How many layers does the cerebral cortex have?
6 layers containing cell bodies & dendrites (remember cortex is grey matter)
Most output from the cortex are via which neurones?
Pyramidal neurones (e.g. upper motor neurones int eh primary cortex are examples of pyramidal neurones)
**Shown in red on diagram
Outputs from motor cortex can be any of the 3 types of fibres in the CNS; remind yourself of these 3 types of fibres and state an example for each
- Assocition fibres: connecting nearby regions of cortex in same hemisphere e.g. arcuate fasciculus
- Comissure fibres: connect two hemispheres e.g. corpus callosum
- Projection fibres: going down to brainstem and/or cord e.g. upper motor neurones
Where do most inputs to the cortex come from? (2)
- Thalamus
- Other cortical areas
*NOTE: an important population of inputs areise from the reticular formation
Interneurones connect inputs and ouputs of the cortex in a complex way; what does this give rise to?
Emotion, behaviour, memory etc…
Can think of it as you are a sum of the inputs and outputs to the cortex
How do we know about lobe function in the human brain?
Most of what we know comes from studying lesions in natural experimetns (e.g. someone has a stroke in lobe x and we look at what deficits they have)
Pyramidal cells do not have dense dendritic trees; true or false?
FALSE; pyramidal cells do have dense dendritic trees allowing them to symapse with lots of interneurones
What is meant by cortical localisation?
Idea that different lobes of brain and different subdivisions have different functions
State 6 functions of frontal lobe. For each function, give a reason as to why it’s function is related to the frontal lobe and state what damage to the frontal lobe could result in (in terms of this function)
- Motor
- Primary motor cortex
- Frontal lobe damage can result in contralateral weakness
- Expression of speech
- Broca’s area
- Damage to left frontal lobe (as speech is generally in left hemisphere) can result in expressive dysphasia
- Behavioural regulation/judgement:
- Prefrontal cortex
- Damage to frontal lobes can lead to (usually) impulsive, disinhibited behavioiurs e.g. sexual inappropriateness, aggression etc…
- Cognition:
- Prefrontal cortex
- Frontal lobe damage (particularly the right) can cause difficulty with tasks such as complex problem solving e.g. calculations
- Eye movements:
- Contain frontal eye fields
- Damage can cause problems with conjugate gaze and other eye movement disturbances (however, diplopia without other cortical features would suggest brainstem or cranil nerve problem)
- Continence:
- Contain cortical areas responsible for maintenance of continence (paracentral lobules)
- Damage can cause urinary incontinece
Alcohol can affect frontal lobes; true or false?
True- this is why people may display impulsive behaviour when drunk
*BUT remember that it is cerebellum that is highly sensitive to alcohol
State 4 (sort of 5) functions of the parietal lobes. For each function, give a reason as to why it’s function is related to the frontal lobe and state what damage to the frontal lobe could result in (in terms of this function)
- Sensory:
- Primary somatosensory cortex
- Damage may result in contralateral anaesthesia affecting all modalities
- Comprehension of speech:
- Contains part of Wernicke’s area
- Damage to left parietal lobe (as speech is generally in the left) can cause receptive dysphasia
- Body image & awareness of external environment:
- Seems to be involved in the acknowledgement that things (including the body) exist
- Damage to right parietal lobe can lead to neglect (right parietal lobe lesion would result in not acknowledging left half of space. This is because the right hemisphere acknowledges both. Whereas left hemisphere only acknowledges the right. So if lesion was on left neglect wouldn’t occur)
- Calculation & writing:
- Parietal lobes works with frontal lobe to perform tasks
- Damage to left parietal lobe can affect calculation ability (but remembe this could mean it is a frontal lobe lesion)
Not exaclty a function but remember that the superior optic radiations project through the parietal lobe
Explain why damage to the right parietal lobe would cause neglect but damage to the left parietal lobe would not cause neglect
Damage to right parietal lobe can lead to neglect (right parietal lobe lesion would result in not acknowledging left half of space). This is because the right hemisphere acknowledges both sides of space. Whereas left hemisphere only acknowledges the right side. So if lesion was in left parietal neglect wouldn’t occur as the right can do both.
State the 4 (sort of 5) functions of the temporal lobe. For each function, give a reason as to why it’s function is related to the frontal lobe and state what damage to the frontal lobe could result in (in terms of this function)
- Hearing:
- Primary auditory cortex sits on superior surface of temporal lobe (near Wernicke’s area)
- Damage can lead to complex effects on hearing (don’t need to know details- however, auditory hallucinations may be feature of temporal lobe lesions)
- Olfactation:
- Primary olfactory cortex sits on infero-medial aspect of temporal lobe
- Damage can lead to complex effects on smell (don’t need to know details however olfactory hallucinations may be a feature of temporal lobe lesions)
- Memory:
- Hippocampus is crucial for consolidating declarative memories
- Damage may lead to amnesia. Epilepsy in the temporallobe could trigger memories
- Emotion:
- Temproal lobes contain number of limbic structures like hippocampus & amygdala
- Effects of lesions are complex but lesions here may be related to pathogenesis of some psychiatric disorders
Not a function: but remember that inferior optic radiations project through temporal lobe
What limbic structure is the emotion centre of the brain?
Amygdala
*NOTE: limbic cortex= cingulate gyrus
Where abouts in temporal lobe do the:
- Primary olfactory cortex
- Primary auditory cortex
…. reside?
- Primary olfactory: inferomedial aspect
- Primary auditory: superior aspect
What do we mean by cerebral dominance?
Idea that some functions are represented more prominently in one hemisphere
State which hemisphere is usually dominant for:
- Language
- Mathematical/logical functions
- Body image/visuospatial awareness
- Emotion
- Musical ability
- Language & mathematical/logical functions= LEFT
- Body image, visuospatial awareness, emotion, musical ability= RIGHT
*This is situation in 95% of people
If someone presents with dysphasia, where is lesion likely to be?
Left hemisphere
What structure connects the two hemispheres?
Corpus callosum
Destruction of corpus callsoum can cause..? (2)
- Interesting syndromes e.g. Alien hand syndrome
- Subtle effects on language & processing
Describe alien hand syndrome
- Inability to control hand/hand seems to act on it’s own without conscious control
- Involuntary and autonomous activity of affected limbs
*Damage to corpus callosum can mean that the primary motor cortex and its motor neurones are no longer able to communicate with pre-motor cortical regions that would tell it what to do
If someone who has had an epileptic seizure describes it as de-ja-vu/triggered a memory where would you suspect the epilepsy to be?
Temporal lobe (as this has hippocampus for memory)
Which hemisphere is dominant in most people?
Left
***NOTE: think- this makes sense as most people are right handed. HOWEVER, in a left handed person the left hemisphere still does language etc….? Bizarre
Is the corpus callosum white or grey matter?
White
-
1b.) Development of Nervous System43
-
1a.) Basic Topography89
-
2a.) Neurones & Glia72
-
3a & 3b.) Somatosensory System45
-
4a.) The Retina & Central Vision Pathways29
-
4b.) Arterial Supply to the Brain29
-
5a & 5b.) Motor System35
-
6a.) Movement Disorders & Basal Ganglia52
-
8c.) Neuropathology67
-
8a.) Higher Cortical Function50
-
8b.) Consciousness49
-
9a.) Confusion in the Elderly57
-
8b.) Headaches44
-
10a.) Stroke37
-
10b.) Intracranial Pressure45
-
10c.) Subarachnoid Haemorrhage & Meningitis45
-
11a & 11b.) Anxiety37
-
12a.) Mood Disorders37
-
12b.) Psychosis39
-
Stroke Week: Clinical Management23
-
Stroke Week: MDT25
