Alpha power during task performance predicts individual language comprehension.

Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized these effects in left temporal-parietal brain regions known to be associated with language processing and their right-hemisphere homologues. Our results support the notion that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance.

Neural networks for harmonic structure in music perception and action.

The ability to predict upcoming structured events based on long-term knowledge and contextual priors is a fundamental principle of human cognition. Tonal music triggers predictive processes based on structural properties of harmony, i.e., regularities defining the arrangement of chords into well-formed musical sequences. While the neural architecture of structure-based predictions during music perception is well described, little is known about the neural networks for analogous predictions in musical actions and how they relate to auditory perception. To fill this gap, expert pianists were presented with harmonically congruent or incongruent chord progressions, either as musical actions (photos of a hand playing chords) that they were required to watch and imitate without sound, or in an auditory format that they listened to without playing. By combining task-based functional magnetic resonance imaging (fMRI) with functional connectivity at rest, we identified distinct sub-regions in right inferior frontal gyrus (rIFG) interconnected with parietal and temporal areas for processing action and audio sequences, respectively. We argue that the differential contribution of parietal and temporal areas is tied to motoric and auditory long-term representations of harmonic regularities that dynamically interact with computations in rIFG. Parsing of the structural dependencies in rIFG is co-determined by both stimulus- or task-demands. In line with contemporary models of prefrontal cortex organization and dual stream models of visual-spatial and auditory processing, we show that the processing of musical harmony is a network capacity with dissociated dorsal and ventral motor and auditory circuits, which both provide the infrastructure for predictive mechanisms optimising action and perception performance.

Left prefrontal cortex activation during sentence comprehension covaries with grammatical knowledge in children.

Children's language skills develop rapidly with increasing age, and several studies indicate that they use language- and age-specific strategies to understand complex sentences. In the present experiment, functional magnetic resonance imaging (fMRI) and behavioral measures were used to investigate the acquisition of case-marking cues for sentence interpretation in the developing brain of German preschool children with a mean age of 6 years. Short sentences were presented auditorily, consisting of a transitive verb and two case-marked arguments with canonical subject-initial or non canonical object-initial word order. Overall group results revealed mainly left hemispheric activation in the perisylvian cortex with increased activation in the inferior parietal cortex (IPC), and the anterior cingulate cortex (ACC) for object-initial compared to subject-initial sentences. However, single-subject analysis suggested two distinct activation patterns within the group which allowed a classification into two subgroups. One subgroup showed the predicted activation increase in the left inferior frontal gyrus (IFG) for the more difficult object-initial compared to subject-initial sentences, while the other group showed the reverse effect. This activation in the left IFG can be taken to reflect the degree to which adult-like sentence processing strategies, necessary to integrate case-marking information, are applied. Additional behavioral data on language development tests show that these two subgroups differ in their grammatical knowledge. Together with these behavioral findings, the results indicate that the use of a particular processing strategy is not dependent on age as such, but rather on the child's individual grammatical knowledge and the ability to use specific language cues for successful sentence comprehension.

Top-down modulation of auditory processing: effects of sound context, musical expertise and attentional focus.

By recording auditory electrical brain potentials, we investigated whether the basic sound parameters (frequency, duration and intensity) are differentially encoded among speech vs. music sounds by musicians and non-musicians during different attentional demands. To this end, a pseudoword and an instrumental sound of comparable frequency and duration were presented. The accuracy of neural discrimination was tested by manipulations of frequency, duration and intensity. Additionally, the subjects' attentional focus was manipulated by instructions to ignore the sounds while watching a silent movie or to attentively discriminate the different sounds. In both musicians and non-musicians, the pre-attentively evoked mismatch negativity (MMN) component was larger to slight changes in music than in speech sounds. The MMN was also larger to intensity changes in music sounds and to duration changes in speech sounds. During attentional listening, all subjects more readily discriminated changes among speech sounds than among music sounds as indexed by the N2b response strength. Furthermore, during attentional listening, musicians displayed larger MMN and N2b than non-musicians for both music and speech sounds. Taken together, the data indicate that the discriminative abilities in human audition differ between music and speech sounds as a function of the sound-change context and the subjective familiarity of the sound parameters. These findings provide clear evidence for top-down modulatory effects in audition. In other words, the processing of sounds is realized by a dynamically adapting network considering type of sound, expertise and attentional demands, rather than by a strictly modularly organized stimulus-driven system.

Brain potentials indicate immediate use of prosodic cues in natural speech processing.

Spoken language, in contrast to written text, provides prosodic information such as rhythm, pauses, accents, amplitude and pitch variations. However, little is known about when and how these features are used by the listener to interpret the speech signal. Here we use event-related brain potentials (ERP) to demonstrate that intonational phrasing guides the initial analysis of sentence structure. Our finding of a positive shift in the ERP at intonational phrase boundaries suggests a specific on-line brain response to prosodic processing. Additional ERP components indicate that a false prosodic boundary is sufficient to mislead the listener's sentence processor. Thus, the application of ERP measures is a promising approach for revealing the time course and neural basis of prosodic information processing.

Musical syntax is processed in Broca's area: an MEG study.

The present experiment was designed to localize the neural substrates that process music-syntactic incongruities, using magnetoencephalography (MEG). Electrically, such processing has been proposed to be indicated by early right-anterior negativity (ERAN), which is elicited by harmonically inappropriate chords occurring within a major-minor tonal context. In the present experiment, such chords elicited an early effect, taken as the magnetic equivalent of the ERAN (termed mERAN). The source of mERAN activity was localized in Broca's area and its right-hemisphere homologue, areas involved in syntactic analysis during auditory language comprehension. We find that these areas are also responsible for an analysis of incoming harmonic sequences, indicating that these regions process syntactic information that is less language-specific than previously believed.

Infant cognition includes the potentially human-unique ability to encode embedding.

Human cognition relies on the ability to encode complex regularities in the input. Regularities above a certain complexity level can involve the feature of embedding, defined by nested relations between sequential elements. While comparative studies suggest the cognitive processing of embedding to be human specific, evidence of its ontogenesis is lacking. To assess infants' ability to process embedding, we implemented nested relations in tone sequences, minimizing perceptual and memory requirements. We measured 5-month-olds' brain responses in two auditory oddball paradigms, presenting standard sequences with one or two levels of embedding, interspersed with infrequent deviant sequences violating the established embedding rules. Brain potentials indicate that infants detect embedding violations and thus appear to track nested relations. This shows that the ability to encode embedding may be part of the basic human cognitive makeup, which might serve as scaffolding for the acquisition of complex regularities in language or music.

The neurobiological nature of syntactic hierarchies.

The review focuses on the neurobiological literature concerning the specific human ability to process linguistic hierarchies. First, we will discuss current ethological studies dedicated to the comparison between human and non-human animals for the processing of different grammar types. We will inspect the functional neuroanatomical structures of human and non-human primates more closely, including human developmental data, thereby suggesting interesting phylogenetic and ontogenetic differences. We then examine the neural reality of the Merge computation, being the most fundamental mechanism regulating natural language syntax, and offer new evidence for a possible localization of Merge in the most ventral anterior portion of BA 44. We conclude that BA 44, with its strong neural connection to the posterior temporal cortex, provides a recent evolutionary neurobiological basis for the unique human faculty of language.

A revival of Homo loquens as a builder of labeled structures: Neurocognitive considerations.

The core capacity of human language is described as the faculty to combine words into hierarchical structures. This review aims to isolate the fundamental computation behind the language faculty together with its neural implementation. First, we present our central hypothesis by confronting recent linguistic theory with evolutionary arguments: linguistic humaniqueness is reflected in the labeling of word combinations forming asymmetric hierarchical structures. Second, we review the neurolinguistic literature, especially focusing on dual-stream connectivity models. We put forward that the dorsal pathway, especially the arcuate fascicle, is responsible for the rule-based combinatorial system, implementing labeling and giving rise to hierarchical structures. Conversely, the ventral stream is rather responsible for semantic associative operations. We further present evolutionary neuroanatomical evidence grounding our hypothesis. We conclude by suggesting further avenues of research as well as open questions to be addressed. With the aim to expand our knowledge on the neurobiology of language, we hope to provide a testable hypothesis for the origin of language syntax bringing together evidence from different fields.

Rapidly induced changes in neuromagnetic fields following repetitive hand movements.

Sensory feedback plays a major role in movement execution and motor learning, particularly in motor rehabilitation. Whilst elaborating therapeutic strategies, it is of interest to visualize the effect of a therapeutic intervention at the moment of its application. We analyzed the effect of repeated execution of a simple extension and flexion movement of the wrist on the sensorimotor cortex of seven healthy subjects using magnetoencephalography. Spatial filtering based on current dipoles was used to quantify the strength of cortical activation. Our results showed an increase of cortical activation reflecting activity of efferent neurons, whereas the activity of proprioceptive afferent neurons was not affected. Since only efferent activity increased, it is suggested that this reflects phenomena of long-term potentiation.

Aphasics' perception of words in sentential context: some real-time processing evidence.

The perception of words belonging to different grammatical classes was investigated in Wernicke's and Broca's aphasics. The experimental used a word monitoring task, which varied the target's word class, as well as the sentential context. The sensitivity to semantic context was very similar for both aphasic groups. Processing differences for the two groups were found, however, with respect to different word classes. It appears that Broca's aphasics are unable to process grammatical morphemes as features of a phrasal frame. Wernicke's aphasics, however, seem to retain the ability to process syntactic as well as some semantic information, at least, during sentence perception.

Double dissociation of processing temporal and spatial information in working memory.

Based on the converging evidence supporting the view of domain specific object and spatial working memory processes, the question was addressed whether the property of domain specificity holds equally for temporal information. Using a selective interference paradigm the objective was to test a dissociation of the processing of temporal duration and spatial location information in working memory of intact human subjects. Subjects performed a temporal and a spatial memory task in which they were required to indicate whether the study and the test stimuli were the same or different in duration (temporal memory) or in location (spatial memory) as primary tasks. Both primary tasks were combined with three types of interference tasks, a spatial classification memory task, a temporal classification memory task and a non-interference baseline task--to be performed in-between the presentation of study and test stimuli. Memory for temporal duration was shown to be impaired by the temporal classification task but not by the spatial classification task; memory for spatial position showed the opposite pattern of impairment. These data thus provide evidence for the view that temporal and spatial working memory contents are subject to selective interference, reflecting a functional dissociation in the processing of temporal duration and spatial location information. The results are interpreted as evidence for the domain specificity in the processing of temporal information in working memory.

Slow cortical potentials during retention of object, spatial, and verbal information.

We used event related potentials (ERPs) to examine both the specificity and the timing of slow cortical scalp potentials (SPs) elicited by the retention of object, spatial, and verbal information in working memory (WM). Participants performed a modified delayed matching task in which a task cue presented in the middle of the delay interval indicated what type of information had to be retained for a subsequent comparison with the test stimulus. The first experiment used nameable objects and spatial locations as stimuli. The retrieval mode (visual vs. verbal) was manipulated by presenting either figural information or printed words as test stimuli. Transient ensembles of frontal and parieto-occipital slow waves with different scalp topographies for object and spatial information were evoked as a function of task cues. When words rather than objects were used as test stimuli highly similar, though more pronounced, fronto-parietal slow wave patterns were obtained. The second experiment using unfamiliar objects and non-nameable spatial locations indicated that neither the left frontal negative SP nor the posterior SPs are exclusively related to verbal working memory operations. The results indicate that a parietal negative SP reflects processes of spatial selective attention whereas a parieto-occipital positive SP indexes the retention of visual object information. Left frontal negative SPs are generated by a compound of higher order frontal control processes and vary as a function of information type.

Event-related brain potentials during natural speech processing: effects of semantic, morphological and syntactic violations.

The present study investigated different aspects of auditory language comprehension. The sentences which were presented as connected speech were either correct or incorrect including a semantic error (selectional restriction), a morphological error (verb inflection), or a syntactic error (phrase structure). After each sentence, a probe word was presented auditorily, and subjects had to decide whether this word was part of the preceding sentence or not. Event-related brain potentials (ERPs) were recorded from 7 scalp electrodes. The ERPs evoked by incorrect sentences differed significantly from the correct ones as a function of error type. Semantic anomalies evoked a 'classical' N400 pattern. Morphological errors elicited a pronounced negativity between 300 and 600 ms followed by a late positivity. Syntactic errors, in contrast, evoked an early negativity peaking around 180 ms followed by a negativity around 400 ms. The early negativity was only significant over the left anterior electrode. The present data demonstrate that linguistic errors of different categories evoke different ERP patterns. They indicate that with using connected speech as input, different aspects of language comprehension processes cannot only be described with respect to their temporal structure, but eventually also with respect to possible brain systems subserving these processes.

Phonological processing during language production: fMRI evidence for a shared production-comprehension network.

Studies of phonological processes during language comprehension consistently report activation of the superior portion of Broca's area. In the domain of language production, however, there is no unequivocal evidence for the contribution of Broca's area to phonological processing. The present event-related fMRI study investigated the existence of a common neural network for phonological decisions in comprehension and production by using production tasks most comparable to those previously used in comprehension. Subjects performed two decision tasks on the initial phoneme of German picture names (/b/ or not? Vowel or not?). A semantic decision task served as a baseline for both phonological tasks. The contrasts between each phonological task and the semantic task were calculated, and a conjunction analysis was performed. There was significant activation in the superior portion of Broca's area (Brodmann's area (BA) 44) in the conjunction analysis, also present in each single contrast. In addition, further left frontal (BA 45/46) and temporal (posterior superior temporal gyrus) areas known to support phonological processing in both production and comprehension were activated. The results suggest the existence of a shared fronto-temporal neural network engaged in the processing of phonological information in both perception and production.

Neurocognition of auditory sentence comprehension: event related fMRI reveals sensitivity to syntactic violations and task demands.

The present study investigates the sensitivity of distinct brain regions to the syntactic processing of running speech. Experimental conditions varied the grammaticality of sentence types (correct vs. incorrect). Moreover, two different groups of subjects listened to the same sentence material, but followed two different task instructions. All participants were asked to listen to the auditory stimuli and to perform in a grammaticality judgment-task, whereas only half of the subjects were instructed to additionally repair incorrect sentences covertly. Significantly increased brain responses occurred in several left temporal areas as a function of sentences' grammaticality, particularly, in the 'pure' judgment-group. Spatial extent as well as the strength of focal brain activation changed as a function of grammaticality and task demand. A generally enhanced pattern of local blood supply to the right peri-sylvian cortex could be observed when individuals additionally realized the repair-task. In particular, the right inferior frontal gyrus (pars opercularis and pars triangularis) and the right temporal transverse gyrus (Heschl's gyrus) were more strongly affected by the repair-task demand. In contrast, an anterior portion of the superior temporal gyrus (planum polare) displayed increased activation bilaterally. Although left hemisphere activation varied clearly as a function of a sentence's grammaticality, the present findings demonstrate an involvement of the right peri-sylvian cortex, in particular, when task demands explicitly require an on-line repair. The results as a whole suggest a reconsideration of the notion that auditory language comprehension is restricted to the left hemisphere. The underlying mechanisms and the respective roles of both the left and the right hemisphere during speech processing are discussed.

Oscillatory neuromagnetic activity induced by language and non-language stimuli.

Event-related oscillatory brain activity during language perception differs from activity occurring during the processing of comparable non-language stimuli. This fact became apparent in the observation of changes in the normalized spectral power of magnetoencephalographic (MEG) signals during the subject's processing of these stimuli. MEG was recorded over the left and right hemispheres of 12 right-handed subjects. During the experimental session, bisyllablic content words and physically similar non-language stimuli were presented with equal probability in a randomized order in either the visual or auditory modality. Approximately 15% of these stimuli were marked and the subject's task was to detect these marked stimuli. As a major characteristic of language vs. non-language processing, we obtained an enhancement of the normalized spectral power around 240 ins in the 60-65-Hz band over the left hemisphere for the language condition and over the right hemisphere for the non-language condition, independent of the modality of stimulus presentation. Starting at approximately the same latency but in lower-frequency bands (15-45-Hz), an extended (250-600 ms) reduction of normalized spectral power was observed. This reduction, although it generally confirmed previous results, differed in the no hemisphere-specific reduction was found for the processing of words. A domain-specific enhancement of normalized spectral power was also evident around 800-1200 ms in the 15-30-Hz band. In the auditory condition, this enhancement of the normalized spectral power was larger after the presentation of language stimuli whereas in the visual condition a larger enhancement of the normalized spectral power was obtained after presentation of non-language stimuli. As this latter effect appears relatively late after the stimulus onset and differs in expression for both modalities of stimulus presentation, a simple relationship between language perception and oscillatory brain dynamics can be excluded for this enhancement. In contrast, the left hemispheric enhancement of the normalized spectral power present around 240 ms in the 60-65-Hz band seems to reflect oscillatory pattern specific to the processing of words.

Syntactic parsing preferences and their on-line revisions: a spatio-temporal analysis of event-related brain potentials.

The present study investigates the processes involved in the recovery from temporarily ambiguous garden-path sentences. Event-related brain potentials (ERP) were recorded while subjects read German subject-object ambiguous relative and complement clauses. As both clause types are initially analyzed as subject-first structures, object-first structures require a revision which is more difficult for complement than for relative clauses. The hypothesis is tested that the revision process consists of two sub-processes, namely diagnosis and actual reanalysis. Applying a spatio-temporal principal component analysis to the ERP data, distinct positive sub-components presumably reflecting different sub-processes could be identified in the time range of the P300 and P600. It will be argued that the P600 is not a monolithic component, and that different sub-processes may be involved at varying time points depending on the type of garden-path sentence.

Electrophysiological correlates of temporal and spatial information processing.

In order to study the neurophysiological correlates of working memory for different types of information, event-related brain potentials (ERPs) were recorded during a visual spatial and visual as well as auditory duration memory tasks. From stimulus onset to 500 ms ERPs were distinguishable by allocation to visual or auditory modality. From 500 to 2000 ms after stimulus onset, the spatial task generated a parieto-occipital focused negative slow wave, while corresponding ERPs of the temporal task showed a negative slow wave with frontolateral focus. From 1200 to 5500 ms a large positivity was found for the auditory temporal task and for good performers of the visual temporal task. The data suggest a distinction of three processing phases: modality-specific encoding, information-specific encoding and retention in conjunction with modality-specific inhibition processes.

Phonological processing in language production: time course of brain activity.

Recent neuroimaging studies provide evidence for a shared neural network for phonological processing in language production and comprehension. The temporal dynamics in this network during comprehension has been investigated by Thierry et al., who showed a primacy for Wernicke's over Broca's area. In the present study, we demonstrate the reversed pattern for language production. These results can be interpreted with respect to the functionality of the different regions within the shared network, with Wernicke's area being the sound form store and Broca's area a processor necessary to extract relevant phonological information from that store.