Language and 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. • Causes: • Deficient phonemic processing (speech sounds). • 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.
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. • Right hemisphere: • Spatial processing. • Face recognition. • Some aspects of music. • 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 hemispheres there is the potential for consciousness (self) in both – P.S.
Attention • The ability to select and differentially process simultaneous sources of information. • Can be focused upon a single modality or upon specific items within a modality (e.g., a single visual object). • Overcomes resource limitations related to processing everything at once. • Processing advantages may result from focusing upon specific sensory inputs.
What is Attention? • Enhanced neural readiness to respond in areas of the brain needed to perform a task. • Attention enhances detection when visual stimuli appear in different locations. • Attention speeds reaction times in response tasks.
Neglect Syndrome • Damage to right parietal lobe causes person to fail to acknowledge left visual field. • Can involve failure to acknowledge left side of own body. • Is it perceptual or attentional? • Without input from right, left hemisphere may assume that what it sees is all that exists.
What is Consciousness? • Bodily awareness • Flow of attention • Focus on internal processes • Encoding in language • The integrated results of unconscious processing • Sense of “self”