Neural Correlates of Auditory Figure-Ground Segregation Based on Temporal Coherence

Abstract

To make sense of natural acoustic environments, listeners must parse complex mixtures of sounds that vary in frequency, space, and time. Emerging work suggests that, in addition to the well-studied spectral cues for segregation, sensitivity to temporal coherence—the coincidence of sound elements in and across time—is also critical for the perceptual organization of acoustic scenes. Here, we examine pre-attentive, stimulus-driven neural processes underlying auditory figure-ground segregation using stimuli that capture the challenges of listening in complex scenes where segregation cannot be achieved based on spectral cues alone. Signals (“stochastic figure-ground”: SFG) comprised a sequence of brief broadband chords containing random pure tone components that vary from 1 chord to another. Occasional tone repetitions across chords are perceived as “figures” popping out of a stochastic “ground.” Magnetoencephalography (MEG) measurement in naïve, distracted, human subjects revealed robust evoked responses, commencing from about 150 ms after figure onset that reflect the emergence of the “figure” from the randomly varying “ground.” Neural sources underlying this bottom-up driven figure-ground segregation were localized to planum temporale, and the intraparietal sulcus, demonstrating that this area, outside the “classic” auditory system, is also involved in the early stages of auditory scene analysis.”

A roadmap for the study of conscious audition and its neural basis

“…Like the multitone masker paradigm described above, this stimulus is also composed of multiple random pure tones, with a target (or ' figure') comprising a set of synchronous tones that repeat over successive presentations of otherwise random chords (figure 1). Listening to these stimuli appears to induce activity in both AC (with N1/N2-like scalp topographies [147]) and the IPS [146,148], with larger activity both for stimuli evoking more distinct perceptual figures and for active over passive listening. When taken together with similar findings from the aforementioned streaming [143,144] and multitone masker [111] studies, these results suggest a role for the IPS in either auditory scene analysis or conscious auditory perception.…”

Computational Models of Auditory Scene Analysis: A Review

“…Because the “figure” is created by manipulating the temporal coherence of a part of the stimulus (i.e., by repeating some tones while the rest of the tones are randomly varied), the temporal coherence theory of ASA provides a good explanation for figure-ground segregation in these cases (Teki et al, 2013). Teki et al (2016) extended their original finding by showing that repetition of the tonal complex is detected even when the tone cloud and, within it, the repeating complex is interspersed with white noise segments, thus making the figure acoustically non-continuous. Connecting non-adjacent segments into a coherent stream has been previously observed for temporal/sequential grouping (Bendixen et al, 2012).…”

“…However, they suffer from some of the same problems that have been described above, because they need to be validated by behavioral measures. To date brain measures have seldom been used for validating computational models of ASA, therefore we do not review them here (for some of the neuroscience methods used for studying ASA, see the next section as well as Fishman et al, 2001; Bee and Klump, 2004; Deike et al, 2004; Gutschalk et al, 2005; Wilson et al, 2007; Alain and Winkler, 2012; Teki et al, 2013; O'Sullivan et al, 2015; Teki et al, 2016). …”

“…Sustained responses in auditory cortex appear to encode perceived repetition rates and increase in response to segregation. Transient responses synchronized with perceptual switching have been found in auditory cortex (Kondo and Kashino, 2009; Schadwinkel and Gutschalk, 2011), thalamus (Kondo and Kashino, 2009), inferior colliculus (Schadwinkel and Gutschalk, 2011), and intraparietal sulcus (Teki et al, 2016). Although it is not clear how or where switching is triggered, these studies provide evidence for a tight interaction between cortical and subcortical processing in resolving the ASA problem.…”

“…Repetition is a powerful grouping and segregation cue, the effects of which can be demonstrated even in the absence of other cues (McDermott et al, 2011; Teki et al, 2011, 2013, 2016). Sensitivity to repetition (in the presence of a variable background) may underlie the robustness of perception with regard to natural variability in signals, such as speech.…”