Cortex Flashcards
What are the three types of fibres in the white matter of the cortex?
- Association fibres - interconection within one hemisphere
- Commissural fibres - interconection between hemispheres
- Projection fibres - : connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord
What is the role of the association fibres?
Connect different areas within the same hemisphere
What is the role of the commissual fibres?
Whicht matter tracts interconnecting the two hemispheres –> biggest being corpus callossum
What are projection fibres in the brain?
connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord
e.g. pyramids
Explain the 6-layered structure of the cortex
Explain the columns in the organisation of the cortex
•More dense vertical connections – basis for topographical organization
•Neurons with similar properties are connected in the same column
What is the difference between neocortex and cortex?
Neocortex is a type of cortex that has 6 laminal layers
Almost all the cortex in humans is neocortex, so they are often used as synonyms
What is a primary cortice?
Areas of cortex where:
- function predictable
- organised topographically
- left-right symmetry
What are the association cortices?
Areas, often around primary cortices where they are
- less predictable in terms of function
- non-topographically organised
- weak/abscent left + right symmetrie
Often interconnection with primary and association for functional sensation/action needed!
What is prospagnosia?
When does this happen?
Lesions of the visual posterior association area
–> inability to recognise faces or learn new faces
What happens when you have a Lesions of the visual posterior association area ?
Prospagnosia –> inability to recognize faces
What is the role of the frontal cortex?
What do lesions in this region lead to?
Frontal cortex:
- involved in decision making, reasoning, inhibition etc,
- In leasion:
- changes in personality
- dishinibition
- agressivity
- sexual inappropritate actions
- impaired concentration span
What is the role of the parietal cortex?
What do lesions in this area lead to?
Posterior parietal association cortex creates a spatial map of the body in surroundings (where the body, different parts are) , from multi-modality information (conjoint sensory information)
Leasions lead to:
- disorientation
- may lead to hemispatial neglect
- inability to read maps or understand spatial relationships
- apraxia
What is hemispatial neglect?
When does it occur?
It occurs when there is damage to the parietal cortex
–> Patient only percieves half of self and objects
What is the role of the temporal cotex?
What do leasions lead to?
Language, object recognition, memory, emotion.
Injury leads to
- agnosia
- receptive aphasia
- anterograde amnesia (no ability to lay down memory)
Explain the inter-hemispheric differences in a brain
Hemispheres often have a specilisation to some degree – >e.g. speech, writing etc.
Explain the possible presentation of a patient with a “split brain”
No interconnection between hemispheres leading to weird findings:
Which imaging modalities can be used to test for lesions in the white matter fibres of the brain?
DTI –> diffusion tensor imaging (form of MRI) perfoming a - tractography
How can you test the brains function in different regions?
- Via stimmulation
- TMS (Transcranial magnetic stimmulation)
- magnetic field causes a current leading to fiering in diffrent areas of the brain
- used to test whether a specific brain area is responsible for a function, e.g. speech
- Transcranial direct current stimulation (TDCS)
- Changes the local excitability of neurons, increasing or decreasing the firing rate –> no direct stimmulaiton of neuron fiering
- TMS (Transcranial magnetic stimmulation)
Explain the way a PET scan works for brain imaging
PET scan –> ligands/ labelled things binding to different parts of the brain
- often used as diagnostic tool
- e.g. metabolism in basal ganglia in Parkinsons decreased –> less binding/uptake
Explain the use of EEG and MEG
Electroencephalography + Magnetoencephalography
- detecting electric currents in brain activity
- very noisi
- normally large number of trials needed to average noise and actually detect reactions in response to stimmulus
Explain the use of an fMRI in brain imaging
Functional magnetic resonance imaging (fMRI)
- measures blood flow to different areas related to their activity
- can see, which parts are active in different situations
What does the anterior comissure connect?
White matter tracts connecting Temporal lobe
