Aphasia: Difficulty in producing or comprehending speech not produced by deafness or a simple motor deficit; caused by brain damage.
Verbal behavior is lateralized on the left side of brain hemisphere= speech comprehension and production.
RH involved in prosody: The normal rhythm and stress found in speech.
Broca’s Aphasia: Damage to inferior left frontal lobe causes the inability to speak. Difficulty producing function words which are prepositions such as a, the, some; but, they are able to say content words which include nouns, verbs, adjectives.
- Review table and understand all conditions.
- Broca’s Aphasia: Can’t say function words but can say content words. - Damage to Broca’s area causes: Agrammatism, anomia, and articulation difficulties. - Agrammatism: Difficulty comprehending or employing grammatical devices, such as verb endings “ed”.
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- Wernicke’s Area: Located in the superior temporal gyrus of the L hemisphere. Damage causes poor speech comprehension and production of meaningless speech. - This person uses function words but not content words that make sense. - Unaware of their deficit.
- Memories of the sequences of sounds that constitute words.
- Wernicke’s Patients suffer from: recognition of spoken words, comprehension of the meaning of words, and the ability to convert thoughts into words.
- Couldn’t tell which picture showed the horse was kicking the cow- problem with agrammatism (speech comprehension) in broca patients. Don't forget about the age old question of Who is paul of tarsus?
- Anomia: Difficulty in finding (remembering) the appropriate word to describe an object, action, or attribute.
- Difficulty with articulation (apraxia of speech): Broca patients mispronounce words often altering the sequence of sounds= damage caused in left precentral gyrus of insula.
- Apraxia of speech: I mpairment in the ability to program movements of the tongue, lips, and throat that is required to produce proper sequence of speech sounds. - TOT is also found to be activated in the left precentral gyrus of insula
- Pure Word Deafness: Cannot understand speech- left temporal lobe. But they can comprehend words, write, read people’s lips.
- Anterior superior temporal gyrus important for intelligible speech.
- Superior temporal lobe: Speech sounds.
- Pure word deafness caused by: disruption of auditory input or any damage to the superior temporal lobe.
- Temporal (auditory) and frontal (motor) cortical language areas were activated when saw lip movements and tongue movements.
- Mirror neurons play a role in speech comprehension.
- Posterior Language Area: Interchanges information between the auditory representation of words and the meanings of these words. Don't forget about the age old question of Who is the target audience of newspapers?
- Damage to this area causes Transcortical Sensory Aphasia: Can repeat what other people say to them (can recognize words), but they cannot comprehend the meaning of what they hear and repeat, nor can they produce meaningful speech of their own. Patients can’t comprehend words (don’t understand what they are saying). - Wernicke’s is different because these patients can’t repeat words.
- How we hear a familiar word and understand its meaning: First we recognize the sequence of sounds that make up the word by finding the auditory entry for the word in our dictionary located in wernicke’s area. Next, the memories that make up the meaning of the word must be activated (posterior language area).
- Right superior temporal cortex: Important for comprehension of metaphors.
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- Arcuate Fasciculus: Bundle of axons that connects the Wernicke’s area with Broca’s area; damage causes conduction aphasia. This area is important for conveying information about the sounds of words but not their meanings.
- Conduction Aphasia: Meaningful, fluent speech and good comprehension but very poor repetition if the words are nonwords and have no meaning.
- Example: They can repeat back bicycle, hippopotamus, but not Blaynge.
- Direct pathway through arcuate fasciculus conveys speech sounds from W to B area. Use this pathway to repeat unfamiliar words or when trying to repeat a nonword. - Indirect pathway between the posterior language area and B area is based on the meaning of words.
- Anterior pathway: Connects B area with the inferior parietal cortex. Damage causes conduction aphasia- direct.
- Posterior pathway: Connects W area with the inferior parietal cortex. Damage causes comprehension impairment but can repeat speech (transcortical sensory aphasia)- indirect.
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- Anomic Aphasia: They are fluent and grammatical, comprehension great, but they have circumlocutions: Difficulty finding the appropriate words.
- When you read words bite slap kick activation in the motor cortex that controlled the relevant part of the body.
- Comprehension of speech includes a flow of information from W area to the posterior language area to various sensory and motor association cortex.
- Mirror neurons located primary motor cortex.
- Broca’s area is active when seeing or imitating hand finger movements because mirror neurons located here.
Figure 14.18- Links between hand and mouth
- Amount of activity codes the amplitude of the thought you are having. - When experimenter grasped a large object, the S opened their mouths more and said the syllable more loudly- states that the region of the brain that controls grasping is also involved in controlling speech movements. We also discuss several other topics like Who had an important role in the development of the radio?
- Normal and deaf when rhyming words. In fMRI scans, pattern of activity between two sides are exactly the same whether you are hearing. Activation is not related whether you are actually hearing the sounds- whether you are hearing or not hearing.
- Right side becomes active when engaging in prosody (pattern/rhythm of speaking). - Deaf and normal humans have activity in LH when language is involved. For example: When a hearing person and deaf person look at written words and asked to determine if they rhyme, Broca’s area shows increased activation for both.
- Prosody- right hemisphere active for pattern for speech.
- People with fluent aphasias and Wernicke’s aphasia have normal prosody. - Broca’s aphasia have bad prosody.
- Phonic Agnosia: Right anterior of superior temporal cortex. Inability to recognize people’s voices.
- Person who is stuttering- larger part of brain is active compared to a fluent (normal speaker using only small part of brain) in Broca’s area and the insula.
- If give stutters some training, increased activation was seen in the temporal lobe.
Figure 14.23- Letter from a person
- Broca’s Aphasia: Difficulty speaking well constructed coherent sentences but does have meaningful words in speech, these people also write very poorly.
- Wernicke’s: Reading problems, they can read but don’t understand. Not aware that they have language problem.
- Pure Alexia: Can write but not read (aka pure word blindness or Alexia without agraphia).
- Right visual cortex is seeing left visual field and vice versa and communicate via corpus callosum in normal people.
- Pure Alexia: Left cortical area is getting info from R visual field but damaged so it is not getting a good copy of what is being presented in the visual field. COnnection of corpus callosum is damaged so R hemisphere cannot communicate with L hemisphere.
- Info from left visual field enters R visual cortex, passes info via corpus callosum to L visual cortex where VWFA , then info is sent to speech mechanisms in L frontal lobe, thus this person can read information aloud, but people with pure alexia have a lesion on corpus callosum therefore info cannot be passed and can’t be read.
- Person with MS- demyelination of axons. If look at spinal column you see a lot of scar tissue.
- Splenium of the corpus callosum
- Acquired dyslexia from brain injury.
- See word and goes down two pathways whole-word recognition and letter recognition. - Letter recognition: Make words out of letters- used for unfamiliar words. - Whole-word recognition: Used for familiar words.
- Surface dyslexia: Damage to whole-word recognition (word form dyslexia). Have difficulty pronouncing words but understand the meaning.
- Damage is located in ventral temporal lobe= VWFM (visual word form area). - Takes time to read things, can’t skim.
- VWFM is in the ventral stream- important for whole-word recognition.
- Phonological Dyslexia- damage in temporoparietal cortex; phonetic coding (sounds of letters). Cannot sound words out. Can say familiar words fine because they don’t need to sound them out, but have difficulty with unfamiliar words
- Letter recognition= temporoparietal cortex.
- Difficulty pronouncing nonwords and new words.
- Can recognize whole words they are familiar with.
- Deep arcuate fasciculus sends sounds of language area to broca’s area. - Dorsal stream: Phonological reading.
- Ventral Stream: Whole-word reading.
- Hearing and reading have similar area activated- processing is the same.
- Our VWFA can recognize a word even if it closely resembles another word such as car and ear.
- VWFA can recognize whole words with different shapes.
- Presented individual stimuli to S and looked how brains lit up.
- VWFA only lit up to actual words.
- Red is greatest activation. When present whole-words that are recognizable it is very activated.
- Less activity in words that are not familiar.
- Broca’s and VWFA both light up.
- Damage to VWFA produces surface dyslexia (impairment of whole-word reading).
- Post surgery presented words again and person still reacts to pictures of houses, tools, faces, but words are absent. He can’t read anymore- whole-word system is lost but phonological system still intact.
- Easier to read words or identify objects with intact vertices (corners).
- We read via object recognition.
- Portion of the fusiform gyrus became the VWFA to help us read letters. - Direct Dyslexia: Person can read words aloud without understanding them.
Figure 14.38 Writing and the Ventral Premotor Cortex
- Left handers are R hemisphere dominant, especially ventral premotor cortex and vice versa.
- Understanding language itself is left hemisphere.
- Left hemisphere broca’s area and ventral precentral gyrus- sounding and writing out words.
- People problems with writing whole words have problems with VWFA.
Developmental dyslexia: difficulty blending sounds- most common (phonological and whole-word disorder less activity in VWFA and large activity in broca’s area), writing, distinguishing word orders.
- Hyperactivation of left prefrontal cortex and less functioning in phonological and whole-word system in developmental dyslexias.
Vicariation: Damage to area A, then lose ability to perform that area- acute effect from a stroke. One possible explanation from getting a stroke losing speech ability and then getting your speech back means that there are parts in the brain with no particular function, but when needed those parts can become speech area (second handed).
Diaschesis: Area A is responsible for function A, but do damage to area B. Since B is destructed it affects area A and these disruptions are critical for area A to be activated. Diaschesis means shock- area A is in shock but once shock is worn off area A works fine again .People try to minimize amount of shock received by the nervous system via anesthetics, boost area A via exercise.
Neural Reorganization: Area A is fine, area B is damaged.
Neurogenesis: Create new neurons to take place of neurons in area B.
Neural Regeneration: Having a damaged neuron regenerate. Not in CNS but in periphery in amphibians. Lose a limb and it can regrow.