Week 10: Language

What is language lateralisation?

The tendency for language functions to be predominantly located in one hemisphere of the brain, usually the left.

In what percentage of the population is the left hemisphere dominant for language?

90% of the population.

Which hemisphere is dominant for language in most left-handed individuals?

The right hemisphere is dominant in 27% of left-handed people.

Name factors involved within language comprehension

Prosody, intonation, and emphasis help convey meaning in language.

Name some roles of the right hemisphere

• Comprehension likely involves right hemisphere

• Damage to the RH might affect:

• Talking about spatial relations

• Maps and complex geometrical forms

• Organising a narrative

• Understanding figurative aspects of language

What is phonagnosia?

The inability to recognise familiar voices, associated with damage to the right temporal lobe.

How is the left and right hemisphere involved in speech production?

LEFT: controls speech output (Broca’s area)

RIGHT: minimal role

How is the left and right hemisphere involved in comprehension?

LEFT: literal meaning, vocabulary, grammar

RIGHT: context, implied meaning

How is the left and right hemisphere involved in grammar and syntax?

LEFT: processes sentence structure

RIGHT: limited role

How is the left and right hemisphere involved in semantics?

LEFT: precise word meaning

RIGHT: broad, associative meaning

How is the left and right hemisphere involved in prosody (tone, rhythm)?

LEFT: basic structure of speech

RIGHT: emotional tone, intonation

How is the left and right hemisphere involved in figurative language?

LEFT: limited alone

RIGHT: metaphor, sarcasm, humour

How is the left and right hemisphere involved in error awareness?

LEFT: often aware

RIGHT: less aware

How is the left and right hemisphere involved in the effect of damage?

LEFT: aphasia

RIGHT: monotone speech, poor emotional understanding

What is the corpus callosum's function?

It connects the two hemispheres of the brain, allowing them to communicate.

What is the purpose of surgically cutting the corpus callosum?

To stop seizures in severe cases of epilepsy.

→ Corpus callosum is cut and communication between hemispheres is disrupted

What does the left hemisphere do in terms of language?

It acts as an 'interpreter' that builds explanations and verbalises thoughts.

Outline the order of language comprehension

1. Hear it

2. Recognise the words

3. Understand the words

4. Remember what happened or imagine

5. Put the words together

6. Tell your muscles to move

7. Answer

What is bilingualism?

The ability to use two languages in everyday life.

Which structure do bilingual babies show stronger responses to?

Prefrontal cortex

What are the potential cognitive advantages of bilingualism?

Enhanced attention, task switching, and inhibitory control (Bialystok et al, 2012)

Where is bilingualism believed to be localised? (Guissani et al, 2007)

• Electrostimulation studies review (Guissani et al, 2007)

• Some overlapping

• Primary or secondary language-specific regions

What is aphasia?

A language disorder resulting from brain damage that affects understanding or producing language.

What are the primary causes of aphasia?

Stroke, brain tumors, and head injuries.

Name two forms of non-fluent aphasia

1. Broca’s

2. Global

What is Broca's aphasia characterised by?

Effortful, agrammatic speech with good comprehension.

What is global aphasia characterised by?

Severe impairment in all language functions.

Name three forms of fluent aphasia

1. Wernicke’s

2. Conduction

3. Anomic

What is Wernicke's aphasia characterized by?

Fluent but meaningless speech with poor comprehension.

What is conduction aphasia characterised by?

Poor repetition, fluent with errors

What is anomic aphasia?

A type of aphasia where individuals have difficulty finding words, especially nouns and verbs.

Name factors associated with Broca’s aphasia/non-fluent aphasia

Broca 1861-1865: case studies of aphasia

• Patient 'Tan'

• Cavity left frontal lobe filled with fluid

• Patient can comprehend but not express speech

• Speech is associated with left hemisphere

• Damage to the inferior left frontal lobe and underlying subcortical white matter

 

• Comprehension of speech is intact

• Speech is slow, broken, effortful

• Loss of the production of complete sentence structures is speech and writing

Name three speech deficits associated with Broca’s aphasia

1. Agrammatism (loss of grammar)

2. Broca’s anomia (accessing the word): word-finding difficulties

3. Articulation problems: mispronunciations, often alter the sequence of sounds

Outline 6 preserved functions in Broca’s aphasia

1. Language comprehension (mostly intact)

2. Meaning of words

3. Awareness of deficits

4. Non-verbal communication (gestures/facial expressions)

5. Understanding humour/sarcasm/tone

6. Prosody/expression of emotions

Outline factors associated with Wernicke’s aphasia

• Repetitive or fluent aphasia

• Main difficulty is understanding language (spoken or written)

• Speech remains smooth and well-paced but might lack meaning

• Linked with damage in the left temporal gyrus

What happens if connections to Wernicke's area are disrupted?

It can lead to pure word deafness, transcortical sensory aphasia, anomic aphasia or conduction aphasia.

What is agrammatism?

Difficulty in using grammatical constructions and word order to decode sentences.

What preserved functions are typically seen in Broca's aphasia?

Intact language comprehension, meaning of words, awareness of deficits, and non-verbal communication.

What is the significance of the Boston diagnostic aphasia test?

It is used to assess language function and diagnose types of aphasia.

What does the term 'pure word deafness' refer to?

• Auditory verbal agnosia

• Rare disorder of the recognition of speech

• Patients cannot understand spoken words despite having normal hearing, reading and writing skills

• Typically caused by disconnection rather than direct destruction of Wernicke's area itself

What is meant by transcortical sensory aphasia?

• Poor comprehension but preserved repetition

• Speech fluent, grammatically correct but meaningless

• May not be aware of difficulty

What is meant by anomic aphasia?

• Problem with word findings and naming things

• Difficulty retrieved certain words, especially nouns and verbs

• They know what they want to say but cant get the words to come out correctly

• Might use substitution words or related words

• Wernicke's area and the broader left posterior temporal and parietal regions involved

Name factors associated with conduction aphasia

• Meaningful fluent speech and comprehension, but poor repetition

• Extreme difficulties repeating lists of words (although related words may be repeated)

• May replace word they are asked to repeat with another with the same meaning

• Caused by damage to pathway between Broca and Wernicke area responsible for conveying sound – arcuate fasciculus

• Hearing sentence evokes imagery, which allows individual to describe the meaning but using different words

What is the difference between Broca’s and Wernicke’s anomia?

Broca’s anomia = can’t get the word out

Wernicke’s anomia = gets the wrong word out

What is the role of Wernicke's area?

Involved in language comprehension, particularly in understanding spoken and written language.

What is the impact of aphasia on mental health?

Nearly 60% of people with aphasia experience depression a year post-stroke.

What are the characteristics of global aphasia?

Severe impairment in all language functions, affecting both comprehension and production.

What is the significance of the arcuate fasciculus?

It is the pathway that connects Broca's and Wernicke's areas, crucial for language processing.