Language and Disconnect Syndromes: Gondre-Lewis Flashcards
Review of the Neocortical Structure
the layers connect different cells to different parts
-Each layer has a distinctive pattern of connections
Where do thalamic inputs primarily go to?
layer IV of primary cortex
Outputs to subcortical structures come from where?
pyramidal cells in layer V
Outputs to other cortical areas come from where?
layer III
Layers II and III are for what?
intra and inter hemispheric connections
What is area 22? 39 and 40?
Wernicke’s area (in temporal and parietal lobe)
on the left hemisphere
What is area 44 and 45?
Broca’s area (in frontal lobe)
Primary sensory and motor areas get major input from where? Where does the output of the primary area go to?
Primary sensory and motor areas get major input from thalamic relay nuclei.
The output of the primary area is primarily to association cortex.
These association cortex areas help us to make sense of the sensory and motor input.
As processing progresses, association areas may be multimodal.
What is important about the superior longitudinal fasciculus association fibers?
- part of it is a group of axons called the arcuate fasciculus
- those are axon bundles that connects the Wernicke’s to Broca’s area
Layer 3 in right brain communicating with layer 3 in left brain is achieved through what type of fibers?
commissural fibers
What is very involved in terms of transmitting information from your less dominant side to your dominant language area?
corpus callosum
What are the functional regions of the corpus callosum?
splenium: connects the visual cortices to one another
- auditory region is in front of the splenium
- postcentral gyrus region in front of auditory region
- precentral gyrus in front of postcentral gyrus
anterior commissure is responsible for connecting the left and right temporal, hippocampal, and olfactory sides;
these are all involved in the expression of language from these several modalities
What is the lateralization of Broca’s and Wernicke’s?
- they do not have counterparts on the right side of brain; only found in the left side of brain
- they are different functions of the equivalent region on the right side
What is the splenium of the corpus callosum responsible for in terms of interhemispheric connections?
occipital lobe, areas of 17/18 representing vertical midline
What is the posterior body of the corpus callosum responsible for in terms of interhemispheric connections?
posterior temporal lobes (including auditory)
What is the mid body of the corpus callosum responsible for in terms of interhemispheric connections?
Primary somatosensory cortex, except for hand and foot areas
postcentral gyrus
What is the anterior body of the corpus callosum responsible for in terms of interhemispheric connections?
Primary and association motor areas, except for hands and feet
(precentral gyrus)
What is the genu of the corpus callosum responsible for in terms of interhemispheric connections?
rostral frontal lobe
What is the anterior commissure responsible for in terms of interhemispheric connections?
anterior and inferior temporal lobes (olfactory)
What are functions that are lateralized in the brain?
language: a system of arbitrary symbols, sounds or gestures used for communication, and the grammatical rules used to manipulate them.
praxis: fine motor functions in terms of expression
attention
lateralization meaning there is no contralateral counterpart
What is the difference between language and speech?
language: a system of arbitrary symbols, sounds, or gestures used for communication, and the grammatical rules used to manipulate them
speech: mechanical process required for vocalization
What is dysarthria?
impaired speech due to muscular problems
muscles in Brocas still have capability to move
What is aphasia?
disorder in the reception or expression of language, although sensory and motor systems are intact
inability to express oneself in their language
you know what you want to say but you can’t get the words ti say them or express yourself (nto a physical problem with your lips)
What is paraphasia?
incorrect use of grammar
What is alexia?
- inability to read
- inability to comprehend writing, although vision is intact.
What is agraphia?
inability to write, although motor systems are intact
Damage to Broca’s area produces Broca’s aphasia which is what?
motor or expressive aphasia; impaired ability to produce language
Patient IS aware of deficit and is frustrated.
Repetition is poor because of poor fluency and inability to use function words.
Individuals with this aphasia can use nouns and verbs haltingly but not articles, pronouns, conjunctions (function words)
No difficulty in comprehension of language unless there is complicated grammar
Damage to Wernicke’s area produces Wernicke’s aphasia which is what?
sensory or receptive aphasia; impaired ability to understand spoken language
Patients have difficulty in comprehending spoken language.
Cannot carry out simple commands. Cannot repeat.
Speech sounds fluent and grammatical, but doesn’t make sense.
Writing is also garbled.
Patient is UNAWARE of deficit, and may be hostile.
What area is lesioned for Broca’s aphasia?
area 44 and surrounding areas supplied by the upper division of middle cerebral artery: surrounding cortex and underlying white matter
What area is lesioned for Wernicke’s aphasia?
area 22 but also surrounding areas supplied by the middle temporal branch of the middle cerebral artery
larger lesion extending posteriorly into angular gyrus will affect reading as well
What is the major artery that impacts language?
middle cerebral artery
What is global aphasia?
a blockage of the ENTIRE middle cerebral artery
you cannot understand, produce, or repeat speech
Which division of middle cerebral artery supplies Broca’s?
superior division
if lesioned would result in a motor aphasia
Which division of middle cerebral artery supplies Wernicke’s?
inferior division
if lesioned would result in a sensory aphasia
If the left middle cerebral artery is blocked, but the territories of the middle cerebral artery is more than just language. Can you hear still?
you have bilateral projections you can hear from the right side of brain
you cannot speak what you hear because the info needs to cross over and be represented in the language area on your dominant side
If you have hypoxia or some sort of cardiac insufficiency what would be impacted? What is transcortical aphasia?
prolonged hypoxia of watershed regions leaves language areas intact but isolated from the rest of the cortex
isolation of speech areas due to a lack of blood flow to watershed regions
you cannot connect with other parts of the cortex
no spontaneous speech; patient can only repeat, echo-lik, what has been spoken
Arcuate fasciculus is part of what fasciculus?
longitudinal fasciculus
Arcuate fasciculus is located deep to the gray matter
What is conduction aphasia?
normal fluency, normal comprehension, but repetition is impaired due to lesion of arcuate fasciculus
Repetition: Poor, because the direct, fast pathway between comprehension (Wernicke’s and speech production (Broca’s) is severed. Nevertheless, patients can substitute for this deficit by substituting for the repeated word long descriptions of it.
flour: the item you use to make cakes fluffy
not due to blood flow problem but rather tumor or trauma compressing on the fiber bundle, etc., because it is not like a localized defect around the watershed region
What are symptoms of pure word deafness?
patient can read and write normally, produce normal speech, but cannot understand or repeat spoken language
Lesions of what can produce pure word deafness?
destruction of auditory association cortex (planum temporale—junction between temporal and parietal lobe) and white matter underlying it, which would carry callosal fibers from non-dominant side
planum temporale is a fiber bundle connecting the primary auditory area with the rest of the parietal areas
Your communication of what you heard onto Wernicke’s area to make sense of speech is impaired
If there is unilateral damage to the transverse temporal gyrus (Heschl’s gyrus, primary auditory cortex), would there be a deficit?
you would not have pure word deafness
because you would be able to hear (because contralateral is working) and you would be able to process it as language (because planum temporale is intact–it’s just unilateral damage)
What is the function of the non-dominant hemisphere?
- even though it doesn’t process language it is responsible for intonation prosody
- involved in the coloring and emotional language
- it cannot speak but can read and understand numbers, letters, and short words, as long as the required response is nonverbal
What would result from lesion to the non-dominant language hemisphere?
result in the loss of prosody: the normal rhythm, stress, and tonal variation of speech; emotional tone
(think of the many ways “I am” could be interpreted through different tones)
What is praxis?
skilled motor formulation
Which side is responsible for praxis?
the dominant hemisphere parietal lobe because there are extensive connections with the premotor cortex on the contralateral side
What results from damage to the dominant hemisphere parietal lobe?
bilateral apraxia
the patient cannot follow instructions if the dominant side is impacted
How do you test for apraxia?
ask the patient to carry out an imaginary action, such as saluting the flag, or lighting and blowing out a match
although the patient has intact motor skills, and can perform the action spontaneously, he cannot do so in response to instruction
Which side controls attention?
attention is controlled by your nondominant area (usually right) and will produce a contralateral projection
non-dominant hemisphere parietal lobe directs attention to both sides
What occurs with lesions to the non-dominant hemisphere in regards to attention?
damage to this area produces contralateral neglect syndrome: inability to attend to objects, or even one’s own body, in a portion of space
What results from lesions to the corpus callosum in regards to language areas?
speech and language areas (primarily in the left hemisphere) impacted as a result of disconnection of the axons from one hemisphere to another (corpus callosum)
the patient is able to pick out the named object only using touch but they cannot see the object
the object in the left visual field is sent to the right visual cortex, however information cannot be relayed to the left visual cortex due to section of the corpus callosum and thus cannot be sent to Broca’s area thereafter and thus patient cannot say “I’m picking up the ball.” instead they say “I don’t see anything.”
the right side of the brain is controlling the left hand
What could one do to the corpus callosum to alleviate epilepsy?
there can be surgical sections of the corpus callosum to control epilepsy
What occurs with lesions to the left visual cortex and parts of the splenium?
you have contralateral hemianopsia
you cannot see because the visual cortex is impacted
you cannot read as well because even though you can see in the left visual cortex, reading needs to cross over to the dominant side
but you can write because the parts of the brain that connect the motor regions are fine
What occurs with lesion of the dominant occipital cortex extending to the splenium of the corpus callosum, usually from an infarct of the posterior cerebral artery?
alexia without agraphia
Produces right hemianopia, but also inability to read, since information from the left visual field, thus right visual cortex cannot cross to the language centers due to lesion in the left visual cortex.
What happens if the splenium is damaged?
hemialexia of the left visual field
not blind
you cannot read on one side (you have hemi-alexia of the left visual field)
you’re right visual cortex cannot send information to your left visual cortex to send to your language area in the left hemisphere due to damaged splenium
only splenium is damaged, so patient cannot read in the left visual field
your right visual field recorded on your left visual cortex can still talk to your language areas on your left
What occurs with lesions to the pre-motor areas of the dominant hemisphere?
the corpus callosum fibers to the opposite hemisphere is impacted and thus would cause dysfunction of the right hand but also cause apraxia of the left hand because praxia is located in the dominant (left) hemisphere
Where are the language areas located?
- Located on left in 95% of right-handers and 70% of left-handers.
- Since 90% of people are right-handed, left hemisphere is dominant for 93%.
- Left-handers only may sometimes have bilateral representation.
- Also used for early sign language or second language, though later-learned languages are segregated.
There is LATERALIZATION of what functions in the brain?
praxia, attention, language
What is the result of lesions to the corpus callosum specifically in the connections between pre-motor areas and not in the premotor areas themselves?
apraxia of the left hand but right hand is normal
left hand is controlled by the right brain but the right hand is controlled by the left hand
Lesions to the body of the corpus callosum can result in patients not being able to name objects held in the left hand, but can draw or select that object from a group. Why?
- the body of the corpus callosum disconnects somatosensory cortex from speech areas thus resulting in tactile aphasia of left hand
- you will be able to feel what it is but you cannot say what it is
