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Cross-correlation of magnetoencephalography (MEG) with time courses derived from the speech signal has shown differences in phase-locking between blind subjects able to comprehend accelerated speech and sighted controls. The present training study contributes to disentangle the effects of blindness and training. Both subject groups (baseline: n = 16 blind, 13 sighted; trained: 10 blind, 3 sighted) were able to enhance speech comprehension up to ca. 18 syllables per second. MEG responses phase-locked to syllable onsets were captured in five pre-defined source locations comprising left and right auditory cortex (A1), right visual cortex (V1), left inferior frontal gyrus (IFG) and left pre-supplementary motor area. Phase locking in A1 was consistently increased while V1 showed opposite training effects in blind and sighted subjects. Also the IFG showed some group differences indicating enhanced top-down strategies in sighted subjects while blind subjects may have a more fine-grained bottom-up resolution for accelerated speech., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Discourse structure enables us to generate expectations based upon linguistic material that has already been introduced. The present magnetoencephalography (MEG) study addresses auditory perception of test sentences in which discourse coherence was manipulated by using presuppositions (PSP) that either correspond or fail to correspond to items in preceding context sentences with respect to uniqueness and existence. Context violations yielded delayed auditory M50 and enhanced auditory M200 cross-correlation responses to syllable onsets within an analysis window of 1.5s following the PSP trigger words. Furthermore, discourse incoherence yielded suppression of spectral power within an expanded alpha band ranging from 6 to 16Hz. This effect showed a bimodal temporal distribution, being significant in an early time window of 0.0-0.5s following the PSP trigger and a late interval of 2.0-2.5s. These findings indicate anticipatory top-down mechanisms interacting with various aspects of bottom-up processing during speech perception., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In many functional magnetic resonance imaging (fMRI) studies blind humans were found to show cross-modal reorganization engaging the visual system in non-visual tasks. For example, blind people can manage to understand (synthetic) spoken language at very high speaking rates up to ca. 20 syllables/s (syl/s). FMRI data showed that hemodynamic activation within right-hemispheric primary visual cortex (V1), bilateral pulvinar (Pv), and left-hemispheric supplementary motor area (pre-SMA) covaried with their capability of ultra-fast speech (16 syllables/s) comprehension. It has been suggested that right V1 plays an important role with respect to the perception of ultra-fast speech features, particularly the detection of syllable onsets. Furthermore, left pre-SMA seems to be an interface between these syllabic representations and the frontal speech processing and working memory network. So far, little is known about the networks linking V1 to Pv, auditory cortex (A1), and (mesio-) frontal areas. Dynamic causal modeling (DCM) was applied to investigate (i) the input structure from A1 and Pv toward right V1 and (ii) output from right V1 and A1 to left pre-SMA. As concerns the input Pv was significantly connected to V1, in addition to A1, in blind participants, but not in sighted controls. Regarding the output V1 was significantly connected to pre-SMA in blind individuals, and the strength of V1-SMA connectivity correlated with the performance of ultra-fast speech comprehension. By contrast, in sighted controls, not understanding ultra-fast speech, pre-SMA did neither receive input from A1 nor V1. Taken together, right V1 might facilitate the "parsing" of the ultra-fast speech stream in blind subjects by receiving subcortical auditory input via the Pv (= secondary visual pathway) and transmitting this information toward contralateral pre-SMA.

Late-blind humans can learn to understand speech at ultra-fast syllable rates (ca. 20 syllables/s), a capability associated with hemodynamic activation of the central-visual system. Thus, the observed functional cross-modal recruitment of occipital cortex might facilitate ultra-fast speech processing in these individuals. To further elucidate the structural prerequisites of this skill, diffusion tensor imaging (DTI) was conducted in late-blind subjects differing in their capability of understanding ultra-fast speech. Fractional anisotropy (FA) was determined as a quantitative measure of the directionality of water diffusion, indicating fiber tract characteristics that might be influenced by blindness as well as the acquired perceptual skills. Analysis of the diffusion images revealed reduced FA in late-blind individuals relative to sighted controls at the level of the optic radiations at either side and the right-hemisphere dorsal thalamus (pulvinar). Moreover, late-blind subjects showed significant positive correlations between FA and the capacity of ultra-fast speech comprehension within right-hemisphere optic radiation and thalamus. Thus, experience-related structural alterations occurred in late-blind individuals within visual pathways that, presumably, are linked to higher order frontal language areas.

The processing of nonverbal auditory stimuli has not yet been sufficiently investigated in patients with aphasia. On the basis of a duration discrimination task, we examined whether patients with left-sided cerebrovascular lesions were able to perceive time differences in the scale of approximately 150 ms. Further linguistic and memory-related tasks were used to characterize more exactly the relationships in the performances between auditory nonverbal task and selective linguistic or mnemonic disturbances. All examined conduction aphasics showed increased thresholds in the duration discrimination task. The low thresholds on this task were in a strong correlative relation to the reduced performances in repetition and working memory task. This was interpreted as an indication of a pronounced disturbance in integrating auditory verbal information into a long-term window (sampling disturbance) resulting in an additional load of working memory. In order to determine the lesion topography of patients with sampling disturbances, the anatomical and psychophysical data were correlated on the basis of a voxelwise statistical approach. It was found that tissue damage extending through the insula, the posterior superior temporal gyrus, and the supramarginal gyrus causes impairments in sequencing of time-sensitive information.

Background: Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate., Results: Besides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv)., Conclusions: Presumably, FG supports the left-hemispheric perisylvian "language network", i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian "language zones", might facilitate - under time-critical conditions - the consolidation of linguistic information at the level of verbal working memory.

Blind people can learn to understand speech at ultra-high syllable rates (ca. 20 syllables/s), a capability associated with hemodynamic activation of the central-visual system. To further elucidate the neural mechanisms underlying this skill, magnetoencephalographic (MEG) measurements during listening to sentence utterances were cross-correlated with time courses derived from the speech signal (envelope, syllable onsets and pitch periodicity) to capture phase-locked MEG components (14 blind, 12 sighted subjects; speech rate=8 or 16 syllables/s, pre-defined source regions: auditory and visual cortex, inferior frontal gyrus). Blind individuals showed stronger phase locking in auditory cortex than sighted controls, and right-hemisphere visual cortex activity correlated with syllable onsets in case of ultra-fast speech. Furthermore, inferior-frontal MEG components time-locked to pitch periodicity displayed opposite lateralization effects in sighted (towards right hemisphere) and blind subjects (left). Thus, ultra-fast speech comprehension in blind individuals appears associated with changes in early signal-related processing mechanisms both within and outside the central-auditory terrain., (Copyright © 2012 Elsevier Inc. All rights reserved.)

During speech perception, acoustic correlates of syllable structure and pitch periodicity are directly reflected in electrophysiological brain activity. Magnetoencephalography (MEG) recordings were made while 10 participants listened to natural or formant-synthesized speech at moderately fast or ultrafast rate. Cross-correlation analysis was applied to show brain activity time-locked to the speech envelope, to an acoustic marker of syllable onsets, and to pitch periodicity. The envelope yielded a right-lateralized M100-like response, syllable onsets gave rise to M50/M100-like fields with an additional anterior M50 component, and pitch (ca. 100 Hz) elicited a neural resonance bound to a central auditory source at a latency of 30 ms. The strength of these MEG components showed differential effects of syllable rate and natural versus synthetic speech. Presumingly, such phase-locking mechanisms serve as neuronal triggers for the extraction of information-bearing elements., (Copyright © 2011 Society for Psychophysiological Research.)

This study investigates the temporal resolution capacities of the central-auditory system in a subject (NP) suffering from repetition conduction aphasia. More specifically, the patient was asked to detect brief gaps between two stretches of broadband noise (gap detection task) and to evaluate the duration of two biphasic (WN-3) continuous noise elements, starting with white noise (WN) followed by 3kHz bandpass-filtered noise (duration discrimination task). During the gap detection task, the two portions of each stimulus were either identical ("intra-channel condition") or differed ("inter-channel condition") in the spectral characteristics of the leading and trailing acoustic segments. NP did not exhibit any deficits in the intra-channel condition of the gap detection task, indicating intact auditory temporal resolution across intervals of 1-3ms. By contrast, the inter-channel condition yielded increased threshold values. Based upon the "multiple-looks" model of central-auditory processing, this profile points at a defective integration window operating across a few tens of milliseconds - a temporal range associated with critical features of the acoustic speech signal such as voice onset time and formant transitions. Additionally, NP was found impaired during a duration discrimination task addressing longer integration windows (ca. 150ms). Concerning speech, this latter time domain approximately corresponds to the duration of stationary segmental units such as fricatives and long vowels. On the basis of our results we suggest, that the patient's auditory timing deficits in non-speech tasks may account, at least partially, for his impairments in speech processing., (2010 Elsevier Inc. All rights reserved.)

Cross-modal fusion phenomena suggest specific interactions of auditory and visual sensory information both within the speech and nonspeech domains. Using whole-head magnetoencephalography, this study recorded M50 and M100 fields evoked by ambiguous acoustic stimuli that were visually disambiguated to perceived /ta/ or /pa/ syllables. As in natural speech, visual motion onset preceded the acoustic signal by 150 msec. Control conditions included visual and acoustic nonspeech signals as well as visual-only and acoustic-only stimuli. (a) Both speech and nonspeech motion yielded a consistent attenuation of the auditory M50 field, suggesting a visually induced "preparatory baseline shift" at the level of the auditory cortex. (b) Within the temporal domain of the auditory M100 field, visual speech and nonspeech motion gave rise to different response patterns (nonspeech: M100 attenuation; visual /pa/: left-hemisphere M100 enhancement; /ta/: no effect). (c) These interactions could be further decomposed using a six-dipole model. One of these three pairs of dipoles (V270) was fitted to motion-induced activity at a latency of 270 msec after motion onset, that is, the time domain of the auditory M100 field, and could be attributed to the posterior insula. This dipole source responded to nonspeech motion and visual /pa/, but was found suppressed in the case of visual /ta/. Such a nonlinear interaction might reflect the operation of a binary distinction between the marked phonological feature "labial" versus its underspecified competitor "coronal." Thus, visual processing seems to be shaped by linguistic data structures even prior to its fusion with auditory information channel.

Blind individuals may learn to understand ultra-fast synthetic speech at a rate of up to about 25 syllables per second (syl)/s, an accomplishment by far exceeding the maximum performance level of normal-sighted listeners (8-10 syl/s). The present study indicates that this exceptional skill engages distinct regions of the central-visual system. Hemodynamic brain activation during listening to moderately- (8 syl/s) and ultra-fast speech (16 syl/s) was measured in a blind individual and six normal-sighted controls. Moderately-fast speech activated posterior and anterior 'language zones' in all subjects. Regarding ultra-fast tokens, the controls showed exclusive activation of supratemporal regions whereas the blind participant exhibited enhanced left inferior frontal and temporoparietal responses as well as significant hemodynamic activation of left fusiform gyrus (FG) and right primary visual cortex. Since left FG is known to be involved in phonological processing, this structure, presumably, provides the functional link between the central-auditory and -visual systems.

Using functional magnetic resonance imaging, the distribution of hemodynamic brain responses bound to the perceptual processing of interjections, that is 'exclamations inserted into an utterance without grammatical connection to it', was determined (vs. a silent baseline condition). These utterances convey information about a speaker's affective/emotional state by their 'tone' (emotional prosody) and/or their lexical content. Both communicative aspects of interjections elicited significant bilateral blood-oxygen-level-dependent signal changes within superior temporal cortex. In addition, affective-prosodic cues yielded hemodynamic activation of the posterior insula as well as cortical/subcortical structures engaged in the control of innate emotional behavior. These observations corroborate the suggestion that interjections might trace back to proto-speech vocalizations of an early stage of language evolution.

Articulate speech represents a unique trait of our species. Besides other structures, the cerebellum pertains to the brain network engaged in spoken language production. Data from different sources point at a dual role of this organ within the verbal domain: (i) the cerebellum appears to subserve the online sequencing of syllables into fast, smooth and rhythmically organized larger utterances, and (ii) furthermore, the cerebellum seems to participate in the temporal organization of internal speech, that is, a prearticulatory verbal code. Impaired prearticulatory verbal coding mechanisms could explain at least some of the perceptual and cognitive deficits observed in cerebellar disorders. Recent genetic studies indicate that distinct mutations of a specific regulatory gene (FOXP2) promoted the emergence of articulate speech during the course of hominid evolution. Conceivably, structural changes of the expressed FOXP2 protein supported the 'vocal elaboration' of phylogenetically older brain networks engaged in upper limb motor control, such as the cerebro-cerebellar loops.

Using whole-head magnetoencephalography (MEG), audiovisual (AV) interactions during speech perception (/ta/- and /pa/-syllables) were investigated in 20 subjects. Congruent AV events served as the 'standards' of an oddball design. The deviants encompassed incongruent /ta/-/pa/ configurations differing from the standards either in the acoustic or the visual domain. As an auditory non-speech control condition, the same video signals were synchronized with either one of two complex tones. As in natural speech, visual movement onset preceded acoustic signals by about 150 ms. First, the impact of visual information on auditorily evoked fields to non-speech sounds was determined. Larger facial movements (/pa/ versus /ta/) yielded enhanced early responses such as the M100 component, indicating, most presumably, anticipatory pre-activation of auditory cortex by visual motion cues. As a second step of analysis, mismatch fields (MMF) were calculated. Acoustic deviants elicited a typical MMF, peaking ca. 180 ms after stimulus onset, whereas visual deviants gave rise to later responses (220 ms) of a more posterior-medial source location. Finally, a late (275 ms), left-lateralized visually-induced MMF component, resembling the acoustic mismatch response, emerged during the speech condition, presumably reflecting phonetic/linguistic operations. There is mounting functional imaging evidence for an early impact of visual information on auditory cortical regions during speech perception. The present study suggests at least two successive AV interactions in association with syllable recognition tasks: early activation of auditory areas depending upon visual motion cues and a later speech-specific left-lateralized response mediated, conceivably, by backward-projections from multisensory areas.

A classical tenet of clinical neurology proposes that cerebellar disorders may give rise to speech motor disorders (ataxic dysarthria), but spare perceptual and cognitive aspects of verbal communication. During the past two decades, however, a variety of higher-order deficits of speech production, e.g., more or less exclusive agrammatism, amnesic or transcortical motor aphasia, have been noted in patients with vascular cerebellar lesions, and transient mutism following resection of posterior fossa tumors in children may develop into similar constellations. Perfusion studies provided evidence for cerebello-cerebral diaschisis as a possible pathomechanism in these instances. Tight functional connectivity between the language-dominant frontal lobe and the contralateral cerebellar hemisphere represents a prerequisite of such long-distance effects. Recent functional imaging data point at a contribution of the right cerebellar hemisphere, concomitant with language-dominant dorsolateral and medial frontal areas, to the temporal organization of a prearticulatory verbal code ('inner speech'), in terms of the sequencing of syllable strings at a speaker's habitual speech rate. Besides motor control, this network also appears to be engaged in executive functions, e.g., subvocal rehearsal mechanisms of verbal working memory, and seems to be recruited during distinct speech perception tasks. Taken together, thus, a prearticulatory verbal code bound to reciprocal right cerebellar/left frontal interactions might represent a common platform for a variety of cerebellar engagements in cognitive functions. The distinct computational operation provided by cerebellar structures within this framework appears to be the concatenation of syllable strings into coarticulated sequences.

Oscillatory activity in the gamma-band range in human magneto- and electroencephalogram is thought to reflect the oscillatory synchronization of cortical networks. Findings of enhanced gamma-band activity (GBA) during cognitive processes like gestalt perception, attention and memory have led to the notion that GBA may reflect the activation of internal object representations. However, there is little direct evidence suggesting that GBA is related to subjective perceptual experience. In the present study, magnetoencephalogram was recorded during an audiovisual oddball paradigm with infrequent visual (auditory /ta/ + visual /pa/) or acoustic deviants (auditory /pa/ + visual /ta/) interspersed in a sequence of frequent audiovisual standard stimuli (auditory /ta/ + visual /ta/). Sixteen human subjects had to respond to perceived acoustic changes which could be produced either by real acoustic or illusory (visual) deviants. Statistical probability mapping served to identify correlations between oscillatory activity in response to visual and acoustic deviants, respectively, and the detection rates for either type of deviant. The perception of illusory acoustic changes induced by visual deviants was closely associated with gamma-band amplitude at approximately 80 Hz between 250 and 350 ms over midline occipital cortex. In contrast, the detection of real acoustic deviants correlated positively with induced GBA at approximately 42 Hz between 200 and 300 ms over left superior temporal cortex and negatively with evoked gamma responses at approximately 41 Hz between 220 and 240 ms over occipital areas. These findings support the relevance of high-frequency oscillatory activity over early sensory areas for perceptual experience.

Both intonation (affective prosody) and lexical meaning of verbal utterances participate in the vocal expression of a speaker's emotional state, an important aspect of human communication. However, it is still a matter of debate how the information of these two 'channels' is integrated during speech perception. In order to further analyze the impact of affective prosody on lexical access, so-called interjections, i.e., short verbal emotional utterances, were investigated. The results of a series of psychoacoustic studies indicate the processing of emotional interjections to be mediated by a divided cognitive mechanism encompassing both lexical access and the encoding of prosodic data. Emotional interjections could be separated into elements with high- or low-lexical content. As concerns the former items, both prosodic and propositional cues have a significant influence upon recognition rates, whereas the processing of the low-lexical cognates rather solely depends upon prosodic information. Incongruencies between lexical and prosodic data structures compromise stimulus identification. Thus, the analysis of utterances characterized by a dissociation of the prosodic and lexical dimension revealed prosody to exert a stronger impact upon listeners' judgments than lexicality. Taken together, these findings indicate that both propositional and prosodic speech components closely interact during speech perception.

Auditory pattern changes have been shown to elicit increases in magnetoencephalographic gamma-band activity (GBA) over left inferior frontal cortex, forming part of the putative auditory ventral "what" processing stream. The present study employed a McGurk-type paradigm to assess whether GBA would be associated with subjectively perceived changes even when auditory stimuli remain unchanged. Magnetoencephalograms were recorded in 16 human subjects during audiovisual mismatch perception. Both infrequent visual (auditory /ta/ + visual /pa/) and acoustic deviants (auditory/pa/ + visual /ta/) were compared with frequent audiovisual standards (auditory /ta/ and visual /ta/). Statistical probability mapping revealed spectral amplitude increases at approximately 75 and approximately 78 Hz to visual deviants. GBA to visual deviants peaked 160 ms after auditory stimulus onset over posterior parietal cortex, at 270 ms over occipital areas and at 320 ms over left inferior frontal cortex. The latter GBA enhancement was consistent with the increase observed previously to pure acoustic mismatch, supporting a role of left inferior frontal cortex for the representation of perceived auditory pattern change. The preceding gamma-band changes over posterior areas may reflect processing of incongruent lip movements in visual motion areas and back-projections to earlier visual cortex.

Using whole-head MEG, time course and hemispheric lateralization effects of phase-locked brain responses to complex periodic acoustic signals (stimulus frequency 13, 22, 40, 67, or 111 Hz) were determined based on a dipole analysis approach. Apart from systematic rate-induced changes in amplitude and shape of the transient evoked magnetic fields (M50, M100), phase-locked brain activity emerged, being more pronounced over the right as compared to the left hemisphere. Furthermore, this MEG component showed a consistent phase angle across subjects, indicating active synchronization mechanisms within auditory cortex that operate upon afferent input. Conceivably, these early side-differences in periodicity encoding contribute to or even snowball into hemispheric lateralization effects of higher-order aspects of central-auditory processing such as melody perception.

The various classes of speech sounds differ in their configuration of acoustic features. Vowels are characterized by specific local maxima of spectral energy distribution (formants). Using whole-head magnetoencephalography, the impact of variation of the first (F1) and second formant (F2) on the evoked N1m component (100 ms latency) was studied based on an oddball design. F1 changes yielded N1m enhancements in parallel to the spectral distance between standard and deviant stimuli. By contrast, F2 shifts gave rise to a non-linear relationship: the N1m effect flattened out above a range of two Barks. This frequency domain accords to critical band characteristics of the peripheral and central auditory system. The differences of early neuronal encoding of both formants relate to the predominant role of F2 for the encoding of stop consonants., (Copyright 2002 Elsevier Science Ireland Ltd.)

A variety of data indicate that the cerebellum participates in perceptual tasks requiring the precise representation of temporal information. Access to the word form of a lexical item requires, among other functions, the processing of durational parameters of verbal utterances. Therefore, cerebellar dysfunctions must be expected to impair word recognition. In order to specify the topography of the assumed cerebellar speech perception mechanism, a functional magnetic resonance imaging study was performed using the German lexical items "Boden" ([bodn], Engl. "floor") and "Boten" ([botn], "messengers") as test materials. The contrast in sound structure of these two lexical items can be signaled either by the length of the wordmedial pause (closure time, CLT; an exclusively temporal measure) or by the aspiration noise of wordmedial "d" or "t" (voice onset time, VOT; an intrasegmental cue). A previous study found bilateral cerebellar disorders to compromise word recognition based on CLT whereas the encoding of VOT remained unimpaired. In the present study, two series of "Boden - Boten" utterances were resynthesized, systematically varying either in CLT or VOT. Subjects had to identify both words "Boden" and "Boten" by analysis of either the durational parameter CLT or the VOT aspiration segment. In a subtraction design, CLT categorization as compared to VOT identification (CLT - VOT) yielded a significant hemodynamic response of the right cerebellar hemisphere (neocerebellum Crus I) and the frontal lobe (anterior to Broca's area). The reversed contrast ( VOT - CLT) resulted in a single activation cluster located at the level of the supratemporal plane of the dominant hemisphere. These findings provide first evidence for a distinct contribution of the right cerebellar hemisphere to speech perception in terms of encoding of durational parameters of verbal utterances. Verbal working memory tasks, lexical response selection, and auditory imagery of word strings have been reported to elicit activation clusters of a similar location. Conceivably, representation of the temporal structure of speech sound sequences represents the common denominator of cerebellar participation in cognitive tasks acting on a phonetic code.

Besides motor, vegetative, and cognitive signs, patients suffering from Parkinson's disease (PD) may show distinct perceptual deficits such as underestimation of time intervals extending across several seconds. Assuming this impairment also to affect the domain of tens of milliseconds, disrupted encoding of the acoustic speech signal with respect to segment durations conveying linguistic information must be expected. To test this hypothesis, 10 PD patients and matched controls performed an identification task using a series of 10 stimuli derived from the utterance "Boten" (/bo:tn/, 'messengers'; produced with nasal plosion) by exclusive manipulation of occlusion length (110-20 ms in steps of 10 ms). Under these conditions, word-medial silence cues the voicing category of the respective stop consonant. Seven PD subjects showed normal identification curves, i.e., categorized the shortest and longest stimuli with high probability each as the minimal pair cognates "Boden" and "Boten," respectively. In contrast, the remaining three patients labeled all items across the complete range of occlusion lengths as "Boden." A subsequent experiment found a horizontal shift of the identification curves toward larger signal durations (> 120 ms) in these three subjects. Bilateral cerebellar degeneration has been found to yield a different response pattern, i.e., near-chance level of performance. Considering recent information-processing models of scalar interval timing, striatal disorders seem to slow down an oscillatory pacemaker, whereas cerebellar dysfunctions may impair comparison of measured durations with stored reference memory traces.

It is still unsettled in how far temporal resolution of dynamic acoustic events (formant transitions) or phonetic/linguistic processes contribute to predominant left-hemisphere encoding of consonant-vowel syllables. To further elucidate the underlying mechanisms, evoked magnetic fields in response to consonant-vowel events (synthetic versus spoken) were recorded (oddball design: standards=binaural/ba/, deviants=dichotic/ba/-/da/; 20 right-handed subjects) under different attentional conditions (visual distraction versus stimulus identification). Spoken events yielded a left-lateralized peak phase of the mismatch field (MMF; 150-200ms post-stimulus onset) in response to right-ear deviants during distraction. By contrast, pre-attentive processing of synthetic items gave rise to a left-enhanced MMF onset (100ms), but failed to elicit later lateralization effects. In case of directed attention, synthetic deviants elicited a left-pronounced MMF peak resembling the pre-attentive response to natural syllables. These interactions of MMF asymmetry with signal structure and attentional load indicate two distinct successive left-lateralization effects: signal-related operations and representation of 'phonetic traces'. Furthermore, a right-lateralized early MMF component (100ms) emerged in response to natural syllables during pre-attentive processing and to synthetic stimuli in case of directed attention. Conceivably, these effects indicate right hemisphere operations prior to phonetic evaluation such as periodicity representation. Two distinct time windows showed correlations between dichotic listening performance and ear effects on magnetic responses reflecting early gain factors (ca. 75ms post-stimulus onset) and binaural fusion strategies (ca. 200ms), respectively. Finally, gender interacted with MMF lateralization, indicating different processing strategies in case of artificial speech signals.

The pre-supplementary motor area (pre-SMA) is engaged in speech comprehension under difficult circumstances such as poor acoustic signal quality or time-critical conditions. Previous studies found that left pre-SMA is activated when subjects listen to accelerated speech. Here, the functional role of pre-SMA was tested for accelerated speech comprehension by inducing a transient "virtual lesion" using continuous theta-burst stimulation (cTBS). Participants were tested (1) prior to (pre-baseline), (2) 10min after (test condition for the cTBS effect), and (3) 60min after stimulation (post-baseline) using a sentence repetition task (formant-synthesized at rates of 8, 10, 12, 14, and 16 syllables/s). Speech comprehension was quantified by the percentage of correctly reproduced speech material. For high speech rates, subjects showed decreased performance after cTBS of pre-SMA. Regarding the error pattern, the number of incorrect words without any semantic or phonological similarity to the target context increased, while related words decreased. Thus, the transient impairment of pre-SMA seems to affect its inhibitory function that normally eliminates erroneous speech material prior to speaking or, in case of perception, prior to encoding into a semantically/pragmatically meaningful message. [ABSTRACT FROM AUTHOR]

Background: The syndrome of conduction aphasia is an umbrella term to label clinically heterogeneous language disorders that all include a deficit of repetition due to impaired immediate memory or, in some patients, impaired speech production. The present article reviews the currently available literature on conduction aphasia. It covers aspects of the history of conduction aphasia as a fascicular disconnection syndrome and the objections to this view and discusses the proposed subtypes of this syndrome and the underlying cortical and white matter lesions. Aims: The primary objectives of this article are to critically review the influence of historical concepts on recent approaches to optimise existing theoretical synergies. In addition, the article seeks to advance our understanding of the first steps of verbal auditory processing in individuals with normal and impaired language skills. Main Contribution: We present first indications for an involvement of the left hemisphere in both short- and long-term integration of auditory information derived by examining patients with (conduction) aphasia. Conclusions: Conduction aphasia may result from left hemisphere cortical lesions or from a disconnection of critical bundles of axons (fibre tract). The exact course of the fibre tract connections and the cortical regions involved in conduction aphasia remains controversial. [ABSTRACT FROM AUTHOR]

Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per seconds (s)--exceeding by far the maximum performance level of untrained listeners (ca. 8 syl/s). Previous findings indicate the central-visual system to contribute to the processing of accelerated speech in blind subjects. As an extension, the present training study addresses the issue whether acquisition of ultra-fast (18 syl/s) speech perception skills induces de novo central-visual hemodynamic activation in late-blind participants. Furthermore, we asked to what extent subjects with normal or residual vision can improve understanding of accelerated verbal utterances by means of specific training measures. To these ends, functional magnetic resonance imaging (fMRI) was performed while subjects were listening to forward and reversed sentence utterances of moderately fast and ultra-fast syllable rates (8 or 18 syl/s) prior to and after a training period of ca. 6 months. Four of six participants showed--independently from residual visual functions--considerable enhancement of ultra-fast speech perception (about 70% points correctly repeated words) whereas behavioral performance did not change in the two remaining participants. Only subjects with very low visual acuity displayed training-induced hemodynamic activation of the central-visual system. By contrast, participants with moderately impaired or even normal visual acuity showed, instead, increased right-hemispheric frontal or bilateral anterior temporal lobe responses after training. All subjects with significant training effects displayed a concomitant increase of hemodynamic activation of left-hemispheric SMA. In spite of similar behavioral performance, trained "experts" appear to use distinct strategies of ultra-fast speech processing depending on whether the occipital cortex is still deployed for visual processing. [ABSTRACT FROM AUTHOR]

Friedreich ataxia (FRDA) is the most frequent recessive ataxia in the Western world. Dysarthria is a cardinal feature of FRDA, often leading to severe impairments in daily functioning, but its exact characteristics are only poorly understood so far. We performed a comprehensive evaluation of dysarthria severity and the profile of speech motor deficits in 20 patients with a genetic diagnosis of FRDA based on a carefully selected battery of speaking tasks and two widely used paraspeech tasks, i.e., oral diadochokinesis and sustained vowel productions. Perceptual ratings of the speech samples identified respiration, voice quality, voice instability, articulation, and tempo as the most affected speech dimensions. Whereas vocal instability predicted ataxia severity, tempo turned out as a significant correlate of disease duration. Furthermore, articulation predicted the overall intelligibility score as determined by a systematic speech pathology assessment tool. In contrast, neurologists' ratings of intelligibility-a component of the 'Scale for the Assessment and Rating of Ataxia'-were found to be related to perceived speech tempo. Obviously, clinicians are more sensitive to slowness of speech than to any other feature of spoken language during dysarthria evaluation. Our results suggest that different components of speech production and trunk/limb motor functions are differentially susceptible to FRDA pathology. Furthermore, evidence emerged that paraspeech tasks do not allow for an adequate scaling of speech deficits in FRDA. [ABSTRACT FROM AUTHOR]

Neurophonetics aims at the elucidation of the brain mechanisms underlying speech communication in our species. Clinical observations in patients with speech impairments following cerebral disorders provided the initial vantage point of this research area and indicated distinct functional-neuroanatomic systems to support human speaking and listening. Subsequent approaches-considering speech production a motor skill-investigated vocal tract movements associated with spoken language by means of kinematic and electromyographic techniques-allowing, among other things, for the evaluation of computational models suggesting elementary phonological gestures or a mental syllabary as basic units of speech motor control. As concerns speech perception, the working characteristics of auditory processing were first investigated based upon psychoacoustic techniques such as dichotic listening and categorical perception designs. More recently, functional hemodynamic neuroimaging and electrophysiological methods opened the door to the delineation of multiple stages of central auditory processing related to signal detection, classification, sensory memory processes, and, finally, lexical access. Beyond the control mechanisms in a stricter sense, both speech articulation and auditory processing represent examples of 'grounded cognition'. For example, both domains cannot be restricted to text-to-speech translation processes, but are intimately interwoven with neuropsychological aspects of speech prosody, including the vocal expression of affects and the actual performance of speech acts, transforming propositional messages to 'real' utterances. Furthermore, during language acquisition, the periphery of language-i.e., hearing and speaking behavior-plays a dominant role for the construction of a language-specific mental lexicon as well as language-specific action plans for the production of a speech message. WIREs Cogn Sci 2013, 4:191-200. doi: 10.1002/wcs.1211 For further resources related to this article, please visit the WIREs website. [ABSTRACT FROM AUTHOR]

Abstract: At the level of clinical speech/language evaluation, the repetition type of conduction aphasia is characterized by repetition difficulties concomitant with reduced short-term memory capacities, in the presence of fluent spontaneous speech as well as unimpaired naming and reading abilities. It is still unsettled which dysfunctions of the pre-lexical processing stage of spoken word recognition contribute to this syndrome and whether there is any relevant top-down impact of the mental lexicon upon the phonetic/phonological level of speech perception. In order to further specify the underlying pathomechanisms, a comprehensive battery of psycholinguistic tests was applied to a patient suffering from repetition conduction aphasia. The obtained results point at a pre-lexical disorder in this subject. To further specify the assumed pre-lexical dysfunction, computer simulations of single-word processing, based upon an interactive activation model (IAM), were conducted. An attenuation of the features-to-phonemes inhibition value was found to simulate the observed profile of psycholinguistic deficits. Conceivably, these pre-lexical disorders interfere with the task-dependent adjustment of the temporal windows of signal analysis, giving rise to compromised sequencing of auditory-verbal information. [Copyright &y& Elsevier]

Clinical and experimental data indicate higher proficiency of the left hemisphere in encoding dynamic acoustic events such as rapid formant transitions (30–40 ms) that distinguish consonant–vowel syllables such as /ba/ or /da/. In order to further elucidate the underlying neurophysiological mechanisms, discrimination of /bi/-like formant transitions of variable duration (18, 36, 54, or 72 ms) from a steady-state /i/-like vowel was investigated by means of whole-head magnetoencephalography (MEG) both during visual distraction and selective attention. Voiced speech-like as well as unvoiced non-speech stimuli, matched for spectral envelope, served as test materials. Based on an oddball design, magnetic mismatch fields (MMF) were determined during an early (170–210 ms) and a late (230–290 ms) time window. Selective attention toward the deviant events resulted in enhanced MMFs particularly within the left hemisphere, indicating attention-dependent left-lateralized processing of dynamic auditory events across both the speech and non-speech domains. Perceptual discrimination improved along with transient lengthening. Accordingly, early MMF was, as a rule, enlarged in case of longer as compared to shorter transients. The 36-ms transitions yielded attention- and voicing-dependent deviations from the linear regression of MMF strength on transition duration. Considering the predominance of 30- to 40-ms formant transients across the world’s languages, these findings indicate an adaptation or predisposition of the human perceptual system to the spectral/temporal characteristics of prototypical speech sounds. Signal voicing had no significant main effect on MMF strength despite superior perceptual performance in case of voiced as compared to voiceless target stimuli. [Copyright &y& Elsevier]