1B cortical organisation and function Flashcards
1
Q
What is the cerebral cortex?
A
- Covers entire surface of brain
- Together with the deep nuclei, it contains the grey matter
- Highly folded with gyri and sulci
- Organised into lobes
2
Q
How is the cortex organised microscopically?
A
- Organised into layers and columns
- 6 layers (I most superficial and VI most deep) and multiple cortical columns
- Entire cortex is only 2-3mm thick and has cell bodies which makes it look grey
3
Q
What is the cytoarchitecture of the cortex?
A
- Cytoarchitecture is cell size, spacing or packing density and layers
- German neurologist Brodmann identified 52 regions of cortex using this
- Many areas are related to their function e.g. primary somatosensory (1, 2, 3) and primary motor (4)
4
Q
What are the lobes of the cortex?
A
- Frontal
- Parietal
- Temporal
- Occipital
5
Q
What is the function of the frontal lobe?
A
- Regulating and initiating motor function
- Cognitive functions (executive functions like planning)
- Language
- Attention
- Memory
6
Q
What is the function of the parietal lobe?
A
- Sensation- touch, pain
- Sensory aspects of language
- Spatial orientation
- Self-perception
7
Q
What is the function of the temporal lobe?
A
- Processing auditory information
- Emotions
- Memories
8
Q
What is the function of the occipital lobe?
A
Processing and interpreting visual information
9
Q
What is the limbic lobe made up of?
A
- Amygdala
- Hippocampus
- Mamillary body
- Cingulate gyrus
10
Q
What functions is the limbic lobe responsible for?
A
- Learning
- Emotion
- Reward
- Motivation
- Memory
11
Q
What is the insular cortex and what is its function?
A
- Lies deep within the lateral fissure
- Concerned with:
- visceral sensations
- autonomic control
- interoception
- auditory processing
- visual-vestibular integration
12
Q
What is grey and white matter?
A
- Grey matter- neuronal cell bodies and glial cells- around 85 bil each
- White matter- myelinated neuronal axons arranged in tracts
13
Q
What do white matter tracts do and what types are there?
A
Connect cortical areas.
There are three types:
- Association fibres
- Commissural fibres
- Projection fibres
14
Q
What do association fibres do?
A
Connect areas within the same hemisphere- there are short and long fibres
15
Q
What does the superior longitudinal fasciculus connect?
A
Frontal and and occipital lobes (pink)
16
Q
What does the arcuate fasciculus connect?
A
Frontal and temporal lobes (purple)
17
Q
What does the inferior longitudinal fasciculus connect?
A
Temporal and occipital lobes (blue)
18
Q
What does the uncinate fasciculus connect?
A
Frontal and temporal lobes (orange)
19
Q
What do commissural fibres do?
A
Connect homologous structure in left and right hemispheres
20
Q
What are these commissural fibres called?
A
The corpus callosum can be disconnected in patients with epilepsy to treat it
21
Q
What do projection fibres do?
A
- Connect cortex with lower brain structures (e.g. thalamus, brain stem and spinal cord)
- Afferent fibres take info towards cortex
- Efferent fibres take info away from cortex
- Deeper to cortex radiate as the corona radiata
- They converge through the internal capsule between the thalamus and basal ganglia
22
Q
What are primary cortices?
A
- Predictable function
- Organised topographically- bits of body close to each other are closely represented on brain
- Symmetry between left and right
23
Q
What are secondary/association cortices?
A
- Less predictable function
- Not organised topographically
- Left-right symmetry is weak or absent
24
Q
What do the primary/secondary cortices in the motor area of frontal lobe do?
A
- Primary motor cortex- controls fine, discrete, precise voluntary movements and provides descending signals to execute movements
- Premotor area- involved in planning movements (e.g. externally cued like seeing and wanting to pick up an object)
- Supplementary area- involved in planning complex movements (e.g. internally cued like production of speech)
25
What do the primary/secondary cortices in the parietal lobe do?
- Primary somatosensory- processes somatic sensations arising from receptors in the body (e.g. fine touch, vibration, two-point discrimination, proprioception, pain and temperature)
- Somatosensory association- interpret significance of sensory information e.g. recognising an object placed in the hand. Also, awareness of self and awareness of personal space
26
What do the primary/secondary cortices in the occipital lobe do?
- Primary visual- processes visual stimuli
- Visual association- gives meaning and interpretation of visual input
27
What do the primary/secondary cortices in the temporal lobe do?
- Primary auditory- processes auditory stimuli- auditory cortex has tonographic organisation (different frequencies are recognised by different parts of it)
- Auditory association- gives meaning and interpretation of auditory input
28
What are some other association areas?
- Prefrontal cortex
- Broca's area
- Wernicke's area
29
What does the prefrontal cortex do?
- Personality expression
- Adjusting social behaviour
- Planning
- Attention
- Decision making
30
What does Broca's area do?
Production of language
31
What does Wernicke's area do?
Understanding of language
32
What do frontal lobe lesions cause?
- Changes in personality
- Inappropriate behaviour
33
What do parietal lobe lesions do?
Contralateral neglect:
e.g. for a lesion in the right hemisphere:
- lack of awareness of self on left side
- lack of awareness of left side of extrapersonal space
34
What do temporal lobe lesions do?
- Leads to **agnosia**- inability to recognise
- A patient had a bilateral resection of anterior medial temporal lobe to cure epilepsy and was left with **anterograde amnesia** (couldn't form new memories)
35
What does a lesion to Broca's area lead to?
Expressive aphasia: poor production of speech, comprehension intact
36
What does a lesion to Wenicke's area do?
Receptive aphasia: poor comprehension of speech, production is fine
37
What does a lesion to the arcuate fasciculus cause?
**Conduction aphasia**- inability to repeat speech (this tract links the Broca’s area and Wernicke’s area)
38
What do occipital lobe lesions do?
- **Primary visual cortex**: blindness in the corresponding part of the visual field
- **Visual association**: deficits in interpretation of visual information e.g. prosopagnosia: inability to recognise familiar faces or learn new faces (face blindness)
39
What does positron emission tomography (PET) do?
Looks at blood flow directly to a brain region by seeing how glucose (radioactive isotope used) is taken up by different parts of brain
40
What does functional magnetic resonance imaging (fMRI) do?
Looks at amount of blood oxygen in a brain region
Image shows cortical activity during movement of right hand
41
What is diffusion tensor imaging (DTI)?
Based on diffusion of water molecules
42
What is DTI with tractography?
3D reconstruction to assess neural tracts
43
What does electroencephalography (EEG) do?
Measures electrical signals produced by brain since brain works on AP travelling around it
Different electrodes are stuck over scalp and each electrode measures its own thing- it's a standard arrangement across the world and accounts for different head sizes
44
What does magnetoencephalography (MEG) do?
Measures magnetic signals produced by brain
45
How are somatosensory evoked potentials measured?
- We can put electrodes along a certain neural pathway and see if there are any issues
- We can see a series of waves that reflect sequential activation of neural structures along the somatosensory pathways (see diagram and order of waves)
46
What do somatosensory evoked potentials help us measure?
Can see nerve degradation and which point it's happened
47
How does transcranial magnetic stimulation (TMS) work?
- Uses electromagnetic induction to stimulate neurones
- Assess functional integrity of neural circuits
48
What can brain stimulation be used to measure?
- Investigate neural interactions controlling movement following spinal cord injury
- Investigate whether a specific brain area is responsible for a function e.g. speech
49
What is transcranial direct current stimulation (tDCS)?
Uses low direct current over the scalp to increase or decrease neuronal firing rates
