The cortex and localisation of function Flashcards
What is grey matter?
Thin (6-8mm) folded sheet of grey matter
What are the grooves in the brain?
Sulci (sulcus)
What are the ridges of the brain?
Gyri (gyrus)
What makes up the white matter?
Corpus callosum
Internal capsule
What is the corpus callosum?
Structure that links cortex of two cerebral hemisphere
What is the internal capsule?
Structure that links the cortex with the brain
Why does folding in the brain occur?
Accommodate massive increases in area of cortex
How much does the cortex represent the human brain?
80%
How much does the cortex represent the rat brain?
30%
What is the Paleocortex/Archicortex?
Phylogenetically oldest part of cortex
Olfaction, emotions and memory
What is the Neocortex (new cortex)?
Additional sensory areas (e.g. vision)
More sophisticated motor areas
What do primary areas of the cortex receive?
Input (sensory) or give rise to a direct output (motor)
What is the association cortex?
Most recent, most expanded cortex
Responsible for most complex cognitive functions e.g. speech and language
How much does the association cortex take up in different mammalian brains?
5% cat brain
20% chimp brain
30% human brain
What was Penfield study?
Effects of electrical stimulation of the cortex in conscious patients being prepared for brain surgery
Located a region where stimulation produced muscle twitches
What did Penfield discover?
Mapping between areas of motor cortex and muscles of the body
Somatotopic map
In what way is the motor map distorted?
Face and hands (fine control) have largest representation- motor homunculusAn are where stimulation produced sensations of numbness or tingling
Somatotopic map within stip of sensory cortex
What is the primary somatosensory cortex?
An are where stimulation produced sensations of numbness or tingling
Somatotopic map within stip of sensory cortex
What is the somatotopic map in the sensory cortex like?
Has a greater representation of body parts (tongue, face, hands) with a high degree of sensitivity and spatial discrimination represented by sensory homunculus
What is decussation?
Crossing of pathways from one side to another
Pathways providing connections between primary sensory and motor areas and the periphery are crossed
What is Broca’s area aphasia?
Inability to speak while retaining comprehension of verbal and written instructions
Where is Broca’s area
Specfific region of the brain close to the motor cortex
What is Broca’s areas function?
Thought to produce instructions for co-ordinated movements (of lips, tongue, mouth and larynx) for producing speech
When is the corpus callosum cut?
A commisurectomy is used as a treatment for intractable epilepsy
What are the hemispheric asymmetries for most CNS structures?
Bilateral and symmetrical
What do some cortical functions show
Hemispheric asymmetry
Two hemispheres perform different functions
If an individual is right handed what does that mean?
Superior motor co-ordination of right hand
What did Sperry identify in the 1960s?
Most patients could name objects identified by feel if placed in right hand but not if held in the left
Where is speech predominantly functioning?
On the left hemisphere in 93% of the population
What is the Wada Procedure?
Injection of short-acting anaesthetic into left internal carotid artery
Selectivity anaesthetises left cerebral hemisphere
Produces paralysis and loss of sensation on right side of body
Patients remain conscious
Most (93%) lose the ability to speak
