1B cortical organisation and function Flashcards
What is the cerebral cortex?
- Covers entire surface of brain
- Together with the deep nuclei, it contains the grey matter
- Highly folded with gyri and sulci
- Organised into lobes
How is the cortex organised microscopically?
- 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
What is the cytoarchitecture of the cortex?
- 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)
What are the lobes of the cortex?
- Frontal
- Parietal
- Temporal
- Occipital
What is the function of the frontal lobe?
- Regulating and initiating motor function
- Cognitive functions (executive functions like planning)
- Language
- Attention
- Memory
What is the function of the parietal lobe?
- Sensation- touch, pain
- Sensory aspects of language
- Spatial orientation
- Self-perception
What is the function of the temporal lobe?
- Processing auditory information
- Emotions
- Memories
What is the function of the occipital lobe?
Processing and interpreting visual information
What is the limbic lobe made up of?
- Amygdala
- Hippocampus
- Mamillary body
- Cingulate gyrus
What functions is the limbic lobe responsible for?
- Learning
- Emotion
- Reward
- Motivation
- Memory
What is the insular cortex and what is its function?
- Lies deep within the lateral fissure
- Concerned with:
- visceral sensations
- autonomic control
- interoception
- auditory processing
- visual-vestibular integration
What is grey and white matter?
- Grey matter- neuronal cell bodies and glial cells- around 85 bil each
- White matter- myelinated neuronal axons arranged in tracts
What do white matter tracts do and what types are there?
Connect cortical areas.
There are three types:
- Association fibres
- Commissural fibres
- Projection fibres
What do association fibres do?
Connect areas within the same hemisphere- there are short and long fibres
What does the superior longitudinal fasciculus connect?
Frontal and and occipital lobes (pink)
What does the arcuate fasciculus connect?
Frontal and temporal lobes (purple)
What does the inferior longitudinal fasciculus connect?
Temporal and occipital lobes (blue)
What does the uncinate fasciculus connect?
Frontal and temporal lobes (orange)
What do commissural fibres do?
Connect homologous structure in left and right hemispheres
What are these commissural fibres called?
The corpus callosum can be disconnected in patients with epilepsy to treat it
What do projection fibres do?
- 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
What do the primary/secondary cortices in the motor area of frontal lobe do?
- 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)
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
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
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
What are some other association areas?
- Prefrontal cortex
- Broca’s area
- Wernicke’s area
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)
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
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
What is diffusion tensor imaging (DTI)?
Based on diffusion of water molecules
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
What do somatosensory evoked potentials help us measure?
Can see nerve degradation and which point it’s happened
