limitation in language research
- can’t use animal models
- animals have many components of language, but are missing syntax!
phonemes
fundamental language sounds that form a word
morphemes
smallest meaningful units of words
for example: anti, or pro
lexicon
collection of all words in a given language
syntax
- rules of grammar
semantics
- meaning of words and sentences that correspond to all lexical items
prosody
“tone of voice”
-rhythm/tone in voice
discourse
-stringing sentences together to form meaningful narrative
Broca
- had a stroke patient who was unable to say anything but tan
- after tan’s death, looked at brain and found relatively focal damage in PFC –> Broca’s area
- area important to SPEECH PRODUCTION
- people with damage here have difficulty producing language, but can comprehend
Wernicke
- damage here = word salad
- create long sentences, but incomprehensible
- damage = people can’t comprehend
- reading impairments
- don’t receive auditory feedback
anatomical areas associated with language
- broca’s area, wernicke’s area, auditory cortex, and connection between them (arcuate fasciculus)
role of premotor cortex in language
matching noun to target word
where are nouns stored
the words are stored in the same visual area is stored for that object (ventral stream)
Wilder Penfield
- identified and mapped neocortical language zones during surgery
- tried to find focus of epilepsy
- ran electrode along cortex and stimulated it
- stimulation of Lhem, espeically frontal = slurring speech, arrest of speech, distortion, naming difficulties
TMS
transcranial magnetic stimulation
- modern way to stimulate neurons without invasive
Wernicke-Geschwind Model
- info comes in through auditory cortex, is processed in Wernicke’s, then travels through arcuate into Broca’s where info for speech production is sent to motor cortex
- to read, visual areas send info to angular gyrus and Wernicke’s or Broca’s area
shortcomings of Wernicke-Geschwind model
- doesn’t take into account other brain regions involved
- overly simplistic: “regions”
- relied on diffuse loss of function studies
Subdivision of Broca’s area
Broca’s area isn’t really an area, comprised of many subregions
- has a dorsal/ventral organization
- dorsal is posterior, ventral is anterior
- ventral/anterior more involved in semantics
- dorsal/posterior involved in production of speech
- dorsal/ventral organization also true for Wernicke’s
Dual language pathway theory
- bidirectional- language moving in multiple directions
- area 6 (motor cortex) and area 47 (semantics) are targets of info
- fundamental organizing feature is dorsal vs ventral (not just for Broca and Wernicke’s areas)
Dorsal: Bottom-up (taking things from basic parts and putting them together)
- short term memory
- phonetics
Ventral: Top-down, long term memory, semantics, separating homonyms
damage to dorsal vs ventral pathways
dorsal: basic problems with production. semantics intact
ventral: interferes with meaning of language = lack of comprehension
fluent aphasia
person is able to talk but has language impairments “word salad”
- impairments in input/reception of language
- aka Wernicke’s aphasia, or Sensory aphasia
- cannot write because cannot discern phonemic characteristics
Types: Conduction (name objects, can’t repeat words) and Anomic/Amnesic (can comprehend speech, produce meaningful speech, can repeat speech. difficulty naming objects)
non fluent aphasia
person cannot speak, has great difficulty speaking
- aka Broca’s aphasia, or expressive aphasia
- can understand speech
Global aphasias (labored speech, poor comprehension)
alexia
problems reading
agraphia
problems writing
