Rapid computations of spectrotemporal prediction error support perception of degraded speech.
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ABSTRACT:
SUBMITTER: Sohoglu E
PROVIDER: S-EPMC7641582 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Spectrotemporal modulation (STM) detection performance was examined for cochlear implant (CI) users. The test involved discriminating between an unmodulated steady noise and a modulated stimulus. The modulated stimulus presents frequency modulation patterns that change in frequency over time. In order to examine STM detection performance for different modulation conditions, two different temporal modulation rates (5 and 10 Hz) and three different spectral modulation densities (0.5, 1.0, and 2.0 cycles/octave) were employed, producing a total 6 different STM stimulus conditions. In order to explore how electric hearing constrains STM sensitivity for CI users differently from acoustic hearing, normal-hearing (NH) and hearing-impaired (HI) listeners were also tested on the same tasks. STM detection performance was best in NH subjects, followed by HI subjects. On average, CI subjects showed poorest performance, but some CI subjects showed high levels of STM detection performance that was comparable to acoustic hearing. Significant correlations were found between STM detection performance and speech identification performance in quiet and in noise. In order to understand the relative contribution of spectral and temporal modulation cues to speech perception abilities for CI users, spectral and temporal modulation detection was performed separately and related to STM detection and speech perception performance. The results suggest that that slow spectral modulation rather than slow temporal modulation may be important for determining speech perception capabilities for CI users. Lastly, test-retest reliability for STM detection was good with no learning. The present study demonstrates that STM detection may be a useful tool to evaluate the ability of CI sound processing strategies to deliver clinically pertinent acoustic modulation information.
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Project description:The value of the environment determines animals' motivational states and sets expectations for error-based learning1-3. How are values computed? Reinforcement learning systems can store or cache values of states or actions that are learned from experience, or they can compute values using a model of the environment to simulate possible futures3. These value computations have distinct trade-offs, and a central question is how neural systems decide which computations to use or whether/how to combine them4-8. Here we show that rats use distinct value computations for sequential decisions within single trials. We used high-throughput training to collect statistically powerful datasets from 291 rats performing a temporal wagering task with hidden reward states. Rats adjusted how quickly they initiated trials and how long they waited for rewards across states, balancing effort and time costs against expected rewards. Statistical modeling revealed that animals computed the value of the environment differently when initiating trials versus when deciding how long to wait for rewards, even though these decisions were only seconds apart. Moreover, value estimates interacted via a dynamic learning rate. Our results reveal how distinct value computations interact on rapid timescales, and demonstrate the power of using high-throughput training to understand rich, cognitive behaviors.
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Project description:Speech perception often benefits from vision of the speaker's lip movements when they are available. One potential mechanism underlying this reported gain in perception arising from audio-visual integration is on-line prediction. In this study we address whether the preceding speech context in a single modality can improve audiovisual processing and whether this improvement is based on on-line information-transfer across sensory modalities. In the experiments presented here, during each trial, a speech fragment (context) presented in a single sensory modality (voice or lips) was immediately continued by an audiovisual target fragment. Participants made speeded judgments about whether voice and lips were in agreement in the target fragment. The leading single sensory context and the subsequent audiovisual target fragment could be continuous in either one modality only, both (context in one modality continues into both modalities in the target fragment) or neither modalities (i.e., discontinuous). The results showed quicker audiovisual matching responses when context was continuous with the target within either the visual or auditory channel (Experiment 1). Critically, prior visual context also provided an advantage when it was cross-modally continuous (with the auditory channel in the target), but auditory to visual cross-modal continuity resulted in no advantage (Experiment 2). This suggests that visual speech information can provide an on-line benefit for processing the upcoming auditory input through the use of predictive mechanisms. We hypothesize that this benefit is expressed at an early level of speech analysis.
| S-EPMC3187777 | biostudies-literature
Project description:Perceptual recalibration allows listeners to adapt to talker-specific pronunciations, such as atypical realizations of specific sounds. Such recalibration can facilitate robust speech recognition. However, indiscriminate recalibration following any atypically pronounced words also risks interpreting pronunciations as characteristic of a talker that are in reality because of incidental, short-lived factors (such as a speech error). We investigate whether the mechanisms underlying perceptual recalibration involve inferences about the causes for unexpected pronunciations. In 5 experiments, we ask whether perceptual recalibration is blocked if the atypical pronunciations of an unfamiliar talker can also be attributed to other incidental causes. We investigated 3 type of incidental causes for atypical pronunciations: the talker is intoxicated, the talker speaks unusually fast, or the atypical pronunciations occur only in the context of tongue twisters. In all 5 experiments, we find robust evidence for perceptual recalibration, but little evidence that the presence of incidental causes block perceptual recalibration. We discuss these results in light of other recent findings that incidental causes can block perceptual recalibration. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Project description:Purpose Age-related sensorineural hearing loss can dramatically affect speech recognition performance due to reduced audibility and suprathreshold distortion of spectrotemporal information. Normal aging produces changes within the central auditory system that impose further distortions. The goal of this study was to characterize the effects of aging and hearing loss on perceptual representations of speech. Method We asked whether speech intelligibility is supported by different patterns of spectrotemporal modulations (STMs) in older listeners compared to young normal-hearing listeners. We recruited 3 groups of participants: 20 older hearing-impaired (OHI) listeners, 19 age-matched normal-hearing listeners, and 10 young normal-hearing (YNH) listeners. Listeners performed a speech recognition task in which randomly selected regions of the speech STM spectrum were revealed from trial to trial. The overall amount of STM information was varied using an up-down staircase to hold performance at 50% correct. Ordinal regression was used to estimate weights showing which regions of the STM spectrum were associated with good performance (a "classification image" or CImg). Results The results indicated that (a) large-scale CImg patterns did not differ between the 3 groups; (b) weights in a small region of the CImg decreased systematically as hearing loss increased; (c) CImgs were also nonsystematically distorted in OHI listeners, and the magnitude of this distortion predicted speech recognition performance even after accounting for audibility; and (d) YNH listeners performed better overall than the older groups. Conclusion We conclude that OHI/older normal-hearing listeners rely on the same speech STMs as YNH listeners but encode this information less efficiently. Supplemental Material https://doi.org/10.23641/asha.7859981.
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Project description:Dopamine (DA) neurons in the ventral tegmental area (VTA) are thought to encode reward prediction errors (RPE) by comparing actual and expected rewards. In recent years, much work has been done to identify how the brain uses and computes this signal. While several lines of evidence suggest the interplay of the DA and the inhibitory interneurons in the VTA implements the RPE computation, it still remains unclear how the DA neurons learn key quantities, for example the amplitude and the timing of primary rewards during conditioning tasks. Furthermore, endogenous acetylcholine and exogenous nicotine, also likely affect these computations by acting on both VTA DA and GABA (? -aminobutyric acid) neurons via nicotinic-acetylcholine receptors (nAChRs). To explore the potential circuit-level mechanisms for RPE computations during classical-conditioning tasks, we developed a minimal computational model of the VTA circuitry. The model was designed to account for several reward-related properties of VTA afferents and recent findings on VTA GABA neuron dynamics during conditioning. With our minimal model, we showed that the RPE can be learned by a two-speed process computing reward timing and magnitude. By including models of nAChR-mediated currents in the VTA DA-GABA circuit, we showed that nicotine should reduce the acetylcholine action on the VTA GABA neurons by receptor desensitization and potentially boost DA responses to reward-related signals in a non-trivial manner. Together, our results delineate the mechanisms by which RPE are computed in the brain, and suggest a hypothesis on nicotine-mediated effects on reward-related perception and decision-making.
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Project description:Prior research has shown that the perception of degraded speech is influenced by within sentence meaning and recruits one or more components of a frontal-temporal-parietal network. The goal of the current study is to examine whether the overall conceptual meaning of a sentence, made up of one set of words, influences the perception of a second acoustically degraded sentence, made up of a different set of words. Using functional magnetic resonance imaging (fMRI), we presented an acoustically clear sentence followed by an acoustically degraded sentence and manipulated the semantic relationship between them: Related in meaning (but consisting of different content words), Unrelated in meaning, or Same. Results showed that listeners' word recognition accuracy for the acoustically degraded sentences was significantly higher when the target sentence was preceded by a conceptually related compared to a conceptually unrelated sentence. Sensitivity to conceptual relationships was associated with enhanced activity in middle and inferior frontal, temporal, and parietal areas. In addition, the left middle frontal gyrus (LMFG), left inferior frontal gyrus (LIFG), and left middle temporal gyrus (LMTG) showed activity that correlated with individual performance on the Related condition. The superior temporal gyrus (STG) showed increased activation in the Same condition suggesting that it is sensitive to perceptual similarity rather than the integration of meaning between the sentence pairs. A fronto-temporo-parietal network appears to consolidate information sources across multiple levels of language (acoustic, lexical, syntactic, semantic) to build, and ultimately integrate conceptual information across sentences and facilitate the perception of a degraded speech signal. However, the nature of the sources of information that are available differentially recruit specific regions and modulate their activity within this network. Implications of these findings for the functional architecture of the network are considered.
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Project description:Comprehension of degraded speech requires higher-order expectations informed by prior knowledge. Accurate top-down expectations of incoming degraded speech cause a subjective semantic 'pop-out' or conscious breakthrough experience. Indeed, the same stimulus can be perceived as meaningless when no expectations are made in advance. We investigated the event-related potential (ERP) correlates of these top-down expectations, their error signals and the subjective pop-out experience in healthy participants. We manipulated expectations in a word-pair priming degraded (noise-vocoded) speech task and investigated the role of top-down expectation with a between-groups attention manipulation. Consistent with the role of expectations in comprehension, repetition priming significantly enhanced perceptual intelligibility of the noise-vocoded degraded targets for attentive participants. An early ERP was larger for mismatched (i.e. unexpected) targets than matched targets, indicative of an initial error signal not reliant on top-down expectations. Subsequently, a P3a-like ERP was larger to matched targets than mismatched targets only for attending participants-i.e. a pop-out effect-while a later ERP was larger for mismatched targets and did not significantly interact with attention. Rather than relying on complex post hoc interactions between prediction error and precision to explain this apredictive pattern, we consider our data to be consistent with prediction error minimization accounts for early stages of processing followed by Global Neuronal Workspace-like breakthrough and processing in service of task goals.
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Project description:The human brain can quickly adapt to changes in the environment. One example is phonetic recalibration: a speech sound is interpreted differently depending on the visual speech and this interpretation persists in the absence of visual information. Here, we examined the mechanisms of phonetic recalibration. Participants categorized the auditory syllables /aba/ and /ada/, which were sometimes preceded by the so-called McGurk stimuli (in which an /aba/ sound, due to visual /aga/ input, is often perceived as 'ada'). We found that only one trial of exposure to the McGurk illusion was sufficient to induce a recalibration effect, i.e. an auditory /aba/ stimulus was subsequently more often perceived as 'ada'. Furthermore, phonetic recalibration took place only when auditory and visual inputs were integrated to 'ada' (McGurk illusion). Moreover, this recalibration depended on the sensory similarity between the preceding and current auditory stimulus. Finally, signal detection theoretical analysis showed that McGurk-induced phonetic recalibration resulted in both a criterion shift towards /ada/ and a reduced sensitivity to distinguish between /aba/ and /ada/ sounds. The current study shows that phonetic recalibration is dependent on the perceptual integration of audiovisual information and leads to a perceptual shift in phoneme categorization.
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Project description:Neuroimaging studies of speech perception have consistently indicated a left-hemisphere dominance in the temporal lobes' responses to intelligible auditory speech signals (McGettigan and Scott, 2012). However, there are important communicative cues that cannot be extracted from auditory signals alone, including the direction of the talker's gaze. Previous work has implicated the superior temporal cortices in processing gaze direction, with evidence for predominantly right-lateralized responses (Carlin & Calder, 2013). The aim of the current study was to investigate whether the lateralization of responses to talker gaze differs in an auditory communicative context. Participants in a functional MRI experiment watched and listened to videos of spoken sentences in which the auditory intelligibility and talker gaze direction were manipulated factorially. We observed a left-dominant temporal lobe sensitivity to the talker's gaze direction, in which the left anterior superior temporal sulcus/gyrus and temporal pole showed an enhanced response to direct gaze - further investigation revealed that this pattern of lateralization was modulated by auditory intelligibility. Our results suggest flexibility in the distribution of neural responses to social cues in the face within the context of a challenging speech perception task.
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