On the Emergence and Awareness of Auditory Objects

Shihab Shamma

doi:10.1371/journal.pbio.0060155

Abstract

Anyone who has walked into a crowded reverberant nightclub, with a hubbub of multiple conversations amidst blaring music, will recall the initial impression of the sound as loud and undifferentiated noise. In short order, however, different sound streams begin to emerge as one attends to individual speakers, listens to the melody from the band, or even hears one instrument in it. Humans perform this remarkable feat effortlessly. Our extraordinary abilities to extract signal from noise have evolved in natural environments that are often extremely auditorily cluttered. Many animals have developed abilities to navigate their complex auditory scenes in order to mate, locate prey, feed their young, and avoid predators. It is likely that these abilities are mediated by similar mechanisms that have evolved in many animals and include a mix of “bottom-up” automatic processes with complex “top-down” behaviors involving attention, expectation, learning, and memory (as illustrated schematically in Figure 1). However, little is known about the underlying computational details, or the manner in which these diverse processes interact to give rise to this auditory ability. And it is therefore no coincidence that we still lack engineering systems that can recognize speech robustly in realistic environments, or reliably transcribe polyphonic music.

Highlights

Anyone who has walked into a crowded reverberant nightclub, with a hubbub of multiple conversations amidst blaring music, will recall the initial impression of the sound as loud and undifferentiated noise
The neural underpinnings of attention, feature selection, object binding, and other perceptual and cognitive phenomena have been the focus of research in the visual system. Addressing these phenomena in the context of auditory perception promotes unique perspectives that stem from the temporal nature of sensory signals in animal communication, human speech, and music
Primers provide a concise introduction into an important aspect of biology highlighted by a current PLoS Biology research article

Summary

Introduction

Anyone who has walked into a crowded reverberant nightclub, with a hubbub of multiple conversations amidst blaring music, will recall the initial impression of the sound as loud and undifferentiated noise. The two papers complement each other well in techniques (psychoacoustics versus behavioral magnetoencephalography (MEG) recordings), scope of their exploration (precortical and cortical phonemic levels versus the primary auditory cortex [A1] and its immediate belt), and their fundamental findings (the conditions that facilitate object formation versus the neural correlate of perceptual awareness of object formation).

Results

Conclusion