2.9 Cortical Networks Flashcards
Describe the cerebrum
The cerebrum is the largest part of the brain (taking up 80% of the brain) and is responsible for higher mental functions. It is derived from the telencephalon and is formed of a right and left hemisphere that is connected by the corpus callosum. The 4 lobes of the cerebum are the frontal lobe, occipital lobe, temporal lobe and parietal lobe.
Describe the specificity of the cortex
The cortex has a high degree of specificity, you can map both sensory and motor areas in the cortex to their corresponding specific areas in the body that they control.
How does the complexity of a movement correspond to the brain area
The more complex the movement, the greater the brain area in the motor cortex given towards it.
How does the degree of sensing in the region correspond to the brain area
The more sensing going on in the region, the greater the brain area in the sensory cortex given towards it.
What is the brain ratio associated with cognitive ability
The ratio of frontal lobe to brain. The human brain has the largest ratio.
What on the brain increases the brain surface area
sulci and gyri
What is significant about frontal lobe development in humans
The maturation of the frontal lobe is late, in adolescence there is synaptic primming to lose unessecary synapses. The dorsolateral prefrontal cortex (involved in control of impulses, judgement and decision making) is one of the latest areas to reach adult levels of cortical thickness
Describe the positioning of the frontal lobe
The frontal lobe extends from the central sulcus anteriorly and extends ventrally along the medial and lateral surfaces
Describe the two areas of the cortical motor area
The pre motor cortex and the primary motor cortex. Stimulation in primary motor causes simple movement, but in premotor causes complex movement.
Describe the effects of disturbance in the primary motor cortex and the pre motor cortex
Disturbance to primary motor causes weakness in affected body parts, disturbance to premotor doesn’t cause paralysis but more complex motor deficits
Describe the primary motor cortex
It sends signals via the corticospinal tract with spinal motorneurons that control the limb, hand, finger, trunk and facial movements. It receives input from the prefrontal cortex and cingulate cortex.
What are some areas outside of the motor cortex also concenrned with motor movements
Subcortical areas such as the basal ganglia and cerebellum
Describe the pre motor cortex
The premotor cortex is involved in movement planning/sequencing. It has 2 distinct regions, the supplementary motor area and the lateral pre motor area. The supplementary motor area is located dorsomedially and is more involved in internally generated movement whereas the lateral pre motor area is involved in externally guided movement. The pre motor cortex has many projections to the primary motor cortex and is also directly connected to motor neurons.
What is the most interconnected cortical region
The prefrontal cortex as it plans complex movements so takes in lots of inputs, it is in the perfect position to do it
Describe the pre frontal cortex
A region in the frontal lobe of the brain hat plays a crucial role in high-level cognitive functions and behavior. It has executive function for flexible, goal driven behaviour in response to internal and external cues. It formulates monitors and adapts for planning, filtering, managing delay, flexibility, contingencies and rules. The bottom area of the prefrontal cortex is more associated with personality and motivations.
What can damage to the ventromedial or orbitofrontal areas of the prefrontal cortex cause and what is a famous case study of this.
It can affect normal intellectual abilities, normal long term memory, impulsivity, lack of awareness etc
As seen in the Phinneas Gage case
Give the different effects of schizophrenia on the brain systems
- positive symptoms (things added)- Delusions, hallucinations, thought disorder
- negative symptoms (things taken away)- Decreased motivation, diminished emotional expression
- cognitive defecits- Impairments in attention, executive function, some types of memory
- Sensory abnormalities: Gating disturbances
- Sensorimotor abnormalities: Eye tracking disturbances
- Motor abnormalities: Posturing, impaired coordination
Schizophrenia has a big impact on the prefrontal cortex
Describe the dopaminergic pathways that are involved in schizophrenic symptoms
The mesocortical pathway innervates the dorsolateral PFC and ventromedial PFC. The mesolimbic pathway innervates the striatum from the ventrotegmentum. Mesolimbic overactivity causes the positive symptoms of schizophrenia and mesocortical underactivity causes the negative, cognitive and affective symptoms of schizophrenia
What are the 2 main dopaminergic pathways that are not involved in schizophrenic symptoms
The nigostriatal and tuberoinfundibular pathways
How do d2 dopamine receptor antagonists impact different schizophrenic symptoms.
As they reduce dopaminergic transmission and therefore cause underactivity in the pathways, it is useful for treating the positive symptoms but worsens the negative symptoms
Describe the 2 ways in which schizophrenia impacts glutamatergic transmission
There is a glutamatergic pathway from the prefrontal cortex that synapses onto a GABA interneuron which then inhibits the mesolimbic dopamatergic transmission. This glutamatergic pathway is normally constituatively active. However with schizophrenia, the glutamatergic neurons are suppressed so the mesolimbic dopamatergic transmission can’t be supressed, hence causing positive symptoms.
The glutamatergic pathway also innervates the mesocortical pathway, but without an inhibitory interneuron, hence supression of the glutamatergic pathway also causes supression of mesocortical, hence negative symptoms.
