Part of brain responsible for memory

Answer 9

Inability to make skilled movements with accuracy

Hippocampus – in temporal

Question 10

What is the temporal lobe involved with?

Answer 10

Language
Object recognition
Memory–hippocampus
Emotion

Question 11

What does injury to the temporal lobe lead to?

Answer 11

Agnosia-

Receptive aphasia

Question 12

What is agnosia?

-not in lecture slides

Answer 12

Disorder of brain whereby patient can’t interpret sensations correctly although the sense organs and nerves conducting sensation to brain function normally
Auditory- can hear but can’t interpret
Tactile- Normal sensation in hands but can’t recognise 3D objects with touch alone
Visual- See but can’t interpret symbols

Question 13

What is receptive aphasia?

-not in lecture slides

Answer 13

Patient is unable to understand language in its spoken or written form

Question 14

Hemispheric specialisation

Left hemisphere dominant
Right hemisphere dominant

Answer 14

Patients who have had a callosotomy -split brain have lateralised deficits in function

Left side of brain - Language dominant
Isabella

Right- Spatial processing-arty

Post callosotomy– corpus callosum

Image on right- Can verbally process cant draw

Image on left side- cant verbally explain, can draw tho

Question 15

How do primary cortices and association cortices compare?

Answer 15

Primary cortices:
Function is predictable
Organised topographically
Left-right symmetry

Association cortices:
Less predictable
Not organised topographically
Left-right symmetry is weak or absent

Question 16

How are image attributes processed?

Answer 16

Separately:
What (colour and form)- ventral stream- visual identification
Where (spatial relationships)- Dorsal stream- localisation

Question 17

What is prosopagnosia?

Where are the lesions located

Answer 17

Where lesions of the visual posterior association area can result in inability to recognise faces or learn new faces but other parts are intact– face blindness

Posterior association area– fusiform gyrus

Question 18

Frontal cortex function

What did frontal cortex lesions show?

Answer 18

judgement, foresight, personality, appreciation of self in relation to world

Characterised by lack of planning, disorganised, reduced attention span and concentration and self control hugely impaired–> inappropriate behaviour

Question 19

What is a callosotomy?

Answer 19

Palliative surgical procedure for treatment of seizures because corpus callosum is key for interhemispheric spread of epileptic activity

Question 20

How is diffusion tensor imaging- tractography used?

Answer 20

Movement of water molecules in brain can be used to infer underlying structure of white matter. This information is used to estimate location and connections between different white matter pathways

to measure the effect of lesions in white matter – or how these lesions might disconnect different brain areas, and lead to complex symptoms.

Question 21

How does transcranial magnetic stimulation (TMS) work?

Answer 21

Magnetic field induces an electridc current in the cortesx, casuing neurons to fire. This can be used to test whether a specific brian area s reponsible for a funcion e.g speech

Question 22

How does transcranial direct current stimulation (TDCS) work?

Answer 22

It changes the local excitability of neurones, increasing or decreasing the firing rate. This doesn’t directly induce neuronal firing like TMS.

Question 23

What can TDCS be used to treat?

Answer 23

It could be used to reduce motion sickness by suppressing the area of cortex associated with processing vestibular information

Question 24

How does positron emission tomography (PET) work?

Answer 24

Put ligand into patient and look for its binding. Diagnostic use look for dopamine metabolism –parkinsons loss of metabolism.

Question 25

What is the difference between magnetoencephalography (MEG) and electroencephalography (EEG)?

Answer 25

MEG:
Measures magnetic fields

EEG:
Measures electric fields

Question 26

What similarities are there between MEG and EEG?

Answer 26

Both non-invasive
MEG/ EEG measures the surface activity of the brain, but cannot directly measure the activity of interior structures.
Both noisy signals
Event related potential/evoked potentials.
Participants perform large numbers of trials then take average, as they are coarse measurements with high background.

Question 27

How does functional magnetic resonance imaging work?

Answer 27

Measures brain activity by detecting changes associated with blood flow. This relies on fact that cerebral blood flow and neuronal activation are coupled- blood flow increases when area of brain in use

Alignment of water molecules soft tissue method of choice – ct: vascular prob acute bleed
infart- mr –spatial resolutiona dn function- activity.

Question 28

How was optimism measured?

Answer 28

When participants imagined positive events in the future or past, the amygdala and rostral anterior cingulate cortex were more active than when they imagined negative events

Question 29

Back of frontal lobe, in front of central sulcus is

Answer 29

Primary motor cortex–> motor association area (premotor cortex)
Skeletal muscle movement

Question 30

Anterior to parietal lobe, behind central sulcus is

Answer 30

Primary somatic sensory cortex

Question 31

Primary cortices

Location of each

Answer 31

Primary Motor cortex, somatic sensory cortex, visual, auditory, gustatory, olfactory

Question 32

Location of each of the primary cortices

Answer 32

Primary motor cortex- back of frontal
Primary somatosensory cortex- anterior of parietal
Visual- Occipital
Auditory- Temporal lobe
Gustatory and olfactory less well defined

Question 33

How is the grey matter organised?

Answer 33

It is organised into layers (laminar structure) with 3-6 cortical layers which are designated by roman numerals with letters for laminar subdivisions

Question 34

What does layer 1 mainly contain?

Answer 34

Neuropil- area composed mostly of unmyelinated axons, dendrites and glial cell processes that form a synaptically dense region containing a relatively low number of cell bodies

Question 35

What is layer 4 typically rich in?

Answer 35

Stellate neurones with locally ramifying axons, in the primary sensory cortices-these neurones receive input from thalamus

Question 36

What do layer 5 and layer 4 to a lesser extent contain?

Answer 36

Pyrimidal neurones whose axons typically leave the cortex