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Lecture 10

Lecture 10

12 Pages
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Department
Psychology
Course Code
PSYB51H3
Professor
Matthias Niemeier

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Lecture 10:
Temporal code: In the inner ear (cochlea) – these neural signals are generated
here!
-there is a limit to how much you could code that way: goes up to a 1000 Hz
(WHY? As hair cells cannot fire much faster than that; hair cell = neuron)
-Fire AP (Action Potential): spike of activity (need minimum time between
2 APs = refractory period – then return to RMP1)
Temporal code: the idea that there is some neuron that sits on the organ of corti, where the organ
of corti is being stimulated then the action potential of this neuron will look like the one in the
graph (slide 30; lec9)
-So, this neuron will fire, not fire, and continue doing that
-This pattern of neural activity/firing carries information about frequency
-Limit to these neurons: only works for certain frequencies, best is below 1000 Hz
-This is reflective of music; we like music of certain frequencies more so than other
frequencies
-Above 1000 Hz temporal code doesnt work, because neurons cant fire any more
We can actually go above 1000 Hz because neurons work together but they need to
communicate with one another to get precision.
Volley principle – neurons will work together to form this temporal code for
frequencies above 1000 Hz [works for up to 4000 or 5000 Hz] – works for a
certain time but at some point, it all breaks down.
Neural Activity in Cochlea*Organ of Corti
-Describe how the release of neurotransmitters results from the deflection of
stereocilia.
1 Resting Membrane Potential

www.notesolution.com
When vibration causes a displacement along the cochlear partition, the tectorial membrane and
hair cells move in opposite directions (shearing motion) and the deflection of stereocilia in this
action results in the release of neurotransmitters.
TO RECAP: So when you just look at the particular pattern of the hair cell/neuron; the Action
Potential carries information about frequency directly related to shearing forces which is then
directly related to the incoming sound pressure wave. = so a single hair cell can tell us about
the frequency! (In temporal code)
--
Music
- Music is associated with emotions; might express or amplify our emotions [we make sounds
that communicate our emotions]
-Music quite common in cultures and societies that ever existed in human kind; quite diff.
from animals who arent really that much interested in music
-Music mimics certain sounds of events [e.g. soundtracks in a film]
- music in therapy [fairly new; needs further development – but could be useful]
-Remember: we can hear up to 20, 000 Hz
-The Hz of a tone is directly indicating the pitch; each tone is composed of multiple
frequencies that come in regular intervals = these intervals are of a harmonic sound
[regular integer steps: 1st frequency = 1x200 Hz, next frequency = 2x200 Hz and etc]
-What we perceive as regular increments of pitch is rather logarithmic = its not the way
that we would probably look at numbers in terms of the frequency so a step of 25 Hz
to 50 Hz is not perceived as regular steps of diff. tones
Basically: the relationship is not direct
So as the frequency increases = the pitch increases but regular steps in frequency doesnt
mean regular steps of perceived pitch (logarithmic relationship)
www.notesolution.com
We prefer frequencies that are lower!
This might have to do with the idea that we are rather used to the human voice (its clearly
lower in frequency than the piccolo – thus piccolo can sound annoying)
It might also have to do with our ability to code frequencies in a temporal fashion (which
works better for lower frequencies) = our sense for what is an octave is much better for lower
frequencies as well
- Example: you would call all these tones “C” on a piano.
Although C3 and E3 are closer in frequency, ppl are more likely to confuse C3 and C4
then C3 and E3 = so more to pitch than just frequency!
Musical Pitch: 2 dimensions
Musical pitch (the pitch of a musical note) has two different dimensions, illustrated by
the helix. As frequency rises, the dimension called tone height rises right along with it.
But the second dimension, tone chroma, is cyclical in nature. Western musicians label
tone chromas with the letters AG. As we move from the bottom of the helix up, tone
chroma repeats at regular intervals. Thus we see that as we move from C3 to D3 to E3 and
on up, we eventually come back to another C (C4).
These repetitions occur at intervals called octaves. If one note is exactly
double the frequency of the other note, then the two notes are separated by
one octave and have the same tone chroma.
As you go up and around this musical helix = we have increase in height; means we have
an increase in pitch = Tone height (its algorithmic still, but monotonically rising)
Tone chroma: is something that cycles; so it goes back to the same kind of tone
chroma; so an A1 & an A2 sound similar = relationship is double or half frequency
depending on which direction you go
A1 -> A2 = doubles; A2-->A1 = half
Tone chroma is something that all the C’s and Es and so forth share
www.notesolution.com

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Description
Lecture 10: Temporal code : In the inner ear (cochlea) these neural signals are generated here! -there is a limit to how much you could code that way: goes up to a 1000 Hz (WHY? As hair cells cannot fire much faster than that; hair cell = neuron) - Fire AP (Action Potential): spike of activity (need minimum time between 2 APs = refractory period then return to RMP ) 1 Temporal code: the idea that there is some neuron that sits on the organ of corti, where the organ of corti is being stimulated then the action potential of this neuron will look like the one in the graph (slide 30; lec9) -So, this neuron will fire, not fire, and continue doing that -This pattern of neural activityfiring carries information about frequency -Limit to these neurons: only works for certain frequencies, best is below 1000 Hz -This is reflective of music; we like music of certain frequencies more so than other frequencies -Above 1000 Hz temporal code doesnt work, because neurons cant fire any more We can actually go above 1000 Hz because neurons work together but they need to communicate with one another to get precision. Volley principle neurons will work together to form this temporal code for frequencies above 1000 Hz [works for up to 4000 or 5000 Hz] works for a certain time but at some point, it all breaks down. Neural Activity in Cochlea*Organ of Corti - Describe how the release of neurotransmitters results from the deflection of stereocilia. 1 Resting Membrane Potential www.notesolution.comWhen vibration causes a displacement along the cochlear partition, the tectorial membrane and hair cells move in opposite directions (shearing motion) and the deflection of stereocilia in this action results in the release of neurotransmitters. TO RECAP: So when you just look at the particular pattern of the hair cellneuron; the Action Potential carries information about frequency directly related to shearing forces which is then directly related to the incoming sound pressure wave. = so a single hair cell can tell us about the frequency! (In temporal code) -- Music - Music is associated with emotions; might express or amplify our emotions [we make sounds that communicate our emotions] - Music quite common in cultures and societies that ever existed in human kind; quite diff. from animals who arent really that much interested in music - Music mimics certain sounds of events [e.g. soundtracks in a film] - music in therapy [fairly new; needs further development but could be useful] - Remember: we can hear up to 20, 000 Hz - The Hz of a tone is directly indicating the pitch; each tone is composed of multiple frequencies that come in regular intervals = these intervals are of a harmonic sound st [regular integer steps: 1 frequency = 1x200 Hz, next frequency = 2x200 Hz and etc] - What we perceive as regular increments of pitch is rather logarithmic = its not the way that we would probably look at numbers in terms of the frequency so a step of 25 Hz to 50 Hz is not perceived as regular steps of diff. tones Basically: the relationship is not direct So as the frequency increases = the pitch increases but regular steps in frequency doesnt mean regular steps of perceived pitch (logarithmic relationship) www.notesolution.com
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