Flashcards in Lesson 11: Cerebrum Deck (86):
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?
1. Primary areas where the sensory information arrives and where the motor instructions are initiated
2. Secondary areas that integrate the primary information with the association areas
3. 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?
2. Executive functions
3. Language (left hemisphere)
4. 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),
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?
Association cortex: unimodal association cortices (visual and auditory association cortices) and heteromodal Heteromodal cortical areas include the parietal cortex and the prefrontal cortex,
What does executive function mean?
Executive function refers to the processes that decide which of the many incoming sensory stimuli should receive attention and in what order and what responses or motor outputs should be activated and in which order
Frontal Lobe: What is part of the precentral gyrus?
The precentral gyrus contains motor cells of the primary motor cortex. This
Frontal Lobe: what is the premotor cortex involved with?
What is anterior to the face area of the motor strip?
Involved in the initiation and planning of skilled motor movements
- Broca area – produces phonemes and words. Damage to this area is Broca’s aphasia, a syndrome of non-fluent speech
What is the function of the superior frontal lobe?
Involved in movement of the eyes and head to the contralateral side.
What does the supplementary motor cortex produce?
Produces complex postures or patterned movements.
What is the function of the dorsolateral frontal lobe?
Critically related to executive functions, and is important for working memory
Frontal lobe: What do the cungulate gyrus/Papez circuit do? Where do their projections travel?
Projections from the hippocampus via the septum and fornix to the mammillary bodies and then to the anterior thalamic nuclei. Projections then go to the cingulate gyrus and then back to hippocampus.
- Important for memory and for elementary limbic functions such as motivation and drive. Also important for experience of pain
What 'areas' does the anterior and inferior parietal lobe contain?
Anterior part contains Brodmann areas 3, 1, 2 which are devoted to sensory function.
Inferior parietal lobule are Brodmann areas 39 and 40 – the angular and supramarginal gyri.
What are 4 deficits associated with lesions of the left inferior parietal lobe?
Right inferior parietal lobe lesions?
Agraphia, acaluclia, right-left confusion, and finger agnosia.
Right inferior parietal lobe lesions produce neglect of the left side of the body.
What are the results of lesions to the right parietal lobe?
Left-side neglect, denial of the presence of a motor deficit and depressing apraxia.
Speech and language are relatively well preserved in patients with right parietal lesions, emotional intonation of speech may be lacking as may the ability to comprehend emotional tone in the speech of others
What is the result of lesions of the primary auditory cortex?
On both sides cause cortical deafness.
What is pure word deafness?
Inability to understand spoken words, with preserved pure tone hearing and recognition of nonverbal sounds
What is the medial temporal lobe connected to and what is its function?
MTL (hippocampus) with connections to thalamus, septal area, and cingulate gyrus of medial frontal lobes are most clearly related to memory
What is: impaired ability to plan and execute skilled motor acts not caused by muscle paralysis, or incoordination, sensory deficits, or incomprehension. When impacting speech, it renders verbal output very effortful and causes articulatory distortions and syllabic disturbance?
(Ideomotor, ideational, limb kinetic, constructional, dressing, oculomotor, gait)
What is: failure to carry out of motor act in response to a verbal command when the patient understands the command and has the motor capacity to perform the same motor act under a different context?
What is: apraxia for objects. Patient is able to name the object but not demonstrate their use. Included to may be the inability to carry out of multi-step activity although each step can be performed individually?
What is: Impaired ability to process language resulting from brain damage.
What is: type of aphasia characterized by relatively preserved auditory comprehension but significant word-finding difficulties and agrammatism, leading to non-fluent or broken verbal output (associated with a lesion in Broca's area +/- in the premotor cortex)?
What is: type of aphasia where auditory comprehension is significantly impaired and verbal output appears nonsensical despite relatively preserved grammatical structure and fluency (associated with a lesion in the posterior two thirds of the left superior temporal gyrus)?
What is: type of aphasia characterized by profound impairment with both comprehension and expression (lesion usually involves a large area of the lateral surface of the left hemisphere, spanning the frontal, temporal and parietal lobe, including both Broca's and Wernicke's areas)?
What is: type of aphasia characterized by relatively preserved auditory comprehension and spontaneous verbal output but difficulty in repetition. Word-finding difficulties may also be present. This is not a common type of aphasia (involves lesions in the "arcuate fibres" connecting Broca's and Wernicke's areas)?
What is: lesions that do not affect the primary language cortex or the circuit from Wernicke's to Broca's areas but rather other areas of the brain that project to the language cortex?
(Can be motor or sensory, or mixed)
What is: condition in which naming/word-finding is the most impacted language function?
What is: acquired progressive impairment of intellectual functions caused by brain damage?
(fluent and non-fluent forms)
What is: disorders of motor speech that result from central or peripheral disturbances of muscular control?
What is: difficulty in swallowing?
What is: impairment with reading comprehension. This is not to be confused with congenital/developmental dyslexia observed in children, as the mechanisms are not entirely the same?
(Can bee deep, phonologic, or surface)
What is: impaired ability to generate written expression. Again, must be considered separately from dysgraphia in children?
(Divided into phonologic and lexical types)
What is: acquired impairment in recognizing objects while the modalities of sensation are normally functioning?
What is: failure to recognize one's disease, specifically the denial of paralysis of the affected limb. (Occurs in the non-dominant hemisphere, and may be associated with sensory loss but is not caused by sensory loss). This is not "denial" which is a conscious process but a physiological syndrome of inability to acknowledge the presence of illness?
What is: complete disregard of the left side of the body due to a deficit in body scheme, associated with lesion in the non-dominant hemisphere in the association area of the parietal lobe. (Occurs in the non-dominant hemisphere, and may be associated with sensory loss but is not caused by sensory loss)?
Spatial or left-side neglect
What is: seen in Parkinson disease, associated with decreased and monotonous loudness and pitch, occasional rushes of syllables, occasional pauses, and some imprecisely articulated consonants?
What is: seen in chorea (including Huntington) characterized by variable rate, excessive variation in loudness and timing and distorted vowels/
What is: speech is usually dysarthric and nonfluent, with mild deficits of repetition and comprehension. Lesions of dominant thalamus produce fluent aphasia with paraphasic error but with relatively spared auditory comprehension; may result in putting the language areas to sleep?
What is: Deficit of fine motor acts involving only one limb?
What is: failure to identify faces, patient cannot recognize family members or friends, though they can describe features such as hair colour, or accessories? .
(subtype of agnosia)
What are some dementias secondary to systemic diseases?
- Toxic disorders include effects of chemical, heavy metals, alcohol and drugs
- Wernicke-Korsakoff syndrome
- Nutritional cause of dementia is vitamin B12
- Infections – meningitis, viral encephalitis, AIDS
- Other causes – strokes
What are neurologic diseases associated with dementia?
Normal pressure hydrocephalus and basal ganglia diseases are most common
What are some primary degenerative dementias?
- AD most common
- Pick disease
- Semantic dementia
- Creutzfeldt-Jakob disease
What is a traumatic brain injury?
An acute blow to the head may cause instantaneous loss of consciousness and a brief period of retrograde amnesia, such that the patient does not remember the blow that cause the loss of consciousness
What is the function of cortical white matter?
- Myelinated fibre form the medullary core of the brain and account for al inter- (between hemispheres) and intrahemispheric (within a hemisphere) axonal connectivity.
- The interconnecting fibres keep all brain areas informed of information processes, decisions made, steps undertaken and actions performed.
Cortical White Matter: What info do the projection fibres carry? Where do they project?
- Carry sensory and motor information, travel vertically to connect the cortex with the brainstem and spinal cord structures.
- Project through corona radiate and coalesce as a large fibre bundle in the internal capsule
Cortical White Matter: Where are the association fibres? What do they do?
- Are confined within the hemisphere.
- Some are short and connect adjacent gyri, whereas some are long and connect distant cortical areas
- Provide efficient bidirectional channels for communication among cortical areas within each hemisphere.
Cortical White Matter: Where do the commissural fibres exist? What do they do? What are the parts?
- Run horizontally and connect the corresponding cortical areas in both cerebral hemispheres.
- Corpus callosum connect the corresponding cortical areas in both hemispheres
- Has 4 parts – rostrum, genu, body and splenium
- Fibers of corpus callosum allow each hemisphere to access the memory traces, experiences, and unique learning abilities of the contralateral hemisphere
Anterior Cerebral Artery: Where does it travel in the brain?
What do some of the terminal branches connect to?
What is the watershed area?
- Travels rostrally in the interhemispheric fissure along the midsagittal surface of the brain.
-Terminal branches cross over to the lateral cortical surface and develop anastomosing continuity with the branches of the MCA in the watershed areas, where the distribution of major cerebral arteries overlaps
- Watershed area is located at the end of arterial distribution and is most affected in the case of critical low cerebral blood flow. This region can also serve as the point of anastomosis
What happens when there is an interruption of blood circulation to the ACA?
- Usually results in decreased blood supply to midsagittal extension of the sensory and motor cortices, causing sensory loss and paralysis in the legs, feet and toes
Middle Cerebral Artery: Where does it travel in the brain?
What does it do?
- Is direct continuation of the internal carotid artery. After leaving circle of Willis, it runs laterally and emerges through the sylvian fissure on lateral brain surface.
- Branches supply blood to the entire lateral surface of the brain – speech, language and sensorimotor areas.
What happens when there is an impaired vascular circulation involving the MCA?
Results in contralateral hemiplegia and impaired sensory functions
Posterior Cerebral Artery: Where does it travel? What do the end branches connect with? What would an occlusion cause in the PCA?
-Two: each curves along the inferior brain surface to supply blood to the anterior and inferior temporal lobe. - End branches of artery also cross over to the lateral surface and anastomose in watershed region with the terminal branches of the MCA
- Occlusion results in homonymous hemianopsia
What are the central arteries and what areas of the brain to they penetrate? How do they facilitate?
- Branches that arise either from the proximal portions of the cortical arteries or from the circle of Willis, and they penetrate the inferior surface of the brain
- Overlapping blood supply facilitates the development of anastomotic channels in response to occlusive or ischemic vascular problems
Where do the central arteries supply blood to?
Thalamus, hypothalamus, caudate nucleus, putamen, globus pallidus, internal capsule, choroid plexus