Broca Area Research Articles

Brief International Cognitive Assessment for Multiple Sclerosis scores are associated with the cortical thickness of specific cortical areas in relapsing-remitting patients

BackgroundCognitive impairment is frequent and disabling in multiple sclerosis (MS). The Brief International Cognitive Assessment in MS (BICAMS) is a recent short battery usable in clinical practice for cognitive evaluation of MS patients. ObjectiveTo find cortical areas or brain volumes on magnetic resonance imaging (MRI) structural sequences associated with BICAMS scores in MS. MethodsIn this cross-sectional single-center study (NCT 03656055, September 4, 2018), 96 relapsing remitting-MS patients under natalizumab and without recent clinical or radiological inflammation were included. Patients underwent brain MRI and the three BICAMS tests, evaluating information processing speed (SDMT), visuo-spatial memory (BVMT-R), and verbal memory (FVLT). ResultsCortical thickness in the left frontal superior and the right precentral gyri was associated with BVMT-R scores whereas cortical thickness in the left Broca's area and the right superior temporal gyrus was associated with FVLT scores. We observed associations between white matter inflammatory lesions connected to these cortical regions and BICAMS subscores. ConclusionsBICAMS scores are associated with specific cortical areas, the cognitive domain matching the known functions of the cortical area. Specific cognitive impairments in MS may be associated with specific cortical regions, themselves influenced by white matter inflammatory lesions and demographical parameters (age, sex, education level).

Microstructural damange of white matter in the frontal Aslant tract in amnestic mild cognitive impairment subtypes

Frontal Aslant Tract (FAT) is a bundle connecting Broca's area to Supplementay Motor Area (SMA) and pre-SMA in both hemispheres, which has been traditionally implicated in speech functions (Catani et al., 2013). A previous study (Serra et al., 2017) showed microstructural damage of FAT in patients with Alzheimer's disease (AD) at the stage of dementia. We assessed here microstructural integrity/damage of FAT in patients with amnestic Mild Cognitive Impairment (aMCI) and its potential role in cognitive dysfunctions.

Changes in Electrical Brain Activity Due to tDCS in Post-Stroke Chronic Aphasia: a Double-Blind Randomized Controlled Study

<h3>Research Objectives</h3> To better understand changes in brain activity related to transcranial direct current stimulation (tDCS) in post-stroke chronic aphasia. <h3>Design</h3> Double-blind randomized placebo controlled study design. <h3>Setting</h3> Casa Colina Research Institute. <h3>Participants</h3> Forty three post-stroke outpatients with chronic aphasia (32 males; age: 61±13y; 0.9-18years post-injury; 32 ischemic stroke; 19 non-fluent aphasia). Twenty patients were in the tDCS group. <h3>Interventions</h3> Participants were randomly assigned either to the tDCS group (cathode on Broca, left side) or to the sham/placebo group. Both groups had five consecutive days of 20 minutes session, using a FDA approved tDCS device (soterixmedical.com). Resting state electrophysiological recordings (5 minutes) and behavioral assessments were performed the week before/after tDCS/sham intervention. <h3>Main Outcome Measures</h3> 1) EEG data: power spectrum as well as coherence in delta, theta, alpha and beta frequencies in fronto-temporal electrodes; 2) Behavioral data: the Western Aphasia Battery-Revised (WAB-R total scores and subscores). <h3>Results</h3> For the behavioral data, groups differed, pre/post intervention, on the WAB-R total score (F=5.22; p=0.028) as well as for the Auditory-Verbal Comprehension (F=4.657; p=0.038) and Repetition (F=4.56; p=0.04) subscores. For the EEG, groups also differed, pre/post intervention, when looking at changes in coherence between Broca and Wernicke on the contralateral side (F8T4, alpha and beta) as well as between Broca area on bilateral sides (F7F8, beta) and other fronto-temporal electrodes (F3T3, beta; FzT5, alpha; F4T5, beta). Post-hoc analyses revealed a significant increase in coherence for the tDCS group (but not for the sham group) for the following electrodes: F8T4 (alpha), F3T3 (beta) and F4T5 (beta). <h3>Conclusions</h3> In this double-blind randomized placebo controlled trial, our findings show a higher improvement in language functions (for both receptive and expressive language skills) in response to treatment as compared to sham. These improvements seem related to an increase in coherence not only in ipsilateral but also contralateral fronto-temporal electrodes, suggesting a higher functional connectivity within the language network due to tDCS in post-stroke chronic aphasia. <h3>Author(s) Disclosures</h3> The authors have nothing to declare.

Safety and efficacy of GammaTile intracranial brachytherapy implanted during awake craniotomy

GammaTile intracranial brachytherapy (cesium-131 seeds) has demonstrated encouraging safety and local control results, and recently received Food and Drug Administration clearance for newly diagnosed and recurrent brain tumors. The authors present the first reported case of GammaTile intraoperative brachytherapy performed during an awake craniotomy. A 50-year-old man had a biopsy-proven, 2.8 cm left lateral frontal glioblastoma lesion nearing Broca's area on MRI. Despite several interventions (craniotomy, adjuvant chemoradiation, tumor treating fields) tumor progression occurred near the left parietal resection cavity. Re-resection was planned with awake craniotomy and language mapping. A preoperative planning session involving Radiation Oncology and Neurosurgery identified the area of the expected postoperative bed, and consequently five GammaTiles were ordered, each containing 4 cesium-131 3.5 U seeds. During surgery, tumor mapping and bipolar stimulation were performed while the patient spoke in complete sentences. Speech arrest occurred upon stimulation at the posterior edge of the gyrus, indicative of language cortex. Microsurgical maximal safe resection subsequently occurred, and areas at risk for residual/recurrence disease were determined in consultation with Radiation Oncology. Subsequently, Neurosurgery placed all five GammaTiles (20 cesium-131 seeds total) after which closure was completed and radioactive surveys of the room remained within state statue. Postoperative dosimetry yielded excellent coverage. The first reported case of GammaTile intraoperative brachytherapy during awake craniotomy supports the safety and feasibility of this treatment strategy. This case indicates that for patients with tumors adjacent to eloquent cortex, awake craniotomy can allow for custom implantation of intraoperative brachytherapy following maximum safe resection.

Neuromodulation: A combined-therapy protocol for speech rehabilitation in a child with cerebral palsy

IntroductionTranscranial direct current stimulation (tDCS) modulates cortical activity and potentiates functional gains achieved during therapeutic protocols. The aim of Integrative Speech Therapy Protocol is to rehabilitate speech in patients with impairments regarding neuropyschomotor development by combining oral motor stimuli, specific articulatory production, and the stimulation of phonological aspects of language. ObjectiveInvestigate the effect of transcranial direct current stimulation combined to integrative speech therapy in a child with cerebral palsy. MethodsWe performed a case study with tDCS and speech therapy in a patient with cerebral palsy and apraxia of speech. To assess the patient's speech, we used a parameterized test for the Brazilian Portuguese speech - ABFW. The CFCS and Vicking Speech Scales presented level IV and III, respectively. The patient underwent two periods with ten stimulation sessions each: first with anodal stimulation over Broca's area; and second over the left dorsolateral prefrontal cortex. Two indices were calculated: the percentage of consonants correct; and percentage of consonants correct-revised. Descriptive statistics were employed for the clinical data. For the outcomes, changes in each score were calculated as the difference in pre-intervention and post-intervention using Wilcoxon-Mann-Whitney test. ResultsIncreases were found in percentage of correct consonants indices as well as to produce two-syllable and three-syllable words after both types of stimulation, characterized mainly by correct vowels that marked the presence of the syllable. Number of phonemes increased 0 to 4 at first the stimulation and 4 to 10 at the second. ConclusionThe combined-therapy program contributed to improve the speech rehabilitation results in a patient with cerebral palsy.

Species and individual differences and connectional asymmetry of Broca's area in humans and macaques

To reveal the connectional specialization of the Broca's area (or its homologue), voxel-wise inter-species and individual differences, and inter-hemispheric asymmetry were respectively inspected in humans and macaques at both whole-brain connectivity and single tract levels. It was discovered that the developed connectivity blueprint approach is able to localize connectionally comparable voxels between the two species in Broca's area, whereas the quantitative differences between blueprints of locationally or connectionally corresponding voxels enable us to generate inter-hemispheric, inter-subject, and inter-species connectional variabilities, respectively. More importantly, the inter-species and inter-subject variabilities exhibited positive correlation in both two primates, and relatively higher variabilities were detected in the anatomically defined pars triangularis. By contrast, negative relationship was identified between the inter-species variability and hemispheric asymmetry in human brain. In particular, relatively higher asymmetry was revealed in the anatomically defined pars opercularis. Therefore, our novel findings demonstrated that pars triangularis, as compared to pars opercularis, might be a more active area during primate evolution, in which the brain connectivity and possible functions of pars triangularis show relatively higher degree in species specialization, yet lower in hemispheric specialization. Meanwhile, brain connectivity and possible functions of pars opercularis manifested an opposite pattern. At the tract level, functional roles related to the ventral stream in speech comprehension were relatively conservative and bilaterally organized, while those related to the dorsal stream in speech production show relatively higher species and hemispheric specializations.

Where in the Brain is “the Other’s” Hand? Mapping Dysfunctional Neural Networks in Somatoparaphrenia

Somatoparaphrenia refers to the delusional belief, typically observed in right brain-damaged patients, that the contralesional limbs belong to someone else. Here, we aimed to uncover the neural activity associated with this productive, i.e. confabulatory, component in a patient, S.P.P., with a large right-sided lesion of both cortical and subcortical gray and white matter. He claimed that his left paralyzed hand belonged to his mother. In a block-design functional magnetic resonance (fMRI) experiment, S.P.P. imagined that the mother would move her (i.e. his left) hand (condition “mother”). Subtraction of the activity elicited by control conditions (imagery of self-generated movement of either left or right hand) from that in the “mother” condition resulted in the focal activation of the pars opercularis of the right inferior frontal gyrus (rIFG). In a separate, resting-state fMRI experiment with S.P.P. and 21 healthy controls, we examined the functional connectivity of the rIFG and the affected hand somatosensory network to the rest of the brain. We found a negative correlation between the activity in the rIFG and that of Broca area and the temporo-parietal junction in the left hemisphere. Furthermore, the affected hand somatosensory network was disconnected from the left secondary somatosensory cortex. Our results link the productive component of somatoparaphrenia to the activity of crucial hubs for integrating the multimodal signals of the affected hand. Furthermore, they provide the first direct evidence supporting the “left narrator model”, proposed by Halligan et al. (1995), according to which the confabulations of somatoparaphrenia are due to a disconnection of left hemisphere language areas from right hemisphere parieto-temporal cortex.

Decoding Activity in Broca's Area Predicts the Occurrence of Auditory Hallucinations Across Subjects

BackgroundFunctional magnetic resonance imaging (fMRI) capture aims at detecting auditory-verbal hallucinations (AVHs) from continuously recorded brain activity. Establishing efficient capture methods with low computational cost that easily generalize between patients remains a key objective in precision psychiatry. To address this issue, we developed a novel automatized fMRI-capture procedure for AVHs in patients with schizophrenia (SCZ). MethodsWe used a previously validated but labor-intensive personalized fMRI-capture method to train a linear classifier using machine learning techniques. We benchmarked the performances of this classifier on 2320 AVH periods versus resting-state periods obtained from SCZ patients with frequent symptoms (n = 23). We characterized patterns of blood oxygen level–dependent activity that were predictive of AVH both within and between subjects. Generalizability was assessed with a second independent sample gathering 2000 AVH labels (n = 34 patients with SCZ), while specificity was tested with a nonclinical control sample performing an auditory imagery task (840 labels, n = 20). ResultsOur between-subject classifier achieved high decoding accuracy (area under the curve = 0.85) and discriminated AVH from rest and verbal imagery. Optimizing the parameters on the first schizophrenia dataset and testing its performance on the second dataset led to an out-of-sample area under the curve of 0.85 (0.88 for the converse test). We showed that AVH detection critically depends on local blood oxygen level–dependent activity patterns within Broca's area. ConclusionsOur results demonstrate that it is possible to reliably detect AVH states from fMRI blood oxygen level–dependent signals in patients with SCZ using a multivariate decoder without performing complex preprocessing steps. These findings constitute a crucial step toward brain-based treatments for severe drug-resistant hallucinations.

Broca's area and the search for anatomical asymmetry: commentary and perspectives.

We present a brief commentary on the field's search for an anatomical asymmetry between Broca's area and its homologue in the non-dominant hemisphere, focusing on a selection of studies, including research from the last decade. We demonstrate that, several years after the influential review of Keller and colleagues from 2009, and despite recent advances in neuroimaging, the existence of a structural asymmetry of Broca's area is still controversial. This is especially the case for studies of the macroanatomy of this region. We point out the inconsistencies in methodology across studies that could account for the discrepancy in results. Investigations of the microstructure of Broca's area show a trend of a leftward asymmetry, but it is still unclear how these results relate to language dominance. We suggest that it may be necessary to combine multiple metrics in a systematic manner to find robust asymmetries and to expand the regional scope of structural investigations. Finally, based on the current state of the literature, we should not rule out the possibility that language dominance may simply not be reflected in local anatomical differences in the brain.

Resting-state functional MRI language network connectivity differences in patients with brain tumors: exploration of the cerebellum and contralesional hemisphere.

Brain tumors can have far-reaching impacts on functional networks. Language processing is typically lateralized to the left hemisphere, but also involves the right hemisphere and cerebellum. This resting-state functional MRI study investigated the proximal and distal effects of left-hemispheric brain tumors on language network connectivity in the ipsilesional and contralesional hemispheres. Separate language resting-state networks were generated from seeding in ipsilesional (left) and contralesional (right) Broca's Area for 29 patients with left-hemispheric brain tumors and 13 controls. Inclusion criteria for all subjects included language left-dominance based on task-based functional MRI. Functional connectivity was analyzed in each network to the respective Wernicke's Area and contralateral cerebellum. Patients were assessed for language deficits prior to scanning. Compared to controls, patients exhibited decreased connectivity in the ipsilesional and contralesional hemispheres between the Broca's Area and Wernicke's Area homologs (mean connectivity for patients/controls: left 0.51/0.59, p < 0.002; right 0.52/0.59, p < 0.0002). No differences in mean connectivity to the contralateral cerebellum were observed between groups (p > 0.09). Crossed cerebro-cerebellar connectivity was correlated in controls (rho = 0.59, p < 0.05), patients without language deficits (rho = 0.74, p < 0.0002), and patients with high-grade gliomas (rho = 0.78, p < 0.0002), but not in patients with language deficits or low-grade gliomas (p > 0.l). These findings demonstrate that brain tumors impact the language network in the contralesional hemisphere and cerebellum, which may reflect neurological deficits and lesion-induced cortical reorganization.

Bidirectional Connectivity Between Broca's Area and Wernicke's Area During Interactive Verbal Communication.

Aim: This investigation aims to advance the understanding of neural dynamics that underlies live and natural interactions during spoken dialogue between two individuals. Introduction: The underlying hypothesis is that functional connectivity between canonical speech areas in the human brain will be modulated by social interaction. Methods: Granger causality was applied to compare directional connectivity across Broca's and Wernicke's areas during verbal conditions consisting of interactive and noninteractive communication. Thirty-three pairs of healthy adult participants alternately talked and listened to each other while performing an object naming and description task that was either interactive or not during hyperscanning with functional near-infrared spectroscopy (fNIRS). In the noninteractive condition, the speaker named and described a picture-object without reference to the partner's description. In the interactive condition, the speaker performed the same task but included an interactive response about the preceding comments of the partner. Causality measures of hemodynamic responses from Broca's and Wernicke's areas were compared between real, surrogate, and shuffled trials within dyads. Results: The interactive communication was characterized by bidirectional connectivity between Wernicke's and Broca's areas of the listener's brain. Whereas this connectivity was unidirectional in the speaker's brain. In the case of the noninteractive condition, both speaker's and listener's brains showed unidirectional top-down (Broca's area to Wernicke's area) connectivity. Conclusion: Together, directional connectivity as determined by Granger analysis reveals bidirectional flow of neuronal information during dynamic two-person verbal interaction for processes that are active during listening (reception) and not during talking (production). Findings are consistent with prior contrast findings (general linear model) showing neural modulation of the receptive language system associated with Wernicke's area during a two-person live interaction. Impact statement The neural dynamics that underlies real-life social interactions is an emergent topic of interest. Dynamically coupled cross-brain neural mechanisms between interacting partners during verbal dialogue have been shown within Wernicke's area. However, it is not known how within-brain long-range neural mechanisms operate during these live social functions. Using Granger causality analysis, we show bidirectional neural activity between Broca's and Wernicke's areas during interactive dialogue compared with a noninteractive control task showing only unidirectional activity. Findings are consistent with an Interactive Brain Model where long-range neural mechanisms process interactive processes associated with rapid and spontaneous spoken social cues.

Effect of High Frequency Transcranial Magnetic Stimulation on Recovery of Chronic Post-Stroke Aphasia

BackgroundBoth hemispheres have role in post-stroke aphasia recovery but better recovery is expected with the restoration of function by the left hemisphere. Transcranial stimulation has been used to favor recruitment of left-hemispheric language networks and increase activity of the left hemisphere, thus helps aphasia recovery . ObjectiveThe aim of this study is to evaluate the effect of excitatory repetitive transcranial magnetic stimulation (rTMS) on recovery of post stroke aphasic patients . Materials and methodsTwenty patients with post stroke chronic aphasia were enrolled in the study. Aphasia severity was assessed using Aphasia Severity Rating Scale (ASRS). Linguistic deficits were assessed using Kasr Al-Aini Arabic Aphasia test (KAAT). Real rTMS was applied three for 10 sessions of 10-Hz stimulation, positioned over the left Broca's area of the affected hemisphere. All patients were evaluated before, after the end of treatment sessions and one month later . ResultsThere was a significant improvement in the mean total score and mean scores of components of KAAT scale before, immediately after and after one month of rTMS (P< 0.05). Moreover, there was a significant improvement in mean scores of ASRS before, immediately after and after one month of rTMS (P= 0.000). There was a significant difference in mean scores of ASRS and KAAT before, immediately after the last session and after one month between small, medium and large brain infarcts. (P< 0.05). ConclusionExcitatory rTMS is a beneficial adjuvant therapy that improves language skills in patients with chronic post-stroke non-fluent aphasia in short and long term.The protocol of this observational study was registered in clinical trial registration: www.ClinicalTrials.gov, identifier: NCT04708197

Neural correlates of subjective comprehension of noise-vocoded speech

Under an acoustically degraded condition, the degree of speech comprehension fluctuates within individuals. Understanding the relationship between such fluctuations in comprehension and neural responses might reveal perceptual processing for distorted speech. In this study we investigated the cerebral activity associated with the degree of subjective comprehension of noise-vocoded speech sounds (NVSS) using functional magnetic resonance imaging. Our results indicate that higher comprehension of NVSS sentences was associated with greater activation in the right superior temporal cortex, and that activity in the left inferior frontal gyrus (Broca's area) was increased when a listener recognized words in a sentence they did not fully comprehend. In addition, results of laterality analysis demonstrated that recognition of words in an NVSS sentence led to less lateralized responses in the temporal cortex, though a left-lateralization was observed when no words were recognized. The data suggest that variation in comprehension within individuals can be associated with changes in lateralization in the temporal auditory cortex.

Hierarchical syntactic processing is beyond mere associating: Functional magnetic resonance imaging evidence from a novel artificial grammar.

Grammar is central to any natural language. In the past decades, the artificial grammar of the AnBn type in which a pair of associated elements can be nested in the other pair was considered as a desirable model to mimic human language syntax without semantic interference. However, such a grammar relies on mere associating mechanisms, thus insufficient to reflect the hierarchical nature of human syntax. Here, we test how the brain imposes syntactic hierarchies according to the category relations on linearized sequences by designing a novel artificial “Hierarchical syntactic structure‐building Grammar” (HG), and compare this to the AnBn grammar as a “Nested associating Grammar” (NG) based on multilevel associations. Thirty‐six healthy German native speakers were randomly assigned to one of the two grammars. Both groups performed a grammaticality judgment task on auditorily presented word sequences generated by the corresponding grammar in the scanner after a successful explicit behavioral learning session. Compared to the NG group, we found that the HG group showed a (a) significantly higher involvement of Brodmann area (BA) 44 in Broca's area and the posterior superior temporal gyrus (pSTG); and (b) qualitatively distinct connectivity between the two regions. Thus, the present study demonstrates that the build‐up process of syntactic hierarchies on the basis of category relations critically relies on a distinctive left‐hemispheric syntactic network involving BA 44 and pSTG. This indicates that our novel artificial grammar can constitute a suitable experimental tool to investigate syntax‐specific processes in the human brain.

Distinct neural correlates of linguistic demand and non-linguistic demand.

In this study, we investigated how the brain responds to task difficulty in linguistic and non-linguistic contexts. This is important for the interpretation of functional imaging studies of neuroplasticity in post-stroke aphasia, because of the inherent difficulty of matching or controlling task difficulty in studies with neurological populations. Twenty neurologically normal individuals were scanned with fMRI as they performed a linguistic task and a non-linguistic task, each of which had two levels of difficulty. Critically, the tasks were matched across domains (linguistic, non-linguistic) for accuracy and reaction time, such that the differences between the easy and difficult conditions were equivalent across domains. We found that non-linguistic demand modulated the same set of multiple demand (MD) regions that have been identified in many prior studies. In contrast, linguistic demand modulated MD regions to a much lesser extent, especially nodes belonging to the dorsal attention network. Linguistic demand modulated a subset of language regions, with the left inferior frontal gyrus most strongly modulated. The right hemisphere region homotopic to Broca's area was also modulated by linguistic but not non-linguistic demand. When linguistic demand was mapped relative to non-linguistic demand, we also observed domain by difficulty interactions in temporal language regions as well as a widespread bilateral semantic network. In sum, linguistic and non-linguistic demand have strikingly different neural correlates. These findings can be used to better interpret studies of patients recovering from aphasia. Some reported activations in these studies may reflect task performance differences, while others can be more confidently attributed to neuroplasticity.

The ventral pathway of the human brain: A continuous association tract system

The brain hemispheres can be divided into an upper dorsal and a lower ventral system. Each system consists of distinct cortical regions connected via long association tracts. The tracts cross the central sulcus or the limen insulae to connect the frontal lobe with the posterior brain. The dorsal stream is associated with sensorimotor mapping. The ventral stream serves structural analysis and semantics in different domains, as visual, acoustic or space processing. How does the prefrontal cortex, regarded as the platform for the highest level of integration, incorporate information from these different domains? In the current view, the ventral pathway consists of several separate tracts, related to different modalities. Originally the assumption was that the ventral path is a continuum, covering all modalities. The latter would imply a very different anatomical basis for cognitive and clinical models of processing. To further define the ventral connections, we used cutting-edge in vivo global tractography on high-resolution diffusion tensor imaging (DTI) data from 100 normal subjects from the human connectome project and ex vivo preparation of fiber bundles in the extreme capsule of 8 humans using the Klingler technique. Our data showed that ventral stream tracts, traversing through the extreme capsule, form a continuous band of fibers that fan out anteriorly to the prefrontal cortex, and posteriorly to temporal, occipital and parietal cortical regions. Introduction of additional volumes of interest in temporal and occipital lobes differentiated between the inferior fronto-occipital fascicle (IFOF) and uncinate fascicle (UF). Unequivocally, in both experiments, in all subjects a connection between the inferior frontal and middle-to-posterior temporal cortical region, otherwise known as the temporo-frontal extreme capsule fascicle (ECF) from nonhuman primate brain-tracing experiments was identified. In the human brain, this tract connects the language domains of “Broca's area” and “Wernicke's area”. The differentiation in the three tracts, IFOF, UF and ECF seems arbitrary, all three pass through the extreme capsule. Our data show that the ventral pathway represents a continuum. The three tracts merge seamlessly and streamlines showed considerable overlap in their anterior and posterior course. Terminal maps identified prefrontal cortex in the frontal lobe and association cortex in temporal, occipital and parietal lobes as streamline endings. This anatomical substrate potentially facilitates the prefrontal cortex to integrate information across different domains and modalities.

Language Familiarity and Proficiency Leads to Differential Cortical Processing During Translation Between Distantly Related Languages.

In the midst of globalization, English is regarded as an international language, or Lingua Franca, but learning it as a second language (L2) remains still difficult to speakers of other languages. This is true especially for the speakers of languages distantly related to English such as Japanese. In this sense, exploring neural basis for translation between the first language (L1) and L2 is of great interest. There have been relatively many previous researches revealing brain activation patterns during translations between L1 and English as L2. These studies, which focused on language translation with close or moderate linguistic distance (LD), have suggested that the Broca area (BA 44/45) and the dorsolateral prefrontal cortex (DLPFC; BA 46) may play an important role on translation. However, the neural mechanism of language translation between Japanese and English, having large LD, has not been clarified. Thus, we used functional near infrared spectroscopy (fNIRS) to investigate the brain activation patterns during word translation between Japanese and English. We also assessed the effects of translation directions and word familiarity. All participants’ first language was Japanese and they were learning English. Their English proficiency was advanced or elementary. We selected English and Japanese words as stimuli based on the familiarity for Japanese people. Our results showed that the brain activation patterns during word translation largely differed depending on their English proficiency. The advanced group elicited greater activation on the left prefrontal cortex around the Broca’s area while translating words with low familiarity, but no activation was observed while translating words with high familiarity. On the other hand, the elementary group evoked greater activation on the left temporal area including the superior temporal gyrus (STG) irrespective of the word familiarity. These results suggested that different cognitive process could be involved in word translation corresponding to English proficiency in Japanese learners of English. These difference on the brain activation patterns between the advanced and elementary group may reflect the difference on the cognitive loads depending on the levels of automatization in one’s language processing.

Recovery of aphemia with pure word dumbness after treatment with repetitive transcranial magnetic stimulation: A case report

Aphemia with pure word dumbness is a relatively rare clinical syndrome caused by injury to the Broca area of the dominant hemisphere. Patients with this syndrome have significant difficulties in oral expression, whereas other language functions, such as written expression and comprehension, are normal. In this study, a patient without no evidence of structural brain lesions presented with aphemia with pure word dumbness after head trauma of the frontal lobe. Through magnetic resonance imaging (MRI) examinations, functional abnormalities (regional homogeneity, degree centrality, and language network) were found in the patient without structural alterations. After four weeks of treatment with repetitive transcranial magnetic stimulation (rTMS) and cognitive evaluation every week, we found that the patient's linguistic function (i.e., spontaneous speech, speech comprehension, rehearsal, naming, reading, writing and the aphasia quotient) recovered gradually. Therefore, rTMS may be an adjuvant therapy for the recovery of aphemia patients with pure word dumbness.

Distinct neural networks for the volitional control of vocal and manual actions in the monkey homologue of Broca's area.

The ventrolateral frontal lobe (Broca's area) of the human brain is crucial in speech production. In macaques, neurons in the ventrolateral prefrontal cortex, the suggested monkey homologue of Broca's area, signal the volitional initiation of vocalizations. We explored whether this brain area became specialized for vocal initiation during primate evolution and trained macaques to alternate between a vocal and manual action in response to arbitrary cues. During task performance, single neurons recorded from the ventrolateral prefrontal cortex and the rostroventral premotor cortex of the inferior frontal cortex predominantly signaled the impending vocal or, to a lesser extent, manual action, but not both. Neuronal activity was specific for volitional action plans and differed during spontaneous movement preparations. This implies that the primate inferior frontal cortex controls the initiation of volitional utterances via a dedicated network of vocal selective neurons that might have been exploited during the evolution of Broca's area.

Damage to Broca's area does not contribute to long-term speech production outcome after stroke.

Broca’s area in the posterior half of the left inferior frontal gyrus has long been thought to be critical for speech production. The current view is that long-term speech production outcome in patients with Broca’s area damage is best explained by the combination of damage to Broca’s area and neighbouring regions including the underlying white matter, which was also damaged in Paul Broca’s two historic cases. Here, we dissociate the effect of damage to Broca’s area from the effect of damage to surrounding areas by studying long-term speech production outcome in 134 stroke survivors with relatively circumscribed left frontal lobe lesions that spared posterior speech production areas in lateral inferior parietal and superior temporal association cortices. Collectively, these patients had varying degrees of damage to one or more of nine atlas-based grey or white matter regions: Brodmann areas 44 and 45 (together known as Broca’s area), ventral premotor cortex, primary motor cortex, insula, putamen, the anterior segment of the arcuate fasciculus, uncinate fasciculus and frontal aslant tract. Spoken picture description scores from the Comprehensive Aphasia Test were used as the outcome measure. Multiple regression analyses allowed us to tease apart the contribution of other variables influencing speech production abilities such as total lesion volume and time post-stroke. We found that, in our sample of patients with left frontal damage, long-term speech production impairments (lasting beyond 3 months post-stroke) were solely predicted by the degree of damage to white matter, directly above the insula, in the vicinity of the anterior part of the arcuate fasciculus, with no contribution from the degree of damage to Broca’s area (as confirmed with Bayesian statistics). The effect of white matter damage cannot be explained by a disconnection of Broca’s area, because speech production scores were worse after damage to the anterior arcuate fasciculus with relative sparing of Broca’s area than after damage to Broca’s area with relative sparing of the anterior arcuate fasciculus. Our findings provide evidence for three novel conclusions: (i) Broca’s area damage does not contribute to long-term speech production outcome after left frontal lobe strokes; (ii) persistent speech production impairments after damage to the anterior arcuate fasciculus cannot be explained by a disconnection of Broca’s area; and (iii) the prior association between persistent speech production impairments and Broca’s area damage can be explained by co-occurring white matter damage, above the insula, in the vicinity of the anterior part of the arcuate fasciculus.