Cerebral Cortex

Question 1

What is the cerebral cortex?

How is the cerebral cortex organised and what is it composed of?

Answer 1

Outer layer of the cerebrum, 2-3mm thick, covers entire surface of the brain, have gyri and sulci and are divided into lobes

Into 6 main layers - composed of grey matter and cell bodies on the outer layers, and white matter beneath the cortex

Question 2

What is cytoarchitecture?

Other than the frontal, parietal, occipital and temporal lobes, what is the one other lobe and its functions?

What is the limbic system?

Answer 2

CNS divided into regions according to cell type, size and density

Limbic - contains deep surfaces of the temporal lobe (e.g. amygdala, hippocampus, mamillary body, cingulate gyrus) and responsible for learning, memory, emotion, motivation and reward

Limbic system = brain structures dealing with emotions and memory

Question 3

What lies within the deep lateral fissure in the brain and what are its functions?

Answer 3

Insular cortex - responsible for visceral sensations, autonomic control (unconscious control), interoception (knowing what is going on inside your body e.g. too hot, too cold, hungry?), auditory processing, visual-vestibular integration (combining the info from vision and balance pathways)

Question 4

What are the differences between grey matter and white matter? Where are they found?

What is white matter organised into?

Answer 4

Grey matter - cell bodies - outer cortex layer

White matter - connections between cell body nuclei i.e. the myelinated axons - beneath the cortex layer

White matter organised into bundles or tracts

Question 5

What are white matter tracts?

What are the names of the fibres in the white matter tracts and how are they distinguished?

Answer 5

Connect cortical areas

Association fibres - connect nuclei within same hemisphere

Commisural fibres - connect similar structures between the left and right hemispheres

Projection fibres - connect cortex with lower brain structures (e.g. thalamus, brain stem and spinal cord)

Question 6

What is the difference between short and long fibres within the association fibres?

Fill in the missing names of the long association fibres in the diagram below:

Answer 6

Short = within same lobe

Long = across different lobes

Question 7

What are the names of the two main commissural fibres and where are they found?

Fill in the missing names below:

Answer 7

Corpus callosum and anterior commissure (more inferiorly placed than the corpus callosum)

Question 8

What is the difference between efferent and afferent fibres within the projection fibres?

What are the fibres below in the image collectively known as? Where do they coverge into?

Answer 8

Afferent = towards cortex

Efferent = away from cortex

Corona Radiata; converge into the internal capsule (between the thalamus and basal ganglia)

Question 9

What is the basis for dividing the brain into cortices?

What are the 3 main differences between the primary and secondary cortices?

Answer 9

Functionality

Primary cortices = predictable functions, arranged precisely in locations, symmetry between left and right

Secondary cortices = less predictable functions, not organised into precise locations, little symmetry between left and right

Question 10

Where are the somatosensory and motor cortices located?

Are they primary or secondary cortices?

Answer 10

Primary somatosensory = parietal lobe

Motor cortex = frontal lobe

Both = primary cortices

Question 11

What are the 3 main areas in the frontal lobe? Label them on the diagram below and explain their functions:

Answer 11

Primary motor cortex = fine, precise movements

Supplementary = planning for movements (according to external cues e.g. pick something up)

Premotor area = planning complex movements (according to internal cues e.g. corticobulbar pathways activating speech production)

Question 12

What are the 2 main areas in the parietal lobe? Fill in the names on the diagram below and explain their functions:

Answer 12

Primary somatosensory cortex - processes somatic sensations arising from receptors in the body (e.g. fine touch, vibration, proprioception, pain and temperature)

Somatosensory association - interpret significance of sensory information, e.g. recognizing an object placed in the hand. Also self + personal space awareness

Question 13

What are the 2 main areas in the occipital lobe? Fill in the names on the diagram below and explain their functions:

Answer 13

Primary visual - processes visual info

Visual Association - gives meaning and interpretation of visual input

Question 14

What are the 2 main areas in the temporal lobe? Fill in the names on the diagram below and explain their functions:

Answer 14

Primary temporal - processes auditory stimuli

Temporal association - gives meaning and interpretation of auditory input

Question 15

What are some other association (secondary) cortices in the brain? Label them on the diagram below and explain their functions:

(HINT: you know 2 of them from psychology)

Answer 15

Prefrontal Cortex: attention, adjusting social behaviour, planning, personality expression, decision making

Broca’s Area: language production

Wernicke’s Area: speech production

Question 16

What are the consequences of frontal lobe lesions?

(HINT: also know this from psychology)

Answer 16

Changes in personality, inappropriate behaviour

e.g. Phineas Gage

Question 17

What are the consequences of parietal lobe lesions?

Answer 17

Lose self-awareness and extrapersonal space (what is going on around them)

Contralateral neglect - ignore / neglect one side (i.e.. damage to right side = neglect on left side) e.g. draw only half an image, dress only half of themselves, eat only half their plate etc.

Question 18

What are the consequences of temporal lobe lesions?

(HINT: also know this from psychology)

Answer 18

Inability to recognise (agnosia)

Patient HM - inability to form new memories (anterogade amnesia)

Question 19

What are the consequences to lesions in Broca’s or Wernicke’s areas?

Answer 19

Broca’s aphasia = poor speech production

Wernicke’s aphasia = poor speech comprehension

Question 20

What are the consequences of occipital lobe lesions?

Answer 20

Damage to primary visual cortex = blindness in corresponding field of vision

Damage to visual association = lack of visual interpretation e.g. prosopagnosia (inability to recognise familar faces, places, etc.)

Question 21

How can cortical function be assessed through imaging?

Answer 21

Getting patients / participants to do tasks then use imaging techniques to see which parts of the brain is being used

PET scans - blood flow directly to brain region

fMRI - amount of blood oxygen in brain region

Question 22

How can cortical function be assessed through encephalography (EG)?

How many stimuli are required to form a brain wave and why?

Answer 22

Electroencephalography (EEG) - measures electrical signals produced by the brain

magnetoencephalography (MEG) - measures magnetic signals produced by the brain

Requires constant or as many as 50-100 stimulations as a single stimulus is barely picked up by the EGs

Question 23

How are the electrodes in EGs placed?

What are the 3 main potentials are observed?

Answer 23

Universal system - electrodes numbered and palced in specific areas

Visual evoked potentials, event-related potentials, evoked potentials

Question 24

How can we assess the integrity of the sensory pathway?

Why is this relevant clinically?

Answer 24

Record impulse path along peripheral nerve up to the brain

This method is often used in people with spinal cord injuries to confirm where along the pathway an injury has occured (if there is one)

Question 25

What is recorded when using somatosensory evoked potentials?

What is the path that should be used when using somatosensory evoked potentials?

Answer 25

Series of waves that reflect sequential activation of neural structures along somatosensory pathways - can be used to track if there is an issue along the pathway

e.g. with the median nerve, impulse arrives at shoulder, mid cervical cord activity, thalamic activity, somatosensory activity - each will generate a trace

Question 26

How can cortical function be assessed via brain stimulation?

Answer 26

Using Transcranial magentic stimulation (TMS), the brain can be stimulated to produce an action, so the signal travelling from the brain to the e.g. muscle, can be assessed instead

e.g. magnetic stimulators can change electrical fields to induce EM fields - the brain acts as a wire and a magnetic coil is held up above the brain

Question 27

How is TMS (transcranial magnetic stimulation) used in practice?

Answer 27

Used to look at neural pathways controlling movement esp. after spinal injuries

Investigate whether a specific brain area is responsible for a function

Could be used in modulating certain brain activities

Research being conducted into whether it can reduce / prevent epilepsy, tinnitus and migraines

Question 28

What is a tDCS? And what does it do?

What is a DTI and what is it used for?

What is DTI with tractography used for?

Answer 28

Transcranial direct current stimulation - uses low direct current over the scalp tp increase or decrease neuronal firings

Diffusion tensor imaging - used to assess structures of the brain and is based on the diffusion of H2O molecules

DTI + tractography = 3D construction to assess neural tracts