Cerebral Cortex Flashcards
What is the cerebral cortex?
How is the cerebral cortex organised and what is it composed of?
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
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?
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
What lies within the deep lateral fissure in the brain and what are its functions?
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)
What are the differences between grey matter and white matter? Where are they found?
What is white matter organised into?
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
What are white matter tracts?
What are the names of the fibres in the white matter tracts and how are they distinguished?
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)
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:
Short = within same lobe
Long = across different lobes
What are the names of the two main commissural fibres and where are they found?
Fill in the missing names below:
Corpus callosum and anterior commissure (more inferiorly placed than the corpus callosum)
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?
Afferent = towards cortex
Efferent = away from cortex
Corona Radiata; converge into the internal capsule (between the thalamus and basal ganglia)
What is the basis for dividing the brain into cortices?
What are the 3 main differences between the primary and secondary cortices?
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
Where are the somatosensory and motor cortices located?
Are they primary or secondary cortices?
Primary somatosensory = parietal lobe
Motor cortex = frontal lobe
Both = primary cortices
What are the 3 main areas in the frontal lobe? Label them on the diagram below and explain their functions:
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)
What are the 2 main areas in the parietal lobe? Fill in the names on the diagram below and explain their functions:
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
What are the 2 main areas in the occipital lobe? Fill in the names on the diagram below and explain their functions:
Primary visual - processes visual info
Visual Association - gives meaning and interpretation of visual input
What are the 2 main areas in the temporal lobe? Fill in the names on the diagram below and explain their functions:
Primary temporal - processes auditory stimuli
Temporal association - gives meaning and interpretation of auditory input
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)
Prefrontal Cortex: attention, adjusting social behaviour, planning, personality expression, decision making
Broca’s Area: language production
Wernicke’s Area: speech production
What are the consequences of frontal lobe lesions?
(HINT: also know this from psychology)
Changes in personality, inappropriate behaviour
e.g. Phineas Gage
What are the consequences of parietal lobe lesions?
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.
What are the consequences of temporal lobe lesions?
(HINT: also know this from psychology)
Inability to recognise (agnosia)
Patient HM - inability to form new memories (anterogade amnesia)
What are the consequences to lesions in Broca’s or Wernicke’s areas?
Broca’s aphasia = poor speech production
Wernicke’s aphasia = poor speech comprehension
What are the consequences of occipital lobe lesions?
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.)
How can cortical function be assessed through imaging?
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
How can cortical function be assessed through encephalography (EG)?
How many stimuli are required to form a brain wave and why?
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
How are the electrodes in EGs placed?
What are the 3 main potentials are observed?
Universal system - electrodes numbered and palced in specific areas
Visual evoked potentials, event-related potentials, evoked potentials
How can we assess the integrity of the sensory pathway?
Why is this relevant clinically?
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)
What is recorded when using somatosensory evoked potentials?
What is the path that should be used when using somatosensory evoked potentials?
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
How can cortical function be assessed via brain stimulation?
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
How is TMS (transcranial magnetic stimulation) used in practice?
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
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?
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
