and Language Attention
Chapter 20 Wednesday, December 3, 2003
Features of Language
Creativity we create meaning by using grammatical rules to generate new sentences. Form language is made up of smaller units (phonemes, morphemes, words, sentences) combined using rules. Content meaning can be abstract, context independent, emotional. Use language has social purpose.
Animal Models of Language
Chimpanzees cannot produce speech sounds because they lack the vocal apparatus. Chimpanzees (Washoe, Kanzi) and other apes can manipulate symbols.
Language development goes to a certain point then stops not fluent and creative like humans. No evidence that animals form abstract mental representations of meaning and think using symbols.
Innateness of Language
Language and sign language are both lateralized to left hemisphere. The planum temporale is larger in the left hemisphere in most (67%) right-handers. This asymmetry is present before birth. Infants can differentiate speech sounds at birth critical period for recognizing phonemes for a particular language. Universal regularities in language acquisition.
Aphasias
Aphasia a disorder of language. Wernicke's aphasia difficulty understanding written or spoken language.
Empty speech. Logorrhea (too much speech).
Broca's aphasia difficulty generating fluent, grammatical speech (omit articles, adjectives). Conduction aphasia disconnection between Broca's & Wernicke's area cannot repeat.
Ideographs
Ideographs characters that stand for an entire concept, representing a root word. Some writing systems have two ways of expressing language:
Katakana (phonetic) vs kanji (ideographic).
Processing of kanji occurs in a different region than processing of katakana, though both are localized to left hemisphere.
American Sign Language
Deaf people who know sign language show deficits similar to Broca's or Wernicke's aphasia lateralized to left hemisphere. Ability to move hands is not impaired just ability to move hands to produce language. A hearing man who knew sign language recovered both verbal and signing language abilities together.
Aprosodia
Prosody musical elements of speech, including stress, pitch, rhythm. Affective components of language convey attitude, value, emotion. Lateralized to right hemisphere.
Damage to frontal cortex results in flat tone of voice regardless of emotional state. Damage to posterior areas of brain result in inability to comprehend other people's prosody.
Reading and Writing Disorders
Alexia and dyslexia inability or difficulty reading.
Dyslexia is congenital, alexia is acquired.
Agraphia inability to write. Word blindness inability to comprehend words.
Pure alexia without agraphia.
Dyslexia
May be congenital or acquired through brain injury.
Inability to read despite normal IQ & cognition. Deficient phonemic processing sounds). (speech Visual processing defects due to abnormalities in connections between visual and language areas. Deficit in development of hemispheric dominance occurs in left-handers, letter reversals.
Causes:
Dyslexia (Cont.)
More causes:
Cytoarchitectonic abnormalities, such as incomplete segregation of layers in planum temporale, clusters of misplaced neurons. Inability to process sensory input with adequate speed magnocellular conduction too slow.
Hemispheric Lateralization
Left hemisphere:
Language (spoken and written). Analytic, serial processing. Spatial processing. Face recognition. Some aspects of music.
Right hemisphere:
Both hemispheres work together.
Split-Brain Studies
Surgery to sever the corpus callosum in epilepsy patients:
N.G.
Wada test anesthetic injected in artery to immobilize one hemisphere. Techniques (e.g., Z lens) are then used to present stimuli to one or the other hemisphere, independently.
Tasks
Matching and naming
Right hemisphere cannot name things.
Four picture identification Block designs
Right hemisphere is better (also Braille).
Figure copying right is global. Music is complex
Perfect pitch localized to left hemisphere.
Handedness and Language
Right handed people (95%+) have language localized to left hemisphere. Left handed people:
70% have language in left hemisphere 15% have language in right hemisphere 15% have language in both hemispheres
With brain injury early in life, the other hemisphere can take over language.
Right Hemisphere Language
Some language processing does occur in right hemisphere:
Recognition of shapes of whole words. Prosody of speech Emotional content of speech
When language exists in both ...