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Recovery from prior stimulation. II: Effects upon intensity discrimination
F G Zeng1, C W Turner, E M Relkin
1House Ear Institute, Los Angeles, CA 90057.
Hearing Research
|October 1, 1991
Summary
Forward masking does not affect pure-tone detection thresholds but yields large just-noticeable differences (jnds) at mid-levels. These large jnds suggest slower neural recovery, impacting intensity coding and challenging assumptions about forward masking duration.
Area of Science:
- Auditory Neuroscience
- Psychoacoustics
- Sensory Physiology
Background:
- Forward masking typically affects auditory detection thresholds.
- Previous research assumed forward masking effects recover within 100-200 ms.
Purpose of the Study:
- Investigate just-noticeable differences (jnds) for pure-tone intensity following a forward masker.
- Examine the recovery time course of these jnds.
- Explore the role of neural populations in coding auditory intensity.
Main Methods:
- Measured jnds for pure-tone intensity using a forward masker (narrow-band noise).
- Varied masker-signal delay and signal intensity (mid-levels: 40-60 dB SPL).
- Analyzed jnd recovery over time up to 400 ms.
Main Results:
- No threshold shift was observed for pure-tone detection.
- Unusually large mid-level jnds were found.
- These large jnds showed incomplete recovery by 400 ms.
Conclusions:
- Large mid-level jnds suggest slower recovery of low-spontaneous rate, high-threshold neurons.
- Provides psychophysical evidence for the role of these neurons in coding wide intensity ranges.
- Challenges the 100-200 ms recovery assumption for forward masking in suprathreshold tasks.