Cerebral cortex Flashcards
What is the cerebrum?
The cerebrum is the largest part of the brain (80% of the weight of the brain) and consists of two hemispheres. It consists of an outer coating of grey matter (cerebral cortex) which contains an inner mass of white matter.
What is the cerebral cortex?
The cerebral cortex (also known as the cerebral mantle) is comprised of grey matter that covers the cerebral hemispheres. It has an intestinal like appearance with folds containing peaks (gyri) and grooves (sulci). The major peaks and grooves create divisions between the four major lobes of the brain.
What does grey matter consists of?
Cell bodes
Neurons
Dendrites
Glial cells
What does white matter consist of?
Axons specifically myelinated axon tracts. It is the myelination of these axons which cause this white colour.
Why is the cerebral cortex highly convoluted?
Firstly the extent of convolution is proportional to the complexity of the animal as the cerebral cortex is the largest site of neural integration, where processing occurs.
With more convolution, this increases the surface area of grey matter and the amount of processing that can occur.
Which side of the brain controls movement?
The hemispheres control movement on opposite sides of the body. For example the left hemisphere controls movement on the right hand side of the body.
How are the two hemispheres able to interact?
The two hemispheres are able to crosstalk by the corpus callosum which is a fibre tract made of 300 million axons that runs between the centre of the two hemispheres.
Why is it important that the two hemispheres are able to crosstalk?
The two hemispheres are not symmetrical in structure or function.
For example language centres are on the left hand side of the brain and therefore need to communicate through the corpus callosum to the right.
Which higher functions are associated with the cerebral cortex (or cerebrum)?
Evolutionary this is the newest part of the brain and its function includes:
Language
Intellect
Conscious thought
Sensory analysis
Motor initiation
What are the four lobes of the cerebral cortex?
Frontal (front)
Parietal (middle, behind frontal)
Occipital (back)
Temporal (below at the side of the brain)
What are the functions of the occipital lobe and what is contained there to aid this function?
It is important in vision and contains the primary and secondary visual cortex (also called association area).
The primary visual cortex is where information directly from the retina is taken to the brain and visual processing occurs.
Adjacent to the primary visual cortex is the secondary visual cortex where further processing occurs.
What is present within the temporal lobe?
Contains the primary auditory cortex which is the first relay centre for auditory information in the cortex. It is then surrounded by the secondary auditory cortex (also called association area) where further processing occurs.
What is the primary function of the parietal lobe?
It is the location where all sensory information processing from the body occurs. Again contained within the temporal lobe is the primary somatic sensory cortex and the somatic sensory association area.
Which inputs does the somatosensory area/cortex receive?
The somatosensory cortex is responsible for processing all sensory information from the body.
This involves analysis from inputs such as:
-Mechanoreceptors (touch and stretch)
-Thermoreceptors
-Nociceptors (skin, muscle, joints and internal organs.
This information travels via the brainstem and then the thalamus to the somatosensory centre.
Where does the parietal lobe receive information from?
From the opposite side of the body
Explain the concept of somatotrophic organisation.
Sensory information from areas of the brain is allocated to areas of the somatosensory cortex. The area of the cortex devoted to each area of the body is proportional to the amount of information received from that area. For example, a big proportion of the cortex is allocated to the lips and therefore is more sensitive. Areas of the cortex devoted to each part of the body can be mapped on to the sensory homunculus.
Define neuroplasticity.
It is the ability of neural networks in the brain to change through growth and reorganization.
Apply the concept of neuroplasticity to the concept of somatosensory organisation.
The area occupied by parts of the body in the somatosensory cortex, whilst is proportional to input is also use-dependent. This means that if one area of the body experiences an increased or decreased stimulation the size of the devoted area occupied in the brain will change accordingly and therefore is use-dependent. If someone was therefore to experience a limb loss for example of the thumb, neuroplasticity would occur in with a loss of area occupied in the cortex by the thumb whilst area occupied by other parts specifically other fingers would increase, becoming more sensitive.
What happens after information is processed in the primary somatosensory cortex?
The information is then passed on to the association areas where further processing occurs and then to another association area where it is integrated with other sensory inputs and then information from past experiences is considered to build an idea of perception. This decides what the appropriate response shall be.
What is the function of the frontal lobe?
This is mainly associated with motor function with the primary motor cortex which is adjacent to the pre-motor area which is involved in planning and initiation of movement.
What is the function of the motor cortex?
It is responsible for voluntary movement which is located at the back of the frontal lobe adjacent to the central sulcus.
Describe Penfield’s studies relating to the development of the motor homunculus.
Penfield, a neurosurgeon treated patients with severe epilepsy and developed the Montreal procedure in which he destroyed nerve cells within the brain in which the seizure originated. He did this by stimulating the areas of the cortex with electrical probes and observing their reactions. This lead to the development of the motor homunculus where it was mapped, as the somatosensory cortex, which parts of the body occupied which areas of the brain, with large areas allocated to the faces and hands.
Again stimulation on one side of the brain, stimulated the other side of the body.
Was the motor cortex also use-dependent?
Yes again allocation within the cortical space of the motor cortex is also muscle use dependent and again there is neuroplasticity.
What is the remainder of the pre-frontal* cortex allocated to?
Involved in processing motor information
What is the function of the premotor cortex and supplementary motor area in application to the motor cortex?
The primary motor cortex is responsible for sending out signals to the alpha motor neurons, however both the premotor cortex and supplementary motor area are responsible for signalling to the primary motor cortex to co-ordinate these movements.
Aside from the pre-frontal cortex and supplementary area which others input to the motor cortex?
Posterior parietal cortex
Basal ganglia
Thalamus
Cerebellum involved in fine motor control
These are involved in the planning, programming and co-ordination of complex movement
What functions are associated with the pre-frontal area?
Thinking
Decision making
Intellect
Personality resides, damage to this area can cause changes in our personality
What is Broca’s area?
Contained within the frontal area it is responsible for the formation of words.
What is our highest mental function?
Language
Which hemisphere is used in relation to language?
In 90% of the population the left hemisphere is used
How is it usually distinguished the function of each part of the brain?
When damage occurs to a part of the brain, the clinical presentation can be observed in a patient and then you can develop an understanding which part of the brain was responsible to carry out a particular function.
Define aphasias.
Language deficits arising due to brain damage which enabled language centres to be identified which was:
Broca’s area
Wernicke’s area
What is the function of Broca’s area?
Located within the motor cortex, this area is responsible for the control of muscles to enable the articulation of speech.
How would a patient present if damage occurred to Broca’s area?
The patient would be able to understand language however couldn’t articulate a response due to the inability to control the muscles in the correct way.
What is the function of Wernicke’s area?
Located within the parietal cortex, this area is responsible for the comprehension, planning and coherence of language.
How would a patient present if damage occurred to Wernicke’s area?
Would be unable to understand language and although could respond by controlling muscles the response would be incoherent.
Input to Wernicke’s area also includes from the auditory and visual cortex for hearing and reading language and additionally from the somatosensory cortex in the interpretation of brail.
