Session 8 L1: Cerebral Cortex Flashcards
What is the fine structure of the cerebral cortex?
- Arranged as 6 layers fo cell bodies and dendrites
- Most outputs from the cortex are the axons of pyramidal neurones
- Most inputs are from the thalamus and other cortical areas. An important population of inputs arise from the reticular formatting, maintaining cortical activation (consciousness)
- Interneurons connect inputs and outputs in a complex way, giving rise to behaviour, emotion, memory etc.
- Information is processed in the complex synaptic network found between input and output.
What are the functions of Frontal Lobe?
- Motor
- Expression of Speech (Broca’s)
- Behavioural Regulation/Judgement
- Cognition
- Eye movements
- Continence
How does damage to the Frontal Cortex affect Eye movements?
- Contain frontal eye fields
- Damage can cause problems with conjugate gaze and other eye movement disturbances (diplopia without other cortical features suggests more brainstem/cranial nerve problem)
What are the functions of parietal lobes?
- Sensory
- Comprehension of speech (Wernicke’s)
- Body image and awareness of external environment
- Calculation and writing
- Visual pathways projecting through white matter
What can damage to the parietal lobe cause?
- Neglect. Visual fields are normal however patients forget half the world exist most likely the left. Patients will eat half their meal for example on one side (left)
- Can affect calculation ability
- Visual field defects are superior optic radiations run. Damage can cause contralateral inferior homonymous quandrantopia
- Receptive dypahsia
- Contralateral anaesthesia
What are the functions of Temporal Lobe?
- Hearing
- Olfaction (olfactory cortex)
- Memory
- Emotion
- Visual pathways projecting through white matter
What are the features of damage to Temporal Lobe?
- Auditory hallucinations may be a feature of temporal lobe lesions
- Olfactory hallucinations or other issues with smell
- Hippocampus is crucial structure for consolidating declarative memories. Damage may lead to amnesia (but theres 2 hippocampus)
- Some pathologies can leads to triggering of memories leading to de ja vu feeling
- Can cause some psychiatric disorders
- Damage can cause a contralateral superior homonymous quadrantanopia due to affecting the inferior optic radiation
What is Cerebral dominance?
Some functions are represented more prominently in one hemisphere
- In 95% of people, the left hemisphere is dominant for language and mathematical/logical functions
- In 95% of people the right hemisphere is dominant for body image, visuospatial awareness, emotion and musical ability
What is the function of the Corpus Callosum when it comes to cerebral dominance?
- Corpus callosum allows the two hemispheres to communicate with one another, meaning we can be thought of as average of two hemispheres
- Destruction of the corpus callosum can cause conditions such as alien hand syndrome and subtle effects on language processing
What is Broca’s area and what can damage to the area lead to?
- Found in inferior lateral frontal lobe involved in production of speech.
- Sits near to mouth/pharynx area of primary motor cortex
- Damage can cause staccato speech, where the patient still understands what’s being said to them so Expressive Aphasia
What is Wernicke’s area and what can damage to the area lead to?
- Found at the parieto-temporal junction
- Sits near to primary auditory cortex in the temporal lobe
- Responsible for the comprehension of speech
- Damage can cause fluent nonsensical speech where the patient does not appear to understand what is being said to them (Receptive Dysphasia)
How are Broca’s area and Wernicke’s Area connected?
-Connected by arcuate fascicles so damage to this white matter pathway cause cause inability to repeat heard words
What is the effect of a Middle cerebral infarct on speech?
-Can cause a dense/global aphasia where both areas are destroyed leading to virtually no verbal language function
What is the pathway for repeating a heard word?
- Auditory cortex hears the word and transmit to Wernicke’s area
- Wernicke’s area interprets the word and sends it to Broca’s area
- Broca’s area transmits the impulses to the motor cortex to form muscular movements
- This allows the words to be spoken
What is the pathway for speaking a written word?
- Visual cortex sees the word and transmits the impulses to Wernicke’s area
- Wernicke’s area interprets the impulse and transmits the impulses to Broca’s area
- Broca’s area transmits the impulses to the motor cortex
- This allows the formation of sound from the mouth
What is the pathway for speaking a thought?
- Impulses form many parts of the brain are transmitted to Wernicke’s area
- Impulses are transmitted from Wernicke’s area to Broca’s area
- Broca’s area interprets these impulses and sends them to the motor cortex to allow the sound to be made by effecting muscle movements
What are the 2 types of memory?
Declarative
Non-declarative memory
What is declarative memory?
Explicit facts which tends to be stored in cerebral cortex
What is non-declarative memory?
Implicit, motor skills and emotions and tends to be stored in subcortical structures (e.g. basal ganglia) and cerebellum
What is short term memory?
-Stored for seconds to minutes as reverberation or echo in cortical circuits
What is long term memory?
-Stored for very long period in the cerebral cortex, cerebellum etc. (up to a lifetime) following consolidation
What is consolidation of memories?
-Converting short term memories into long term memories
What is are the factors influencing consolidation of memory?
- Emotional context
- Rehearsal
- Association
Which part of the brain is involved in consolidating declarative memory?
Hippocampus
Where is the hippocampus found?
-Sits deep in the temporal lobe in the medial edge
What is the role of the hippocampus?
-Oscillator facilitating consolidation of memories in the cortex via its output pathways (primarily the fornix to mammillary bodies to thalamus to cortex)
Where are the inputs to Hippocampus?
Has multimodal inputs from many brain systems
- Visual
- Auditory
- Somatosensory
- Limbic
Good at association stimuli
Describe long term potentiation
- Changes in glutamate receptors in synapses leading to synaptic strengthening
- New physical connections can also form between neurones to further strengthen connections (axonal sprouting)
