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Studies have highlighted an association between motor laterality and speech production laterality. It is thought that common demands for sequential processing may underlie this association. However, most studies in this area have relied on relatively small samples and have infrequently explored the reliability of the tools used to assess lateralization. We, therefore, established the validity and reliability of an online battery measuring sequence-based motor laterality and language laterality before exploring the associations between laterality indices on language and motor tasks. The online battery was completed by 621 participants, 52 of whom returned to complete the battery a second time. The three motor tasks included in the battery showed good between-session reliability (r ≥.78) and were lateralized in concordance with hand preference. The novel measure of speech production laterality was left lateralized at population level as predicted, but reliability was less satisfactory (r =.62). We found no evidence of an association between sequence-based motor laterality and language laterality. Those with a left-hand preference were more strongly lateralized on motor tasks requiring midline crossing; this effect was not observed in right-handers. We conclude that there is little evidence of the co-lateralization of language and sequence-based motor skill on this battery. [ABSTRACT FROM AUTHOR]

Background. Previous studies have shown that brain response to a written word depends on the task: whether the word is a target in a version of lexical decision task or should be read silently. Although this effect has been interpreted as an evidence for an interaction between word recognition processes and task demands, it also may be caused by greater attention allocation to the target word. Objective. We aimed to examine the task effect on brain response evoked by non- target written words. Design. Using MEG and magnetic source imaging, we compared spatial-temporal pattern of brain response elicited by a noun cue when it was read silently either without additional task (SR) or with a requirement to produce an associated verb (VG). Results.The task demands penetrated into early (200-300 ms) and late (500-800 ms) stages of a word processing by enhancing brain response under VG versus SR condition. The cortical sources of the early response were localized to bilateral inferior occipitotemporal and anterior temporal cortex suggesting that more demanding VG task required elaborated lexical-semantic analysis. The late effect was observed in the associative auditory areas in middle and superior temporal gyri and in motor representation of articulators. Our results suggest that a remote goal plays a pivotal role in enhanced recruitment of cortical structures underlying orthographic, semantic and sensorimotor dimensions of written word perception from the early processing stages. Surprisingly, we found that to fulfil a more challenging goal the brain progressively engaged resources of the right hemisphere throughout all stages of silent reading. Conclusion. Our study demonstrates that a deeper processing of linguistic input amplifies activation of brain areas involved in integration of speech perception and production. This is consistent with theories that emphasize the role of sensorimotor integration in speech understanding.

Magnetoencephalography was used to study interhemisphere asymmetry of word priming in the window of the N400 semantic component in a group of 28 healthy, right-handed subjects. The overall effects of activation of the 'semantic' neural networks in the left and right hemispheres of the brain were evaluated in terms of the total power of responses to sensors (root mean square, RMS) as an analog of the global power field in the EEG. The main results of this study provide evidence that 'new' (i.e., not previously encountered in the context of the experiment) words evoked asymmetrical left-hemisphere responses in the window of the N400 component. Repetition of words presented for memorization led to a drop in the amplitude of the 'semantic' component in the left hemisphere and was accompanied by a decrease in left-hemisphere asymmetry. The index of differential asymmetry, which considers changes in asymmetry associated with implicit memorization of words, was lateralized to the left hemisphere in most subjects. Differences in the magnitude of asymmetry were related to the level of success of implicit remembering, indicating that it is functional in nature, i.e., it interacts with word memory processes. [ABSTRACT FROM AUTHOR]

Abstract: Before performing neurosurgery, an exhaustive presurgical assessment is required, usually including an investigation of language cerebral lateralization. Among the available procedures, the intracarotid amobarbital test (IAT) was formerly the most widely used. However, this procedure has many limitations: it is invasive and potentially traumatic, especially for children. To overcome these limitations, neuroimaging techniques such as functional magnetic resonance imaging (fMRI) have been used. Again, these methods are difficult to use with children, who must remain motionless during data acquisition. Functional near-infrared spectroscopy (fNIRS) is a noninvasive functional imaging technique that is easily applied to pediatric and cognitively limited patients. It has been used recently in epileptic children for presurgical assessment of expressive and receptive language brain lateralization. The aim of this review is to present the contribution of fNIRS to the presurgical assessment of language function in children with neurological diseases. [Copyright &y& Elsevier]

Abstract: The present study examined the relationship between individual differences in dichotic listening (DL) and the susceptibility to left–right confusion (LRC). Thirty-six men and 59 women completed a consonant–vowel DL test, a behavioral LRC task, and an LRC self-rating questionnaire. Significant negative correlations between overall DL accuracy and LRC rates in men (behavioral task) and self-ratings in women, indicated that the more participants struggled with left–right discrimination, the fewer DL syllables they reported correctly. However, there was no relationship between LRC and the typical right ear advantage. Thus, there is a sex- and task-dependent relationship between LRC and overall DL accuracy, but not between LRC and ear asymmetry. It is concluded that (a) atypical ear asymmetries, as in certain clinical populations, cannot be explained by associated deficits in left–right discrimination, and (b) LRC can negatively affect task performance, even when participants do not have to make explicit “left” versus “right” decisions. [Copyright &y& Elsevier]

Past research shows that the lower nonverbal frequencies of the human voice, beneath .5 kHz, transmit an acoustic signal promoting social convergence and status accommodation between human interlocutors. We conducted a laboratory experiment and a validation study to explore the possible communications benefits of targeting the low-frequency band to the left ears of human participants and the high-frequency band to the right ears. We compare this “Enhanced” condition with two other conditions: a “Confounded” condition, in which the low-frequency band was targeted to participants' right ears and the higher-frequency band to their left ears; and a Control condition, in which the entire unaltered frequency band was targeted to both ears. For the duration of their interaction, experiment participants engaged in dyadic conversations while attempting to complete a task via an audio-visual communication system. Our results show that both the speed and accuracy of task completion were significantly improved in the Enhanced condition. In the second validation study, groups of participants rated the quality of videotaped conversations from the experiment using a semantic differential instrument. The Enhanced condition conversations were rated significantly more affectively favourable than either the unaltered Control or Confounded condition conversations. Overall, our results exhibit potential for enhancing two-way electronic communications and improving task performances in media environments. [ABSTRACT FROM AUTHOR]

Abstract: Background noise has become part of our everyday life in modern societies. Its presence affects both the ability to concentrate and communicate. Some individuals, like children, the elderly, and non-native speakers have pronounced problems in noisy environments. Here we review evidence suggesting that background noise has both transient and sustained detrimental effects on central speech processing. Studies on the effects of noise on neural processes have demonstrated hemispheric reorganization in speech processing in adult individuals during background noise. During noise, the well-known left hemisphere dominance in speech discrimination became right hemisphere preponderant. Furthermore, long-term exposure to noise has a persistent effect on the brain organization of speech processing and attention control. These results both stress the importance to re-evaluate which noise levels can be considered safe for brain functions and raise concerns on the speech and cognitive abilities of individuals living in noisy environments. [Copyright &y& Elsevier]

Abstract: The intracarotid amobarbital test (IAT) is used for presurgical evaluation of language lateralization. However, this procedure has many limitations, especially in children. As an alternative to IAT, in the case described here, near-infrared spectroscopy (NIRS) was used to investigate expressive and receptive language lateralization as part of the presurgical evaluation of a 9-year-old Yiddish-speaking boy with a probable left temporal epileptic focus. This child could not tolerate IAT or functional MRI. He underwent two NIRS recording sessions while performing expressive and receptive language tasks. Results indicated predominantly left-sided expressive language in Broca’s area with ipsilateral cortical recruitment of more posterior regions. Receptive language showed a bilateral cerebral pattern, perhaps as an expression of cerebral plasticity or compensation in this young patient. This case report illustrates that NIRS may contribute to presurgical investigation and could become a noninvasive alternative to IAT and functional MRI in determining speech lateralization in children. [Copyright &y& Elsevier]

The article describes the case of a 34-year-old right-handed man who had epilepsy for 31 years accompanied by ictal spitting in left temporal lobe epilepsy. The patient's habitual seizures comprised epigastric aura followed by behavioral arrest with staring. He underwent epilepsy surgery and postoperative neuropsychological assessment did not find impaired speech and memory functions.

Infant brain development incorporates several intermingled mechanisms leading to intense and asynchronous maturation across cerebral networks and functional modalities. Combining electroencephalography (EEG) and diffusion magnetic resonance imaging (MRI), previous studies in the visual modality showed that the functional maturation of the event-related potentials (ERP) during the first postnatal semester relates to structural changes in the corresponding white matter pathways. Here investigated similar issues in the auditory modality. We measured ERPs to syllables in 1- to 6-month-old infants and related them to the maturational properties of underlying neural substrates measured with diffusion tensor imaging (DTI). We first observed a decrease in the latency of the auditory P2, and in the diffusivities in the auditory tracts and perisylvian regions with age. Secondly, we highlighted some of the early functional and structural substrates of lateralization. Contralateral responses to monoaural syllables were stronger and faster than ipsilateral responses, particularly in the left hemisphere. Besides, the acoustic radiations, arcuate fasciculus, middle temporal and angular gyri showed DTI asymmetries with a more complex and advanced microstructure in the left hemisphere, whereas the reverse was observed for the inferior frontal and superior temporal gyri. Finally, after accounting for the age-related variance, we correlated the inter-individual variability in P2 responses and in the microstructural properties of callosal fibers and inferior frontal regions. This study combining dedicated EEG and MRI approaches in infants highlights the complex relation between the functional responses to auditory stimuli and the maturational properties of the corresponding neural network. [ABSTRACT FROM AUTHOR]