Abstract
Under a “cocktail party” environment, listeners can utilize prior knowledge of the content and voice of the target speech [i.e., auditory speech priming (ASP)] and perceived spatial separation to improve recognition of the target speech among masking speech. Previous studies suggest that these two unmasking cues are not processed independently. However, it is unclear whether the unmasking effects of these two cues are supported by common neural bases. In the current study, we aimed to first confirm that ASP and perceived spatial separation contribute to the improvement of speech recognition interactively in a multitalker condition and further investigate whether there exist intersectant brain substrates underlying both unmasking effects, by introducing these two unmasking cues in a unified paradigm and using functional magnetic resonance imaging. The results showed that neural activations by the unmasking effects of ASP and perceived separation partly overlapped in brain areas: the left pars triangularis (TriIFG) and orbitalis of the inferior frontal gyrus, left inferior parietal lobule, left supramarginal gyrus, and bilateral putamen, all of which are involved in the sensorimotor integration and the speech production. The activations of the left TriIFG were correlated with behavioral improvements caused by ASP and perceived separation. Meanwhile, ASP and perceived separation also enhanced the functional connectivity between the left IFG and brain areas related to the suppression of distractive speech signals: the anterior cingulate cortex and the left middle frontal gyrus, respectively. Therefore, these findings suggest that the motor representation of speech is important for both the unmasking effects of ASP and perceived separation and highlight the critical role of the left IFG in these unmasking effects in “cocktail party” environments.
Highlights
The results showed that the benefit of auditory speech priming (ASP) under the perceived co-location condition was greater than that under the perceived separation condition (t35 = 3, p = 0.005, see Figure 2B)
We introduced ASP and perceived spatial separation to investigate how they improve recognition of the target speech in a “cocktail party” environment
The behavioral results showed that the benefits of ASP and perceived separation for speech recognition cannot be added
Summary
How do our brains deal with a complex scene where listeners need to selectively detect, follow, and recognize a speaker’s words (target) when multiple people are talking (masker) at the same time (i.e., the “cocktail party” problem) (Cherry, 1953; Schneider et al, 2007; McDermott, 2009; Bronkhorst, 2015)? Previous studies have shown that listeners can take advantage of diverse perceptual and/or cognitive cues, such as prior knowledge of the contents of the speech and/or the speaker’s voice (Freyman et al, 2004; Yang et al, 2007), information obtained from lip reading (Wu et al, 2017b), and perceived spatial separation (Freyman et al, 1999), to improve their recognition of target speech masked by non-target sounds (i.e., release from masking or unmasking). Despite age-related declines in hearing, older adults can utilize ASP and perceived separation to improve their recognition of the targets under a noisy environment just as well as do younger adults (Li et al, 2004; Ezzatian et al, 2011) These studies propose that certain topdown auditory mechanisms underlying the unmasking effects of ASP and perceived separation are preserved in patients with schizophrenia and older adults (Li et al, 2004; Ezzatian et al, 2011; Wu et al, 2012, 2017a). Researchers have claimed that the ASP helps listeners maintain the target’s voice and content in working memory and may facilitate grouping the target speech to enhance the listener’s selective attention to the target (Freyman et al, 2004; Schneider et al, 2007; McDermott, 2009; Ezzatian et al, 2011; Wu et al, 2012a,b; Carlile, 2015; Wang et al, 2019)
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