Table 1.
Comparison of properties of forward masking in the auditory system
| Auditory Nerve | MNTB | Inferior Colliculus | Auditory Cortex | Psychophysics | |
|---|---|---|---|---|---|
|
Probe Threshold Increase |
Up to 21 dB1 | Mean of 9.95 dB; Up to 54 dB (Fig. 3) |
Mean of 18.8 dB2; Up to 50 dB |
Mean of 15 – 25 dB; Up to > 40 – 50dB3, 4 |
|
|
GOM Function; Slope |
Saturating; 0.26 dB/dB over monotonic part of function1 |
Monotonic; 0.23 dB/dB over entire function (Fig. 4) |
Monotonic; 0.36 dB/dB2 |
Complex; Non-monotonic may occur5 |
|
|
Masking Depends on |
Masker-evoked firing rate6 |
Masker intensity (Fig. 5) |
Masker intensity2 | ||
|
Strongest Frequency Dependence |
On-CF maskers (Fig. 7) |
On-CF maskers2 | On-CF maskers7 | ||
|
Facilitation by off-CF Maskers |
Occurs with some off-CF maskers (Fig. 7) |
Occurs with some off-CF maskers2 |
Occurs with some off-CF maskers8 | ||
|
Masker-to-probe delay (recovers to half-max. response magnitude) |
10 ms delay9 | 0 – 30 ms delay (data not shown) |
2 – 100 ms10 | 20 – 150 ms7,11,12,13 | |
|
Effects of Increasing Masker Duration on Probe Threshold Shifts |
Increases for maskers up to 100 ms duration6 |
Increases for maskers up to 200 ms duration (Fig. 9) |
Increases with longer masker durations14,15,16 |
16