LANGUAGE

What Is Language?

Language is a systematic means of communication, which uses symbols and has a hierarchical structure.

• Semantic information: meaning associated with words.

• Syntax: rules for how words are combined to form sentences that people understand.

• Phonology: the structure of the sounds of the words in a language.

• Orthography: the written system of language.

Theories of Language

Mental lexicon: the mental store of information about words, including semantic information, syntactic information, and

word forms (how letters and sounds are combined to form words).

• Normal adults store about 55,000 words in their mental lexicon.

• More frequently used words are accessed more quickly.

Language Networks

Language Production: the ability to use words, phrases, and sentences to convey information.

Language Comprehension: the ability to understand the messages conveyed by words, phrases, and sentences.

Neural substrates of speech perception

• Left perisylvian language network.

• Superior temporal gyrus (STG).

o Lesion causes pure word deafness: inability to recognize speech sounds, although can recognize non-speech

sounds.

o Activation is modulated by whether the incoming auditory signal is speech or non-

speech sounds.

o Acoustic sensitivity decreases moving anteriorly and posteriorly away from

primary auditory cortex.

o Speech sensitivity increases moving anterior and posteriorly away from the area

immediately surrounding the primary auditory cortex.

Aphasia and Language Deficits

Broca’s aphasia: problems related to producing and understanding syntactic relationships.

• Lesions to (but not limited to) the left inferior frontal gyrus (Broca’s area), typically also involve surrounding

white matter and subcortical connections.

• Known as expressive aphasia: impairment is mainly in expressing language using writing and sign languages.

• Telegraphic speech: use mainly content words (nouns, pronouns, etc) and lack function words (prepositions, etc),

speak in short, simple phrases, many pauses and not fluent.

• Agrammatism: deficits in processing grammatical aspects of language. Ex: “The boy was kicked by the girl" vs.

"The boy kicked the girl.

" The first sentence has a more complicated grammar, confusing patients with Broca's

aphasia about who kicked whom.

Wernicke’s aphasia: disturbance in comprehension in the presence of fluent (but meaningless) speech.

• Lesions to the posterior third of the left superior temporal gyrus (Wernicke’s area)

• Known as receptive aphasia: impairment mainly in comprehending language.

• Word salad; neologisms.

• Semantic paraphasias: generate words related to the meaning of the intended word (saying “cow” while wanting

to say “horse”).

Conduction aphasia: problems spontaneously repeating speech.

• Damage to the arcuate fasciculus, a bundle of axons that links Broca’s and Wernicke’s areas.

• Have problems in moving linguistic information rapidly from input to output stages.

• Can understand words and hear their own speech errors.

Global aphasia: inability to comprehend or produce speech.

• Produced by extensive lesions in the left perisylvian area.

• Symptoms may include the disabilities of the other three types of aphasia.

Dyslexia: difficulty in reading, not due to a sensory or intellectual impairment.

• Surface dyslexia: difficulty with the appearance of language

• Deep dyslexia: difficulty with the sound structure of language

• The problem is associated with the language networks

• Due to problems with the language network: less activity in Wernicke’s area.

• Compensatory activity in the left anterior language areas and the right hemisphere.

APHASIA TESTS & BATTERIES

Objectives: diagnose the type and severity of aphasia and related disorders & plan intervention for the identified deficits

Screening tests

Comprehensive aphasia tests

Tests of specific linguistic or communicative function