Cerebral Cortex Flashcards
What is the general arrangement of white and grey matter in the cortex?
Grey matter ribbon around outside
White matter within
What are the three types of fibre that make up white matter?
Association - Within hemisphere
Commisural - Across hemisphere (E.g Corpus callosum, ant commisural and post commisural - join hippcampi)
Projection - to lower brain structures (E.g Corticospinal tract)
How many cortical layers of grey matter are there in the neocortex? What are they?
6 layers
1-3 Cortico-cortical connection
4 Thalalmic input (Larger cells)
5-6 Subcortical, brain stem and spinal cord input (Extremely large pyramidal cells e.g Betz in precentral gyrus layer 5)
What does cortical layer 1 contain in abundance?
Neutropil – an area composed mostly of unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies
What type of neurone is found in layers 4 and 5?
4= Stellate neurones
5= Pyramidal neurones
What are Brodmann’s areas?
42 different areas in the cortex classified based on differences seen in the 6 cortical layers
Describe the vertical arrangement of the cortex.
Columnar arrangement/laminal structure
Denser vertical connection - basis for topography
Similar property neurones connected in same column
Where are the primary cortices located?
Primary motor - precentral gyrus (frontal)
Primary sensory - Post central gyrus (parietal)
Olfactory cortex - temporal lobe
Gustatory cortex (taste) - Insula, Inf frontal
Visual cortex - occipital lobe
Auditory cortex - Superior temporal
(Symmetry observed across hemispheres)
Where are the association cortices located?
Premotor cortex - frontal, skeletal muscle movement
Wernicke’s area - post sup temporal gyrus, language
Brocha’s area - inf frontal gyrus (usually left) , speech
Auditory association area - Sup Temporal
Sensory association area - parietal, info from viscera
Prefrontal association area - frontal, co-ordinates infomation
Visual association areas - Movement, colour, facial recognition etc
(Weak or absent symmetry)
What are the two parts of the visual association cortex and what are they responsible for?
Dorsal Pathway – ‘Where Pathway’ responsible for interpretation of spatial relationships and movements
Ventral Pathway – ‘What pathway’ responsible for form and colour
What is the role of the posterior parietal association cortex? What happens in injury?
It creates a SPATIAL MAP of the body in its surroundings from multi-modality information
Injury would lead to disorientation, inability to read a map or understand spatial relationships apraxia and hemispatial neglect
Define apraxia.
Inability to make skilled movements with accuracy
What is the temporal association cortex responsible for? What happens in injury?
Language
Object Recognition
Memory
Emotions
Injury results in agnosia (inability for the brain to interpret sensory information although it is correctly received) and receptive aphasia (unable to understand language in the spoken or written forms)
What are the consequences of visual association cortex (fusiform gyrus) lesions?
Prosopagnosia – inability to recognise faces
What is the role of the frontal lobe? What happens in injury?
Executive functions e.g. planning, judgement, foresight, personality
In injury (E.G Prefrontal lobotomy) change in personality observed. Inappropriate behaviour, lack of ability to remember and relate things over time. Attention span and ability to concentrate are diminished
What two areas does the prefrontal cortex receive massive inputs from?
Sensory association cortex (somatosensory, visual and auditory)
Dorsomedial Nucleus of the thalamus
NOTE: lesion of the dorsomedial nucleus will have similar consequences to prefrontal lobotomy
If you give someone with a unilateral parietal lobe lesion something to draw, what will you expect them to do?
Hemispatial neglect – they will only draw half of it
What effect do temporal cortex lesions have on memory?
Impaired short-term memory. They are effectively trapped in a 30 second window of memory
What is a callosotomy?
A palliative procedure used for the treatment of seizures. The corpus callosum is key for the interhemispheric spread of epileptic activity
Leads to very subtle unilateral defects
State a type of imaging that uses the movement of water molecules in the brain to infer the underlying structure of white matter.
Diffusion Tensor Imaging – Tractography
State two types of brain stimulation testing and what it can be used for.
Transcranial Magnetic Stimulation (TMS)
Magnetic field induces current in cortex, This is method of focally stimulating different areas of the cortex and testing what each area is responsible for.
Transcranial Direct Current Stimulation (TDCS)
This changes the excitability of neurones but does NOT directly induce neuronal firing
Anode = increases neuronal excitability
Cathode = decreases neuronal excitability
TDCS could be used to reduce motion sickness by suppressing the area of the cortex associated with perceiving vestibular information
Describe and explain how PET scans work. What can it be used for?
A radioactive tracer is attached to a molecule to locate areas of the brain where that molecule is being absorbed The tracer emits positrons, which are then detected by the receptors It can be used in Parkinson’s disease to see the uptake of dopamine precursors by dopaminergic neurones
What is the difference between MEGs and EEGs?
MEGs = magnetoencephalography – measures magnetic fields EEGs = electroencephalography – measures electric fields
(Both have ‘noisy signals’ so repeats are needed to try and pick out the differences between repeats)
What is fMRI?
Function MRI It detects changes in blood flow in the brain It relies on the fact that blood flow in the brain and neuronal activity are coupled – more active parts of the brain require increased blood flow.
Which areas of the brain become more active when participants imagine positive events?
Amygdala
Rostral anterior
cingulate cortex
