Build-up of auditory stream segregation induced by tone sequences of constant or alternating frequency and the resetting effects of single deviants.

Abstract

A sequence of constant-frequency tones can promote streaming in a subsequent sequence of alternating-frequency tones, but why this effect occurs is not fully understood and its time course has not been investigated. Experiment 1 used a 2.0-s-long constant-frequency inducer (10 repetitions of a low-frequency pure tone) to promote segregation in a subsequent, 1.2-s test sequence of alternating low- and high-frequency tones. Replacing the final inducer tone with silence substantially reduced reported test-sequence segregation. This reduction did not occur when either the 4th or 7th inducer was replaced with silence. This suggests that a change at the induction/test-sequence boundary actively resets build-up, rather than less segregation occurring simply because fewer inducer tones were presented. Furthermore, Experiment 2 found that a constant-frequency inducer produced its maximum segregation-promoting effect after only three tones--this contrasts with the more gradual build-up typically observed for alternating-frequency sequences. Experiment 3 required listeners to judge continuously the grouping of 20-s test sequences. Constant-frequency inducers were considerably more effective at promoting segregation than alternating ones; this difference persisted for ∼10 s. In addition, resetting arising from a single deviant (longer tone) was associated only with constant-frequency inducers. Overall, the results suggest that constant-frequency inducers promote segregation by capturing one subset of test-sequence tones into an ongoing, preestablished stream, and that a deviant tone may reduce segregation by disrupting this capture. These findings offer new insight into the dynamics of stream segregation, and have implications for the neural basis of streaming and the role of attention in stream formation.

The Contribution of Primary Auditory Cortex to Auditory Categorization in Behaving Monkeys

“…In our earlier behavioral study (which used the same animals and same experimental stimuli as in the current study) (Christison-Lagay and Cohen, 2014), we included three control conditions that support that monkeys stream the stimuli used in the current paradigm. First, the monkeys were more likely to report “large” frequency differences with longer listening times (Christison-Lagay and Cohen, 2014), similar to human listeners who are also more likely to report two streams with longer listening times (Micheyl et al, 2005) and consistent with the idea that one’s perception of two streams “builds up” over time (Micheyl et al, 2005; Haywood and Roberts, 2013). Second, similar to human listeners (Elhilali et al, 2009; Micheyl et al, 2013), when the tone bursts were presented simultaneously (vs. asynchronously as shown in Figure 1A ) and the frequency difference was large (which normally elicits reports of “two auditory streams”), the monkeys’ reports were biased toward those of when they had heard a “small” frequency difference (Christison-Lagay and Cohen, 2014).…”

The effect of stimulus context on the buildup to stream segregation

“…However, Beauvois and Meddis (1997) used a constant frequency induction sequence with no silence between the induction and test sequence. Haywood and Roberts (2013), in contrast, showed that an alternating frequency induction sequence had less of an effect on the perception of streaming. Even if the effect was smaller, our neurophysiologic results may be partially explained by their results.…”

Stimulus Pauses and Perturbations Differentially Delay or Promote the Segregation of Auditory Objects: Psychoacoustics and Modeling

“…Even for a context of a single stream of tones, say A_A_A_A_, that would alone promote segregation for subsequent test triplets ABA_ ABA_…, similar disruptions as above at the end of the context sequence lead to integration, as if the effect of the context was undone (Rogers and Bregman, 1993, 1998; Beauvois and Meddis, 1997). Also, a single deviant A' at the end of an A_A_A_…context can reduce or eliminate the expected bias toward segregation (Roberts et al, 2008; Haywood and Roberts, 2010, 2013). So while these various disruptions favor integration and may a priori lead one to a generalized expectation that a single transient distractor tone (between triplets) or a single deviant tone (within a triplet) should also promote integration, we found the opposite — promotion of segregation in the subsequent triplets.…”

“…Nevertheless our results do not contradict these previous studies. Studies looking at the effects of deviant tones did so by placing these at the end of a single stream context (Roberts et al, 2008; Haywood and Roberts, 2010, 2013); in our study we placed the deviant or distractor at the end of context triplets. Thompson et al (2011) included an experiment with a single delayed-onset deviant B tone, but did not report promotion of segregation or resetting.…”

“…Haywood and Roberts (2013) showed that hearing a single A tone before the triplets could make that stream more salient. Could there be a similar effect in our data, where the distractor tone makes one of the streams more salient, or briefly directs attention toward it?…”