Response-related patterns in discrimination of FM narrow-band noise

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Noise stimuli were used to investigate weighting patterns for detecting dynamic frequency changes. For one stimulus set, a tonal glide was modulated by a narrow band of noise (gliding narrow-band noise, GNBN, condition). For the second set, the glide was preceded and followed by steady-state tones before modulation (SS condition). The task was to indicate whether the stimulus had a frequency glide or not. Weighting patterns (as a function of time) were derived for each subject based on a linear classification model. First, the deviation of the instantaneous carrier for each stimulus was calculated and then weighted by the squared envelope of the stimulus. This was followed by the linear classifications of the squared-envelope-weighted deviation of instantaneous carrier (SEWDOIC) according to the subjects responses [A. Ahumada, J. Vis., 2, 121–131 (2002)]. The weighting patterns were consistent across subjects although individual differences in pattern details were observed. The comparison between the patterns from the GNBN and SS conditions indicates the use of dynamic information rather than only comparing the beginning and ending frequencies, consistent with Lyzenga et al. [J. Acoust. Soc. Am. 116, 491–501 (2004)]. Similar weighting patterns were also estimated when the center frequency of the stimuli was random.