Broca's region: novel organizational principles and multiple receptor mapping

Reading a suspenseful literary text activates brain areas related to social cognition and predictive inference

Stories can elicit powerful emotions. A key emotional response to narrative plots (e.g., novels, movies, etc.) is suspense. Suspense appears to build on basic aspects of human cognition such as processes of expectation, anticipation, and prediction. However, the neural processes underlying emotional experiences of suspense have not been previously investigated. We acquired functional magnetic resonance imaging (fMRI) data while participants read a suspenseful literary text (E.T.A. Hoffmann's “The Sandman”) subdivided into short text passages. Individual ratings of experienced suspense obtained after each text passage were found to be related to activation in the medial frontal cortex, bilateral frontal regions (along the inferior frontal sulcus), lateral premotor cortex, as well as posterior temporal and temporo-parietal areas. The results indicate that the emotional experience of suspense depends on brain areas associated with social cognition and predictive inference.

Co-Activation-Based Parcellation of the Lateral Prefrontal Cortex Delineates the Inferior Frontal Junction Area

The inferior frontal junction (IFJ) area, a small region in the posterior lateral prefrontal cortex (LPFC), has received increasing interest in recent years due to its central involvement in the control of action, attention, and memory. Yet, both its function and anatomy remain controversial. Here, we employed a meta-analytic parcellation of the left LPFC to show that the IFJ can be isolated based on its specific functional connections. A seed region, oriented along the left inferior frontal sulcus (IFS), was subdivided via cluster analyses of voxel-wise whole-brain co-activation patterns. The ensuing clusters were characterized by their unique connections, the functional profiles of associated experiments, and an independent topic mapping approach. A cluster at the posterior end of the IFS matched previous descriptions of the IFJ in location and extent and could be distinguished from a more caudal cluster involved in motor control, a more ventral cluster involved in linguistic processing, and 3 more rostral clusters involved in other aspects of cognitive control. Overall, our findings highlight that the IFJ constitutes a core functional unit within the frontal lobe and delineate its borders. Implications for the IFJ's role in human cognition and the organizational principles of the frontal lobe are discussed.

Prefrontal cortex and the dysconnectivity hypothesis of schizophrenia

Schizophrenia is hypothesized to arise from disrupted brain connectivity. This "dysconnectivity hypothesis" has generated interest in discovering whether there is anatomical and functional dysconnectivity between the prefrontal cortex (PFC) and other brain regions, and how this dysconnectivity is linked to the impaired cognitive functions and aberrant behaviors of schizophrenia. Critical advances in neuroimaging technologies, including diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI), make it possible to explore these issues. DTI affords the possibility to explore anatomical connectivity in the human brain in vivo and fMRI can be used to make inferences about functional connections between brain regions. In this review, we present major advances in the understanding of PFC anatomical and functional dysconnectivity and their implications in schizophrenia. We then briefly discuss future prospects that need to be explored in order to move beyond simple mapping of connectivity changes to elucidate the neuronal mechanisms underlying schizophrenia.

A human homologue of monkey F5c

Area F5c is a monkey premotor area housing mirror neurons which responds more strongly to grasping observation when the actor is visible than when only the actor's hand is visible. Here we used this characteristic fMRI signature of F5c in seven imaging experiments – one in macaque monkeys and six in humans – to identify the human homologue of monkey F5c. By presenting the two grasping actions (actor, hand) and varying the low level visual characteristics, we localized a putative human homologue of area F5c (phF5c) in the inferior part of precentral sulcus, bilaterally. In contrast to monkey F5c, phF5c is asymmetric, with a right-sided bias, and is activated more strongly during the observation of the later stages of grasping when the hand is close to the object. The latter characteristic might be related to the emergence, in humans, of the capacity to precisely copy motor acts performed by others, and thus imitation.

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We use parallel fMRI to identify the human homologue of macaque F5c.

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In premotor cortex only F5c reacts more to observing grasping with the actor visible.

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Two bilateral inferior precentral sulcus sites respond similarly for many stimuli.

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The human homologues of F5c are asymmetric and require fixation near the target.

White-matter pathways for speech and language processing

The language-relevant brain regions, Brodmann's area in the inferior frontal cortex and Wernicke's area in the superior temporal cortex, are connected via long-range fiber bundles, which are located dorsally and ventrally to the sylvian fissure. These dorsal and ventral pathways consist of a number of partly parallel-running fiber tracts, which can be differentiated by their termination regions and by the particular language functions of these termination regions. Dorsally, there are two major fiber tracts connecting the posterior temporal cortex with the frontal cortex: one terminating in the premotor cortex that subserves sensory-to-motor mapping and one terminating in posterior Broca's area, the pars opercularis, that supports the processing of complex syntactic structures. Ventrally, two language-related fiber tracts are discussed: one connects the inferior frontal cortex, i.e., the pars triangularis and orbitalis, with Wernicke's area and supports semantic processes and another one connects the most ventral portions of the inferior frontal cortex, including the frontal operculum, with the anterior temporal cortex. This latter ventral tract is suggested to subserve elementary combinatorial processes in language. Together these fiber tracts guarantee the transmission of information between different brain regions within the neural language network.

Convergent transcriptional specializations in the brains of humans and song-learning birds

Song-learning birds and humans share independently evolved similarities in brain pathways for vocal learning that are essential for song and speech and are not found in most other species. Comparisons of brain transcriptomes of song-learning birds and humans relative to vocal nonlearners identified convergent gene expression specializations in specific song and speech brain regions of avian vocal learners and humans. The strongest shared profiles relate bird motor and striatal song-learning nuclei, respectively, with human laryngeal motor cortex and parts of the striatum that control speech production and learning. Most of the associated genes function in motor control and brain connectivity. Thus, convergent behavior and neural connectivity for a complex trait are associated with convergent specialized expression of multiple genes.

Manual praxis in stone tool manufacture: implications for language evolution

Alternative functions of the left-hemisphere dominant Broca's region have induced hypotheses regarding the evolutionary parallels between manual praxis and language in humans. Many recent studies on Broca's area reveal several assumptions about the cognitive mechanisms that underlie both functions, including: (1) an accurate, finely controlled body schema, (2) increasing syntactical abilities, particularly for goal-oriented actions, and (3) bilaterality and fronto-parietal connectivity. Although these characteristics are supported by experimental paradigms, many researchers have failed to acknowledge a major line of evidence for the evolutionary development of these traits: stone tools. The neuroscience of stone tool manufacture is a viable proxy for understanding evolutionary aspects of manual praxis and language, and may provide key information for evaluating competing hypotheses on the co-evolution of these cognitive domains in our species.

Coupled neural systems underlie the production and comprehension of naturalistic narrative speech

Neuroimaging studies of language have typically focused on either production or comprehension of single speech utterances such as syllables, words, or sentences. In this study we used a new approach to functional MRI acquisition and analysis to characterize the neural responses during production and comprehension of complex real-life speech. First, using a time-warp based intrasubject correlation method, we identified all areas that are reliably activated in the brains of speakers telling a 15-min-long narrative. Next, we identified areas that are reliably activated in the brains of listeners as they comprehended that same narrative. This allowed us to identify networks of brain regions specific to production and comprehension, as well as those that are shared between the two processes. The results indicate that production of a real-life narrative is not localized to the left hemisphere but recruits an extensive bilateral network, which overlaps extensively with the comprehension system. Moreover, by directly comparing the neural activity time courses during production and comprehension of the same narrative we were able to identify not only the spatial overlap of activity but also areas in which the neural activity is coupled across the speaker's and listener's brains during production and comprehension of the same narrative. We demonstrate widespread bilateral coupling between production- and comprehension-related processing within both linguistic and nonlinguistic areas, exposing the surprising extent of shared processes across the two systems.

Fronto-parietal network supports context-dependent speech comprehension

Knowing the context of a discourse is an essential prerequisite for comprehension. Here we used functional magnetic resonance imaging (fMRI) to disclose brain networks supporting context-dependent speech comprehension. During fMRI, 20 participants listened to 1-min spoken narratives preceded by pictures that were either contextually matching or mismatching with the narrative. Matching pictures increased narrative comprehension, decreased hemodynamic activity in Broca׳s area, and enhanced its functional connectivity with left anterior superior frontal gyrus, bilateral inferior parietal cortex, as well as anterior and posterior cingulate cortex. Further, the anterior (BA 45) and posterior (BA 44) portions of Broca׳s area differed in their functional connectivity patterns. Both BA 44 and BA 45 have shown increased connectivity with right angular gyrus and supramarginal gyrus. Whereas BA 44 showed increased connectivity with left angular gyrus, left inferior/middle temporal gyrus and left postcentral gyrus, BA 45 showed increased connectivity with right posterior cingulate cortex, right anterior inferior frontal gyrus, lateral occipital cortex and anterior cingulate cortex. Our results suggest that a fronto-parietal functional network supports context-dependent narrative comprehension, and that Broca׳s area is involved in resolving ambiguity from speech when appropriate contextual cues are lacking.

Motor system evolution and the emergence of high cognitive functions

In human and nonhuman primates, the cortical motor system comprises a collection of brain areas primarily related to motor control. Existing evidence suggests that no other mammalian group has the number, extension, and complexity of motor-related areas observed in the frontal lobe of primates. Such diversity is probably related to the wide behavioral flexibility that primates display. Indeed, recent comparative anatomical, psychophysical, and neurophysiological studies suggest that the evolution of the motor cortical areas closely correlates with the emergence of high cognitive abilities. Advances in understanding the cortical motor system have shown that these areas are also related to functions previously linked to higher-order associative areas. In addition, experimental observations have shown that the classical distinction between perceptual and motor functions is not strictly followed across cortical areas. In this paper, we review evidence suggesting that evolution of the motor system had a role in the shaping of different cognitive functions in primates. We argue that the increase in the complexity of the motor system has contributed to the emergence of new abilities observed in human and nonhuman primates, including the recognition and imitation of the actions of others, speech perception and production, and the execution and appreciation of the rhythmic structure of music.

Common molecular basis of the sentence comprehension network revealed by neurotransmitter receptor fingerprints

The language network is a well-defined large-scale neural network of anatomically and functionally interacting cortical areas. The successful language process requires the transmission of information between these areas. Since neurotransmitter receptors are key molecules of information processing, we hypothesized that cortical areas which are part of the same functional language network may show highly similar multireceptor expression pattern ("receptor fingerprint"), whereas those that are not part of this network should have different fingerprints. Here we demonstrate that the relation between the densities of 15 different excitatory, inhibitory and modulatory receptors in eight language-related areas are highly similar and differ considerably from those of 18 other brain regions not directly involved in language processing. Thus, the fingerprints of all cortical areas underlying a large-scale cognitive domain such as language is a characteristic, functionally relevant feature of this network and an important prerequisite for the underlying neuronal processes of language functions.

The neuroanatomic and neurophysiological infrastructure for speech and language

New tools and new ideas have changed how we think about the neurobiological foundations of speech and language processing. This perspective focuses on two areas of progress. First, focusing on spatial organization in the human brain, the revised functional anatomy for speech and language is discussed. The complexity of the network organization undermines the well-regarded classical model and suggests looking for more granular computational primitives, motivated both by linguistic theory and neural circuitry. Second, focusing on recent work on temporal organization, a potential role of cortical oscillations for speech processing is outlined. Such an implementational-level mechanism suggests one way to deal with the computational challenge of segmenting natural speech.

Nodes and networks in the neural architecture for language: Broca's region and beyond

Current views on the neurobiological underpinnings of language are discussed that deviate in a number of ways from the classical Wernicke-Lichtheim-Geschwind model. More areas than Broca's and Wernicke's region are involved in language. Moreover, a division along the axis of language production and language comprehension does not seem to be warranted. Instead, for central aspects of language processing neural infrastructure is shared between production and comprehension. Three different accounts of the role of Broca's area in language are discussed. Arguments are presented in favor of a dynamic network view, in which the functionality of a region is co-determined by the network of regions in which it is embedded at particular moments in time. Finally, core regions of language processing need to interact with other networks (e.g. the attentional networks and the ToM network) to establish full functionality of language and communication.

A new myeloarchitectonic map of the human neocortex based on data from the Vogt-Vogt school

The human cerebral cortex contains numerous myelinated fibres, the arrangement and density of which is by no means homogeneous throughout the cortex. Local differences in the spatial organization of these fibres render it possible to recognize areas with a different myeloarchitecture. The neuroanatomical subdiscipline aimed at the identification and delineation of such areas is known as myeloarchitectonics. During the period extending from 1910 to 1970, Oscar and Cécile Vogt and their numerous collaborators (The Vogt-Vogt school) published a large number of myeloarchitectonic studies on the cortex of the various lobes of the human cerebrum. Recently, one of us (Nieuwenhuys in Brain Struct Funct 218: 303-352, 2013) extensively reviewed these studies. It was concluded that the data available are adequate and sufficient for the composition of a myeloarchitectonic map of the entire human neocortex. The present paper is devoted to the creation of this map. Because the data provided by the Vogt-Vogt school are derived from many different brains, a standard brain had to be introduced to which all data available could be transferred. As such, the colin27 structural scan, aligned to the MNI305 template was selected. The procedure employed in this transfer involved computer-aided transformations of the lobar maps available in the literature, to the corresponding regions of the standard brain, as well as local adjustments in the border zones of the various lobes. The resultant map includes 180 myeloarchitectonic areas, 64 frontal, 30 parietal, 6 insular, 17 occipital and 63 temporal. The designation of the various areas with simple Arabic numbers, introduced by Oscar Vogt for the frontal and parietal cortices, has been extended over the entire neocortex. It may be expected that combination of the myeloarchitectonic data of the Vogt-Vogt school, as expressed in our map, with the results of the detailed cytoarchitectonic and receptor architectonic studies of Karl Zilles and Katrin Amunts and their numerous associates, will yield a comprehensive 'supermap' of the structural organization of the human neocortex. For the time being, i. e., as long as this 'supermap' is not yet available, our map may provide a tentative frame of reference for (a) the morphological interpretation of the results of functional neuroimaging studies; (b) the selection of starting points (seed voxels, regions-of-interest) in diffusion tractography studies and

Brain and language: evidence for neural multifunctionality

This review paper presents converging evidence from studies of brain damage and longitudinal studies of language in aging which supports the following thesis: the neural basis of language can best be understood by the concept of neural multifunctionality. In this paper the term "neural multifunctionality" refers to incorporation of nonlinguistic functions into language models of the intact brain, reflecting a multifunctional perspective whereby a constant and dynamic interaction exists among neural networks subserving cognitive, affective, and praxic functions with neural networks specialized for lexical retrieval, sentence comprehension, and discourse processing, giving rise to language as we know it. By way of example, we consider effects of executive system functions on aspects of semantic processing among persons with and without aphasia, as well as the interaction of executive and language functions among older adults. We conclude by indicating how this multifunctional view of brain-language relations extends to the realm of language recovery from aphasia, where evidence of the influence of nonlinguistic factors on the reshaping of neural circuitry for aphasia rehabilitation is clearly emerging.

Grey matter volumetric changes related to recovery from hand paresis after cortical sensorimotor stroke

Preclinical studies using animal models have shown that grey matter plasticity in both perilesional and distant neural networks contributes to behavioural recovery of sensorimotor functions after ischaemic cortical stroke. Whether such morphological changes can be detected after human cortical stroke is not yet known, but this would be essential to better understand post-stroke brain architecture and its impact on recovery. Using serial behavioural and high-resolution magnetic resonance imaging (MRI) measurements, we tracked recovery of dexterous hand function in 28 patients with ischaemic stroke involving the primary sensorimotor cortices. We were able to classify three recovery subgroups (fast, slow, and poor) using response feature analysis of individual recovery curves. To detect areas with significant longitudinal grey matter volume (GMV) change, we performed tensor-based morphometry of MRI data acquired in the subacute phase, i.e. after the stage compromised by acute oedema and inflammation. We found significant GMV expansion in the perilesional premotor cortex, ipsilesional mediodorsal thalamus, and caudate nucleus, and GMV contraction in the contralesional cerebellum. According to an interaction model, patients with fast recovery had more perilesional than subcortical expansion, whereas the contrary was true for patients with impaired recovery. Also, there were significant voxel-wise correlations between motor performance and ipsilesional GMV contraction in the posterior parietal lobes and expansion in dorsolateral prefrontal cortex. In sum, perilesional GMV expansion is associated with successful recovery after cortical stroke, possibly reflecting the restructuring of local cortical networks. Distant changes within the prefrontal-striato-thalamic network are related to impaired recovery, probably indicating higher demands on cognitive control of motor behaviour.

Functional neuroanatomy of developmental dyslexia: the role of orthographic depth

Orthographic depth (OD) (i.e., the complexity, consistency, or transparency of grapheme-phoneme correspondences in written alphabetic language) plays an important role in the acquisition of reading skills. Correspondingly, developmental dyslexia is characterized by different behavioral manifestations across languages varying in OD. This review focuses on the question of whether these different behavioral manifestations are associated with different functional neuroanatomical manifestations. It provides a review and critique of cross-linguistic brain imaging studies of developmental dyslexia. In addition, it includes an analysis of state-of-the-art functional neuroanatomical models of developmental dyslexia together with orthography-specific predictions derived from these models. These predictions should be tested in future brain imaging studies of typical and atypical reading in order to refine the current neurobiological understanding of developmental dyslexia, especially with respect to orthography-specific and universal aspects.

Shared vs. specific brain activation changes in dyslexia after training of phonology, attention, or reading

Whereas the neurobiological basis of developmental dyslexia has received substantial attention, only little is known about the processes in the brain during remediation. This holds in particular in light of recent findings on cognitive subtypes of dyslexia which suggest interactions between individual profiles, training methods, and also the task in the scanner. Therefore, we trained three groups of German dyslexic primary school children in the domains of phonology, attention, or visual word recognition. We compared neurofunctional changes after 4 weeks of training in these groups to those in untrained normal readers in a reading task and in a task of visual attention. The overall reading improvement in the dyslexic children was comparable over groups. It was accompanied by substantial increase of the activation level in the visual word form area (VWFA) during a reading task inside the scanner. Moreover, there were activation increases that were unique for each training group in the reading task. In contrast, when children performed the visual attention task, shared training effects were found in the left inferior frontal sulcus and gyrus, which varied in amplitude between the groups. Overall, the data reveal that different remediation programmes matched to individual profiles of dyslexia may improve reading ability and commonly affect the VWFA in dyslexia as a shared part of otherwise distinct networks.

Hierarchical processing in music, language, and action: Lashley revisited

Sixty years ago, Karl Lashley suggested that complex action sequences, from simple motor acts to language and music, are a fundamental but neglected aspect of neural function. Lashley demonstrated the inadequacy of then-standard models of associative chaining, positing a more flexible and generalized "syntax of action" necessary to encompass key aspects of language and music. He suggested that hierarchy in language and music builds upon a more basic sequential action system, and provided several concrete hypotheses about the nature of this system. Here, we review a diverse set of modern data concerning musical, linguistic, and other action processing, finding them largely consistent with an updated neuroanatomical version of Lashley's hypotheses. In particular, the lateral premotor cortex, including Broca's area, plays important roles in hierarchical processing in language, music, and at least some action sequences. Although the precise computational function of the lateral prefrontal regions in action syntax remains debated, Lashley's notion-that this cortical region implements a working-memory buffer or stack scannable by posterior and subcortical brain regions-is consistent with considerable experimental data.

A hierarchical method for whole-brain connectivity-based parcellation

In modern neuroscience there is general agreement that brain function relies on networks and that connectivity is therefore of paramount importance for brain function. Accordingly, the delineation of functional brain areas on the basis of diffusion magnetic resonance imaging (dMRI) and tractography may lead to highly relevant brain maps. Existing methods typically aim to find a predefined number of areas and/or are limited to small regions of grey matter. However, it is in general not likely that a single parcellation dividing the brain into a finite number of areas is an adequate representation of the function-anatomical organization of the brain. In this work, we propose hierarchical clustering as a solution to overcome these limitations and achieve whole-brain parcellation. We demonstrate that this method encodes the information of the underlying structure at all granularity levels in a hierarchical tree or dendrogram. We develop an optimal tree building and processing pipeline that reduces the complexity of the tree with minimal information loss. We show how these trees can be used to compare the similarity structure of different subjects or recordings and how to extract parcellations from them. Our novel approach yields a more exhaustive representation of the real underlying structure and successfully tackles the challenge of whole-brain parcellation.

Longitudinal changes in brains of patients with fluent primary progressive aphasia

Primary progressive aphasia (PPA) is a rare clinical dementia syndrome with predominant, progressive language impairment. Clinical symptoms, linguistic impairment and the course of the disease may vary considerably between patients. In order to capture these aspects, longitudinal assessments of neurofunctional changes in PPA including their relationship to behaviour and clinical symptoms are mandatory, ideally at intervals shorter than 1 year. Here, we report a longitudinal fMRI study investigating the development of lexical processing and their neural basis in PPA patients over 1year. Four logopenic PPA patients and four matched controls were scanned 3 times (T1, T2, T3, at 6months intervals) while performing a visual lexical decision task on German words and pseudowords. Group differences for the lexicality effect (pseudowords>words) were assessed at time point T1 and its longitudinal changes in the BOLD signal associated with the lexicality effect were analysed. Brain atrophy was assessed with a high-resolution MPRAGE sequence and analysed using deformation based morphometry (DBM). From the very beginning of the study, PPA patients showed reduced left-hemispheric and increased right-hemispheric activations compared to controls. During the progression of the disease, activation increased predominantly in left posterior middle temporal gyrus (pMTG) and inferior frontal junction area, whereas the same regions decreased in activity in control brains. Interestingly, DBM data showed that this increase in activation in PPA patients was accompanied by progressing atrophy in the same regions. At a behavioural level, the accuracy in the lexical decision task was comparably high for both groups during the whole period of examination, despite some large variability between patients. To conclude, the dissociation between (i) maintained high performance, (ii) increased activity in regions involved in lexical access such as pMTG, and (iii) progressive atrophy of the very same regions supports the notion of a compensatory mechanism in brains of PPA patients for maintaining language while brain atrophy is progressing. The activity increase within a left-lateralised fronto-temporal network seems vital for high-level performance, whereas initial right-hemispheric recruitment of homologue language regions, which is reminiscent of that in vascular aphasics, has no continuous impact on lexical performance.

Brain atrophy in primary progressive aphasia involves the cholinergic basal forebrain and Ayala's nucleus

Primary progressive aphasia (PPA) is characterized by left hemispheric frontotemporal cortical atrophy. Evidence from anatomical studies suggests that the nucleus subputaminalis (NSP), a subnucleus of the cholinergic basal forebrain, may be involved in the pathological process of PPA. Therefore, we studied the pattern of cortical and basal forebrain atrophy in 10 patients with a clinical diagnosis of PPA and 18 healthy age-matched controls using high-resolution magnetic resonance imaging (MRI). We determined the cholinergic basal forebrain nuclei according to Mesulam's nomenclature and the NSP in MRI reference space based on histological sections and the MRI scan of a post-mortem brain in cranio. Using voxel-based analysis, we found left hemispheric cortical atrophy in PPA patients compared with controls, including prefrontal, lateral temporal and medial temporal lobe areas. We detected cholinergic basal forebrain atrophy in left predominant localizations of Ch4p, Ch4am, Ch4al, Ch3 and NSP. For the first time, we have described the pattern of basal forebrain atrophy in PPA and confirmed the involvement of NSP that had been predicted based on theoretical considerations. Our findings may enhance understanding of the role of cholinergic degeneration for the regional specificity of the cortical destruction leading to the syndrome of PPA.

Evolutionarily dynamic alternative splicing of GPR56 regulates regional cerebral cortical patterning

The human neocortex has numerous specialized functional areas whose formation is poorly understood. Here, we describe a 15-base pair deletion mutation in a regulatory element of GPR56 that selectively disrupts human cortex surrounding the Sylvian fissure bilaterally including "Broca's area," the primary language area, by disrupting regional GPR56 expression and blocking RFX transcription factor binding. GPR56 encodes a heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor required for normal cortical development and is expressed in cortical progenitor cells. GPR56 expression levels regulate progenitor proliferation. GPR56 splice forms are highly variable between mice and humans, and the regulatory element of gyrencephalic mammals directs restricted lateral cortical expression. Our data reveal a mechanism by which control of GPR56 expression pattern by multiple alternative promoters can influence stem cell proliferation, gyral patterning, and, potentially, neocortex evolution.

Selection and stopping in voluntary action: a meta-analysis and combined fMRI study

Voluntary action control requires selection of appropriate responses and stopping of inappropriate responses. Selection and stopping are often investigated separately, but they appear to recruit similar brain regions, including the pre-supplementary motor area (preSMA) and inferior frontal gyrus. We therefore examined the evidence for overlap of selection and stopping using two approaches: a meta-analysis of existing studies of selection and stopping, and a novel within-subject fMRI study in which action selection and a stop signal task were combined factorially. The novel fMRI study also permitted us to investigate hypotheses regarding a common mechanism for selection and stopping. The preSMA was identified by both methods as common to selection and stopping. However, stopping a selected action did not recruit preSMA more than stopping a specified action, nor did stop signal reaction times differ significantly across the two conditions. These findings suggest that the preSMA supports both action selection and stopping, but the two processes may not require access to a common inhibition mechanism. Instead, the preSMA might represent information about potential actions that is used in both action selection and stopping in order to resolve conflict between competing available responses.

Age-related decrease of functional connectivity additional to gray matter atrophy in a network for movement initiation

Healthy aging is accompanied by a decrease in cognitive and motor capacities. In a network associated with movement initiation, we investigated age-related changes of functional connectivity (FC) as well as regional atrophy in a sample of 232 healthy subjects (age range 18-85 years). To this end, voxel-based morphometry and whole-brain resting-state FC were analyzed for the supplementary motor area (SMA), anterior midcingulate cortex (aMCC) and bilateral striatum (Str). To assess the specificity of age-related effects, bilateral primary sensorimotor cortex (S1/M1) closely associated with motor execution was used as control seeds. All regions showed strong reduction of gray matter volume with age. Corrected for this regional atrophy, the FC analysis revealed an age × seed interaction for each of the bilateral Str nodes against S1/M1 with consistent age-related decrease in FC with bilateral caudate nucleus and anterior putamen. Specific age-dependent FC decline of SMA was found in bilateral central insula and the adjacent frontal operculum. aMCC showed exclusive age-related decoupling from the anterior cingulate motor area. The present study demonstrates network as well as node-specific age-dependent FC decline of the SMA and aMCC to highly integrative cortical areas involved in cognitive motor control. FC decrease in addition to gray matter atrophy within the Str may provide a substrate for the declining motor control in elderly. Finally, age-related FC changes in both the network for movement initiation as well as the network for motor execution are not explained by regional atrophy in the healthy aging brain.

Probabilistic fiber tracking of the language and motor white matter pathways of the supplementary motor area (SMA) in patients with brain tumors

BACKGROUND AND PURPOSE

Accurate localization of anatomically and functionally separate SMA tracts is important to improve planning prior to neurosurgery. Using fMRI and probabilistic DTI techniques, we assessed the connectivity between the frontal language area (Broca's area) and the rostral pre-SMA (language SMA) and caudal SMA proper (motor SMA).

MATERIALS AND METHODS

Twenty brain tumor patients completed motor and language fMRI paradigms and DTI. Peaks of functional activity in the language SMA, motor SMA and Broca's area were used to define seed regions for probabilistic tractography.

RESULTS

fMRI and probabilistic tractography identified separate and unique pathways connecting the SMA to Broca's area - the language SMA pathway and the motor SMA pathway. For all subjects, the language SMA pathway had a larger number of voxels (P<0.0001) and higher connectivity (P<0.0001) to Broca's area than did the motor SMA pathway. In each patient, the number of voxels was greater in the language and motor SMA pathways than in background pathways (P<0.0001). No differences were found between patients with ipsilateral and those with contralateral tumors for either the language SMA pathway (degree of connectivity: P<0.36; number of voxels: 0.35) or the motor SMA pathway (degree of connectivity, P<0.28; number of voxels, P<0.74).

CONCLUSION

Probabilistic tractography can identify unique white matter tracts that connect language SMA and motor SMA to Broca's area. The language SMA is more significantly connected to Broca's area than is the motor subdivision of the SMA proper.

A time and place for language comprehension: mapping the N400 and the P600 to a minimal cortical network

We propose a new functional-anatomical mapping of the N400 and the P600 to a minimal cortical network for language comprehension. Our work is an example of a recent research strategy in cognitive neuroscience, where researchers attempt to align data regarding the nature and time-course of cognitive processing (from ERPs) with data on the cortical organization underlying it (from fMRI). The success of this "alignment" approach critically depends on the functional interpretation of relevant ERP components. Models of language processing that have been proposed thus far do not agree on these interpretations, and present a variety of complicated functional architectures. We put forward a very basic functional-anatomical mapping based on the recently developed Retrieval-Integration account of language comprehension (Brouwer et al., 2012). In this mapping, the left posterior part of the Middle Temporal Gyrus (BA 21) serves as an epicenter (or hub) in a neurocognitive network for the retrieval of word meaning, the ease of which is reflected in N400 amplitude. The left Inferior Frontal Gyrus (BA 44/45/47), in turn, serves a network epicenter for the integration of this retrieved meaning with the word's preceding context, into a mental representation of what is being communicated; these semantic and pragmatic integrative processes are reflected in P600 amplitude. We propose that our mapping describes the core of the language comprehension network, a view that is parsimonious, has broad empirical coverage, and can serve as the starting point for a more focused investigation into the coupling of brain anatomy and electrophysiology.

Frontal and parietal cortical interactions with distributed visual representations during selective attention and action selection

Using multivoxel pattern analysis (MVPA), we studied how distributed visual representations in human occipitotemporal cortex are modulated by attention and link their modulation to concurrent activity in frontal and parietal cortex. We detected similar occipitotemporal patterns during a simple visuoperceptual task and an attention-to-working-memory task in which one or two stimuli were cued before being presented among other pictures. Pattern strength varied from highest to lowest when the stimulus was the exclusive focus of attention, a conjoint focus, and when it was potentially distracting. Although qualitatively similar effects were seen inside regions relatively specialized for the stimulus category and outside, the former were quantitatively stronger. By regressing occipitotemporal pattern strength against activity elsewhere in the brain, we identified frontal and parietal areas exerting top-down control over, or reading information out from, distributed patterns in occipitotemporal cortex. Their interactions with patterns inside regions relatively specialized for that stimulus category were higher than those with patterns outside those regions and varied in strength as a function of the attentional condition. One area, the frontal operculum, was distinguished by selectively interacting with occipitotemporal patterns only when they were the focus of attention. There was no evidence that any frontal or parietal area actively inhibited occipitotemporal representations even when they should be ignored and were suppressed. Using MVPA to decode information within these frontal and parietal areas showed that they contained information about attentional context and/or readout information from occipitotemporal cortex to guide behavior but that frontal regions lacked information about category identity.

Neuronal basis of speech comprehension

Verbal communication does not rely only on the simple perception of auditory signals. It is rather a parallel and integrative processing of linguistic and non-linguistic information, involving temporal and frontal areas in particular. This review describes the inherent complexity of auditory speech comprehension from a functional-neuroanatomical perspective. The review is divided into two parts. In the first part, structural and functional asymmetry of language relevant structures will be discus. The second part of the review will discuss recent neuroimaging studies, which coherently demonstrate that speech comprehension processes rely on a hierarchical network involving the temporal, parietal, and frontal lobes. Further, the results support the dual-stream model for speech comprehension, with a dorsal stream for auditory-motor integration, and a ventral stream for extracting meaning but also the processing of sentences and narratives. Specific patterns of functional asymmetry between the left and right hemisphere can also be demonstrated. The review article concludes with a discussion on interactions between the dorsal and ventral streams, particularly the involvement of motor related areas in speech perception processes, and outlines some remaining unresolved issues. This article is part of a Special Issue entitled Human Auditory Neuroimaging.

The role of anterior midcingulate cortex in cognitive motor control: evidence from functional connectivity analyses

The rostral cingulate cortex has been associated with a multitude of cognitive control functions. Recent neuroimaging data suggest that the anterior midcingulate cortex (aMCC) has a key role for cognitive aspects of movement generation, i.e., intentional motor control. We here tested the functional connectivity of this area using two complementary approaches: (1) resting-state connectivity of the aMCC based on fMRI scans obtained in 100 subjects, and (2) functional connectivity in the context of explicit task conditions using meta-analytic connectivity modeling (MACM) over 656 imaging experiment. Both approaches revealed a convergent functional network architecture of the aMCC with prefrontal, premotor and parietal cortices as well as anterior insula, area 44/45, cerebellum and dorsal striatum. To specifically test the role of the aMCC's task-based functional connectivity in cognitive motor control, separate MACM analyses were conducted over "cognitive" and "action" related experimental paradigms. Both analyses confirmed the same task-based connectivity pattern of the aMCC. While the "cognition" domain showed higher convergence of activity in supramodal association areas in prefrontal cortex and anterior insula, "action" related experiments yielded higher convergence in somatosensory and premotor areas. Secondly, to probe the functional specificity of the aMCC's convergent functional connectivity, it was compared with a neural network of intentional movement initiation. This exemplary comparison confirmed the involvement of the state independent FC network of the aMCC in the intentional generation of movements. In summary, the different experiments of the present study suggest that the aMCC constitute a key region in the network realizing intentional motor control.

Competitive mechanisms in sentence processing: common and distinct production and reading comprehension networks linked to the prefrontal cortex

Despite much interest in language production and comprehension mechanisms, little is known about the relationship between the two. Previous research suggests that linguistic knowledge is shared across these tasks and that the left inferior frontal gyrus (LIFG) may be commonly recruited. However, it remains unclear the extent to which production and comprehension share competition mechanisms. Here we investigate this issue and specifically examine competition in determining the event roles in a sentence (agent or affected participant). We used both behavioral and fMRI methods and compared the reading and production of high- and low-competition sentences, specifically targeting LIFG. We found that activity in pars opercularis (PO), independently identified by a competition-driven localizer, was modulated by competition in both tasks. Psychophysiological interaction analyses seeded in PO revealed task-specific networks: In comprehension, PO only interacted with the posterior temporal lobe, whereas in production, it interacted with a large network including hippocampal, posterior temporal, medial frontal and subcortical structures. Production and comprehension therefore recruit partially distinct functional networks but share competitive processes within fronto-temporal regions. We argue that these common regions store long-term linguistic associations and compute their higher-order contingencies, but competition in production ignites a larger neural network implementing planning, as required by task demands.

Tension-related activity in the orbitofrontal cortex and amygdala: an fMRI study with music

Tonal music is characterized by a continuous flow of tension and resolution. This flow of tension and resolution is closely related to processes of expectancy and prediction and is a key mediator of music-evoked emotions. However, the neural correlates of subjectively experienced tension and resolution have not yet been investigated. We acquired continuous ratings of musical tension for four piano pieces. In a subsequent functional magnetic resonance imaging experiment, we identified blood oxygen level-dependent signal increases related to musical tension in the left lateral orbitofrontal cortex (pars orbitalis of the inferior frontal gyrus). In addition, a region of interest analysis in bilateral amygdala showed activation in the right superficial amygdala during periods of increasing tension (compared with decreasing tension). This is the first neuroimaging study investigating the time-varying changes of the emotional experience of musical tension, revealing brain activity in key areas of affective processing.

Dissociating frontal regions that co-lateralize with different ventral occipitotemporal regions during word processing

The ventral occipitotemporal sulcus (vOT) sustains strong interactions with the inferior frontal cortex during word processing. Consequently, activation in both regions co-lateralize towards the same hemisphere in healthy subjects. Because the determinants of lateralisation differ across posterior, middle and anterior vOT subregions, we investigated whether lateralisation in different inferior frontal regions would co-vary with lateralisation in the three different vOT subregions. A whole brain analysis found that, during semantic decisions on written words, laterality covaried in (1) posterior vOT and the precentral gyrus; (2) middle vOT and the pars opercularis, pars triangularis, and supramarginal gyrus; and (3) anterior vOT and the pars orbitalis, middle frontal gyrus and thalamus. These findings increase the spatial resolution of our understanding of how vOT interacts with other brain areas during semantic categorisation on words.

The concept of allosteric interaction and its consequences for the chemistry of the brain

Throughout this Reflections article, I have tried to follow up on the genesis in the 1960s and subsequent evolution of the concept of allosteric interaction and to examine its consequences within the past decades, essentially in the field of the neuroscience. The main conclusion is that allosteric mechanisms built on similar structural principles operate in bacterial regulatory enzymes, gene repressors (and the related nuclear receptors), rhodopsin, G-protein-coupled receptors, neurotransmitter receptors, ion channels, and so on from prokaryotes up to the human brain yet with important features of their own. Thus, future research on these basic cybernetic sensors is expected to develop in two major directions: at the elementary level, toward the atomic structure and molecular dynamics of the conformational changes involved in signal recognition and transduction, but also at a higher level of organization, the contribution of allosteric mechanisms to the modulation of brain functions.

Revisiting the functional specialization of left inferior frontal gyrus in phonological and semantic fluency: the crucial role of task demands and individual ability

Despite a large body of research, extant findings on the functional role of left inferior frontal gyrus (LIFG) in phonological and semantic fluency are still controversial. Based on cross-study comparisons, a recent meta-analysis of neuroimaging results suggests that posterior-dorsal (Brodmann area, BA, 44) and anterior-ventral parts (BA 45) of LIFG contribute differentially to processes of phonologically and semantically cued word retrieval, respectively. In contrast, a subsequent functional magnetic resonance imaging experiment failed to validate the proposed dissociation using a within-subjects design. In particular, no evidence for a specific role of BA 45 in semantic fluency was found. Here, we resolve this apparent controversy by showing that the conflicting findings can be accounted for when considering the influence of task demands and individual ability on resulting functional magnetic resonance imaging activation patterns. By comparing phonological versus semantic fluency, higher activation was robustly observed in BA 44. For the opposite comparison, higher activation was found in dorsal BA 45; however, this was more pronounced in posterior-dorsal parts of BA 45 for low-performing subjects and was only apparent in anterior-dorsal parts of BA 45 under high demands on controlled semantic retrieval. Our results thus disclose important determinants for detecting a functional segregation of LIFG in verbal fluency that also have implications for the controversial findings in previous lesion studies. Moreover, the present parcellation of dorsal BA 45 corresponds well with anatomical evidence suggesting a subdivision into an anterior (45A) and posterior part (45B) and may therefore represent evidence for its functional significance in humans.

Tackling the multifunctional nature of Broca's region meta-analytically: co-activation-based parcellation of area 44

Cytoarchitectonic area 44 of Broca's region in the left inferior frontal gyrus is known to be involved in several functional domains including language, action and music processing. We investigated whether this functional heterogeneity is reflected in distinct modules within cytoarchitectonically defined left area 44 using meta-analytic connectivity-based parcellation (CBP). This method relies on identifying the whole-brain co-activation pattern for each area 44 voxel across a wide range of functional neuroimaging experiments and subsequently grouping the voxels into distinct clusters based on the similarity of their co-activation patterns. This CBP analysis revealed that five separate clusters exist within left area 44. A post-hoc functional characterization and functional connectivity analysis of these five clusters was then performed. The two posterior clusters were primarily associated with action processes, in particular with phonology and overt speech (posterior-dorsal cluster) and with rhythmic sequencing (posterior-ventral cluster). The three anterior clusters were primarily associated with language and cognition, in particular with working memory (anterior-dorsal cluster), with detection of meaning (anterior-ventral cluster) and with task switching/cognitive control (inferior frontal junction cluster). These five clusters furthermore showed specific and distinct connectivity patterns. The results demonstrate that left area 44 is heterogeneous, thus supporting anatomical data on the molecular architecture of this region, and provide a basis for more specific interpretations of activations localized in area 44.

Effects of lexicality and word frequency on brain activation in dyslexic readers

We investigated the neural basis of lexical access to written stimuli in adult dyslexics and normal readers via the Lexicality effect (pseudowords>words) and the Frequency effect (low>high frequent words). The participants read aloud German words (with low or high lexical frequency) or pseudowords while being scanned. In both groups, both Lexicality effect and Frequency effect involved Broca's region (areas 44 and 45). Whereas the effects were stronger for dyslexic than normal readers in area 44, area 45 showed the reverse pattern. These findings mimic recent results from an fMRI study on dyslexic primary school children, indicating that lexical access to written stimuli poses increased and enduring difficulties on dyslexic readers, at least in a language with a transparent orthography. Additionally, data from four compensated adult dyslexics are reported and discussed, which hint at the importance of both Broca's and Wernicke's region for recovery from childhood dyslexia.

The maps problem and the mapping problem: two challenges for a cognitive neuroscience of speech and language

Research on the brain basis of speech and language faces theoretical and empirical challenges. Most current research, dominated by imaging, deficit-lesion, and electrophysiological techniques, seeks to identify regions that underpin aspects of language processing such as phonology, syntax, or semantics. The emphasis lies on localization and spatial characterization of function. The first part of the paper deals with a practical challenge that arises in the context of such a research programme. This maps problem concerns the extent to which spatial information and localization can satisfy the explanatory needs for perception and cognition. Several areas of investigation exemplify how the neural basis of speech and language is discussed in those terms (regions, streams, hemispheres, networks). The second part of the paper turns to a more troublesome challenge, namely how to formulate the formal links between neurobiology and cognition. This principled problem thus addresses the relation between the primitives of cognition (here speech, language) and neurobiology. Dealing with this mapping problem invites the development of linking hypotheses between the domains. The cognitive sciences provide granular, theoretically motivated claims about the structure of various domains (the "cognome"); neurobiology, similarly, provides a list of the available neural structures. However, explanatory connections will require crafting of computationally explicit linking hypotheses at the right level of abstraction. For both the practical maps problem and the principled mapping problem, developmental approaches and evidence can play a central role in the resolution.

The Role of Human Parietal Area 7A as a Link between Sequencing in Hand Actions and in Overt Speech Production

Research on the evolutionary basis of the human language faculty has proposed the mirror neuron system as a link between motor processing and speech development. Consequently, most work has focused on the left inferior frontal cortex, in particular Broca's region, and the left inferior parietal cortex. However, the direct link between planning of hand motor and speech actions has yet to be elucidated. Thus, the present study investigated whether motor sequencing of hand vs. speech actions has a common neural denominator. For the hand motor task, 25 subjects performed single, repeated, or sequenced button presses with either the left or right hand. The speech task was in analogy; the same subjects produced the syllable "po" once or repeatedly, or a sequence of different syllables ("po-pi-po"). Speech motor vs. hand motor effectors resulted in increased perisylvian activation including Broca's region (left area 44 and areas medially adjacent to left area 45). In contrast, common activation for sequenced vs. repeated production of button presses and syllables revealed the effector-independent involvement of left area 7A in the superior parietal lobule (SPL) in sequencing. These data demonstrate that sequencing of vocal gestures, an important precondition for ordered utterances and ultimately human speech, shares area 7A, rather than inferior parietal regions, as a common cortical module with hand motor sequencing. Interestingly, area 7A has previously also been shown to be involved in the observation of hand and non-hand actions. In combination with the literature, the present data thus suggest a distinction between area 44, which is specifically recruited for (cognitive aspects of) speech, and SPL area 7A for general aspects of motor sequencing. In sum, the study demonstrates a previously underspecified role of the SPL in the origins of speech, and may be discussed in the light of embodiment of speech and language in the motor system.

Speech entrainment enables patients with Broca's aphasia to produce fluent speech

A distinguishing feature of Broca's aphasia is non-fluent halting speech typically involving one to three words per utterance. Yet, despite such profound impairments, some patients can mimic audio-visual speech stimuli enabling them to produce fluent speech in real time. We call this effect 'speech entrainment' and reveal its neural mechanism as well as explore its usefulness as a treatment for speech production in Broca's aphasia. In Experiment 1, 13 patients with Broca's aphasia were tested in three conditions: (i) speech entrainment with audio-visual feedback where they attempted to mimic a speaker whose mouth was seen on an iPod screen; (ii) speech entrainment with audio-only feedback where patients mimicked heard speech; and (iii) spontaneous speech where patients spoke freely about assigned topics. The patients produced a greater variety of words using audio-visual feedback compared with audio-only feedback and spontaneous speech. No difference was found between audio-only feedback and spontaneous speech. In Experiment 2, 10 of the 13 patients included in Experiment 1 and 20 control subjects underwent functional magnetic resonance imaging to determine the neural mechanism that supports speech entrainment. Group results with patients and controls revealed greater bilateral cortical activation for speech produced during speech entrainment compared with spontaneous speech at the junction of the anterior insula and Brodmann area 47, in Brodmann area 37, and unilaterally in the left middle temporal gyrus and the dorsal portion of Broca's area. Probabilistic white matter tracts constructed for these regions in the normal subjects revealed a structural network connected via the corpus callosum and ventral fibres through the extreme capsule. Unilateral areas were connected via the arcuate fasciculus. In Experiment 3, all patients included in Experiment 1 participated in a 6-week treatment phase using speech entrainment to improve speech production. Behavioural and functional magnetic resonance imaging data were collected before and after the treatment phase. Patients were able to produce a greater variety of words with and without speech entrainment at 1 and 6 weeks after training. Treatment-related decrease in cortical activation associated with speech entrainment was found in areas of the left posterior-inferior parietal lobe. We conclude that speech entrainment allows patients with Broca's aphasia to double their speech output compared with spontaneous speech. Neuroimaging results suggest that speech entrainment allows patients to produce fluent speech by providing an external gating mechanism that yokes a ventral language network that encodes conceptual aspects of speech. Preliminary results suggest that training with speech entrainment improves speech production in Broca's aphasia providing a potential therapeutic method for a disorder that has been shown to be particularly resistant to treatment.