Cerebral cortex Flashcards
Organisation of grey and white matter of the brain
Grey matter: on the surface of the brain. Nerve cell bodies. (cerebral cortex)
White matter: the circuitry (axons and connections).
Types of fibres cerebral white matter contains
3 types of connections
Fibre relate to the connections
- Association fibres: connect areas within the same hemisphere – local circuitry
- Commissural fibres: connect left hemisphere to right hemisphere
- Projection fibres: connect cortex with lower brain structures (e.g. thalamus), brain stem and spinal cord
Neocortex
Part of the cerebral cortex involved in higher functions
Organisation of neocortex
6 layers, but also cortical columns (basis for topographical organisation- similar neurones connected in the same column)
Layers 1-3- have mainly cortico-cortical connections
Layer 4- receives input from the thalamus
Layers 5 and 6- have connections with subcortical (e.g basal ganglia) , brain stem and spinal cord
Lobes of the neocortex- what primary cortex they contain and its location
Occipital- Primary visual cortex
Parietal- primary somatosensory cortex in post central gyrus
Temporal- auditory cortex in the superior temporal gyrus
Frontal- primary motor cortex- part of the pre-central gyrus
Function fo occipital lobe
Visual association cortex analyses different attributes of visual image in different places. The form & colour is analysed along the ventral pathway; spatial relationships & movement along dorsal pathway.
Injury to occipital lobe
Lesions affect specific aspects of visual perception.
Function of parietal lobe
Posterior parietal association cortex creates spatial map of body in surroundings, from multi-modality information.
Parietal lobe lesion causes
Injury may cause disorientation, inability to read map or understand spatial relationships, apraxia (diifuclty in performing motor functions on command) , hemispatial neglect (only draw half of something).
Function of temporal lobe
Language, object recognition, memory, emotion.
Temporal lobe lesion causes
Injury leads to agnosia (inability to process sensory input) , receptive aphasia (difficulty with language or speech)
Function of frontal lobe
Judgement, foresight, personality, appreciation of self in relation to world
Frontal lobe lesion causes
Lesion leads to deficits in planning and inappropriate behaviour
Difference in primary and association cortices
In primary cortices- function is predictable, organised topographically, left-right symmetry
In association cortices- less predictable function, not organised topographically and left-right symmetry is weak/absent
Association areas
Speech areas: Broca’s area (inferior frontal lobe), Wernicke’s area (junction between parietal/temporal)
These areas are specific, but they are lateralised to the left hemisphere
Anterior to the PMC in the frontal lobe are the motor association areas (pre-motor cortex)
In the parietal cortex, we have parietal association areas
This is where integration occurs of multiple sensory modalities
There are auditory association areas immediately adjacent to the primary auditory cortex
What does a lesion in the visual posterior association area cuase
Prosopagnosia- face blindness (inability to recognise or learn new faces)
Hemispheric specialisation
The left hemisphere is language dominant, the right hemisphere is largely spatial processing.
What impairment occurs to patients born without corpus callosum or who have had callosotomy
This means their hemispheres are divided and are unable to send information to each other
This causes the patient to have impaired processing.
This is shown in the experiment where if an image is shown on the right hand side they are able to say what they saw (since left hemisphere is verbal dominant)
However if shown on left hand side they are unable to say what they saw but are able to draw it (right hemisphere is spatial dominant).
This is due to the dominant activities on either hemisphere
Diffusion tensor imagine (DTI)
DTI measures alignment of water molecules – coincident alignment is taken to mean fibre connectivity
This way, you can build up a fibre network of the brain
We can use DTI in brain tumour patients to show break down of such connections
Transcranial magnetic stimulation
The magnetic field induces an electric current in the cortex, causing neurons to fire. This can be used to test whether a specific brain area is responsible for a function
Transcranial direct current stimulation (TDCS)- and what it could be used to treat
Uses constant, low direct current delivered via electrodes on the head.
This does not directly induce neuronal firing). However, it changes the threshold for decreasing/increasing the firing rate.
Recent research suggests that TDCS could be used to reduce motion sickness by suppressing the area of the cortex associated with processing vestibular information. It may be a potential treatment for vertigo.
PET scan
Shows activity in the brain
And can be used to show injuries to the brain
Has also allows to look at potential us of psychedelic drugs
Magnetoencephalography and Electroencephalography
MEG- measures magnetic fields using a large machine
EEG- measures electric fields using lots of electrodes
Shows activity in the brain
Functional MRI
Get information in vivo about connectivity (particularly in CNS conditions)
This is usually about monitoring blood flow and glucose metabolism
Where there is more glucose and more blood flow, there is probably higher activity
