Perceptual learning of auditory spectral modulation detection

Abstract

Normal sensory perception requires the ability to detect and identify patterns of activity distributed across the receptor surface. In the visual system, the ability to perceive these patterns across the retina improves with training. This learning differs in magnitude for different trained stimuli and does not generalize to untrained spatial frequencies or retinal locations. Here we asked whether training to detect patterns of activity across the cochlea yields learning with similar characteristics. Differences in learning between the visual and auditory systems would be inconsistent with the suggestion that the ability to detect these patterns is limited by similar constraints in these two systems. We trained three groups of normal-hearing listeners to detect spectral envelopes with a sinusoidal shape (spectral modulation) at either 0.5, 1, or 2 cycles/octave and compared the performance of each group to that of a separate group that received no training. On average, as the trained spectral modulation frequency increased, the magnitude of training-induced improvement and the time to reach asymptotic performance decreased, while the tendency for performance to worsen within a training session increased. The training-induced improvements did not generalize to untrained spectral modulation frequencies or untrained carrier spectra. Thus, for both visual-spatial and auditory-spectral modulation detection, learning depended upon and was specific to analogous features of the trained stimulus. Such similarities in learning could arise if, as has been suggested, similar constraints limit the ability to detect patterns across the receptor surface between the auditory and visual systems.

Effect of long-term training on sound localization performance with spectrally warped and band-limited head-related transfer functions

“…On the other hand, a recent study on learning monaural spectral modulation detection showed that the magnitude of training-induced improvements decreased with increasing spectral modulation frequency (from 0.5 to 2 ripples/octave, Sabin et al, 2012), potentially complicating the comparison between our two groups. However, if the spectral modulation frequency had indeed played a large role, the training effect would be expected to be more restricted for the warped group then for the control group, opposite to what we have observed.…”

“…This process, called perceptual training (Wright and Fitzgerald, 2001), seems to underlie the process of supervised learning in which neural networks calibrate each other in a goal-directed way (Knudsen, 1994). Since the auditory system is tonotopically organized even up to the auditory cortex (Kaas and Hackett, 2000), perceptual training can be restricted to specific frequencies as shown for frequency discrimination (Recanzone et al, 1993), sensitivity to binaural cues (Wright and Fitzgerald, 2001) and spectral modulation detection (Sabin et al, 2012). Even though the exact neural mechanisms are still the subject of investigation, our training with band-limited DTFs might be considered as frequency-specific supervised training: Over the course of the training, listeners associated the spectral cues below 8.5 kHz with the visually provided spatial information, while the frequencies above 8.5 kHz were not stimulated at all.…”

Perceptual factors contribute more than acoustical factors to sound localization abilities with virtual sources

“…Non-acoustical factors, such as perceptual processes, have been proposed to explain the large individual differences reported in studies about discrimination between front and rear sources (Wightman and Kistler, 1999 ) and about sound localization in noise (Andéol et al, 2011 , 2013 ). The perceptual processes involved in the analysis of spectral cues (Drennan and Watson, 2001 ; Sabin et al, 2012 ) and sound localization accuracy with individual HRTFs (Majdak et al, 2010 ) were both found to improve with training in the auditory task. In the latter study, acoustical cues were kept constant but sensory (visual) feedback was provided during training.…”

Auditory sensitivity to spectral modulation phase reversal as a function of modulation depth

“…All stimuli were 168 ms in duration, including 20-ms raised-cosine ramps. While some studies of spectral modulation perception have used longer-duration stimuli, on the order of 400 ms [ 14 , 19 ], there is precedent in the literature for using stimulus durations as short as 30–100 ms [ 20 , 21 ]. Briefer stimuli may be preferable if they provide the listener with less robust temporal cues to spectral shape.…”

“…As illustrated in Fig 3 , performance in both tasks improved with increasing modulation rate up to 1–2 rpo. This result has been attributed to difficulties comparing spectral features that are distributed widely in frequency [ 21 ]. Above 2–4 rpo, thresholds worsened with increasing modulation rate, a finding attributed to detrimental effects of limited frequency resolution [ 19 ].…”