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Previous studies have shown that perceptual segregation increases after listening to longer tone sequences, an effect known as buildup. More recently, an effect of prior frequency separation (Δƒ) has been discovered: presenting tone sequences with a small Δƒ biases following sequences with an intermediate Δƒ to be segregated into two separate streams, whereas presenting context sequences with a large Δƒ biases following sequences to be integrated into one stream. Here we investigated how attention and task demands influenced these effects of prior stimuli by having participants perform one of three tasks during the context: making streaming judgments on the tone sequences, detecting amplitude modulation in the tones, and performing a visual task while ignoring the tones. Results from two experiments showed that although the effect of prior Δƒ was present across all conditions, the effect was reduced whenever streaming judgments were not made during the context. Experiment 2 showed that streaming was reduced during the beginning of a test sequence only when participants performed the visual task during the context. These experiments suggest that task-based and stimulus-based attention differentially affect distinct influences of prior stimuli, and are consistent with the contribution of distinct levels of processing that affect auditory segregation. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Understanding the neural underpinning of conscious perception remains one of the primary challenges of cognitive neuroscience. Theories based mostly on studies of the visual system differ according to whether the neural activity giving rise to conscious perception occurs in modality-specific sensory cortex or in associative areas, such as the frontal and parietal cortices. Here, we search for modality-specific conscious processing in the auditory cortex using a bistable stream segregation paradigm that presents a constant stimulus without the confounding influence of physical changes to sound properties. ABA_ triplets (i.e., alternating low, A, and high, B, tones, and _ gap) with a 700 ms silent response period after every third triplet were presented repeatedly, and human participants reported nearly equivalent proportions of 1- and 2-stream percepts. The pattern of behavioral responses was consistent with previous studies of visual and auditory bistable perception. The intermittent response paradigm has the benefit of evoking spontaneous perceptual switches that can be attributed to a well-defined stimulus event, enabling precise identification of the timing of perception-related neural events with event-related potentials (ERPs). Significantly more negative ERPs were observed for 2-streams compared to 1-stream, and for switches compared to non-switches during the sustained potential (500-1000 ms post-stimulus onset). Further analyses revealed that the negativity associated with switching was independent of switch direction, suggesting that spontaneous changes in perception have a unique neural signature separate from the observation that 2-streams has more negative ERPs than 1-stream. Source analysis of the sustained potential showed activity associated with these differences originating in anterior superior temporal gyrus, indicating involvement of the ventral auditory pathway that is important for processing auditory objects.Significance StatementWhen presented with ambiguous stimuli, the auditory system takes the available information and attempts to construct a useful percept. When multiple percepts are possible from the same stimuli, however, perception fluctuates back and forth between alternating percepts in a bistable manner. Here, we examine spontaneous switches in perception using a bistable auditory streaming paradigm with a novel intermittent stimulus paradigm, and measure sustained electrical activity in anterior portions of auditory cortex using event-related potentials. Analyses revealed enhanced sustained cortical activity when perceiving 2-streams compared to 1-stream, and when a switch occurred regardless of switch direction. These results indicate that neural responses in auditory cortex reflect both the content of perception and neural dynamics related to switches in perception.

The present study sought to test whether perceptual segregation of concurrently played sounds is impaired in schizophrenia (SZ), whether impairment in sound segregation predicts difficulties with a real-world speech-in-noise task, and whether auditory-specific or general cognitive processing accounts for sound segregation problems. Participants with SZ and healthy controls (HCs) performed a mistuned harmonic segregation task during recording of event-related potentials (ERPs). Participants also performed a brief speech-in-noise task. Participants with SZ showed deficits in the mistuned harmonic task and the speech-in-noise task, compared to HCs. No deficit in SZ was found in the ERP component related to mistuned harmonic segregation at around 150 ms (the object-related negativity or ORN), but instead showed a deficit in processing at around 400 ms (the P4 response). However, regression analyses showed that indexes of education level and general cognitive function were the best predictors of sound segregation difficulties, suggesting non-auditory specific causes of concurrent sound segregation problems in SZ.

Past research has identified several candidate neural correlates of consciousness (NCCs) during visual perception. Recent research on auditory perception shows promise for establishing the generality of various NCCs across sensory modalities, as well as for revealing differences in how conscious processing unfolds in different sensory systems.

Past empirical work on perception of complex auditory scenes has demonstrated striking effects of attention on perception. Here, we present data from recent studies of auditory stream segregation and change deafness, demonstrating that different types of attention influence what is perceived. During auditory stream segregation, we found that the increasing tendency to perceive segregation as more alternations of low and high tones are presented (i.e., buildup) is facilitated by attending to the tone patterns, regardless of whether participants were actively making judgments of segregation. In contrast, performing the segregation task was necessary to enhance the influence of the frequency separation of the immediately prior tone pattern, suggesting a form of task-based (as opposed to stimulus-based) attention. During change detection, we found that cueing participants to which object is likely to be replaced in a scene of multiple objects facilitates successful detection of changes, while providing an inv...