Chapter 3 of Moore (1997)

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Frequency Selectivity (II)

Scope

Contrast between Masking & Excitation Patterns

When the f of signal is held constant while varying the masker, we get an estimate of the shape of the auditory filter (as in those experiments we talked about last time).
When the f of masker is held constant while varying the signal, we get an estimate of the excitation pattern over a group of responding filters (Figs. 3.12; 3.13).

What's the Physiological Basis of the Psychophysically Derived Auditory Filters?

The mechanical frequency tuning function of the BM must has something to do with it.
It has been reported that in many species, the CB of the auditory filter corresponds to a constant distance along the BM (Fig. 3.14).
Whether there's an additional sharpening process and at what level does such a process occur are less clear.

Evidence for an Additional Sharpening Process

Lateral suppression, the concept of.
It takes about 30 ms for the LS to develop.=> CB determined by a brief signal should be broader than that by a more sustained signal.
Cons: loudness summation for short stimuli; notched-noise masking, both render negative results.
Pros: tonal maskers and signals; overshoot effect

Mechanism(s) of Masking

Swapping: Weber's law.
Suppression
Linear v.s. nonlinear processes
So far, a pure linear model seems adequate to account for the masking data, but….

Decision Making: What's the Neural Code for Signal Detection?

The most common assumption: Detection is mediated by the increment in the response of a given filter.
Another alternitive: The temporal pattern of the neural response provides information for detection.
Phase locking in two-tone situations.
Rethinking about Plomp's (1964) hearing-out-partials data (Fig. 3.15).

Comodulation Masking Release (CMR): The Case of Cross-Filter Comparison

Standard power spectrum model assumes detection is served by the most active filter.
Hall et al. (1984) demonstrated that the comparison of the responses across different filters could enhance the detection of a sinusoidal signal embedded in a fluctuated noise masker (Fig. 3.16).
Two band paradigm: An on-frequency band and flanking band, either comodulated or out of synchrony.
Complications by within-channel cues. Absent in cross-ear presentation; brief signal in band-widening exps; or on-freq. & flanking bands are wide apart.
CF-independent; Proximity effect; Noise-BW dependent.

Models to Account for CMR

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