Processing references in context: when the polar bear does not meet a polar bear.

Discourse understanding is hampered when missing or conflicting context information is given. In four experiments, we investigated what happens (a) when the definite determiner "the," which presupposes existence and uniqueness, does not find a unique referent in the context or (b) when the appropriate use of the indefinite determiner is violated by the presence of a unique referent (Experiment 1 and Experiment 2). To focus on the time-course of processing the uniqueness presupposition of the definite determiner, we embedded the determiner in different sentence structures and varied the context (Experiment 3 and Experiment 4). Reading time served as an index of processing difficulty in a word-by-word self-paced reading task and acceptability judgments provided hints for a possible repair of a presupposition violation. Our results showed that conflicting and missing context information lowered acceptability ratings and was associated with prolonged reading times. The pattern of results differed depending on the nature of the presupposition (Experiments 1 and 2) and whether supplementing missing context information was possible (Experiment 3 and Experiment 4). Our findings suggest that different cognitive processes come into play when interpreting presuppositions in order to get a meaningful interpretation of a discourse.

Discourse management during speech perception: A functional magnetic resonance imaging (fMRI) study.

Discourse structures enable us to generate expectations based upon linguistic material that has already been introduced. We investigated how the required cognitive operations such as reference processing, identification of critical items, and eventual handling of violations correlate with neuronal activity within the language network of the brain. To this end, we conducted a functional magnetic resonance imaging (fMRI) study in which we manipulated spoken discourse coherence by using presuppositions (PSPs) that either correspond or fail to correspond to items in preceding context sentences. Definite and indefinite determiners were used as PSP triggers, referring to (non-) uniqueness or (non-) existence of an item. Discourse adequacy was tested by means of a behavioral rating during fMRI. Discourse violations yielded bilateral hemodynamic activation within the inferior frontal gyrus (IFG), the inferior parietal lobe including the angular gyrus (IPL/AG), the pre-supplementary motor area (pre-SMA), and the basal ganglia (BG). These findings illuminate cognitive aspects of PSP processing: (1) a reference process requiring working memory (IFG), (2) retrieval and integration of semantic/pragmatic information (IPL/AG), (3) cognitive control of inconsistency management (pre-SMA/BG) in terms of "successful" comprehension despite PSP violations at the surface. These results provide the first fMRI evidence needed to develop a functional neuroanatomical model for context-dependent sentence comprehension based on the example of PSP processing.

Consensus paper: Language and the cerebellum: an ongoing enigma.

In less than three decades, the concept "cerebellar neurocognition" has evolved from a mere afterthought to an entirely new and multifaceted area of neuroscientific research. A close interplay between three main strands of contemporary neuroscience induced a substantial modification of the traditional view of the cerebellum as a mere coordinator of autonomic and somatic motor functions. Indeed, the wealth of current evidence derived from detailed neuroanatomical investigations, functional neuroimaging studies with healthy subjects and patients and in-depth neuropsychological assessment of patients with cerebellar disorders shows that the cerebellum has a cardinal role to play in affective regulation, cognitive processing, and linguistic function. Although considerable progress has been made in models of cerebellar function, controversy remains regarding the exact role of the "linguistic cerebellum" in a broad variety of nonmotor language processes. This consensus paper brings together a range of different viewpoints and opinions regarding the contribution of the cerebellum to language function. Recent developments and insights in the nonmotor modulatory role of the cerebellum in language and some related disorders will be discussed. The role of the cerebellum in speech and language perception, in motor speech planning including apraxia of speech, in verbal working memory, in phonological and semantic verbal fluency, in syntax processing, in the dynamics of language production, in reading and in writing will be addressed. In addition, the functional topography of the linguistic cerebellum and the contribution of the deep nuclei to linguistic function will be briefly discussed. As such, a framework for debate and discussion will be offered in this consensus paper.

Ultra-fast speech comprehension in blind subjects engages primary visual cortex, fusiform gyrus, and pulvinar - a functional magnetic resonance imaging (fMRI) study.

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.

Cross-modal interactions during perception of audiovisual speech and nonspeech signals: an fMRI study.

During speech communication, visual information may interact with the auditory system at various processing stages. Most noteworthy, recent magnetoencephalography (MEG) data provided first evidence for early and preattentive phonetic/phonological encoding of the visual data stream--prior to its fusion with auditory phonological features [Hertrich, I., Mathiak, K., Lutzenberger, W., & Ackermann, H. Time course of early audiovisual interactions during speech and non-speech central-auditory processing: An MEG study. Journal of Cognitive Neuroscience, 21, 259-274, 2009]. Using functional magnetic resonance imaging, the present follow-up study aims to further elucidate the topographic distribution of visual-phonological operations and audiovisual (AV) interactions during speech perception. Ambiguous acoustic syllables--disambiguated to /pa/ or /ta/ by the visual channel (speaking face)--served as test materials, concomitant with various control conditions (nonspeech AV signals, visual-only and acoustic-only speech, and nonspeech stimuli). (i) Visual speech yielded an AV-subadditive activation of primary auditory cortex and the anterior superior temporal gyrus (STG), whereas the posterior STG responded both to speech and nonspeech motion. (ii) The inferior frontal and the fusiform gyrus of the right hemisphere showed a strong phonetic/phonological impact (differential effects of visual /pa/ vs. /ta/) upon hemodynamic activation during presentation of speaking faces. Taken together with the previous MEG data, these results point at a dual-pathway model of visual speech information processing: On the one hand, access to the auditory system via the anterior supratemporal "what" path may give rise to direct activation of "auditory objects." On the other hand, visual speech information seems to be represented in a right-hemisphere visual working memory, providing a potential basis for later interactions with auditory information such as the McGurk effect.

The Role of the Dorsolateral Prefrontal Cortex for Speech and Language Processing.

This review article summarizes various functions of the dorsolateral prefrontal cortex (DLPFC) that are related to language processing. To this end, its connectivity with the left-dominant perisylvian language network was considered, as well as its interaction with other functional networks that, directly or indirectly, contribute to language processing. Language-related functions of the DLPFC comprise various aspects of pragmatic processing such as discourse management, integration of prosody, interpretation of nonliteral meanings, inference making, ambiguity resolution, and error repair. Neurophysiologically, the DLPFC seems to be a key region for implementing functional connectivity between the language network and other functional networks, including cortico-cortical as well as subcortical circuits. Considering clinical aspects, damage to the DLPFC causes psychiatric communication deficits rather than typical aphasic language syndromes. Although the number of well-controlled studies on DLPFC language functions is still limited, the DLPFC might be an important target region for the treatment of pragmatic language disorders.

The contribution of mesiofrontal cortex to the preparation and execution of repetitive syllable productions: an fMRI study.

Clinical data indicate that the brain network of speech motor control can be subdivided into at least three functional-neuroanatomical subsystems: (i) planning of movement sequences (premotor ventrolateral-frontal cortex and/or anterior insula), (ii) preparedness for/initiation of upcoming verbal utterances (supplementary motor area, SMA), and (iii) on-line innervation of vocal tract muscles, i.e., motor execution (corticobulbar system, basal ganglia, cerebellum). Using an event-related design, this functional magnetic resonance imaging (fMRI) study sought to further delineate the contribution of SMA to pre-articulatory processes of speech production (preceding the innervation of vocal tract muscles) during an acoustically paced syllable repetition task forewarned by a tone signal. Hemodynamic activation across the whole brain and the time courses of the responses in five regions of interest (ROIs) were computed. First, motor preparation was associated with a widespread bilateral activation pattern, encompassing brainstem structures, SMA, insula, premotor ventrolateral-frontal areas, primary sensorimotor cortex (SMC), basal ganglia, and the superior cerebellum. Second, calculation of the time courses of BOLD ("blood oxygenation level-dependent") signal changes revealed the warning stimulus to elicit synchronous onset of hemodynamic activation in these areas. However, during 4-s intervals of syllable repetitions SMA and cerebellum showed opposite temporal activation patterns in terms of a shorter (SMA) and longer (cerebellum) latency of the entire BOLD response-as compared to SMC, indicating different pacing mechanisms during the initial and the ongoing phase of the task. Nevertheless, the contribution of SMA was not exclusively restricted to the preparation/initiation of verbal responses since the extension of mesiofrontal activation varied with task duration.

Temporal processing capabilities in repetition conduction aphasia.

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.

Enhanced speech perception capabilities in a blind listener are associated with activation of fusiform gyrus and primary visual cortex.

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.

Predictability modulates motor-auditory interactions in self-triggered audio-visual apparent motion.

We studied an effect of predictability in an audio-visual apparent motion task using magnetoencephalography. The synchronous sequences of audio-visual stimuli were self-triggered by subjects. The task was to detect the direction of the apparent motion in experimental blocks in which the motion either started from the side selected by subjects (predictable condition) or was random (unpredictable condition). Magnetic fields yielded three patterns of activity in the motor, auditory, and visual areas. Comparison of the dipole strength between predictable and unpredictable conditions revealed a significant difference of the preparatory motor activity in the time interval from -450 to -100 ms before self-triggering the stimulus. Perception of the audio-visual apparent motion was also modulated by predictability. However, the modulation was found only for the auditory activity but not for the visual one. The effect of predictability was selective and modulated only the auditory component N1 (100 ms after stimulus), which reflects initial evaluation of stimulus meaning. Importantly, the preparatory motor activity correlates with the following auditory activity mainly in the same hemisphere. Similar modulation by predictability of the motor and auditory activities suggests interactions between these two systems within an action-perception cycle. The mechanism of these interactions can be understood as an effect of anticipation of the own action outcomes on the preparatory motor and perceptual activity.

Cortical phase locking to accelerated speech in blind and sighted listeners prior to and after training.

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.

Reduced Performance During a Sentence Repetition Task by Continuous Theta-Burst Magnetic Stimulation of the Pre-supplementary Motor Area.

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) 10 min after (test condition for the cTBS effect), and (3) 60 min 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.

Sequential audiovisual interactions during speech perception: a whole-head MEG study.

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.

Who is telling what from where? A functional magnetic resonance imaging study.

The human central-auditory system exhibits distinct lateralization effects (speech, space) and encompasses different processing pathways (where, what, who). Using spatialized pseudoword utterances, attentional modulation of the networks bound to sound source localization ('where'), voice recognition ('who'), and the encoding of phonetic-linguistic information ('what') was evaluated by silent functional magnetic resonance imaging. The 'where'-pathway was found to be restricted to posterior parts of the left superior temporal gyrus, speaker ('auditory face') identification exclusively activated temporal lobe structures, and the representation of the sound structure of the utterances was associated with hemodynamic activation of Broca's area. Speech perception in space, therefore, engages at least three distinct neural networks. Furthermore, the findings indicate that voice recognition may depend upon template matching within auditory association cortex whereas the sequencing of phonetic-linguistic information extends to frontal areas.

Semiotic aspects of human nonverbal vocalizations: a functional imaging study.

Humans produce a variety of distinct nonverbal vocalizations. Whereas affective bursts, for example, laughter, have an intrinsic communicative role bound to social behavior, vegetative sounds, for example, snoring, just signal autonomic-physiological states. However, the latter events, for example, belching, may also be used as intentional communicative actions (vocal gestures), characterized by an arbitrary culture-dependent sound-to-meaning (semiotic) relationship, comparable to verbal utterances. Using a decision task, hemodynamic responses to affective bursts, vegetative sounds, and vocal gestures were measured by means of functional magnetic resonance imaging. Affective bursts elicited activation of anterior left superior temporal gyrus. In contrast, arbitrary vocal gestures yielded hemodynamic reactions of the left temporo-parietal junction. Conceivably, a listener's interpretation of nonverbal utterances as intentional events depends upon a left-hemisphere temporo-parietal 'auditory-to-meaning interface' related to our mechanisms of speech processing.

The role of the supplementary motor area for speech and language processing.

Apart from its function in speech motor control, the supplementary motor area (SMA) has largely been neglected in models of speech and language processing in the brain. The aim of this review paper is to summarize more recent work, suggesting that the SMA has various superordinate control functions during speech communication and language reception, which is particularly relevant in case of increased task demands. The SMA is subdivided into a posterior region serving predominantly motor-related functions (SMA proper) whereas the anterior part (pre-SMA) is involved in higher-order cognitive control mechanisms. In analogy to motor triggering functions of the SMA proper, the pre-SMA seems to manage procedural aspects of cognitive processing. These latter functions, among others, comprise attentional switching, ambiguity resolution, context integration, and coordination between procedural and declarative memory structures. Regarding language processing, this refers, for example, to the use of inner speech mechanisms during language encoding, but also to lexical disambiguation, syntax and prosody integration, and context-tracking.

Neuromagnetic signatures of syllable processing in fetuses and infants provide no evidence for habituation.

BACKGROUND: Habituation, as a basic form of learning, is characterized by decreasing amplitudes of neuronal reaction following repeated stimuli. Recent studies indicate that habituation to pure tones of different frequencies occurs in fetuses and infants. AIMS: Neural processing of different syllables in fetuses and infants was investigated. STUDY DESIGN: An auditory habituation paradigm including two different sequences of syllables was presented to each subject. Each sequence consisted of eight syllables (sequence /ba/: 5× /ba/, 1× /bi/ (dishabituator), 2× /ba/; sequence /bi/: 5× /bi/, 1× /ba/ (dishabituator), 2× /bi/). Each subject was stimulated with 140 sequences. Neuromagnetic signatures of auditory-evoked responses (AER) were recorded by fetal magnetoencephalography (fMEG). SUBJECTS: Magnetic brain signals of N=30 fetuses (age: 28-39weeks of gestation) and N=28 infants (age: 0-3months) were recorded. Forty-two of the 60 fetal recordings and 29 of the 58 infant recordings were included in the final analysis. OUTCOME MEASURES: AERs were recorded and amplitudes were normalized to the amplitude of the first stimulus. RESULTS: In both fetuses and infants, the amplitudes of AERs were found not to decrease with repeated stimulation. In infants, however, amplitude of syllable 6 (dishabituator) was significantly increased compared to syllable 5 (p=0.026). CONCLUSIONS: Fetuses and infants showed AERs to syllables. Unlike fetuses, infants showed a discriminative neural response to syllables. Habituation was not observed in either fetuses or infants. These findings could be important for the investigation of early cognitive competencies and may help to gain a better understanding of language acquisition during child development.

MEG responses to rippled noise and Huggins pitch reveal similar cortical representations.

The onset of pitch within an ongoing noise signal evokes a particular brain activity, the pitch onset response (POR). Using whole-head MEG, PORs to iterated rippled noise (IRN) and Huggins pitch (HP), representing prototypical pitch-in-noise signals, were measured in twenty subjects during a pitch identification task (333 Hz, 400 Hz, randomized). HP and IRN yielded similar responses, lateralized to the left hemisphere and peaking about 180 ms after pitch onset. The initial phase (140 ms) showed stronger activations to 400 than to 333 Hz whereas later stages (200-300 ms) showed target vs nontarget effects. These results suggest, first, that different pitches converge into a common cortical representation and, second, that the POR encompasses various successive processing stages.

Network Modeling for Functional Magnetic Resonance Imaging (fMRI) Signals during Ultra-Fast Speech Comprehension in Late-Blind Listeners.

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.

Experience-related structural changes of degenerated occipital white matter in late-blind humans - a diffusion tensor imaging study.

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.