PSYC 3F40 Lecture Notes - Frontal Lobe, White Matter, Noam Chomsky

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4 Feb 2013
Speech and Comprehension
Psycholinguistics: branch of psychology devoted to study verbal behaviour.
Speech is social, it is learned and used in interaction with others.
We extract words from a stream of speech.
Our auditory systems recognize patterns underlying speech.
Belin, Zatorre, and Ahad: used fMRI scans to find that some regions of the
brain responded more to human vocalizations rather than just other natural
sounds. Left hemisphere showed larger contrast and thus, it plays a larger
role in analyzing speech.
Phonemes: elements (smallest units) of speech. Eg: pin is three phonemes
oVoice-onset time: a way in which we discriminate among phonemes.
It is the delay between the initial consonant sound and vibrating vocal
chords (voicing). Eg: there is a delay in voicing for “pa” compared to
“ba” although the initial sound (made with the mouth) is the same.
oPhonemic discriminations initially occur in both hemispheres. Some
areas of the brain in the left hemisphere respond solely to intelligible
speech even if it is highly distorted.
oOur ability to recognize highly distorted speech supports that our
perception of a phoneme is affected by the sounds that follow it
(Ganong). We recognize speech sounds in larger chunks such as
Sanders, Newport, and Neville: played a continuous string of nonsense
syllables to listeners. Chunks of this stream were given to participants to
study as words. When the string was played once again the N100 response
(electrical signal that occurs when a word is first recognized) showed up.
Context affects word perception through top-down processing.
Syntax/grammar: all languages follow certain principles called syntactical
rules: grammatical rules for combining words to form phrases, clauses, and
oSyntax is learned implicitly and is automatic. Involves different brain
mechanisms than learning word meanings.
oSyntactical clues are designed by:
Word order: tell us who does what do whom (in English), for
example “A Xs the B”: A does something to B.
Word class: grammatical categories such as noun and verb.
Function words: adds little meaning but conveys
important information about the sentence’s structure
such as prepositions and articles. When they are omitted,
we can often guess at function words.
Content words: express meaning such as nouns and
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Content words express meaning and function words
express the relationships between the content words.
Affixes: Sounds we add to beginning (prefix) or ends (suffix) of
words. Adding affixes to nonsense words make them seems
more like sentences (Epstein).
Semantics: the meaning represented by words.
Prosody: using changes in intonation and emphasis to convey
meaning in speech. Important for emotion. In writing,
syntactical clues and interfere with prosody producing brain
activity similar to that of unexpected experiences.
Syntax is necessary but not sufficient for semantics. Things can make
syntactical sense but we may not extract meaning from it. Likewise,
semantics requires syntax for the entire picture.
We remember what is meant in sentences but quickly forget their form.
Chomsky (linguist) suggested a model:
oDeep structure is the essential meanings of a sentence. It is converted
to speech by adding surface structure (grammatical features).
oThis model is not generally accepted by psychologists.
Aphasia: loss of language, recognition or comprehension or both.
oConduction aphasia: difficulty repeating words and phrases, but they
are comprehended. Retain deep structure but not surface structure.
Pragmatics is knowledge of the world. Used in conversations and is involved
in speech comprehension. Scripts: characteristics of typical situations that
assist in comprehending a verbal discourse. A conversation can bring up
certain scripts in the listener so the speaker can convey information without
all the gritty details.
Areas important for speech:
oBroca’s area: motor association cortex in left frontal lobe. Speech
production occurs here. Sign language users also show activity in this
area, meaning it is for more than just speech production.
Damage here (extending to underlying white matter) causes
Broca’s aphasia which involves severe difficulty articulating
words, especially function words.
Agrammatism: inability to properly use or comprehend
function words and grammatical features.
Comprehension of word order, for example, is affected in
Broca’s aphasia.
Deficit in comprehension parallels their deficit in
production (grammatical and syntactical loss)
Wernicke suggested that Broca’s area contains memories of
sequences of muscle movements needed to articulate words.
Broca’s area is located just in front of the primary motor cortex.
oWernicke’s area: upper part of the left temporal lobe, involved in the
recognition of speech.
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