PSYB65 Textbook notesChapter 8: Auditory System1
THE AUDITORY SYSTEM
The Properties of Sound
•Frequency: refers to the rate of vibration (number of wave cycles completed per unit of time).
•Human ear can perceive vibrations between 20 and 20,000 Hz.
•Human are maximally sensitive to sounds between 1000 and 4000 Hz, roughly the frequencies
human voice can produce.
•Pitch: sounds of different frequencies. The higher the frequency, the higher the pitch.
•Loudness: loudness corresponds to the amplitude (measured in decibels <dB>, the sound
measure of a source when compared to a standard intensity of 10^-12 watts.) of the sound wave.
•Complexity: perceived as the sound's timbre. Instruments usually produces overtones that are
at frequencies higher than the fundamental frequency, these overtones also vary in their
•primary auditory cortex is hidden behind the secondary auditory cortex.
•The neurons are arranged in columns, and the columns in the more anterior regions respond
maximally to higher frequencies, whereas neurons in posterior regions respond more to lower
•Most right handers have a left Heschl's gyrus that is larger than the right.
LANGUAGE SYSTEMS IN THE BRAIN
•Broca's Area: responsible for the output of language.
•Wernicke's area: responsible for mapping sounds to words (comprehension).
•The two areas need to be connected to provide meaningful verbal output arcuate fasciculus.
•Concept Center: ascribing meaning to the sounds. It is connected to both Wernicke's and
Broca's areas. Thus making this model Spoken and Heard.
•Wernicke-Lichtheim-Geschwind (WLG) model
Added angular gyrus: located at the junction between the temporal, parietal, and occipital
lobes. It receives projections from primary and secondary visual areas and provide a basis
for visual language.
This accounts for why you hear a voice in your head when you read (the words go through
the primary and secondary visual cortex angular gyrus Wernicke's area to be
transcribed into sound images, which is then ascribed meaning.
Models of Visual Language
•2 models: single-route models and dual-route models both describe 2 ways in which words
be read: sounding out the words or reading the words as a whole.
•Phoneme-grapheme conversion rules: reading book as 2 parts buh....ooock.
•Pseudo-homophones the letter strings form sounds that sound like real words “i lyke dis”.
Since words can be read either way, some argued that there are 2 functionally distinct routes
for receptive visual language (reading) dual route model (phonological route <phoneme-
grapheme> and whole-word route)
Some argue that both types of reading could be subserved by a single distributed network
single route model.