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.

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.

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.

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.

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.

A locus for an auditory processing deficit and language impairment in an extended pedigree maps to 12p13.31-q14.3.

Despite the apparent robustness of language learning in humans, a large number of children still fail to develop appropriate language skills despite adequate means and opportunity. Most cases of language impairment have a complex etiology, with genetic and environmental influences. In contrast, we describe a three-generation German family who present with an apparently simple segregation of language impairment. Investigations of the family indicate auditory processing difficulties as a core deficit. Affected members performed poorly on a nonword repetition task and present with communication impairments. The brain activation pattern for syllable duration as measured by event-related brain potentials showed clear differences between affected family members and controls, with only affected members displaying a late discrimination negativity. In conjunction with psychoacoustic data showing deficiencies in auditory duration discrimination, the present results indicate increased processing demands in discriminating syllables of different duration. This, we argue, forms the cognitive basis of the observed language impairment in this family. Genome-wide linkage analysis showed a haplotype in the central region of chromosome 12 which reaches the maximum possible logarithm of odds ratio (LOD) score and fully co-segregates with the language impairment, consistent with an autosomal dominant, fully penetrant mode of inheritance. Whole genome analysis yielded no novel inherited copy number variants strengthening the case for a simple inheritance pattern. Several genes in this region of chromosome 12 which are potentially implicated in language impairment did not contain polymorphisms likely to be the causative mutation, which is as yet unknown.

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.

Overlap of musical and linguistic syntax processing: intracranial ERP evidence.

The present study investigated the co-localization of musical and linguistic syntax processing in the human brain. EEGs were recorded from subdural electrodes placed on the left and right perisylvian cortex. The neural generators of the early potentials elicited by syntactic errors in music and language were localized by means of distributed source modeling and compared within subjects. The combined results indicated a partial overlap of the sources within the bilateral superior temporal gyrus, and, to a lesser extent, in the left inferior frontal gyrus, qualifying these areas as shared anatomic substrates of early syntactic error detection in music and language.

Connectivity-Based Parcellation of Broca's Area.

It is generally agreed that the cerebral cortex can be segregated into structurally and functionally distinct areas. Anatomical subdivision of Broca's area has been achieved using different microanatomical criteria, such as cytoarchitecture and distribution of neuroreceptors. However, brain function also strongly depends upon anatomical connectivity, which therefore forms a sensible criterion for the functio-anatomical segregation of cortical areas. Diffusion-weighted magnetic resonance (MR) imaging offers the opportunity to apply this criterion in the individual living subject. Probabilistic tractographic methods provide excellent means to extract the connectivity signatures from diffusion-weighting MR data sets. The correlations among these signatures may then be used by an automatic clustering method to identify cortical regions with mutually distinct and internally coherent connectivity. We made use of this principle to parcellate Broca's area. As it turned out, 3 subregions are discernible that were identified as putative Brodmann area (BA) 44, BA45, and the deep frontal operculum. These results are discussed in the light of previous evidence from other methods in both human and nonhuman primates. We conclude that plausible results can be achieved by the proposed technique, which cannot be obtained by any other method in vivo. For the first time, there is a possibility to investigate the anatomical subdivision of Broca's area noninvasively in the individual living human subject.

Auditory language comprehension in children with developmental dyslexia: evidence from event-related brain potentials.

In the present study, event-related brain potentials (ERPs) were used to compare auditory sentence comprehension in 16 children with developmental dyslexia (age 9-12 years) and unimpaired controls matched on age, sex, and nonverbal intelligence. Passive sentences were presented, which were either correct or contained a syntactic violation (phrase structure) or a semantic violation (selectional restriction). In an overall sentence correctness judgment task, both control and dyslexic children performed well. In the ERPs, control children and dyslexic children demonstrated a similar N400 component for the semantic violation. For the syntactic violation, control children demonstrated a combined pattern, consisting of an early starting bilaterally distributed anterior negativity and a late centro-parietal positivity (P600). Dyslexic children showed a different pattern that is characterized by a delayed left lateralized anterior negativity, followed by a P600. These data indicate that dyslexic children do not differ from unimpaired controls with respect to semantic integration processes (N400) or controlled processes of syntactic reanalyses (P600) during auditory sentence comprehension. However, early and presumably highly automatic processes of phrase structure building reflected in the anterior negativity are delayed in dyslexic children. Moreover, the differences in hemispheric distribution of the syntactic negativity indicate different underlying processes in dyslexic children and controls. The bilateral distribution in controls suggests an involvement of right hemispherically established prosodic processes in addition to the left hemispherically localized syntactic processes, supporting the view that prosodic information may be used to facilitate syntactic processing during normal comprehension. The left hemispheric distribution observed for dyslexic children, in contrast, suggests that these children do not rely on information about the prosodic contour during auditory sentence comprehension as much as controls do. This finding points toward a phonological impairment in dyslexic children that might hamper the development of syntactic processes.

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.

Cognitive priming in sung and instrumental music: activation of inferior frontal cortex.

Neural correlates of the processing of musical syntax-like structures have been investigated via expectancy violation due to musically unrelated (i.e., unexpected) events in musical contexts. Previous studies reported the implication of inferior frontal cortex in musical structure processing. However - due to the strong musical manipulations - activations might be explained by sensory deviance detection or repetition priming. Our present study investigated neural correlates of musical structure processing with subtle musical violations in a musical priming paradigm. Instrumental and sung sequences ended on related and less-related musical targets. The material controlled sensory priming components, and differences in target processing required listeners' knowledge on musical structures. Participants were scanned with functional Magnetic Resonance Imaging (fMRI) while performing speeded phoneme and timbre identification judgments on the targets. Behavioral results acquired in the scanner replicated the facilitation effect of related over less-related targets. The blood oxygen level-dependent (BOLD) signal linked to target processing revealed activation of right inferior frontal areas (i.e., inferior frontal gyrus, frontal operculum, anterior insula) that was stronger for less-related than for related targets, and this was independent of the material carrying the musical structures. This outcome points to the implication of inferior frontal cortex in the processing of syntactic relations also for musical material and to its role in the processing and integration of sequential information over time. In addition to inferior frontal activation, increased activation was observed in orbital gyrus, temporal areas (anterior superior temporal gyrus, posterior superior temporal gyrus and sulcus, posterior middle temporal gyrus) and supramarginal gyrus.

Revisiting the role of Broca's area in sentence processing: syntactic integration versus syntactic working memory.

Most previous neuroimaging studies of sentence processing have associated Broca's area with syntactic processing; however, the exact nature of the processes subserved by this brain region is yet not well understood. Although some authors suggest that Brodmann area (BA) 44 of the left inferior frontal gyrus (i.e., Broca's area) is relevant for syntactic integration processes, others claim that it is associated with working memory mechanisms relevant for language processing. To dissociate these two possible functions, the present study investigated hemodynamic responses elicited while participants processed German indirect wh-questions. Activation increases were observed in left BA 44 together with superior temporal areas and right hemispheric homologues for sentences with noncanonical word order, in which a verb argument was dislocated from its canonical position over a relatively long distance. In these sentences, syntactic working memory load was assumed to be greatest. In contrast, no activation increase was elicited by object-initial as opposed to subject-initial sentences that did not differ with respect to working memory costs but with respect to syntactic integration costs. These data strongly suggest that Broca's area plays a critical role in syntactic working memory during online sentence comprehension.

Morphosyntax, prosody, and linking elements: the auditory processing of German nominal compounds.

The morphosyntactic decomposition of German compound words and a proposed function of linking elements were examined during auditory processing using event-related brain potentials. In Experiment 1, the syntactic gender agreement was manipulated between a determiner and the initial compound constituent (the ''nonhead'' constituent), and between a determiner and the last constituent (''head''). Although only the head is (morpho)syntactically relevant in German, both constituents elicited a left-anterior negativity if its gender was incongruent. This strongly suggests that compounds are morphosyntactically decomposed. Experiment 2 tested the function of those linking elements which are homophonous to plural morphemes. It has been previously suggested that these indicate the number of nonhead constituents. The number agreement was manipulated for both constituents analogous to Experiment 1. Number-incongruent heads, but not nonhead constituents, elicited an N400 and a subsequent broad negativity, suggesting that linking elements are not processed as plural morphemes. Experiment 3 showed that prosodic cues (duration and fundamental frequency) are employed to differentiate between compounds and single nouns and, thereby, between linking elements and plural morphemes. Number-incongruent words elicited a broad negativity if they were produced with a single noun prosody; the same words elicited no event-related potential effect if produced with a compound prosody. A dual-route model can account for the influence of prosody on morphosyntactic processing.

Electrophysiological evidence for delayed mismatch response in infants at-risk for specific language impairment.

The present study investigated whether delayed auditory processing typically found in children with specific language impairment (SLI) can already be observed in the event-related potentials of 2-month-old infants. Infants with and without a family history of SLI were tested in a passive auditory oddball paradigm with CV-syllables differing in vowel duration. For the long syllable, a positive mismatch response occurred in the difference wave between deviant and standard. Its amplitude was higher in infants during quiet sleep than in awake infants, although its peak latency remained unaffected by alertness. Awake infants showed an adultlike mismatch negativity preceding the positivity. Risk for SLI was reflected in the latency of the positive mismatch response, which was delayed in infants with risk compared to infants without risk. This latency difference suggests that 2-month-old infants at risk for SLI are already affected in processing an auditory stimulus change of duration.

The relative timing of syntactic and semantic processes in sentence comprehension.

The functional primacy of syntactic over semantic processes was put to test in an auditory event-related brain potentials study using sentences in which the final words were semantically and/or syntactically incongruent with the prior context. Crucially, these words encoded the syntactically relevant word category information in the suffix, available only after the word stem which carried the semantic information. Semantic violations elicited an N400 and syntactic violations a biphasic LAN-P600 pattern. Words that were semantically and syntactically incongruent with the context evoked a biphasic LAN-P600 ERP pattern, but no N400. The similarity of the ERP pattern for the pure syntactic and the double violation condition provides strong evidence for a functional primacy of initial syntactic over lexical-semantic processes.

The influence of volume conduction effects on the EEG/MEG reconstruction of the sources of the Early Left Anterior Negativity.

To achieve a deeper understanding of language processing in the human brain, scientists and clinicians use Electroencephalography (EEG) and Magnetoencephalography (MEG) inverse methods to reconstruct sources of Event Related Potentials. There exists a persistent uncertainty regarding the influence of volume conduction effects such as the anisotropy of tissue conductivity of the skull and the white matter layers on the inverse results. In this paper, we will study the sensitivity to anisotropy of the source reconstruction of the Early Left Anterior Negativity (ELAN) component in language processing. For EEG, the presence of tissue anisotropy substantially compromises the restoration ability of an L1-norm current density approach. The centers of activity are strongly shifted along the Sylvian fissure in the anterior direction. In contrast, MEG in combination with the L1 norm approach is able to reconstruct the main features of the ELAN source distribution even in the presence of anisotropic conductivity.

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.

Distributed cortical networks for syntax processing: Broca's area as the common denominator.

Different types of syntactic information (word category, grammatical gender) are processed at different times during word recognition. However, it is an open issue which brain systems support these processes. In the present event-related fMRI study, subjects performed either a syntactic gender decision task on German nouns (GEN), a word category decision task (WC, nouns vs. prepositions), or a physical baseline task (BASE). Reaction times in WC were faster than in GEN, supporting earlier electrophysiological results. Relative to BASE, both syntactic tasks activated the inferior tip of BA 44. In addition, BA 45 showed activation in GEN, whereas BA 47 was activated in WC. The imaging data indicate that the inferior portion of BA 44 together with type-specific prefrontal areas supports both initial word category related and later syntactic processes.