Understanding Pitch Perception as a Hierarchical Process with Top-Down Modulation

Pitch is one of the most important features of natural sounds, underlying the perception of melody in music and prosody in speech. However, the temporal dynamics of pitch processing are still poorly understood. Previous studies suggest that the auditory system uses a wide range of time scales to integrate pitch-related information and that the effective integration time is both task- and stimulus-dependent. None of the existing models of pitch processing can account for such task- and stimulus-dependent variations in processing time scales. This study presents an idealized neurocomputational model, which provides a unified account of the multiple time scales observed in pitch perception. The model is evaluated using a range of perceptual studies, which have not previously been accounted for by a single model, and new results from a neurophysiological experiment. In contrast to other approaches, the current model contains a hierarchy of integration stages and uses feedback to adapt the effective time scales of processing at each stage in response to changes in the input stimulus. The model has features in common with a hierarchical generative process and suggests a key role for efferent connections from central to sub-cortical areas in controlling the temporal dynamics of pitch processing.Author Summary: Pitch is one of the most important features of natural sounds. The pitch sensation depends strongly on its temporal context, as happens, for example, in the perception of melody in music and prosody in speech. However, the temporal dynamics of pitch processing are poorly understood. Perceptual studies have shown that there is apparently a wide range of time scales over which pitch-related information is integrated. This multiplicity in perceptual time scales requires a trade-off between temporal resolution and temporal integration, which is not exclusive to pitch perception but applies to auditory perception in general. As far as we are aware, no existing model can account simultaneously for the wide range and stimulus-dependent nature of the perceptual phenomenology. This article presents a neurocomputational model, which explains the temporal resolution–integration trade-off observed in pitch perception in a unified fashion. The main contribution of this work is to propose that top-down, efferent mechanisms are crucial for pitch processing. The model replicates perceptual responses in a wide range of perceptual experiments not simultaneously accounted for by previous approaches. Moreover, it accounts quantitatively for the stimulus-dependent latency of the pitch onset response measured in the auditory cortex.