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Repeated exposure to a stimulus results in reduced neural response, or repetition suppression, in brain regions responsible for processing that stimulus. This rapid accommodation to repetition is thought to underlie learning, stimulus selectivity, and strengthening of perceptual expectations. Importantly, reduced sensitivity to repetition has been identified in several neurodevelopmental, learning, and psychiatric disorders, including autism spectrum disorder (ASD), a neurodevelopmental disorder characterized by challenges in social communication and repetitive behaviors and restricted interests. Reduced ability to exploit or learn from repetition in ASD is hypothesized to contribute to sensory hypersensitivities, and parallels several theoretical frameworks claiming that ASD individuals show difficulty using regularities in the environment to facilitate behavior. Using fMRI in autistic and neurotypical human adults (females and males), we assessed the status of repetition suppression across two modalities (vision, audition) and with four stimulus categories (faces, objects, printed words, and spoken words). ASD individuals showed domain-specific reductions in repetition suppression for face stimuli only, but not for objects, printed words, or spoken words. Reduced repetition suppression for faces was associated with greater challenges in social communication in ASD. We also found altered functional connectivity between atypically adapting cortical regions and higher-order face recognition regions, and microstructural differences in related white matter tracts in ASD. These results suggest that fundamental neural mechanisms and system-wide circuits are selectively altered for face processing in ASD and enhance our understanding of how disruptions in the formation of stable face representations may relate to higher-order social communication processes.SIGNIFICANCE STATEMENTA common finding in neuroscience is that repetition results in plasticity in stimulus-specific processing regions, reflecting selectivity and adaptation (repetition suppression [RS]). RS is reduced in several neurodevelopmental and psychiatric conditions including autism spectrum disorder (ASD). Theoretical frameworks of ASD posit that reduced adaptation may contribute to associated challenges in social communication and sensory processing. However, the scope of RS differences in ASD is unknown. We examined RS for multiple categories across visual and auditory domains (faces, objects, printed words, spoken words) in autistic and neurotypical individuals. We found reduced RS in ASD for face stimuli only and altered functional connectivity and white matter microstructure between cortical face-recognition areas. RS magnitude correlated with social communication challenges among autistic individuals.

Phonetic variability across talkers imposes additional processing costs during speech perception, evident in performance decrements when listening to speech from multiple talkers. However, within-talker phonetic variation is a less well-understood source of variability in speech, and it is unknown how processing costs from within-talker variation compare to those from between-talker variation. Here, listeners performed a speeded word identification task in which three dimensions of variability were factorially manipulated: between-talker variability (single vs multiple talkers), within-talker variability (single vs multiple acoustically distinct recordings per word), and word-choice variability (two- vs six-word choices). All three sources of variability led to reduced speech processing efficiency. Between-talker variability affected both word-identification accuracy and response time, but within-talker variability affected only response time. Furthermore, between-talker variability, but not within-talker variability, had a greater impact when the target phonological contrasts were more similar. Together, these results suggest that natural between- and within-talker variability reflect two distinct magnitudes of common acoustic–phonetic variability: Both affect speech processing efficiency, but they appear to have qualitatively and quantitatively unique effects due to differences in their potential to obscure acoustic–phonemic correspondences across utterances.

The mapping between speech acoustics and phonemic representations is highly variable across talkers, and listeners are slower to recognize words when listening to multiple talkers compared with a single talker. Listeners' speech processing efficiency in mixed-talker settings improves when given time to reorient their attention to each new talker. However, it remains unknown how much time is needed to fully reorient attention to a new talker in mixed-talker settings so that speech processing becomes as efficient as when listening to a single talker. In this study, we examined how speech processing efficiency improves in mixed-talker settings as a function of the duration of continuous speech from a talker. In single-talker and mixed-talker conditions, listeners identified target words either in isolation or preceded by a carrier vowel of parametrically varying durations from 300 to 1,500 ms. Listeners' word identification was significantly slower in every mixed-talker condition compared with the corresponding single-talker condition. The costs associated with processing mixed-talker speech declined significantly as the duration of the speech carrier increased from 0 to 600 ms. However, increasing the carrier duration beyond 600 ms did not achieve further reduction in talker variability-related processing costs. These results suggest that two parallel mechanisms support processing talker variability: A stimulus-driven mechanism that operates on short timescales to reorient attention to new auditory sources, and a top-down mechanism that operates over longer timescales to allocate the cognitive resources needed to accommodate uncertainty in acoustic-phonemic correspondences during contexts where speech may come from multiple talkers.

In the real world, listeners seem to implicitly learn talkers' vocal identities during interactions that prioritize attending to the content of talkers' speech. In contrast, most laboratory experiments of talker identification employ training paradigms that require listeners to explicitly practice identifying voices. Here, we investigated whether listeners become familiar with talkers' vocal identities during initial exposures that do not involve explicit talker identification. Participants were assigned to one of three exposure tasks, in which they heard identical stimuli but were differentially required to attend to the talkers' vocal identity or to the verbal content of their speech: (1) matching the talker to a concurrent visual cue (talker-matching); (2) discriminating whether the talker was the same as the prior trial (talker 1-back); or (3) discriminating whether speech content matched the previous trial (verbal 1-back). All participants were then tested on their ability to learn to identify talkers from novel speech content. Critically, we manipulated whether the talkers during this post-test differed from those heard during training. Compared to learning to identify novel talkers, listeners were significantly more accurate learning to identify the talkers they had previously been exposed to in the talker-matching and verbal 1-back tasks, but not the talker 1-back task. The correlation between talker identification test performance and exposure task performance was also greater when the talkers were the same in both tasks. These results suggest that listeners learn talkers' vocal identity implicitly during speech perception, even if they are not explicitly attending to the talkers' identity.

Nonword repetition, a common clinical measure of phonological working memory, involves component processes of speech perception, working memory, and speech production. Autistic children often show behavioral challenges in nonword repetition, as do many individuals with communication disorders. It is unknown which subprocesses of phonological working memory are vulnerable in autistic individuals, and whether the same brain processes underlie the transdiagnostic difficulty with nonword repetition. We used functional magnetic resonance imaging (fMRI) to investigate the brain bases for nonword repetition challenges in autism. We compared activation during nonword repetition in functional brain networks subserving speech perception, working memory, and speech production between neurotypical and autistic children. Autistic children performed worse than neurotypical children on nonword repetition and had reduced activation in response to increasing phonological working memory load in the supplementary motor area. Multivoxel pattern analysis within the speech production network classified shorter vs longer nonword-repetition trials less accurately for autistic than neurotypical children. These speech production motor-specific differences were not observed in a group of children with reading disability who had similarly reduced nonword repetition behavior. These findings suggest that atypical function in speech production brain regions may contribute to nonword repetition difficulties in autism.

According to several influential theoretical frameworks, phonological deficits in dyslexia result from reduced sensitivity to acoustic cues that are essential for the development of robust phonemic representations. Some accounts suggest that these deficits arise from impairments in rapid auditory adaptation processes that are either speech-specific or domain-general. Here, we examined the specificity of auditory adaptation deficits in dyslexia using a nonlinguistic tone anchoring (adaptation) task and a linguistic selective adaptation task in children and adults with and without dyslexia. Children and adults with dyslexia had elevated tone-frequency discrimination thresholds, but both groups benefited from anchoring to repeated stimuli to the same extent as typical readers. Additionally, although both dyslexia groups had overall reduced accuracy for speech sound identification, only the child group had reduced categorical perception for speech. Across both age groups, individuals with dyslexia had reduced perceptual adaptation to speech. These results highlight broad auditory perceptual deficits across development in individuals with dyslexia for both linguistic and nonlinguistic domains, but speech-specific adaptation deficits. Finally, mediation models in children and adults revealed that the causal pathways from basic perception and adaptation to phonological awareness through speech categorization were not significant. Thus, rather than having causal effects, perceptual deficits may co-occur with the phonological deficits in dyslexia across development. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

The neural representation of a repeated stimulus is the standard against which a deviant stimulus is measured in the brain, giving rise to the well-known mismatch response. It has been suggested that individuals with dyslexia have poor implicit memory for recently repeated stimuli, such as the train of standards in an oddball paradigm. Here, we examined how the neural representation of a standard emerges over repetitions, asking whether there is less sensitivity to repetition and/or less accrual of “standardness” over successive repetitions in dyslexia. We recorded magnetoencephalography (MEG) as adults with and without dyslexia were passively exposed to speech syllables in a roving-oddball design. We performed time-resolved multivariate decoding of the MEG sensor data to identify the neural signature of standard vs. deviant trials, independent of stimulus differences. This “multivariate mismatch” was equally robust and had a similar time course in the two groups. In both groups, standards generated by as few as two repetitions were distinct from deviants, indicating normal sensitivity to repetition in dyslexia. However, only in the control group did standards become increasingly different from deviants with repetition. These results suggest that many of the mechanisms that give rise to neural adaptation as well as mismatch responses are intact in dyslexia, with the possible exception of a putatively predictive mechanism that successively integrates recent sensory information into feedforward processing.

A perceptual adaptation deficit often accompanies reading difficulty in dyslexia, manifesting in poor perceptual learning of consistent stimuli and reduced neurophysiological adaptation to stimulus repetition. However, it is not known how adaptation deficits relate to differences in feedforward or feedback processes in the brain. Here we used electroencephalography (EEG) to interrogate the feedforward and feedback contributions to neural adaptation as adults with and without dyslexia viewed pairs of faces and words in a paradigm that manipulated whether there was a high probability of stimulus repetition versus a high probability of stimulus change. We measured three neural dependent variables: expectation (the difference between prestimulus EEG power with and without the expectation of stimulus repetition), feedforward repetition (the difference between event-related potentials (ERPs) evoked by an expected change and an unexpected repetition), and feedback-mediated prediction error (the difference between ERPs evoked by an unexpected change and an expected repetition). Expectation significantly modulated prestimulus theta- and alpha-band EEG in both groups. Unexpected repetitions of words, but not faces, also led to significant feedforward repetition effects in the ERPs of both groups. However, neural prediction error when an unexpected change occurred instead of an expected repetition was significantly weaker in dyslexia than the control group for both faces and words. These results suggest that the neural and perceptual adaptation deficits observed in dyslexia reflect the failure to effectively integrate perceptual predictions with feedforward sensory processing. In addition to reducing perceptual efficiency, the attenuation of neural prediction error signals would also be deleterious to the wide range of perceptual and procedural learning abilities that are critical for developing accurate and fluent reading skills., National Institutes of Health (Grants UL1RR025758, R03HD096098, T32DC000038 and F31HD100101)

The human voice is a complex acoustic signal that conveys talker identity via individual differences in numerous features, including vocal source acoustics, vocal tract resonances, and dynamic articulations during speech. It remains poorly understood how differences in these features contribute to perceptual dissimilarity of voices and, moreover, whether linguistic differences between listeners and talkers interact during perceptual judgments of voices. Here, native English- and Mandarin-speaking listeners rated the perceptual dissimilarity of voices speaking English or Mandarin from either forward or time-reversed speech. The language spoken by talkers, but not listeners, principally influenced perceptual judgments of voices. Perceptual dissimilarity judgments of voices were always highly correlated between listener groups and forward/time-reversed speech. Representational similarity analyses that explored how acoustic features (fundamental frequency mean and variation, jitter, harmonics-to-noise ratio, speech rate, and formant dispersion) contributed to listeners' perceptual dissimilarity judgments, including how talker- and listener-language affected these relationships, found the largest effects relating to voice pitch. Overall, these data suggest that, while linguistic factors may influence perceptual judgments of voices, the magnitude of such effects tends to be very small. Perceptual judgments of voices by listeners of different native language backgrounds tend to be more alike than different.

Project AbstractMaking sense of our environment requires us to extract simultaneous temporal and spatial information from multiple sensory modalities, particularly audition and vision. This sensory information can be stored in working memory (WM) to guide future actions, at which point it must be safeguarded against interference from ongoing sensory processing. Recent fMRI research has uncovered regions in human frontal cortex well-suited to coordinate this interplay between attention and WM for multisensory and multidimensional information. Which of these brain regions are engaged depends on both the sensory modality of the input and the information domain of the task, forming the basis of two complementary networks specialized for auditory/temporal and visual/spatial processing. Motivated by the functional specializations of these networks, we examined whether similarity in sensory modality and information domain modulates neural and perceptual interference between two concurrent tasks. Participants stored temporal or spatial information about auditory or visual stimuli in WM, and on some trials, performed an intervening temporal or spatial auditory task during WM retention. WM recall and auditory perceptual judgments were impaired when the two tasks relied on the same sensory modality and/or information domain. Pupil dilations were also larger in these conditions, indicating increased cognitive effort. Event-related potentials (ERPs) revealed a neural signature of domain-based interference that was masked by behavioral ceiling effects. These results demonstrate that modality and information domain jointly affect how task information is represented in WM, and concomitantly, how tasks engage the complementary auditory-temporal and visual/spatial cognitive control networks.

Speech is processed less efficiently from discontinuous, mixed talkers than one consistent talker, but little is known about the neural mechanisms for processing talker variability. Here, we measured psychophysiological responses to talker variability using electroencephalography (EEG) and pupillometry while listeners performed a delayed recall of digit span task. Listeners heard and recalled seven-digit sequences with both talker (single- vs. mixed-talker digits) and temporal (0- vs. 500-ms inter-digit intervals) discontinuities. Talker discontinuity reduced serial recall accuracy. Both talker and temporal discontinuities elicited P3a-like neural evoked response, while rapid processing of mixed-talkers’ speech led to increased phasic pupil dilation. Furthermore, mixed-talkers’ speech produced less alpha oscillatory power during working memory maintenance, but not during speech encoding. Overall, these results are consistent with an auditory attention and streaming framework in which talker discontinuity leads to involuntary, stimulus-driven attentional reorientation to novel speech sources, resulting in the processing interference classically associated with talker variability.

Purpose Child language acquisition is marked by an optional infinitive period (ages 2–4 years) during which children use nonfinite (infinitival) verb forms and finite verb forms interchangeably in grammatical contexts that require finite forms. In English, children's errors include omissions of past tense /– ed / and 3rd-person singular /– s /. This language acquisition period typically ends by the age of 4 years, but it persists in children with language impairments. It is unknown if adults still process optional infinitives differently than other kinds of morphosyntax errors. Method We compared behavior and functional brain activation during grammaticality judgments across sentences with developmental optional infinitive tense/agreement errors (“Yesterday I play the song”), nondevelopmental agreement errors (“He am tall”) that do not occur in typical child language acquisition, and grammatically correct sentences. Results Adults ( N = 25) were significantly slower and less accurate in judging sentences with developmental errors relative to other sentences. Sentences with developmental errors yielded greater activation in bilateral inferior frontal gyri relative to nondevelopmental error sentences in both auditory and visual modalities. Conclusions These findings suggest that the heightened computational demands for finiteness extend well beyond early childhood and continue to exert their influence on grammatical mental and brain function in adulthood.

The nondeterministic relationship between speech acoustics and abstract phonemic representations imposes a challenge for listeners to maintain perceptual constancy despite the highly variable acoustic realization of speech. Talker normalization facilitates speech processing by reducing the degrees of freedom for mapping between encountered speech and phonemic representations. While this process has been proposed to facilitate the perception of ambiguous speech sounds, it is currently unknown whether talker normalization is affected by the degree of potential ambiguity in acoustic-phonemic mapping. We explored the effects of talker normalization on speech processing in a series of speeded classification paradigms, parametrically manipulating the potential for inconsistent acoustic-phonemic relationships across talkers for both consonants and vowels. Listeners identified words with varying potential acoustic-phonemic ambiguity across talkers (e.g., beet/boat vs. boot/boat) spoken by single or mixed talkers. Auditory categorization of words was always slower when listening to mixed talkers compared to a single talker, even when there was no potential acoustic ambiguity between target sounds. Moreover, the processing cost imposed by mixed talkers was greatest when words had the most potential acoustic-phonemic overlap across talkers. Models of acoustic dissimilarity between target speech sounds did not account for the pattern of results. These results suggest (i) that talker normalization incurs the greatest processing cost when disambiguating highly-confusable sounds and (ii) that talker normalization appears to be an obligatory component of speech perception, taking place even when the acoustic-phonemic relationships across sounds are unambiguous.

Autism spectrum disorder (ASD) is associated with widespread receptive language impairments, yet the neural mechanisms underlying these deficits are poorly understood. Neuroimaging has shown that processing of socially-relevant sounds, including speech and non-speech, is atypical in ASD. However, it is unclear how the presence of lexical-semantic meaning affects speech processing in ASD. Here, we recorded magnetoencephalography data from individuals with ASD (N = 22, ages 7-17, 4 females) and typically developing (TD) peers (N = 30, ages 7-17, 5 females) during unattended listening to meaningful auditory speech sentences and meaningless jabberwocky sentences. After adjusting for age, ASD individuals showed stronger responses to meaningless jabberwocky sentences than to meaningful speech sentences in the same left temporal and parietal language regions where TD individuals exhibited stronger responses to meaningful speech. Maturational trajectories of meaningful speech responses were atypical in temporal, but not parietal, regions in ASD. Temporal responses were associated with ASD severity, while parietal responses were associated with aberrant involuntary attentional shifting in ASD. Our findings suggest a receptive speech processing dysfunction in ASD, wherein unattended meaningful speech elicits abnormal engagement of the language system, while unattended meaningless speech, filtered out in TD individuals, engages the language system through involuntary attention capture.

[Correction Notice: An Erratum for this article was reported in Vol 31(5) of Neuropsychology (see record 2017-22816-001). Errors in the dataset owing to two incorrect scores have skewed results. In the 2nd paragraph of the Results section, the 2nd sentence should read: "Within the typical reader group, FA in the left AF correlated negatively with pseudoword reading (WRMT-III Word Attack: rs = .37, p = .064), but not real-word reading (WRMT-III Word Identification: rs = .07, p = .75)." The 4th sentence of the 3rd paragraph should read: "The negative correlation between FA and Word Attack in the typical reader group was driven by Daxial (Dradial: rs = .19, p = .373, Daxial: rs = .38, p = .060)." The 2nd sentence of the 4th paragraph should read: "Results of this analysis replicated those of the larger reading disability group, with a statistically greater reduction of FA in this more severely affected group (p = .008) that was associated with a significant increase in Dradial (p = .008) and no difference in Daxial (p = .47)." In Table 1, for the typical reader group, the resulting values should read: age, 94.00 ± 7.66; KBIT-2-Matrices, 118.31 ± 15.24; WRMT-III-Word Identification, 119.00 ± 9.33; WRMT-III-Word Attack, 114.04 ± 9.31; and TOWRE-2-Sight Word Efficiency, 114.48 ± 8.07. For the reading disability group, the resulting values for age and TOWRE-2- Phonemic Decoding Efficiency should be 93.65 ± 7.81 and 81.76 ± 9.33, respectively. The p values for age and KBIT-2-Matrices should be .87 and .172, respectively. In Figure 3, the image for the typical reader group has been replaced. All versions of this article have been corrected.] Objective: We examined the white-matter microstructure of the left arcuate fasciculus, which has been associated with reading ability, in beginning readers with or without reading disability. METHOD Groups were typically reading children (n = 26) or children with reading disability (n = 26), Ages 6-9, and equated on nonverbal cognitive abilities. Diffusion-weighted images were collected and TRACULA was used to extract fractional anisotropy measures from the left arcuate fasciculus. RESULTS White-matter microstructure was altered in children with reading disability, who exhibited significantly reduced fractional anisotropy in the left arcuate fasciculus. Among typically reading children, lower fractional anisotropy of the left arcuate fasciculus was associated with superior pseudoword reading performance. Both the group differences and variation in reading scores among the children with reading disability were associated with radial diffusivity (but not axial diffusivity), whereas variation in reading scores among typically reading children was associated with axial diffusivity (but not radial diffusivity). CONCLUSIONS The paradoxical findings that lower fractional anisotropy was associated both with reading disability and also with better phonological awareness in typical reading development suggest that there are different maturational trajectories of white-matter microstructure in typical readers and children with reading disability, and that this difference is unique to the beginning stages of reading acquisition. The finding that reading disability was associated with radial diffusivity, but that variation in ability among typically developing readers was associated with axial diffusivity, suggests that different neural mechanisms may be associated with reading development in children with or without reading disability. (PsycINFO Database Record

Phonological working memory is the capacity to briefly maintain and recall representations of sounds important for speech and language and is believed to be critical for language and reading acquisition. Whether phonological working memory is supported by fronto-parietal brain regions associated with short-term memory storage or perisylvian brain structures implicated in speech perception and production is unclear, perhaps due to variability in stimuli, task demands, and individuals. We used fMRI to assess neurophysiological responses while individuals performed two tasks with closely matched stimuli but divergent task demands-nonword repetition and nonword discrimination-at two levels of phonological working memory load. Using analyses designed to address intersubject variability, we found significant neural responses to the critical contrast of high vs. low phonological working memory load in both tasks in a set of regions closely resembling those involved in speech perception and production. Moreover, within those regions, the voxel-wise patterns of load-related activation were highly correlated between the two tasks. These results suggest that brain regions in the temporal and frontal lobes encapsulate the core neurocomputational components of phonological working memory; an architecture that becomes increasingly evident as neural responses are examined in successively finer-grained detail in individual participants.

Listeners identify talkers more accurately when listening to their native language compared to an unfamiliar, foreign language. This language-familiarity effect in talker identification has been shown to arise from familiarity with both the sound patterns (phonetics and phonology) and the linguistic content (words) of one's native language. However, it has been unknown whether these two sources of information contribute independently to talker identification abilities, particularly whether hearing familiar words can facilitate talker identification in the absence of familiar phonetics. To isolate the contribution of lexical familiarity, we conducted three experiments that tested listeners' ability to identify talkers saying familiar words, but with unfamiliar phonetics. In two experiments, listeners identified talkers from recordings of their native language (English), an unfamiliar foreign language (Mandarin Chinese), or "hybrid" speech stimuli (sentences spoken in Mandarin, but which can be convincingly coerced to sound like English when presented with subtitles that prime plausible English-language lexical interpretations based on the Mandarin phonetics). In a third experiment, we explored natural variation in lexical-phonetic congruence as listeners identified talkers with varying degrees of a Mandarin accent. Priming listeners to hear English speech did not improve their ability to identify talkers speaking Mandarin, even after additional training, and talker identification accuracy decreased as talkers' phonetics became increasingly dissimilar to American English. Together, these experiments indicate that unfamiliar sound patterns preclude talker identification benefits otherwise afforded by familiar words. These results suggest that linguistic representations contribute hierarchically to talker identification; the facilitatory effect of familiar words requires the availability of familiar phonological forms.

Speech processing is slower and less accurate when listeners encounter speech from multiple talkers compared to one continuous talker. However, interference from multiple talkers has been investigated only using immediate speech recognition or long-term memory recognition tasks. These tasks reveal opposite effects of speech processing time on speech recognition - while fast processing of multi-talker speech impedes immediate recognition, it also results in more abstract and less talker-specific long-term memories for speech. Here, we investigated whether and how processing multi-talker speech disrupts working memory maintenance, an intermediate stage between perceptual recognition and long-term memory. In a digit sequence recall task, listeners encoded seven-digit sequences and recalled them after a 5-s delay. Sequences were spoken by either a single talker or multiple talkers at one of three presentation rates (0-, 200-, and 500-ms inter-digit intervals). Listeners' recall was slower and less accurate for sequences spoken by multiple talkers than a single talker. Especially for the fastest presentation rate, listeners were less efficient when recalling sequences spoken by multiple talkers. Our results reveal that talker-specificity effects for speech working memory are most prominent when listeners must rapidly encode speech. These results suggest that, like immediate speech recognition, working memory for speech is susceptible to interference from variability across talkers. While many studies ascribe effects of talker variability to the need to calibrate perception to talker-specific acoustics, these results are also consistent with the idea that a sudden change of talkers disrupts attentional focus, interfering with efficient working-memory processing.

Listeners identify voices more accurately in their native language than an unknown, foreign language, in a phenomenon known as the language-familiarity effect in talker identification. This effect has been reliably observed for a wide range of different language pairings and using a variety of different methodologies, including voice line-ups, talker-identification training, and talker discrimination. What do listeners know about their native language that helps them recognize voices more accurately? Do listeners gain access to this knowledge when they learn a second language? Is linguistic competence necessary, or can mere exposure to a foreign language help listeners identify voices more accurately? This chapter reviews the more than three decades of research on the language-familiarity effect in talker identification, with an emphasis on how attention to this phenomenon can inform not only better psychological and neural models of memory for voices, but also better models of speech processing.

Phonetic variability across talkers imposes additional processing costs during speech perception, often measured by performance decrements between single- and mixed-talker conditions. However, models differ in their predictions about whether accommodating greater phonetic variability (i.e., more talkers) imposes greater processing costs. We measured speech processing efficiency in a speeded word identification task, in which we manipulated the number of talkers (1, 2, 4, 8, or 16) listeners heard. Word identification was less efficient in every mixed-talker condition compared to the single-talker condition, but the magnitude of this performance decrement was not affected by the number of talkers. Furthermore, in a condition with uniform transition probabilities between two talkers, word identification was more efficient when the talker was the same as the prior trial compared to trials when the talker switched. These results support an auditory streaming model of talker adaptation, where processing costs associated with changing talkers result from attentional reorientation.

Perceptual adaptation to a talker enables listeners to efficiently resolve the many-to-many mapping between variable speech acoustics and abstract linguistic representations. However, models of speech perception have not delved into the variety or the quantity of information necessary for successful adaptation, nor how adaptation unfolds over time. In three experiments using speeded classification of spoken words, we explored how the quantity (duration), quality (phonetic detail), and temporal continuity of talker-specific context contribute to facilitating perceptual adaptation to speech. In single- and mixed-talker conditions, listeners identified phonetically-confusable target words in isolation or preceded by carrier phrases of varying lengths and phonetic content, spoken by the same talker as the target word. Word identification was always slower in mixed-talker conditions than single-talker ones. However, interference from talker variability decreased as the duration of preceding speech increased but was not affected by the amount of preceding talker-specific phonetic information. Furthermore, efficiency gains from adaptation depended on temporal continuity between preceding speech and the target word. These results suggest that perceptual adaptation to speech may be understood via models of auditory streaming, where perceptual continuity of an auditory object (e.g., a talker) facilitates allocation of attentional resources, resulting in more efficient perceptual processing.

Foreign language learning in adulthood often takes place in classrooms where learning outcomes vary widely among students, for both initial learning and long-term retention. Despite the fundamental role of speech perception in first language acquisition, its role in foreign language learning outcomes remains unknown. Using a speech discrimination functional magnetic resonance imaging (fMRI) task and resting-state fMRI before and after an intensive, classroom-based, Mandarin Chinese course, we examined how variations in pre-training organization and pre-to-post reorganization of brain functions predicted successful language learning in male and female native English-speakers. Greater pre-training activation in right inferior frontal gyrus (IFG) to Mandarin speech was associated with better Mandarin attainment at the end of the course. After four weeks of class, learners showed overall increased activation in left IFG and left superior parietal lobule (SPL) to Mandarin speech, but in neither region was variation related to learning outcomes. Immediate attainment was associated with greater pre-to-post reduction of right IFG activation to Mandarin speech but also greater enhancement of resting-state connectivity between this region and both left IFG and left SPL. Long-term retention of Mandarin skills measured three months later was more accurately predicted by models using features of neural preparedness (pre-training activation) and neural plasticity (pre-to-post activation change) than models using behavior preparedness and plasticity features (pre-training speech discrimination accuracy and Mandarin attainment, respectively). These findings suggest that successful holistic foreign language acquisition in human adulthood requires right IFG engagement during initial learning but right IFG disengagement for long-term retention of language skills.

A classic finding in speech perception is that speech is processed more efficiently from a single, continuous talker than from mixed talkers. Given enormous variation in the acoustic realization of speech, it is thought that talker adaptation is necessary to ascertain the mappings between talkers’ speech acoustics and listeners’ abstract phonological representations. However, a suite of empirical studies from our laboratory may suggest a predominately attention-based explanation for effects attributed to talker adaptation: using behavioral experiments, neuroimaging, and noninvasive brain stimulation, we have probed how speech processing efficiency under talker variability is affected by temporal, phonological, contextual, and expectational factors. We find that processing benefits from talker continuity are automatic and feedforward, depending on temporal continuity in the source of speech but not the amount of talker-specific phonetic detail or listeners’ expectations about source continuity. Correspondingly, processing costs from talker discontinuity occur even when phonetic contrasts are unambiguous across talkers but are insensitive to the magnitude of phonetic variability, amount of preceding exposure to a talker, or top-down expectation about discontinuity. We consider how domain-general models of attention and auditory streaming may parsimoniously account for these differences in the speech processing efficiency between single and mixed talkers.A classic finding in speech perception is that speech is processed more efficiently from a single, continuous talker than from mixed talkers. Given enormous variation in the acoustic realization of speech, it is thought that talker adaptation is necessary to ascertain the mappings between talkers’ speech acoustics and listeners’ abstract phonological representations. However, a suite of empirical studies from our laboratory may suggest a predominately attention-based explanation for effects attributed to talker adaptation: using behavioral experiments, neuroimaging, and noninvasive brain stimulation, we have probed how speech processing efficiency under talker variability is affected by temporal, phonological, contextual, and expectational factors. We find that processing benefits from talker continuity are automatic and feedforward, depending on temporal continuity in the source of speech but not the amount of talker-specific phonetic detail or listeners’ expectations about source continuity. Correspondi...

Purpose The purpose of this study was to determine listeners' ability to learn talker identity from speech produced with an electrolarynx, explore source and filter differentiation in talker identification, and describe acoustic-phonetic changes associated with electrolarynx use. Method Healthy adult control listeners learned to identify talkers from speech recordings produced using talkers' normal laryngeal vocal source or an electrolarynx. Listeners' abilities to identify talkers from the trained vocal source (Experiment 1) and generalize this knowledge to the untrained source (Experiment 2) were assessed. Acoustic-phonetic measurements of spectral differences between source mechanisms were performed. Additional listeners attempted to match recordings from different source mechanisms to a single talker (Experiment 3). Results Listeners successfully learned talker identity from electrolarynx speech but less accurately than from laryngeal speech. Listeners were unable to generalize talker identity to the untrained source mechanism. Electrolarynx use resulted in vowels with higher F1 frequencies compared with laryngeal speech. Listeners matched recordings from different sources to a single talker better than chance. Conclusions Electrolarynx speech, although lacking individual differences in voice quality, nevertheless conveys sufficient indexical information related to the vocal filter and articulation for listeners to identify individual talkers. Psychologically, perception of talker identity arises from a “gestalt” of the vocal source and filter.

Identification of specific neurophysiological dysfunctions resulting in selective reading difficulty (dyslexia) has remained elusive. In addition to impaired reading development, individuals with dyslexia frequently exhibit behavioral deficits in perceptual adaptation. Here, we assessed neurophysiological adaptation to stimulus repetition in adults and children with dyslexia for a wide variety of stimuli, spoken words, written words, visual objects, and faces. For every stimulus type, individuals with dyslexia exhibited significantly diminished neural adaptation compared to controls in stimulus-specific cortical areas. Better reading skills in adults and children with dyslexia were associated with greater repetition-induced neural adaptation. These results highlight a dysfunction of rapid neural adaptation as a core neurophysiological difference in dyslexia that may underlie impaired reading development. Reduced neurophysiological adaptation may relate to prior reports of reduced behavioral adaptation in dyslexia and may reveal a difference in brain functions that ultimately results in a specific reading impairment., NIH (Grant UL1RR025758)

Talker adaptation improves speech processing efficiency by reducing possible mappings between talkers' speech acoustics and listeners' phonemic representations. We investigated the functional neuroanatomy of talker adaptation by applying noninvasive neurostimulation (high-definition transcranial direct current stimulation; HD-tDCS) to left superior temporal lobe while participants performed an auditory word identification task. We factorially manipulated talker variability (single vs. mixed talkers) and speech context (isolated words vs. connected speech), measuring listeners' speech processing efficiency under anodal, cathodal, or sham stimulation. Speech processing was faster for single talkers than mixed talkers, and connected speech reduced the additional processing costs associated with mixed-talker speech. However, the beneficial effect of connected speech in the mixed-talker condition was significantly attenuated under both anodal and cathodal stimulation versus sham. Stimulation of left superior temporal lobe disrupts the brain's ability to use local phonetic context to rapidly adapt to a talker, revealing this region's causal role in talker adaptation.

Speech processing is faster for one continuous talker than mixed talkers. However, it is unknown whether listeners’ expectations about talker continuity affect this facilitation. We measured response times during three speeded word identification experiments that manipulated listeners’ expectations about talker continuity. First, we manipulated expectations about talker continuity by presenting words in pairs where both words were frequently produced by the same talker (talker-repeat trials) and rarely by different talkers (talker-change trials), or vice-versa. Word identification was faster in talker-repeat trials than talker-change trials, with equal facilitation from both expected and unexpected talker continuity. Unexpected talker changes did not slow processing more than expected changes. Second, a control experiment demonstrated that listeners’ expectations about repetitions of the word itself did affect word identification speed. Third, listeners identified words in conditions with one talker, two talkers presented randomly, or two alternating talkers. Word identification was faster whenever the talker was repeated compared to when the talker switched between trials, even if listeners could perfectly predict the talker switch (i.e., alternating-talker condition); talker continuity also facilitated word identification in the random condition. These results provide converging evidence that talker continuity facilitates speech processing in an automatic, feed-forward way, irrespective of listeners’ expectations.Speech processing is faster for one continuous talker than mixed talkers. However, it is unknown whether listeners’ expectations about talker continuity affect this facilitation. We measured response times during three speeded word identification experiments that manipulated listeners’ expectations about talker continuity. First, we manipulated expectations about talker continuity by presenting words in pairs where both words were frequently produced by the same talker (talker-repeat trials) and rarely by different talkers (talker-change trials), or vice-versa. Word identification was faster in talker-repeat trials than talker-change trials, with equal facilitation from both expected and unexpected talker continuity. Unexpected talker changes did not slow processing more than expected changes. Second, a control experiment demonstrated that listeners’ expectations about repetitions of the word itself did affect word identification speed. Third, listeners identified words in conditions with one talker, two ...

Background Individuals with reading disability and individuals with autism spectrum disorder (ASD) are characterized, respectively, by their difficulties in reading and social communication, but both groups often have impaired phonological working memory (PWM). It is not known whether the impaired PWM reflects distinct or shared neuroanatomical abnormalities in these two diagnostic groups. Methods White-matter structural connectivity via diffusion weighted imaging was examined in 64 children, age 5 to 17 years, with reading disability, ASD, or typical development, who were matched on age, gender, intelligence, and diffusion data quality. Results Children with reading disability and children with ASD exhibited reduced PWM compared with children with typical development. The two diagnostic groups showed altered white matter microstructure in the temporoparietal portion of the left arcuate fasciculus and in the occipitotemporal portion of the right inferior longitudinal fasciculus (ILF), as indexed by reduced fractional anisotropy and increased radial diffusivity. Moreover, the structural integrity of the right ILF was positively correlated with PWM ability in the two diagnostic groups but not in the typically developing group. Conclusions These findings suggest that impaired PWM is transdiagnostically associated with shared neuroanatomical abnormalities in ASD and reading disability. Microstructural characteristics in left arcuate fasciculus and right ILF may play important roles in the development of PWM. The right ILF may support a compensatory mechanism for children with impaired PWM.

Listeners demonstrate reliable perceptual biases favoring voices speaking their native language versus those speaking a foreign language. This “language-familiarity effect” for voice processing has been found even for perceptual similarity judgments: Voices speaking listeners’ native language sound less alike, even when those recordings have been rendered incomprehensible via time-reversal. Here, we sought to replicate and extend this finding of linguistic effects on voice similarity. Native English- and Mandarin-speaking listeners (both N = 40) rated the perceptual similarity of voices speaking English or Mandarin (both N = 20) for either time-reversed or forward speech. Both listener groups tended to find Mandarin-speaking voices more dissimilar, but this effect was reduced for English-speaking listeners, especially for forward speech. Perceptual similarity judgments of voices were always highly correlated between listener groups and between forward/time-reversed speech. Acoustic measurements (voice fun...

Talker adaptation is known to facilitate immediate speech recognition. However, it is unclear whether and how talker adaptation also facilitates working memory for speech. Using electroencephalography (EEG) during a delayed recall of digit span task, we investigated whether talker adaptation facilitates working memory performance. We also investigated whether neural alpha oscillatory power reflects facilitatory effects of talker adaptation. Listeners encoded sequences of seven randomly ordered digits, recalling them after a 5-s retention. Digit sequences were spoken by either a single talker or multiple talkers, and were presented at either faster or slower speech rates (0-ms vs. 500-ms inter-digit intervals). Overall, listeners responded faster and more accurately for single-talker sequences compared to multiple-talker sequences. Especially for the faster presentation rate, listeners were more efficient (faster and more accurate) in recalling sequences spoken by a single talker. For the faster presentation rate, processing digit sequences spoken by single vs. multiple talkers also elicited reduced alpha power during both speech encoding and working memory retention. These results suggest that talker adaptation reduces cognitive effort during both speech encoding and memory retention, thereby producing more efficient working memory for speech information, especially when listeners process speech rapidly.Talker adaptation is known to facilitate immediate speech recognition. However, it is unclear whether and how talker adaptation also facilitates working memory for speech. Using electroencephalography (EEG) during a delayed recall of digit span task, we investigated whether talker adaptation facilitates working memory performance. We also investigated whether neural alpha oscillatory power reflects facilitatory effects of talker adaptation. Listeners encoded sequences of seven randomly ordered digits, recalling them after a 5-s retention. Digit sequences were spoken by either a single talker or multiple talkers, and were presented at either faster or slower speech rates (0-ms vs. 500-ms inter-digit intervals). Overall, listeners responded faster and more accurately for single-talker sequences compared to multiple-talker sequences. Especially for the faster presentation rate, listeners were more efficient (faster and more accurate) in recalling sequences spoken by a single talker. For the faster presentati...

Lexical tones are a phonetic contrast necessary for conveying meaning in a majority of the world’s languages. Various hearing, speech, and language disorders affect the ability to perceive or produce lexical tones, thereby seriously impairing individuals’ communicative abilities. The number of tone language speakers is increasing, even in otherwise English-speaking nations, yet insufficient emphasis has been placed on clinical assessment and rehabilitation of lexical tone disorders. The similarities and dissimilarities between lexical tones and other speech sounds make a richer scientific understanding of their physiological bases paramount to more effective remediation of speech and language disorders in general. Here we discuss the cognitive and biological bases of lexical tones, emphasizing the neural structures and networks that support their acquisition, perception, and cognitive representation. We present emerging research on lexical tone learning in the context of the clinical disorders of hearing, speech, and language that this body of research will help to address.

Cultural experiences come in many different forms, such as immersion in a particular linguistic community, exposure to faces of people with different racial backgrounds, or repeated encounters with music of a particular tradition. In most circumstances, these cultural experiences are asymmetric, meaning one type of experience occurs more frequently than other types (e.g., a person raised in India will likely encounter the Indian todi scale more so than a Westerner). In this paper, we will discuss recent findings from our laboratories that reveal the impact of short- and long-term asymmetric musical experiences on how the nervous system responds to complex sounds. We will discuss experiments examining how musical experience may facilitate the learning of a tone language, how musicians develop neural circuitries that are sensitive to musical melodies played on their instrument of expertise, and how even everyday listeners who have little formal training are particularly sensitive to music of their own culture(s). An understanding of these cultural asymmetries is useful in formulating a more comprehensive model of auditory perceptual expertise that considers how experiences shape auditory skill levels. Such a model has the potential to aid in the development of rehabilitation programs for the efficacious treatment of neurologic impairments.

� Advances in neuroimaging technology have led to an explosion in the number of studies investigating the living human brain, and thereby our understanding of its structure and function.Withthe proliferation of dazzling imagesfrom brain scansin both scientific and popular media, researchers from other fields in the social and behavioral sciences have naturally become interested in the application of neuroimaging to their own research. Commercial enterprises have long been interested in the prospects of literally ‘‘getting inside the heads’’ of customers and partners, with a variety of goals in mind. Here we consider the ways in which scholars of consumer behavior may draw upon neuroscientific advances to inform their own research. We describe the motivation of neuroscientific inquiry from the point of view of neuroscientists, including an introduction to the technologies and methodologies available; correspondingly, we consider major questions in consumer behavior that are likely to be of interest to neuroscientists and why. Recent key discoveries in neuroscienceare presented which will likely have a direct impact on the development of a neuromarketing subdiscipline and for neuroimaging as a marketing research technique. We discuss where and how neuroscience methodologies may reasonably be added to the research inventory of marketers. In sum, we aim to show not only that a neuromarketing subdiscipline may fruitfully contribute to our understanding of the biological bases of human behavior, but also that developing this as a productive research field will rest largely in framing marketing research questions in the braincentric mindset of neuroscientists. Copyright # 2008 John Wiley & Sons, Ltd.

The current study investigates the learning of nonnative suprasegmental patterns for word identification. Native English-speaking adults learned to use suprasegmentals (pitch patterns) to identify a vocabulary of six English pseudosyllables superimposed with three pitch patterns (18 words). Successful learning of the vocabulary necessarily entailed learning to use pitch patterns in words. Two major facets of sound-to-word learning were investigated: could native speakers of a nontone language learn the use of pitch patterns for lexical identification, and what effect did more basic auditory ability have on learning success. We found that all subjects improved to a certain degree, although large individual differences were observed. Learning success was found to be associated with the learners' ability to perceive pitch patterns in a nonlexical context and their previous musical experience. These results suggest the importance of a phonetic–phonological–lexical continuity in adult nonnative word learning, including phonological awareness and general auditory ability.

Perceiving speech under informational masking requires listeners to distinguish and attend to one talker from among competing talkers. However, it is unknown how well listeners are even able to identify a target talker in the presence of noise, much less how this ability is affected by factors such as noise type, signal-to-noise ratio (SNR), and speech content. In a two-day training paradigm, young adults with normal hearing learned to identify five talkers by the sound of their voice in quiet. We then tested talker identification accuracy during masking by speech-shaped noise, multi-talker babble, and a single, unfamiliar competing talker. Test stimuli contained both trained and novel sentences and were presented at three different SNRs. Talker identification was highest in quiet and fell as a function of SNR for all noise types. The change in accuracy as a function of SNR was greatest for multi-talker babble. Across all noise types and SNRs, talkers were identified more accurately from trained sentences...