Lesson 11: Cerebrum Flashcards
What is the difference between the short and long association fibres?
Long association fibres: across distances within the same hemisphere
Short association fibres: in adjacent or nearby gyri
What are 3 important long associations fibres?
Superior longitudinal fasciculus, inferior longitudinal fasciculus, and the uncinate fasciculus
What is the role of the arcuate fibres?
The arcuate fibers connect the Wernicke’s area and the Broca’s area and are part of the superior longitudinal fasciculus
What is the role of the unicate fasciculus?
Connects the frontal lobe and the temporal lobe (deep within the lateral fissure) and is associated with the inferior longitudinal fasciculus
What is the role of the inferior longitudinal fasciculus?
Travels inferior to the core of nuclei, thalamus and basal ganglia.
What is the role of the longitudinal fasciculus?
Collective term for many bundles of fibers travelling from frontal to occipital and curving down to the temporal lobe.
What is important to know about projection fibres?
Most of the motor and sensory pathways go through the “internal capsule”
That area is the major highway for all information heading between the brainstem and the cerebral cortex.
This area is supplied by the striate branches of the middle cerebral artery and is VERY important clinically as a site of stroke.
Levels of functional complexity: what are the 3 levels of processing?
- Primary areas where the sensory information arrives and where the motor instructions are initiated
- Secondary areas that integrate the primary information with the association areas
- Association areas that connects the primary area with diverse areas of the brain
Dominance: what is the dominant hemisphere for most people?
The left cerebral hemisphere is the “dominant hemisphere”
What occurs when there are lesions in a hemisphere?
Lesions of the hemisphere that is opposite to the one responsible for that function will still result in subtle functional losses, usually of quality
- When there is an injury to one hemisphere, the opposite hemisphere may be recruited to support lost functions after injury, but never as effectively
Where is the supplementary motor area?
What do the premotor and other motor association areas form?
The supplementary motor area (SMA) is on the medial side of the frontal lobe is an extension of the pre-motor area.
The pre-motor area and a few other motor association areas, such as the Frontal Eye field, Area 8 can be considered to combine the functions of a secondary motor area and a motor association area
What are the 4 main functions of the frontal lobe?
- Motor
- Executive functions
- Language (left hemisphere)
- Reward (limbic) functions
Frontal Lobe: Where and what does the primary motor area do?
- Anterior to the central sulcus; with secondary and association areas of the premotor, frontal eye field, and supplementary motor area.
- Area 4, initiates voluntary movement with precise and skilled movements, especially to the upper limb
Frontal Lobe: What is the function of the premotor area?
Area 6; involves timing and smoothness of motor skills.
Involved with complex and skilled movements and regulates the responsiveness of the primary motor cortex. There are specific areas within for controlling speech, hand and finger movements and eye-head coordination.
Frontal Lobe: What is the supplementary motor area part of and what is it involved with?
What are the executive functions of the prefrontal cortex?
Part of the premotor area and particularly involved with initiation of movements and speech.
The executive functions in the prefrontal cortex, located in the anterolateral aspect of the frontal lobe include those activities of self-care, decision-making, ethical behaviour, organization and socially responsible behaviour
Frontal Lobe: what is the function of the cingulate gyrus? What do areas 44 and 45 do?
Responsible for functions associated with the limbic system, including memory, olfaction, visceral functions and emotions.
Areas 44 and 45 in the dominant hemisphere are located just anterior to the motor area for the mouth and control expression of language
What is the role of the parietal lobe?
Primarily involved with sensory functions, association of sensory input with other functions, body awareness, proprioception, and calculation
What occurs as a result of lesions to the parietal lobe?
Lesions in either hemisphere may cause the patient to ignore the affected limb, but lesions in the non-dominant hemisphere may result in profound neglect or anasagnosia.
-Lesions in the angular and supramarginal gyrus result in problems with writing (agraphia), reading (alexia or dyslexia) and calculation (acalculi)
In the occipital lobe, where is the actual perception of vision found?
Where is the connection between perception of vision and other areas found?
Where does the meaning of these signals occur?
Actual perception of vision is found in area 17 on either side of the calcarine sulcus. The connection between the perception of vision and other areas occurs in area 18 (on either side of area 17). Meaning of these signals occurs in the association area (on either side of area 18) in area 19.
What is a major function of the temporal lobe? Where does this occur?
Hearing is a major function.
Connections with areas involving hearing occur in the secondary area and the association area produce meaning (Wernicke’s area).
In the temporal lobe, what are the inferior and medial aspects involved with?
Inferior and medial aspects are involved with the limbic system including olfaction.
What is motor speech?
Our ability to use our oral musculature to physically produce speech. When we try to speak, out respiratory, laryngeal, nasopharyngeal, and articulatory muscles must have adequate range of motion (ROM) and strength to perform the movements for speech generation.
What structures does motor speech rely on?
The integrity of the motor cortex, the coritcobulbar tracts (i.e., the UMN) and the cranial nerves (i.e., the LMN). On top of ROM and strength, these muscles must also have the right tone to begin with and the coordination of their movements must be precise in order to get their job done.
- This relies on subcortical (e.g., the basal ganglia) and cerebellar modulation of the motor signal that travels from the cortex down the corticobulbar tracts.
What is the disorder and damages to these speech generation component (i.e., the primary motor cortex, corticobulbar tracts, subcortical motor input, cerebellum, and cranial nerves),
Dysarthria
What is motor planning?
When our body is performing a motor task (e.g., putting on a shirt, combing our hair, writing, swallowing, speaking etc.), it is not the work of just one muscle; a group of muscles must work together to complete the task. Not only do they work together, but also their movements must be planned, sequenced and timed perfectly
What is language?
This refers to our ability to process and use meaning (semantics), speech sounds (phonology) and grammar (morphology and syntax) appropriately to comprehend and express ourselves
Where are language functions housed? What are the most common ones?
Language functions are believed to be housed in the left hemisphere.
The most common ones are probably the Broca’s area and the Wernicke’s area, which are thought to be responsible for expressive language and receptive language respectively.
What is the result of damage to Broca’s/Wernicke’s area?
Damages to these areas produce Broca’s aphasia and Wernicke’s aphasia. The former is characterized by relatively preserved comprehension, agrammatism, significant word-finding difficulties and dysfluent speech, while the latter is characterized by poor comprehension and fluent but non-sensical verbal output.
Strokes: What are they, and what do they result from?
A stroke is the loss of function resulting from a vascular lesion in the cerebrum, or brainstem that impairs blood flow and causes tissue ischemia and possibly cellular death (necrosis).
What are the reasons that strokes can occur? (4)
- Blood flow can be impaired because of a vascular blockage
- Pathology affecting the integrity of the vessel walls leading to hemorrhage.
- Blockage can be due to occlusive plaque within a vessel (as with atherosclerosis), from a blood clot (thrombosis), or from a release of part of a clot (embolis).
- Haemorrhage from the cerebral blood vessel can be due to weakened and subsequently ruptured vessel walls due to aneurysm or from systemic factors such as hypertension.
If a person experiences a stroke, what happens to the tissue?
If they develop an area of necrotic tissue, the areas surrounding the necrosis may suffer partial loss as well, in part due to loss of blood flow, in addition to the effects of not receiving input from necrotic presynaptic neurons.
This partially affected area may recover or there may be some rerouting of information.
What is the function of gyri? How are they organized?
- Gyri, or parts of them operate as modules dedicated to specific cognitive or behavioural functions. They are organized not as individual centers but as parts of interacting networks, interconnecting modules in different regions or lobes of the brain.
What are the three areas the brain is divided into?
Primary motor areas, primary sensory area, and association area.
What is involved in the association cortex?
Heteromodal cortex?
Association cortex: unimodal association cortices (visual and auditory association cortices) and heteromodal Heteromodal cortical areas include the parietal cortex and the prefrontal cortex,
