Week 10 - topic 1

Question 1

Aphasia

Answer 1

• Aphasia is difficulty in producing or comprehending speech not produced by deafness or a simple motor deficit. It is caused by brain damage.
• Two of the main types of aphasia studied are Broca’s and Wernicke’s aphasia
• > Fluent aphasia (receptive) is when there is poor comprehension and words lack meaning
• > Non-fluent aphasia (expressive) is when there is good comprehension but difficulty finding words

Question 2

Broca’s area

Answer 2

• front left frontal lobe

- involved in language production and speech gestures

Question 3

Wernicke’s area

Answer 3

• back left temporal lobe

- involved in language comprehension

Question 4

Primary progressive aphasia

Answer 4

• not caused by brain injury, a form of dementia

- speech is the first thing lost

Question 5

Right hemisphere involvement in speech

Answer 5

• Left hemisphere dominant for comprehension and production in 90% of the population.
• This doesn’t mean that the right hemisphere isn’t important.
• For instance, when we hear something, we have to think about it’s meaning etc. which will involve the right side of the brain.
• Right hemisphere also involved in prosody = rhythm in speech.
-> The comprehension of the figurative aspects of
language appears to involve the right hemisphere

Question 6

Speech production after corpus callosum cut

Answer 6

• Results in 2 hemispheres being independent
• Sensory mechanisms, motor systems and memories no longer exchange information
• If you show a split brain patient a word in their left visual field – the information would go to the right hemisphere.
• BUT, because the CC is cut, the info doesn’t go to the left for processing.
• Therefore, a person with a split brain would be unable to name the object.

Question 7

Auditory comprehension

Answer 7

• We find the audio entry in our “brain dictionary” to
recognize the sequence of sounds that constitute the
word = Wernicke’s area in the auditory association cortex of the left temporal lobe
• Next, memories associated with the word are activated. This is done via Wernicke’s area being connected to the neural circuits involved in memory (sensory association areas) through the posterior language area

Question 8

Bilingual brain

Answer 8

• Some brain regions in bilingual individuals are devoted to specific languages and some common to both languages; identifiable using imaging studies

• Electro-stimulation studies of the cortex in bilingual patients - common and language-specific areas found in the frontal and posterior temporal/parietal cortexes.
-> Language-specific areas were also found in some subcortical structures

Question 9

Prosody and the brain

Answer 9

• Prosody refers to rhythmic, emphatic, and melodic
aspects of speech
• Function of the right hemisphere
• Likely related to musical skills, expression and recognition of emotions
• However, Broca’s aphasia (left hemisphere damage)
can also cause deficits in prosody

Question 10

Phonagnosia

Answer 10

• Most cases of phonagnosia are caused by brain damage (acquired brain injury).
• Recognition of a particular voice is independent of the recognition of words and their meanings: Some people have lost the ability to understand words but can still recognize voices, while others display the opposite deficits (Belin et al., 2004)
• So far, all cases of acquired phonagnosia show damage in the right hemisphere (parietal lobe or the anterior superior temporal cortex)

Question 11

Functional imaging and phonagnosia

Answer 11

Functional-imaging studies have implicated the right anterior superior temporal cortex in voice recognition.

For example, von Kriegstein et al. (2003) found that this region was activated by a task that required participants to recognize particular voices but not particular words

Question 12

Broca’s aphasia

Answer 12

• Caused by damage to frontal lobe: slow, laborious nonfluent speech
• Word are mispronounced, but the words are usually
meaningful
• The posterior part of the cerebral hemispheres has
something to communicate, but the frontal damage
means the person cannot express these thoughts

Question 13

How Broca’s aphasia appears in speech

Answer 13

• Can comprehend language better than produce it
• Difficulty in using function words – small words with
grammatical meaning (a, the)
• Reliance on content words including nouns, verbs,
adjectives and adverbs (apple, house)

Question 14

Broca’s aphasia and lesioning

Answer 14

• Lesions that cause Broca’s aphasia are (of course) going to include Broca’s area
• BUT, the damage has to extend to areas surrounding
Broca’s area to produce symptoms including other
regions of the frontal lobe and to subcortical white matter
• Lesions to the basal ganglia (caudate) also produce
Broca’s

Question 15

Motor memories and Broca’s aphasia

Answer 15

• The neural circuits damaged in Broca’s are likely
important for motor memories—in particular, memories of the sequences of muscular movements that are needed to articulate words (Wernicke, 1874)
• Perhaps Broca’s area contains the “programs” for how to articulate words – makes sense because of it’s direct connections to motor cortex

Question 16

Broca’s aphasia - three main symptoms

Answer 16

• However, the frontal lobes do far more than help us
articulate words, and Broca’s is NOT just a deficit in
pronouncing words.
• Three main symptoms:
1. Agrammatism
2. Anomia
3. Articulation Difficulties

Question 17

Broca’s aphasia - agrammatism

Answer 17

• A difficulty in comprehending or properly employing
grammatical devices, such as verb endings and word
order

Picture of a boy being hit in the head by a baseball
The boy is catch… the boy is hitch… the boy is hit the ball.
(Saffran et al., 1980, p. 229)

Picture of a girl giving flowers to her teacher
Girl… wants to… flowers… flowers and wants to…. The
woman… wants to…. The girl wants to… the flowers and
the woman. (Saffran et al., 1980, p. 234)

Question 18

Broca’s aphasia - agrammatism and impairment to comprehension

Answer 18

• Broca’s is characterized as a disorder of production
• However, there are also impairments in comprehension.
• Broca’s aphasia patients perform poorly when given
“passive” sentences, suggesting that comprehension is impacted.
- can better understand “the truck pulls the car” than “ the car is pulled by the truck”

Question 19

Broca’s aphasia - anomia

Answer 19

• Difficulty finding (remembering) the appropriate word to describe an object, action or attribute
• Because all people with aphasias omit words or use the wrong words, it is actually considered the primary
symptom of all types of aphasia
• Anomia is like having a partial amnesia for words
• The most likely location of lesions that result in anomia without other symptoms of aphasia like comprehension deficits, agrammatism, or difficulties in articulation occur in the left temporal or parietal lobe, usually sparing Wernicke’s area.

Question 20

Broca’s aphasia - articulation difficulties

Answer 20

• Patients will mispronounce words, often altering the
sequence of sounds
• E.g. “Lipstick” becomes “Likstip”
• Broca’s patients know they are making these mistakes and will correct them

Question 21

Broca’s aphasia - various combinations and degrees of impairment, depending on lesion and recovery

Answer 21

1. Low = control of sequence of muscle movements; results in articulation difficulties
2. Medium = damage to particular “programs” for individual words; results in anomia
3. High = damage impacting selection of grammatical structure; results in agrammatism

• Categories might involve different brain regions

Question 22

Recognition of speech

Answer 22

• Speech comprehension begins in the auditory system, which detects and recognizes sounds
• Recognition does not equate to comprehension
• Recognizing a spoken word is a complex perceptual task that relies on memories of sequences of sounds
• Accomplished by neural circuits in the superior temporal gyrus of the left hemisphere (i.e. Wernicke’s area)

Question 23

Wernicke’s aphasia

Answer 23

• Primary symptoms = poor language comprehension and production of meaningless speech
• Speech is unlabored and fluent with prosody. It also
appears to be grammatical with the use of function words (“the”, “but”)
• What they say doesn’t make sense, and they use few content words
- word vomit

Question 24

Wernicke’s aphasia - communicating socially

Answer 24

• Often unaware of their deficit – they don’t realise their language is impaired and do not recognize that they don’t understand others (even thought they look like they understand what people are saying to them).
• Still follow social conventions – e.g. wait for pauses in conversation to respond
• Remain sensitive to others facial expressions and tone of voice – e.g. respond when asked a question

Question 25

Main symptoms of Wernicke's aphasia

Answer 25

• Wernicke’s is more than word comprehension: 1. Recognition of spoken words 2. Comprehension of the meaning of words 3. Ability to convert thoughts into words

Question 26

Wernicke's aphasia - deficits in spoken word recognition

Answer 26

• If you hear a new word several times, you will learn to recognize it; but unless someone tells you what it means, you will not comprehend it. • Recognition is a perceptual task. • Comprehension involves retrieval of additional (linguistic) information from memory.

Question 27

Wernicke's aphasia - pure word deafness

Answer 27

The ability to hear, to speak, and usually to | read and right without being able to comprehend the meaning of speech

Question 28

Two types of injury that cause pure word deafness

Answer 28

1. Disruption of auditory input to the superior temporal cortex 2. Damage to the superior temporal cortex Both types of damage disturb the analysis of the sounds of words and prevents people from recognizing other people’s speech

Question 29

How speech is recognised

Answer 29

When we hear a word, it automatically engages brain mechanisms that are involved in speech production. • Contains mirror neurons activated by the sounds of words Feedback from subvocal articulation (very slight movements of the muscles involved in speech that do not cause obvious movement) facilitate speech recognition

Question 30

Posterior language area and comprehension difficulty

Answer 30

Difficulties in comprehending language and expressing thoughts in meaningful speech appear to be produced by brain damage extending beyond Wernicke’s area = posterior language area • Acts as a place for interchanging information between the auditory representation of words and the meanings of these words, stored as memories in the rest of the sensory association cortex

Question 31

Transcortical sensory aphasia

Answer 31

• Damage to the posterior language area alone results in a condition called transcortical sensory aphasia = a person has difficulty comprehending speech and producing meaningful spontaneous speech, but can repeat speech. • Therefore, they can recognize words, but cannot comprehend the meaning of what they hear and repeat.

Question 32

Wernicke's area and the posterior language area

Answer 32

- posterior language area damage that causes transcortical sensory aphasia, patients can still repeat words - because patients can still repeat words even without comprehension, means that there must be a direct connection between Wernicke's and Broca's area that bypasses the posterior language area

Question 33

Wernicke's aphasia - the basics of thought conversation

Answer 33

• The third ability impaired in Wernicke’s aphasia is the ability to convert thoughts and memories into words. • The meaning of a word is defined by the particular memories associated with it • These memories are not located in the primary speech and language areas, but in other parts of the brain (i.e. association cortex) • The hippocampal formation is involved in this process of tying related memories together

Question 34

Circumlocutions

Answer 34

speaking in a roundabout way to get around missing words

Question 35

Wernicke's aphasia - thought conversion and anomic aphasia

Answer 35

• Anomia (word finding) is a primary symptom of aphasia • But word finding difficulties alone is different from having Wernicke’s • Instead, it is distinct and called anomic aphasia: these people have fluent and grammatical speech, but have difficulty finding the appropriate words. These people can understand what is being said, and what they say makes sense - use circumluctions

Question 36

Arcuate fasciculus (AF)

Answer 36

area that directly connects Wernicke’s Area and Broca’s area • Transmits information about the sounds of words, but not their meanings • Evidence for the function of the AF comes from studying those with conduction aphasia.

Question 37

Conduction aphasia

Answer 37

• Conduction aphasia occurs when there is damages to the inferior parietal lobe that extends into subcortical white matter and damages the AF • An aphasia characterized by inability to repeat words that are heard but the ability to speak normally and comprehend the speech of others • Sometimes, when asked to repeat a word someone with conduction aphasia will not say the same word, but a semantically related one (e.g., “house” – “home”)

Question 38

Pathways between Wernicke's and Broca's

Answer 38

• The direct pathway from Broca’s Area to Wernicke’s area via the AF must just convey speech sounds. We would use the AF pathway to repeat unfamiliar words • The second pathway between the posterior language area and Broca’s area is indirect and is based on the meaning of words, not on the sounds they make. -> damage to the AF would see patients repeat the semantic meaning of a sentence but use different words as the second pathway communicating meaning only, is still available

Question 39

Sign language and mirror neurons

Answer 39

* Mirror neurons are active when we see or perform particular grasping, holding, or manipulating movements * Some mirror neurons are found in Broca’s area and likely help us in learning to mimic others hand movements. * Broca’s area active when we observe and imitate finger movements

Question 40

Stuttering

Answer 40

• Characterized by pauses, prolongation of sounds, or repetitions of sounds, syllables or words that disrupt normal flow of speech • Influenced by genetic factors • Disorder of selection, initiation, and execution of motor sequences necessary for fluent speech production (Watkins et al., 2008).

Question 41

How does stuttering occur from the brain

Answer 41

• Not due to abnormalities in neural circuits that contain motor programs for speech (e.g. stuttering eliminated when a person sings) • Perhaps abnormalities in mechanisms involved in planning and speech initiation • Brown et al. (2005) – stutter was associated with overactivation of Broca’s area and the insula (articulation), supplementary motor area, and cerebellum. -> There was no activation in auditory regions of temporal lobe

Question 42

Stuttering - Brown et al 2005

Answer 42

• Brown et al. (2005) suggested that stuttering might be caused by faulty auditory feedback from sounds of the person’s own speech, shown by the lack of activity in the temporal lobe. • Related to the idea that delayed auditory feedback interferes with speech in fluent speakers, but facilitates the speech of many individuals who stutter.