Lecture 12 Flashcards
What is temporal processing?
A system’s ability to characterize the temporal features of an input.
Doing this over time.
Taking short periods of time and seeing if there is a change in the stimulus. Time chunks will be recording the same amount, brain integrates this over a long integrator, and groups is into one object.
In the temporal window model, what happens in the DRNL and Square Law models?
DNRL: BM, OHC adding energy, IHC, input causing deflection of the BM, IHC output causing nerve fibre response
Square Law: aspect of the auditory nerve fibre activation, BM, auditory nerve fibre and temporal window integrator - long duration, can detect discrete windows (central auditory - cochlear nucleus and above)
What is temporal resolution?
Sensitivity of the auditory system to detect small acoustical changes over time , or is the minimum time that can separate two events so that they are just barely non-simultaneous or successive
How discrete of gap or change in sound can be detected in time? See gaps in time - energy changes over time (acoustic change)
What is temporal ordering?
The ability of the auditory system to determine the order in time of two events that are perceived as successive or separate.
One sound and another sound and flip it, sound A+B, are they the same? Can you detect it was B->A/A->B?
What is temporal integration?
The combination or integration of acoustical information across a period of time.
How much time do you integrate to say there is an object…? Take a bunch of sounds, smash them together as an object. Connecting spectral and temporal aspects/features into a single integrated object (higher order)
What is temporal masking?
AKA non-simultaneous masking; occurs of the signal (target sound) by another masking sound that preceded (forward masking) or followed (backward masking) the target sound.
How can we mask sounds over time? Take noise and beep, gap short enough - can’t detect beep (can do forward and reverse)
In temporal resolution, how might people doing gap detection testing have trouble?
Between the word “say” and “stay”
People with temporal resolution problems will get these mixed up because they don’t hear this gap - delayed ability to detect context on next sentence - very hard to comprehend speech.
Can determine temporal resolution/integration - blur together of phonemes
Difference in no gap, 20ms gap, 10ms gap.
Normally gap detection is 20ms for screening.
What is the anatomical process going on for temporal processing deficits?
Stimulus comes in, stereocilia move back and forth, release NT, NT cause action potential
If no stimulus deflecting stereocilia - shouldn’t see action potential.
Cause NT to be dumped with action potential - will see high levels of postsynaptic potentials excitation in cochlear nucleus, with gap - no action potential from nerve fibre, none or very little postsynaptic potentials.
You hear stuff then you don’t - higher neurons get into your awareness, then you notice the stop of firing, and notice the gap.
Many million neurons saying fire or not - gap = something that changed (higher integrators)
In temporal resolution measurement, how is this helpful diagnostically?
Change gap going from 20-0ms (response gets smaller). Record from auditory cortex, get squiggle at onset, gap creates a slow cortical response.
Helpful in head trauma - for medical/legal cases - proves they have temporal processing problems.
Temporal window model for gap detection - how does this work?
Includes sliding neural integrator, noise, gap, output response.
Sliding neural integrator samples across time, what is the neural output at the level of the cochlear nucleus?
Our system has to be able to parse out sounds at timing intensity, frequencies and put back together…
With a small gap: there is a drop because not much activation, due to gap. Intensity coding is happening, many frequencies in the noise will detect a change in frequency.
Temporal coding, intensity coding in parallel.
With larger gap: lot more drop in neural output. Significant drop, detected gap, higher order systems are aware of this drop.
With temporal processing deficits, what occurs with normal vs. desynchrony individuals?
Auditory nerve fibres aren’t getting input in time/not firing in time. Input comes in, resonating stereocilia, can happen where NT aren’t being dumped out in time, with stereocilia going back and forth = gap.
Still receiving activation from stimulus, but going slow, fires during the gap. Activating the CN neuron-postsynaptic potential - might fire (system thinks something still happening and isn’t, so hear the pause)
How could you help someone with desynchrony?
Can initiate cortical plasticity so you can detect small changes. Use principles about context, so communication skills straight on, client needs to help themselves.
Train client to recognize gaps - eventually shorter and shorter. Use other systems to help filter out, attend to small changes so they can hear the difference between say and stay.
In temporal resolution, how is someone with auditory neuropathy affected?
At a sensation level of 40, still have gap of 11ms = high for stay vs. say. Will have troubles recognizing.
In temporal resolutions, what effect do sinusoidally amplitude modulated sounds have?
Put in the sound tones, and change the level/depth of the AM tones - making is more or less wavy.
Temporal processing will allow you to detect a change in amplitude over time.
Can change modulation so it fluctuates more or less rapidly - change modulation frequency depth require for threshold will do down in modulation depth - threshold gets higher and higher.
At a level of 40, most people can get it at 25, at -20, need 10% modulation.
How do SAM frequencies in temporal resolution transfer functions affect our brain?
Higher modulation frequencies, you need more depth.
For example, our brain is creating the 40Hz signal, brain also shows the in-out signal the brain detects the roughness - signal that neurons are creating, that our higher awareness is detecting (really shouldn’t have 40Hz brain response)
