Handedness and hemispheric language dominance in healthy humans

Clinical Findings in Temporal Lobe Epilepsy Associated With Isolated Amygdala Enlargement

BACKGROUND

Mesial temporal lobe epilepsy (mTLE) infrequently presents with isolated amygdala enlargement (AE), but its relevance remains ambiguous. We therefore investigated clinical, imaging, and histopathological findings in mTLE-AE compared to non-lesional mTLE (mTLE-NL) patients, and additionally strategies for identifying AE.

METHODS

We detected AE by automated volumetry of otherwise unremarkable magnetic resonance images of mTLE patients, compared with a healthy comparator. Autoimmune inflammation as an AE cause was excluded using the Graus criteria. We compared clinical and neuropsychological variables between mTLE-AE and mTLE-NL. Secondary assessment of AE was by neuroradiologist visual detection.

RESULTS

Of 63 mTLE patients, 15 had mTLE-AE. In these, normalized mean volume was 1857.58 mm3 (SD = 207.38) for the left, 1973.09 mm3 (SD = 214.91) for the right amygdala, 2003.34 mm3 (SD = 218.85) for the larger and 1827.34 mm3 (SD = 179.85) for the smaller amygdala. Mean volume in the healthy control subjects was 1853.4 mm3 for the left (SD = 212.44) and 1895.2 mm3 for the right amygdala (SD = 224.29). Clinical parameters including age, sex, epilepsy duration, history of febrile convulsions, drug resistance, neuropsychological performance, surgical outcome, and medications did not differ significantly between mTLE-AE and mTLE-NL. Histopathological findings in mTLE-AE included dysmorphic neurons, potential tumors, and focal cortical dysplasia. Neuroradiologists independently described AE in 37 of 63 mTLE patients.

CONCLUSIONS

mTLE-AE has no specific clinical profile compared to non-lesional mTLE and features diverse underlying pathologies. Volumetric detection appears more conservative than conventional qualitative visual analysis, but may miss cases of subtle AE. Combining automated volumetry with visual assessment may improve AE detection.

The mind & muscles: Introducing a validated EEG/EMG protocol for recording cognitive-muscular interactions in experimental archaeology

Despite extensive research into the biomechanical and cognitive dimensions of early hominin material culture, no study has explored these aspects together in the context of stone tool production and use. In contrast to fields like rehabilitation and sports science, where electroencephalography (EEG) and surface electromyography (sEMG) are often integrated, experimental archaeology lacks such a combined approach. This paper introduces and validates a new protocol that integrates EEG and sEMG to measure neuromechanical activity during a classic stone tool task: cutting leather with a flake. Our experimental design divides the task into three phases: Hold, Aim, and Execute. Consistent with our expectations, results show that all eight muscles are most active during task execution, with the non-dominant hand playing a key role in stabilization during both the Aim and Execute phases. In the preparatory Aim stage, we observed increased beta power in the left frontal region (linked to planning, problem-solving, and working memory) as well as heightened motor activity associated with using the non-dominant hand, which contributes to the stabilization of the target material during this stage. During the Execute phase, beta power in these cortical areas decreased, with peak muscle activation occurring alongside suspected beta desynchronization in the motor region, reflecting intensified movement activity. Overall, these findings closely align with our expectations, validating our combined EEG-sEMG protocol and highlighting the importance of segmenting tool-using tasks into distinct phases, which allows for the identification of dynamic brain-hand interactions throughout the process. The proposed step-by-step protocol offers a new methodological basis for future research into the complexities of hominin behaviors and tool use.

Neuromodulation through brain stimulation-assisted cognitive training in patients with post-chemotherapy subjective cognitive impairment (Neuromod-PCSCI) after breast cancer: study protocol for a double-blinded randomised controlled trial

INTRODUCTION

Breast cancer is the most common form of cancer in women. A considerable number of women with breast cancer who have been treated with chemotherapy subsequently develop neurological symptoms such as concentration and memory difficulties (also known as 'chemobrain'). Currently, there are no validated therapeutic approaches available to treat these symptoms. Cognitive training holds the potential to counteract cognitive impairment. Combining cognitive training with concurrent transcranial direct current stimulation (tDCS) could enhance and maintain the effects of this training, potentially providing a new approach to treat post-chemotherapy subjective cognitive impairment (PCSCI). With this study, we aim to investigate the effects of multi-session tDCS over the left dorsolateral prefrontal cortex in combination with cognitive training on cognition and quality of life in women with PCSCI.

METHODS AND ANALYSIS

The Neuromod-PCSCI trial is a monocentric, randomised, double-blind, placebo-controlled study. Fifty-two women with PCSCI after breast cancer therapy will receive a 3-week tDCS-assisted cognitive training with anodal tDCS over the left dorsolateral prefrontal cortex (target intervention), compared with cognitive training plus sham tDCS (control intervention). Cognitive training will consist of a letter updating task. Primary outcome will be the performance in an untrained task (n-back task) after training. In addition, feasibility, safety and tolerability, as well as quality of life and performance in additional untrained tasks will be investigated. A follow-up visit will be performed 1 month after intervention to assess possible long-term effects. In an exploratory approach, structural and functional MRI will be acquired before the intervention and at post-intervention to identify possible neural predictors for successful intervention.

ETHICS AND DISSEMINATION

Ethical approval was granted by the ethics committee of the University Medicine Greifswald (BB236/20). Results will be available through publications in peer-reviewed journals and presentations at national and international conferences.

TRIAL REGISTRATION NUMBER

ClinicalTrials.gov; NCT04817566, registered on 26 March 2021.

Functional language lateralization during sentence completion in the healthy brain is not associated with the quantitative estimate of familial sinistrality

Familial sinistrality (left-handedness) has been suggested as a proxy for functional language lateralization in the healthy adult brain. Previous studies show that individuals with familial sinistrality tend to have less lateralized language-related brain activation, while individuals without familial sinistrality show greater left-hemispheric lateralization for language. However, familial sinistrality trait has always been treated as a binary categorical variable. In this study a more sensitive quantitative estimate of familial sinistrality (LH load) has been modelled in 39 participants with different direction and degree of handedness by applying a standard genetic multifactorial model. This LH load was tested for an association with functional language lateralization based on an fMRI sentence completion task. Using frequentist and Bayesian statistical frameworks, the association between LH load and language lateralization was not confirmed. The findings of the present research suggest that a quantitative measure of familial sinistrality is not related to individual language representation in the brain measured by a sentence completion fMRI paradigm. However, considering the context of our study and previous research we suggest that familial sinistrality being related to personal handedness could drive functional language lateralization through it.

Predictive coding and dimension-selective attention enhance the lateralization of spoken language processing

Hemispheric lateralization in speech and language processing exemplifies functional brain specialization. Seminal work in patients with left hemisphere damage highlighted the left-hemispheric dominance in language functions. However, speech processing is not confined to the left hemisphere. Hence, some researchers associate lateralization with auditory processing asymmetries: slow temporal and fine spectral acoustic information is preferentially processed in right auditory regions, while faster temporal information is primarily handled by left auditory regions. Other scholars posit that lateralization relates more to linguistic processing, particularly for speech and speech-like stimuli. We argue that these seemingly distinct accounts are interdependent. Linguistic analysis of speech relies on top-down processes, such as predictive coding and dimension-selective auditory attention, which enhance lateralized processing by engaging left-lateralized sensorimotor networks. Our review highlights that lateralization is weaker for simple sounds, stronger for speech-like sounds, and strongest for meaningful speech. Evidence shows that predictive speech processing and selective attention enhance lateralization. We illustrate that these top-down processes rely on left-lateralized sensorimotor networks and provide insights into the role of these networks in speech processing.

Dynamics and concordance alterations of intrinsic brain activity indices in stroke-induced Broca's aphasia varies based on first language: A resting-state fMRI analysis

OBJECTIVE

This study aimed to investigate the changes in intrinsic brain activity (IBA) among individuals with Broca aphasia (BA) after a stroke.

METHODS

We collected information from 60 participants. The participants were categorized into four groups according to language (Uyghur and Chinese) and BA status (BA and healthy): Uyghur aphasia patients (UA), Uyghur healthy control subjects (UH), Chinese aphasia patients (CA), and Chinese healthy control subjects (CH). Each group comprised 15 individuals. The shifting dynamics and concordance of regional IBA indices were examined via sliding time-window analysis. A two-way analysis of variance (ANOVA) was conducted with the IBA indices to test for regions with interactions between language and BA status. Partial correlation analysis was employed to evaluate the relationships between various indices and language behaviors.

RESULTS

Participants with head motion exceeding 3 mm translation or 3° rotation were excluded, leaving 9, 12, 13, and 15 participants in the UA, CA, UH, and CH groups, respectively. Seven IBA indices were activated in 16 brain regions in the four groups. In detail, two-way ANOVA revealed a significant interaction between language and BA status in four IBA dynamic indices (amplitude of low-frequency fluctuations (ALFF), Regional homogeneity (ReHo), degree centrality (DC), and functional connectivity (FC)) in 11 brain regions (P < 0.000). For the other three dynamic indices (fractional amplitude of low-frequency fluctuation (fALFF), Voxel-mirrored homotopic connectivity (VMHC), and Global signal connectivity (GSCorr)), no interaction was observed among the four groups. However, the main effect analysis of the BA state demonstrated significant differences across a total of six brain regions (P < 0.000). The concordance alterations in fALFF, ReHo, VMHC, DC, and GSCorr in the right calcarine fissure and the surrounding cortex were significantly lower in CA than in CH (P = 0.000), significantly higher in UA than in CA (P = 0.025), and significantly lower in UH than CH (P = 0.000).

CONCLUSION

In conclusion, alterations in IBA dynamics and concordance were observed in individuals from UA, UH, CA, and CH. These findings suggest that the IBA dynamic index varies across brain regions of BA patients with different local languages, providing a novel perspective for investigating brain alterations by analyzing temporal dynamics using rs-fMRI data.

A new instrument for the assessment of laterality: evidence from confirmatory analysis

Despite its importance, the assessment of laterality in scientific and clinical contexts remains inconsistent. Many studies rely on self-reports or outdated questionnaires (in terms of daily-related actions), often neglecting lateralization of the lower limbs, eyes, and ears without considering the four effectors at the same time. To address these limitations, we developed the Florence Laterality Inventory (FLI), a 16-item scale designed to provide a comprehensive assessment of hand, foot/leg, eye, and ear preference through more contemporary and relevant questions. Our study, conducted with 225 participants, confirmed a four-factor structure through confirmatory factor analysis (CFA), demonstrating good reliability for the hand, eye, and ear subscales and, to a lesser extent, also for foot/leg. Correlations with established measures of laterality and handedness supported the concurrent validity of the scale. The FLI scale offers an updated multidimensional instrument to measure lateralization, addressing the shortcomings of previous questionnaires and adapting to modern contexts.

Cortical neural activity during responses to mechanical perturbation: Effects of hand preference and hand used

Handedness is an important feature of human behavioral lateralization that has often been associated with hemispheric specialization. Existing neuroimaging research on the effect of handedness during motor control has focused on well-practiced or predictable tasks, but not tasks that involve unpredictable perturbations. We examined the extent to which handedness (measured by self-reported hand preference) and whether the dominant hand is used or not influence the motor and neural response during unimanual voluntary corrective actions. The experimental task involved controlling a robotic manipulandum to move a cursor from a center start point to a target presented above or below the start. In some trials, a mechanical perturbation of the hand was randomly applied by the robot either consistent or against the target direction, while electroencephalography (EEG) was recorded. Fourteen left-handers and fourteen right-handers completed the experiment. Left-handed individuals had a greater negative peak in the frontal event-related potential (ERP) during the initial voluntary response stage (N140) than right-handed individuals. Furthermore, left-handed individuals showed more symmetrical ERP distributions between two hemispheres than right-handed individuals in the frontal and parietal regions during the late voluntary response stage (P380). To the best of our knowledge, this is the first evidence to demonstrate the differences in the cortical control of voluntary corrective actions between left-handers and right-handers.

Long-Term Outcome and Social-Intellectual Ability of Patients With Basal Ganglia Germinoma

BACKGROUND

In this study, we aimed at delineating the still ambiguous clinical characteristics and long-term outcomes of basal ganglia (BG) germinoma from the aspect of recurrence-free survival as well as social and intellectual activity.

METHODS

We retrospectively reviewed medical records and imaging data for 12 patients with BG germinoma diagnosed and treated between 1996 and 2020, collecting the most recent status via medical records or telephone from the patients.

RESULTS

The tumors involved the right and left sides and bilateral locations in three, seven, and two cases, respectively. The median follow-up period was 179 months. Six patients exhibited onset neuropsychologic symptoms, for example, cognitive decline or behavior disorder. We evaluated the intelligence quotient (IQ) in 10 patients and observed significantly lower IQ scores in six patients with neuropsychologic symptoms. Patients with right-sided lesions displayed average IQ levels (median 106), whereas those with left-sided or bilateral lesions had reduced IQ (median 67). A complete response was achieved by primary chemoradiotherapy in all patients. Three patients who underwent focal or whole-ventricle irradiation experienced recurrence, whereas no recurrence was observed in patients who received whole-brain irradiation (WBI). Concerning the neurocognitive outcomes, three and six patients with unilateral right and left lesions were living self-independently (Karnofsky Performance Status [KPS] ≧ 70), whereas the three remaining patients (one with left and two with bilateral lesions) had a dependent status (KPS <70).

CONCLUSIONS

WBI is crucial for disease control in BG germinoma. Furthermore, lesion laterality might affect neuropsychologic symptoms including IQ at diagnosis and neurocognitive outcomes in BG germinoma.

Brain asymmetry and its association with inattention and heritability during neurodevelopment

The relationship between brain asymmetry and inattention, and their heritability is not well understood. Utilizing advanced neuroimaging, we examined brain asymmetry with data from the Adolescent Brain Cognitive Development (ABCD; n = 8943; 9-10 y) and the Human Connectome Project (HCP) cohorts (n = 1033; 5-100 y). Data-driven metrics from resting-state fMRI and morphometrics revealed reproducible and stable brain asymmetry patterns across the lifespan. In children, high levels of inattention were highly heritable (61%) and linked to reduced leftward asymmetry of functional connectivity in the dorsal posterior superior temporal sulcus (dpSTS), a region interconnected with a left-lateralized language network. However, reduced dpSTS asymmetry had low heritability (16%) and was associated with lower cognitive performance suggesting that non-genetic factors, such as those mediating cognitive performance, might underlie its association with dpSTS asymmetry. Interventions that enhance cognition might help optimize brain function and reduce inattention.

Right-Lateralization of the Visual Word Form Area after Left-Hemisphere Perinatal Stroke

In literate adults, an area along the left posterior fusiform gyrus that is often referred to as the "visual word form area" (VWFA) responds particularly strongly to written characters compared with other visually similar stimuli. Theoretical accounts differ in whether they attribute the strong left-lateralization of the VWFA to a left-hemisphere (LH) bias toward visual features used in script, to competition of visual word form processing with that of other visual stimuli processed in the same general cortical territory (especially faces), or to the well established left-lateralization of the language system. Here we used functional magnetic resonance imaging to test the last hypothesis by investigating lateralization of the VWFA in participants (male and female) who have right-hemisphere language due to a large LH perinatal stroke. Demographically matched controls were included for comparison. All participants had intact language skills and were proficient readers; age at testing ranged from 9.75 years to early adulthood. Activation maps contrasting activation during rapid presentation of pseudowords and pictures of places revealed left-lateralized fusiform activation in controls, as expected. In participants with left-hemisphere perinatal stroke and right-lateralized language, the VWFA was instead found in the right fusiform gyrus, despite the fact that the left-hemisphere tissue normally occupied by the VWFA was intact and responded normally to pictures of places. Region-of-interest analyses confirmed right-lateralization for visual word form processing, both relative to place stimuli and relative to a resting baseline. This provides compelling evidence that the lateralization of the VWFA indeed follows that of the frontotemporal language system.

The Neurocognitive Bases of Meaningful Intransitive Gestures: A Systematic Review and Meta-analysis of Neuropsychological Studies

Researchers and clinicians have long used meaningful intransitive (i.e., not tool-related; MFI) gestures to assess apraxia-a complex and frequent motor-cognitive disorder. Nevertheless, the neurocognitive bases of these gestures remain incompletely understood. Models of apraxia have assumed that meaningful intransitive gestures depend on either long-term memory (i.e., semantic memory and action lexicons) stored in the left hemisphere, or social cognition and the right hemisphere. This meta-analysis of 42 studies reports the performance of 2659 patients with either left or right hemisphere damage in tests of meaningful intransitive gestures, as compared to other gestures (i.e., MFT or meaningful transitive and MLI or meaningless intransitive) and cognitive tests. The key findings are as follows: (1) deficits of meaningful intransitive gestures are more frequent and severe after left than right hemisphere lesions, but they have been reported in both groups; (2) we found a transitivity effect in patients with lesions of the left hemisphere (i.e., meaningful transitive gestures more difficult than meaningful intransitive gestures) but a "reverse" transitivity effect in patients with lesions of the right hemisphere (i.e., meaningful transitive gestures easier than meaningful intransitive gestures); (3) there is a strong association between meaningful intransitive and transitive (but not meaningless) gestures; (4) isolated deficits of meaningful intransitive gestures are more frequent in cases with right than left hemisphere lesions; (5) these deficits may occur in the absence of language and semantic memory impairments; (6) meaningful intransitive gesture performance seems to vary according to the emotional content of gestures (i.e., body-centered gestures and emotional valence-intensity). These findings are partially consistent with the social cognition hypothesis. Methodological recommendations are given for future studies.

Hemispheric co-lateralization of language and spatial attention reduces performance in dual-task

Hemispheric specialization of different functions is proposed to confer evolutionary benefits, yet the behavioral impacts of lateralization and its cognitive and neural mechanisms remain unclear. This study investigated the effect of lateralization pattern between language and spatial attention on dual-task performance and its association with callosal connectivity. Functional lateralization was assessed using fMRI verbal fluency and landmark tasks, and interhemispheric connections were evaluated through diffusion-weighted imaging. The typical lateralization pattern enhanced overall performance and reduced interference in dual-task compared to the co-lateralized pattern (both functions lateralized to one hemisphere). However, no differences were observed between the mirrored pattern (right language dominance and left attention dominance) and the co-lateralized pattern. While callosal connectivity did not significantly differ among groups, a negative correlation was observed between the lateralization degree and callosal connectivity. Our findings partially support the functional crowding hypothesis and offer insights into neurocognitive mechanisms underlying functional reorganization after brain lesions.

Gray matter volume and asymmetry in Broca's and Wernicke's area homologs in chimpanzees (Pan troglodytes) using a probabilistic region of interest approach

Broca's and Wernicke's areas are comprised of Brodmann areas 44, 45 and 22 in the human brain. Because of their roles in higher cognitive and linguistic function, there has been historical and contemporary interest in comparative studies on the morphology and cytoarchitectonic organization in Broca's and Wernicke's between primate species. One challenge to comparative morphological studies between human and nonhuman primates for Broca's and Wernicke's areas is the absence in homologous sulci used to define these regions. To address this limitation, we created probabilistic atlas maps of BA44, BA45 and BA22 based on previously reported cytoarchitectonic maps of these regions in chimpanzees. We then applied the maps to segmented gray matter volume to estimate gray matter within each region and hemisphere. Females were found to have significantly higher gray matter volumes for BA44 and BA45 compared males. Significant negative associations were found between age and gray matter volume for BA44 and BA45 but not BA22. Population-level asymmetries were found for BA44, BA45 and BA22 but there are some limitations in the interpretation of these findings. Lastly, using quantitative genetic analyses, we found significant heritability in the average gray matter volume for BA44 and BA45 but not BA22. The sex and age effects found in chimpanzees are consistent with previous studies in humans.

Cognition in Meningioma: Effects of Tumor Location and Tumor Removal

BACKGROUND

Meningiomas are the most common type of primary intracranial tumor, yet very few studies have assessed the effects of tumor removal.

METHODS

Here we report analysis of patients with meningiomas who underwent routine neuropsychological assessment and surgery at a National Health Service (NHS) hospital in the North East of England over a 6-year period.

RESULTS

Surgical removal of tumors significantly improved both phonemic and semantic verbal fluency and some measures of working memory and declarative memory. There were no signs of deleterious effects of surgery. Postoperative improvements in cognition did not appear to rely upon changes in anxiety and mood.

CONCLUSIONS

In summary, we conclude that tumor removal in meningioma can be associated with some benefits in cognition.

A Neural Network Approach to Identify Left-Right Orientation of Anatomical Brain MRI

PURPOSE

This study presents a novel application of deep learning to enhance the accuracy of left-right orientation identification in anatomical brain MRI scans. Left-right orientation misidentification in brain MRIs presents significant challenges due to several factors, including metadata loss or ambiguity, which often occurs during the de-identification of medical images for research, conversion between image formats, software operations that strip or overwrite metadata, and the use of older imaging systems that stored orientation differently.

METHOD

A three-dimensional convolutional neural network model was trained using 350 MRIs and evaluated on the basis of eight distinct brain MRI databases, totaling 3056 MRIs, to assess its performance across various conditions, including neurodegenerative diseases.

FINDING

The proposed deep-learning framework demonstrated a 99.8% accuracy in identifying the left-right orientation, thus, addressing challenges associated with the loss of orientation metadata. GradCAM was used to visualize areas of the brain where the model focused, demonstrating the importance of the right planum temporale and surrounding areas in judging left-right orientation. The planum temporale is known to exhibit notable left-right asymmetry related to language functions, underscoring the biological validity of the model. The half of the four left-right misidentified MRIs involved notable brain feature variations, such as a large arachnoidal cyst adjacent to the temporal lobe or ventricular asymmetry, indicating areas for further investigation.

CONCLUSION

This approach offers a potential solution to the persistent issue of left-right misorientation in brain MRIs and supports the reliability of neuroscientific research by ensuring accurate data interpretation.

Impaired speaking-induced suppression predicts degraded agency and hallucination severity in schizophrenia

Background

Agency is the awareness of being the originator of one's own thoughts and actions. Patients with schizophrenia (SZ) show deficits in agency that contribute to distortions in reality-monitoring (distinguishing self-generated from externally-produced information) and result in psychotic symptoms. Agency is also critical for speech-monitoring (monitoring what we hear ourselves say while speaking). For example, disruptions in agency that manifest as hallucinations are thought to result from the misattribution of the source of patients' inner thoughts/speech as external voices.

Methods

We used magnetoencephalography (MEG) to assay assess agency during reality-monitoring (RM) and speech-monitoring (SM) tasks. In healthy controls (HC) during SM, the auditory cortical (A1) response is smaller while speaking (speak condition) compared to listening to the same speech (listen condition). This is known as speaking-induced suppression (SIS) M100 response which is measured using MEG 100ms after speech onset.

Results

During RM, SZ (N=30) showed impairments in both self-agency (identification of self-generated information) and external-agency (identification of externally-produced information), compared to HC (N=30). During SM, SZ failed to enhance M100 A1 responses during the listen condition and suppress M100 A1 responses while speaking, revealing impaired SIS. Weakened SIS predicted worsening hallucination severity.

Conclusions

SZ showed degraded neural M100 responses in A1 during the listen condition which drove impaired suppression of M100 SIS during highly-predictable self-generated speech. Impaired SIS induced noisier auditory sensory predictions, making it more likely for SZ to misattribute the source of inner thoughts/speech as externally-derived, giving rise to disruptions in agency during RM and more severe hallucinations.

Intrahemispheric White Matter Asymmetries and Interhemispheric Connections Underlying the Lateralization of Language Production and Spatial Attention in Left-Handers

Leftward language production and rightward spatial attention are salient features of functional organization in most humans, but their anatomical basis remains unclear. Interhemispheric connections and intrahemispheric white matter asymmetries have been proposed as important factors underlying functional lateralization. To investigate the role of white matter connectivity in functional lateralization, we first identified 96 left-handers using visual half field naming tasks. They were then divided into atypical and typical functional dominance based on the lateralization of brain activation in a word generation task (for language production) and a landmark task (for spatial attention). Using a novel fixel-based framework, we obtained fiber-specific properties of white matter pathways. Results showed, first, that differences between two language dominance groups occurred in the asymmetry of the superior longitudinal fasciculus-III (SLF-III), whereas differences between two spatial attention dominance groups occurred in the rostrum and rostral body of the corpus callosum. However, the directions of functional lateralization were not associated with the directions of white matter asymmetries. Second, the degree of language lateralization was predicted by SLF-III asymmetry and the rostral body of the corpus callosum, whereas the degree of spatial attention lateralization was predicted by the rostrum of the corpus callosum. Notably, the degree of each functional lateralization was negatively correlated with the anterior and middle callosal connections, supporting the excitatory model of the corpus callosum. The results suggest that language lateralization is shaped by a combined effect of intra- and interhemispheric connections, whereas spatial attention lateralization relies more on interhemispheric connections.

Functional and structural brain asymmetries in language processing

The lateralization of language to the left hemisphere of the human brain constitutes one of the classic examples of asymmetry in biology. At the same time, it is also commonly understood that damage to the left hemisphere does not lead to a complete loss of all linguistic abilities. These seemingly contradictory findings indicate that neither our cognitive capacity for language nor its neural substrates are monolithic. This chapter reviews the functional and structural lateralization of the neural substrates of different aspects of language as revealed in the past decades by neuroimaging research. Most aspects of language processing indeed tend to be functionally lateralized to the left hemisphere in the adult human brain. Nevertheless, both hemispheres exhibit a certain equipotentiality with regard to some aspects of language processing, especially with regard to processing meaning and sound. In contrast, the so-called "core language network" in the left hemisphere constitutes a functional and structural asymmetry: This network (i) is crucial for a core aspect of language processing, namely syntax, which refers to the generation of hierarchically structured representations of utterances linking meaning and sound, (ii) matures in accordance with a genetically determined biologic matrix, and (iii) its emergence may have constituted a prerequisite for the evolution of the human language capacity.

Handedness and brain asymmetries in nonhuman primates

A majority of humans are right-handed and exhibit left hemisphere specialization for the comprehension and production of language. To what extent population-level behavioral and brain asymmetries are unique to humans remains a topic of interest across a wide range of scientific disciplines. In this chapter, we present current findings on the expression of population-level behavioral and brain asymmetries in nonhuman primates. We further present data on the association between communication functions, and especially gestures and individual variation in neuroanatomic asymmetries in nonhuman primates, with an emphasis on data from chimpanzees and baboons. The collective data are interpreted within the context of different theories on the evolution of language lateralization.

Brain activation patterns in normal hearing adults: An fNIRS Study using an adapted clinical speech comprehension task

OBJECTIVES

Understanding brain processing of auditory and visual speech is essential for advancing speech perception research and improving clinical interventions for individuals with hearing impairment. Functional near-infrared spectroscopy (fNIRS) is deemed to be highly suitable for measuring brain activity during language tasks. However, accurate data interpretation also requires validated stimuli and behavioral measures.

DESIGN

Twenty-six adults with normal hearing listened to sentences from the Oldenburg Sentence Test (OLSA), and brain activation in the temporal, occipital, and prefrontal areas was measured by fNIRS. The sentences were presented in one of the four different modalities: speech-in-quiet, speech-in-noise, audiovisual speech or visual speech (i.e., lipreading). To support the interpretation of our fNIRS data, and to obtain a more comprehensive understanding of the study population, we performed hearing tests (pure tone and speech audiometry) and collected behavioral data using validated questionnaires, in-task comprehension questions, and listening effort ratings.

RESULTS

In the auditory conditions (i.e., speech-in-quiet and speech-in-noise), we observed cortical activity in the temporal regions bilaterally. During the visual speech condition, we measured significant activation in the occipital area. Following the audiovisual condition, cortical activation was observed in both regions. Furthermore, we established a baseline for how individuals with normal hearing process visual cues during lipreading, and we found higher activity in the prefrontal cortex in noise conditions compared to quiet conditions, linked to higher listening effort.

CONCLUSIONS

We demonstrated the applicability of a clinically inspired audiovisual speech-comprehension task in participants with normal hearing. The measured brain activation patterns were supported and complemented by objective and behavioral parameters.

Unveiling the hemispheric specialization of language: Organization and neuroplasticity

The advancements in understanding hemispheric specialization of language (HSL) have been following two primary avenues: the development of neuroimaging techniques and the study of its reorganizations in patients with various neuropathologic conditions. Hence, the objectives of this chapter are twofold. First, to provide an overview of the key neuroimaging techniques employed to investigate HSL, along with the notable findings derived from them in the healthy population. Second, it focuses on the reorganization of HSL in physiologic (healthy aging) and pathologic (poststroke aphasia and temporal lobe epilepsy) conditions. The chapter emphasizes the importance of employing multimodal methodologies to comprehend the complex relationship between underlying HSL mechanisms affected by disease and resulting language impairments. Combining the neuroimaging techniques can help us understand how different characteristics of language networks combine into general mechanisms that support their plasticity. Nevertheless, it highlights the need for standardized HSL metrics, as the absence of such metrics poses challenges in synthesizing findings across studies. Additionally, while HSL findings are being accumulated, albeit multimodal, there is a lack of integration within a robust theoretical framework. In conclusion, there is a need for novel models acknowledging multimodal aspects of HSL while positioning it within the context of other cognitive functions.

Improved Navigation Performance Through Memory Triggering Maps: A Neurocartographic Approach

When using navigation devices the "cognitive map" created in the user's mind is much more fragmented, incomplete and inaccurate, compared to the mental model of space created when reading a conventional printed map. As users become more dependent on digital devices that reduce orientation skills, there is an urgent need to develop more efficient navigation systems that promote orientation skills. This paper proposes to consider brain processes for creating more efficient maps that use a network of optimally located cardinal lines and landmarks organized to support and stabilize the neurocognitive structures in the brain that promote spatial orientation. This new approach combines neurocognitive insights with classical research on the efficiency of cartographic visualizations. Recent neuroscientific findings show that spatially tuned neurons could be linked to navigation processes. In particular, the activity of grid cells, which appear to be used to process metric information about space, can be influenced by environmental stimuli such as walls or boundaries. Grid cell activity could be used to create a new framework for map-based interfaces that primarily considers the brain structures associated with the encoding and retrieval of spatial information. The new framework proposed in this paper suggests to arrange map symbols in a specific way that the map design helps to stabilize grid cell firing in the brain and by this improve spatial orientation and navigational performance. Spatially oriented cells are active in humans not only when moving in space, but also when imagining moving through an area-such as when reading a map. It seems likely that the activity of grid cells can be stabilized simply by map symbols that are perceived when reading a map.

Anatomical-based classification of dorsolateral parametrectomy for deep endometriosis. Correlation with surgical complications and functional outcomes: A single- center prospective study

OBJECTIVE

To evaluate complication rate and functional outcomes of nerve-sparing parametrectomy for deep endometriosis in relation to the extension of the surgical procedure, based on recognizable anatomical landmarks.

METHODS

This was a prospective single-center study including all patients undergoing parametrectomy for deep endometriosis from September 2020 to June 2023 at our tertiary center. Dorsolateral parametrectomies were divided into parametrectomies medial to the presacral fascia and cranial to the medial rectal artery (superficial parametrectomy), and parametrectomies in which one of the two landmarks was overcome during the surgical procedure, leading to the excision of tissue lateral to the presacral fascia (deep parametrectomy type 1, or DP1) or caudal to the medial rectal artery (DP2). Finally, we used the hypogastric fascia as landmark to define type 3 deep parametrectomy (DP3), when the procedure was deeply lateral to the fascia.

RESULTS

Bladder voiding deficit occurred in 9.7% of cases, with higher rates in DP2 (20.8%) and DP3 (30%) groups. Regarding postoperative gastrointestinal function, our data showed a significant improvement over time in all groups, with the exception of DP2; instead an improvement in postoperative bladder function was only shown in DP3. Parametrectomy was not associated with a simultaneous improvement in sexual function expressed with the female sexual function index, in any of the four groups.

CONCLUSION

Our classification constitutes a concrete approach for comparing, in a standardized way, the complications and functional outcomes of parametrectomy, which, even if carried out by expert surgeons, demonstrates a non-negligible rate of bladder voiding deficit.

Cortical neural activity during responses to mechanical perturbation: Effects of hand preference and hand used

Handedness, as measured by self-reported hand preference, is an important feature of human behavioral lateralization that has often been associated with hemispheric specialization. We examined the extent to which hand preference and whether the dominant hand is used or not influence the motor and neural response during voluntary unimanual corrective actions. The experimental task involved controlling a robotic manipulandum to move a cursor from a center start point to a target presented above or below the start. In some trials, a mechanical perturbation of the hand was randomly applied by the robot either consistent or against the target direction, while electroencephalography (EEG) was recorded. Twelve left-handers and ten right-handers completed the experiment. Left-handed individuals had a greater negative peak in the frontal event-related potential (ERP) than right-handed participants during the initial response phase (N150) than right-handed individuals. Furthermore, left-handed individuals showed more symmetrical ERP distributions between two hemispheres than right-handed individuals in the frontal and parietal regions during the late voluntary response phase (P390). To the best of our knowledge, this is the first evidence that demonstrates the differences in the cortical control of voluntary corrective actions between left-handers and right-handers.

Functional partitioning of sentence processing and emotional prosody in the right perisylvian cortex after perinatal stroke

In healthy adults different language abilities-sentence processing versus emotional prosody-are supported by the left (LH) versus the right hemisphere (RH), respectively. However, after LH stroke in infancy, RH regions often support both abilities with normal outcomes. This finding raises an important question: How does the functional map of RH regions change to support both emotional prosody and also typically left-lateralized language functions after an early LH stroke? Does sentence processing simply become reflected into RH frontotemporal regions and overlap with emotional prosody processing? Or do these functions overlap less than would be expected with simple mirroring? In the current work we used task fMRI to examine precisely how sentence processing and emotional prosody processing are both organized in the intact RH of individuals who suffered a large LH perinatal arterial ischemic stroke (LHPS participants). We evaluated the activation of two fMRI tasks that probed auditory sentence processing and emotional prosody processing, comparing the overlap for these two functions in the RH of individuals with perinatal stroke with the symmetry of these functions in the LH and RH of their healthy siblings. We found less activation overlap in the RH of individuals with LH perinatal stroke than would be expected if both functions retained their typical spatial layout, suggesting that their spatial segregation may be an important feature of a functioning language system.

Language Dominance in Left-Handers: Unveiling Left Hemisphere Global Dominance With Specific Right Hemisphere Regional Dominance

Introduction The degree to which each human brain hemisphere governs specific cognitive processes, such as language and handedness (the preference or dominance of one hand over the other), varies across individuals. Research has explored the nature of language laterality in left-handed (LH) individuals, indicating that left-hemisphere dominance for language is commonly observed across both left- and right-handed populations. Advanced imaging techniques, including functional transcranial Doppler sonography and fMRI, have revealed subtle differences in language lateralization between LH and right-handed (RH) individuals, particularly in semantic processing tasks. These findings underscore the complex relationship between handedness and language lateralization. This study investigates the spatial patterns of language lateralization in LH and RH individuals using high-resolution fMRI data and the Human Connectome Project (HCP) multimodal parcellation (MMP).  Method We utilized pre-processed MRI scans from the HCP database, comprising 140 healthy young adults, with 70 individuals in each of the RH and LH groups. The language task includes two contrasts: the STORY contrast, where participants listened to brief auditory stories compared to a baseline, and the STORY-MATH contrast, where participants listened to stories versus solving addition and subtraction problems. Data processing involved the HCP Pipelines and the MMP atlas was applied for analysis. The Edinburgh Handedness Inventory categorized participants as either LH or RH. For analysis, we focused on the number of brain surface elements (3D surface vertices) with positive elements (PEs) within each brain region, indicating blood-oxygen-level-dependent (BOLD) activity. The study's methodology aimed to quantify and compare PEs across the hemispheres (paired sample) and handedness groups (independent sample), providing insights into language lateralization. Statistical analysis involved Mann-Whitney U tests for differences across gender and handedness groups and robust t-tests for hemispheric dominance. Results were visualized by projecting mean and effect size values onto a 3D brain surface. Results The analysis of hemispheric mean differences in PEs revealed robust left hemisphere dominance in both the STORY and STORY-MATH contrasts among the RH group, while the LH group exhibited more balanced activity. Significant variations in PEs were observed across numerous MMP regions, with LH individuals showing pronounced asymmetry in 67 and 76 MMP regions (out of 180 regions) in the STORY and STORY-MATH contrasts, respectively, compared to 83 and 99 regions in RH individuals. Additionally, when comparing LH and RH groups, significant differences in PEs were identified within 14 MMP regions (out of 360 regions), all demonstrating significant asymmetry in LH individuals and primarily located in the right hemisphere (12 regions), notably in the inferior parietal lobule (Brodmann 39 and 40). No differences were found in the STORY-MATH contrast. Conclusion We identified hemispheric left-lateralization dominance in brain areas associated with language processing, irrespective of handedness. However, employing multimodal brain parcellation with fMRI language tasks unveiled notable differences in specific regions. Particularly striking was the heightened activity observed in certain right hemisphere regions among LH individuals.

Static and dynamic changes in amplitude of Low-Frequency fluctuations in patients with Self-Limited epilepsy with centrotemporal Spikes (SeLECTS): A Resting-State fMRI study

OBJECTIVE

This study aims to explore differences in the static and dynamic amplitude of low-frequency fluctuations (sALFF and dALFF) in resting-state functional MRI (rs-fMRI) data between patients with Benign childhood epilepsy with centrotemporal spikes (SeLECTS) and healthy controls (HCs).

MATERIALS AND METHODS

We recruited 45 patient with SeLECTS and 55 HCs, employing rs-fMRI to assess brain activity. The analysis utilized a two-sample t-test for primary comparisons, supplemented by stratification and matching based on clinical and demographic characteristics to ensure comparability between groups. Post hoc analyses assessed the relationships between sALFF/dALFF alterations and clinical demographics, incorporating statistical adjustments for potential confounders and performing sensitivity analysis to test the robustness of our findings.

RESULTS

Our analysis identified significant differences in sALFF and dALFF between patient with SeLECTS and HCs. Notably, increases in sALFF and dALFF were observed in the right middle temporal gyrus and left superior temporal gyrus among patient with SeLECTS, while a decrease in dALFF was seen in the right cerebellum crus 1. Additionally, a positive correlation was found between abnormal dALFF variability in specific brain regions and various clinical and demographic factors of patient with SeLECTS, with age being one such influential factor.

CONCLUSION

This investigation provides insights into the assessment of local brain activity in SeLECTS through both static and dynamic approaches. It highlights the significance of non-invasive neuroimaging techniques in understanding the complexities of epilepsy syndromes like SeLECTS and emphasizes the need to consider a range of clinical and demographic factors in neuroimaging studies of neurological disorders.

Identification of perceived sentences using deep neural networks in EEG

Objetive. Decoding speech from brain activity can enable communication for individuals with speech disorders. Deep neural networks (DNNs) have shown great potential for speech decoding applications. However, the limited availability of large datasets containing neural recordings from speech-impaired subjects poses a challenge. Leveraging data from healthy participants can mitigate this limitation and expedite the development of speech neuroprostheses while minimizing the need for patient-specific training data.Approach. In this study, we collected a substantial dataset consisting of recordings from 56 healthy participants using 64 EEG channels. Multiple neural networks were trained to classify perceived sentences in the Spanish language using subject-independent, mixed-subjects, and fine-tuning approaches. The dataset has been made publicly available to foster further research in this area.Main results. Our results demonstrate a remarkable level of accuracy in distinguishing sentence identity across 30 classes, showcasing the feasibility of training DNNs to decode sentence identity from perceived speech using EEG. Notably, the subject-independent approach rendered accuracy comparable to the mixed-subjects approach, although with higher variability among subjects. Additionally, our fine-tuning approach yielded even higher accuracy, indicating an improved capability to adapt to individual subject characteristics, which enhances performance. This suggests that DNNs have effectively learned to decode universal features of brain activity across individuals while also being adaptable to specific participant data. Furthermore, our analyses indicate that EEGNet and DeepConvNet exhibit comparable performance, outperforming ShallowConvNet for sentence identity decoding. Finally, our Grad-CAM visualization analysis identifies key areas influencing the network's predictions, offering valuable insights into the neural processes underlying language perception and comprehension.Significance. These findings advance our understanding of EEG-based speech perception decoding and hold promise for the development of speech neuroprostheses, particularly in scenarios where subjects cannot provide their own training data.

Handedness in Alzheimer's disease: A systematic review

Handedness has traditionally been employed as a proxy of brain lateralization in research. Alzheimer's disease (AD) manifests as a neurodegenerative disorder characterized by impairments across various neuropsychological functions, including visuospatial and language, many of which exhibit lateralization in the human brain. While previous studies have investigated the relationship between AD and handedness, findings have been inconsistent. This article aims to provide an up-to-date overview of studies investigating hand preference in AD and the subtypes, specifically early- and late-onset AD. Through a synthesis of these studies, we conclude that handedness currently lacks utility as a diagnostic biomarker for AD and its subtypes, and this is further supported by the meta-analytic results based on data from over 10,000 AD patients. We emphasize the necessity for future research endeavors, particularly those leveraging advanced neuroimaging techniques to explore the role of brain asymmetry in AD.

Bilateral Deep Brain Stimulation of the Ventral Intermediate Nucleus of the Thalamus Improves Objective Acoustic Measures of Essential Vocal Tremor

BACKGROUND AND OBJECTIVES

Deep brain stimulation of the ventral intermediate nucleus of the thalamus (VIM-DBS) is an established treatment for medically refractory essential tremor. However, the effect of VIM-DBS on vocal tremor remains poorly understood, with results varying by method of vocal tremor assessment and stimulation laterality. This single-center study measures the effect of bilateral VIM-DBS on essential vocal tremor using blinded objective acoustic voice analysis.

METHODS

Ten patients with consecutive essential tremor with comorbid vocal tremor receiving bilateral VIM-DBS underwent voice testing before and after implantation of DBS in this prospective cohort study. Objective acoustic measures were extracted from the middle one second of steady-state phonation including cepstral peak prominence, signal-to-noise ratio, percentage voicing, tremor rate, extent of fundamental frequency modulation, and extent of intensity modulation. DBS surgery was performed awake with microelectrode recording and intraoperative testing. Postoperative voice testing was performed after stable programming.

RESULTS

Patients included 6 female and 4 male, with a mean age of 67 ± 6.7 years. The VIM was targeted with the following coordinates relative to the mid-anterior commissure:posterior commissure point: 13.2 ± 0.6 mm lateral, 6.2 ± 0.7 mm posterior, and 0.0 mm below. Mean programming parameters were amplitude 1.72.0 ± 0.6 mA, pulse width 63.0 ± 12.7 µs, and rate 130.6 ± 0.0 Hz. VIM-DBS significantly improved tremor rate from 4.43 ± 0.8 Hz to 3.2 ± 0.8 Hz ( P = .001) CI (0.546, 1.895), jitter from 1 ± 0.94 to 0.53 ± 0.219 ( P = .02) CI (-0.124, 1.038), cepstral peak prominence from 13.6 ± 3.9 to 18.8 ± 2.9 ( P = .016) CI (-4.100, -0.235), signal-to-noise ratio from 15.7 ± 3.9 to 18.5 ± 3.7 ( P = .02) CI (-5.598, -0.037), and articulation rate from 0.77 ± 0.2 to 0.82 ± .14 ( P = .04) CI (-0.097, 0.008). There were no major complications in this series.

CONCLUSION

Objective acoustic voice analyses suggest that bilateral VIM-DBS effectively reduces vocal tremor rate and improves voicing. Further studies using objective acoustic analyses and laryngeal imaging may help refine surgical and stimulation techniques and evaluate the effect of laterality on vocal tremor.

Atypical lateralization of visuospatial attention can be associated with better or worse performance on line bisection

The causal and statistical hypotheses diverge in determining whether the lateralization of language function in one cerebral hemisphere entails the lateralization of visuospatial function in the opposite hemisphere. Additionally, it remains unclear if the atypical segregation of these functions could influence cognitive performance. This study addresses these questions by examining the hemispheric lateralization of visuospatial attention during a line bisection judgement (landmark) task in three groups of healthy non-right-handed individuals with different language production segregations: left (typical), ambilateral (atypical), and right (atypical). Consistent with the causal hypothesis, results indicate that the groups with left and right language lateralization primarily utilize the opposite hemisphere for visuospatial attention. The ambilateral group, however, displays a pattern compatible with an independent segregation, supporting the statistical hypothesis. Behavioral analyses reveal that atypical lateralization of visuospatial attention (non-right) can lead to either better or worse performance during the landmark task, depending on the specific pattern. Bilateral organization is associated with reduced overall accuracy, whereas the left segregation results in improved performance during the most challenging trials. These findings suggest the existence of diverse pathways to lateralization, akin to either the causal or statistical hypothesis, which can result in cognitive advantages or disadvantages.

An MRI Study of Morphology, Asymmetry, and Sex Differences of Inferior Precentral Sulcus

Numerous studies utilizing magnetic resonance imaging (MRI) have observed sex and interhemispheric disparities in sulcal morphology, which could potentially underpin certain functional disparities in the human brain. Most of the existing research examines the precentral sulcus comprehensively, with a rare focus on its subsections. To explore the morphology, asymmetry, and sex disparities within the inferior precentral sulcus (IPCS), we acquired 3.0T magnetic resonance images from 92 right-handed Chinese adolescents. Brainvisa was used to reconstruct the IPCS structure and calculate its mean depth (MD). Based on the morphological patterns of IPCS, it was categorized into five distinct types. Additionally, we analyzed four different types of spatial relationships between IPCS and inferior frontal sulcus (IFS). There was a statistically significant sex disparity in the MD of IPCS, primarily observed in the right hemisphere. Females exhibited significantly greater asymmetry in the MD of IPCS compared to males. No statistically significant sex or hemispheric variations were identified in sulcal patterns. Our findings expand the comprehension of inconsistencies in sulcal structure, while also delivering an anatomical foundation for the study of related regions' function.

Associations between sex, systemic iron and inflammatory status and subcortical brain iron

Brain iron increases in several neurodegenerative diseases are associated with disease progression. However, the causes of increased brain iron remain unclear. This study investigates relationships between subcortical iron, systemic iron and inflammatory status. Brain magnetic resonance imaging (MRI) scans and blood plasma samples were collected from cognitively healthy females (n = 176, mean age = 61.4 ± 4.5 years, age range = 28-72 years) and males (n = 152, mean age = 62.0 ± 5.1 years, age range = 32-74 years). Regional brain iron was quantified using quantitative susceptibility mapping. To assess systemic iron, haematocrit, ferritin and soluble transferrin receptor were measured, and total body iron index was calculated. To assess systemic inflammation, C-reactive protein (CRP), neutrophil:lymphocyte ratio (NLR), macrophage colony-stimulating factor 1 (MCSF), interleukin 6 (IL6) and interleukin 1β (IL1β) were measured. We demonstrated that iron levels in the right hippocampus were higher in males compared with females, while iron in the right caudate was higher in females compared with males. There were no significant associations observed between subcortical iron levels and blood markers of iron and inflammatory status indicating that such blood measures are not markers of brain iron. These results suggest that brain iron may be regulated independently of blood iron and so directly targeting global iron change in the treatment of neurodegenerative disease may have differential impacts on blood and brain iron.

Tumors Affect the Metabolic Connectivity of the Human Brain Measured by 18 F-FDG PET

PURPOSE

18 F-FDG PET captures the relationship between glucose metabolism and synaptic activity, allowing for modeling brain function through metabolic connectivity. We investigated tumor-induced modifications of brain metabolic connectivity.

PATIENTS AND METHODS

Forty-three patients with left hemispheric tumors and 18 F-FDG PET/MRI were retrospectively recruited. We included 37 healthy controls (HCs) from the database CERMEP-IDB-MRXFDG. We analyzed the whole brain and right versus left hemispheres connectivity in patients and HC, frontal versus temporal tumors, active tumors versus radiation necrosis, and patients with high Karnofsky performance score (KPS = 100) versus low KPS (KPS < 70). Results were compared with 2-sided t test ( P < 0.05).

RESULTS

Twenty high-grade glioma, 4 low-grade glioma, and 19 metastases were included. The patients' whole-brain network displayed lower connectivity metrics compared with HC ( P < 0.001), except assortativity and betweenness centrality ( P = 0.001). The patients' left hemispheres showed decreased similarity, and lower connectivity metrics compared with the right ( P < 0.01), with the exception of betweenness centrality ( P = 0.002). HC did not show significant hemispheric differences. Frontal tumors showed higher connectivity metrics ( P < 0.001) than temporal tumors, but lower betweenness centrality ( P = 4.5 -7 ). Patients with high KPS showed higher distance local efficiency ( P = 0.01), rich club coefficient ( P = 0.0048), clustering coefficient ( P = 0.00032), betweenness centrality ( P = 0.008), and similarity ( P = 0.0027) compared with low KPS. Patients with active tumor(s) (14/43) demonstrated significantly lower connectivity metrics compared with necroses.

CONCLUSIONS

Tumors cause reorganization of metabolic brain networks, characterized by formation of new connections and decreased centrality. Patients with frontal tumors retained a more efficient, centralized, and segregated network than patients with temporal tumors. Stronger metabolic connectivity was associated with higher KPS.

Asymmetries in event-related potentials part 1: A systematic review of face processing studies

The human brain shows distinct lateralized activation patterns for a range of cognitive processes. One such function, which is thought to be lateralized to the right hemisphere (RH), is human face processing. Its importance for social communication and interaction has led to a plethora of studies investigating face processing in health and disease. Temporally highly resolved methods, like event-related potentials (ERPs), allow for a detailed characterization of different processing stages and their specific lateralization patterns. This systematic review aimed at disentangling some of the contradictory findings regarding the RH specialization in face processing focusing on ERP research in healthy participants. Two databases were searched for studies that investigated left and right electrodes while participants viewed (mostly neutral) facial stimuli. The included studies used a variety of different tasks, which ranged from passive viewing to memorizing faces. The final data selection highlights, that strongest lateralization to the RH was found for the N170, especially for right-handed young male participants. Left-handed, female, and older participants showed less consistent lateralization patterns. Other ERP components like the P1, P2, N2, P3, and the N400 were overall less clearly lateralized. The current review highlights that many of the assumed lateralization patterns are less clear than previously thought and that the variety of stimuli, tasks, and EEG setups used, might contribute to the ambiguous findings.

Morphological Features of Language Regions in Individuals with Tuberous Sclerosis Complex

A significant number of individuals with tuberous sclerosis complex (TSC) exhibit language difficulties. Here, we examined the language-related brain morphometry in 59 participants (7 participants with TSC and comorbid autism spectrum disorder (ASD) (TSC + ASD), 13 with TSC but no ASD (TSC-ASD), 10 with ASD-only (ASD), and 29 typically developing (TD) controls). A hemispheric asymmetry was noted in surface area and gray matter volume of several cortical language areas in TD, ASD, and TSC-ASD groups, but not in TSC + ASD group. TSC + ASD group demonstrated increased cortical thickness and curvature values in multiple language regions for both hemispheres, compared to other groups. After controlling for tuber load in the TSC groups, within-group differences stayed the same but the differences between TSC-ASD and TSC + ASD were no longer statistically significant. These preliminary findings suggest that comorbid ASD in TSC as well as tuber load in TSC is associated with changes in the morphometry of language regions. Future studies with larger sample sizes will be needed to confirm these findings.

Handedness in Animals and Plants

Structural and functional asymmetries are traceable in every form of life, and some lateralities are homologous. Functionally speaking, the division of labour between the two halves of the brain is a basic characteristic of the nervous system that arose even before the appearance of vertebrates. The most well-known expression of this specialisation in humans is hand dominance, also known as handedness. Even if hand/limb/paw dominance is far more commonly associated with the presence of a nervous system, it is also observed in its own form in aneural organisms, such as plants. To date, little is known regarding the possible functional significance of this dominance in plants, and many questions remain open (among them, whether it reflects a generalised behavioural asymmetry). Here, we propose a comparative approach to the study of handedness, including plants, by taking advantage of the experimental models and paradigms already used to study laterality in humans and various animal species. By taking this approach, we aim to enrich our knowledge of the concept of handedness across natural kingdoms.

Imagined speech event detection from electrocorticography and its transfer between speech modes and subjects

Speech brain-computer interfaces aim to support communication-impaired patients by translating neural signals into speech. While impressive progress was achieved in decoding performed, perceived and attempted speech, imagined speech remains elusive, mainly due to the absence of behavioral output. Nevertheless, imagined speech is advantageous since it does not depend on any articulator movements that might become impaired or even lost throughout the stages of a neurodegenerative disease. In this study, we analyzed electrocortigraphy data recorded from 16 participants in response to 3 speech modes: performed, perceived (listening), and imagined speech. We used a linear model to detect speech events and examined the contributions of each frequency band, from delta to high gamma, given the speech mode and electrode location. For imagined speech detection, we observed a strong contribution of gamma bands in the motor cortex, whereas lower frequencies were more prominent in the temporal lobe, in particular of the left hemisphere. Based on the similarities in frequency patterns, we were able to transfer models between speech modes and participants with similar electrode locations.

Motor-sensory biases are associated with cognitive and social abilities in humans

Across vertebrates, adaptive behaviors, like feeding and avoiding predators, are linked to lateralized brain function. The presence of the behavioral manifestations of these biases are associated with increased task success. Additionally, when an individual's direction of bias aligns with the majority of the population, it is linked to social advantages. However, it remains unclear if behavioral biases in humans correlate with the same advantages. This large-scale study (N = 313-1661, analyses dependent) examines whether the strength and alignment of behavioral biases associate with cognitive and social benefits respectively in humans. To remain aligned with the animal literature, we evaluate motor-sensory biases linked to motor-sequencing and emotion detection to assess lateralization. Results reveal that moderate hand lateralization is positively associated with task success and task success is, in turn, associated with language fluency, possibly representing a cascade effect. Additionally, like other vertebrates, the majority of our human sample possess a 'standard' laterality profile (right hand bias, left visual bias). A 'reversed' profile is rare by comparison, and associates higher self-reported social difficulties and increased rate of autism and/or attention deficit hyperactivity disorder. We highlight the importance of employing a comparative theoretical framing to illuminate how and why different laterization profiles associate with diverging social and cognitive phenotypes.

Electroconvulsive therapy disrupts functional connectivity between hippocampus and posterior default mode network

BACKGROUND

The mechanisms underlying memory deficits after electroconvulsive therapy (ECT) remain unclear but altered functional interactions between hippocampus and neocortex may play a role.

OBJECTIVES

To test whether ECT reduces functional connectivity between hippocampus and posterior regions of the default mode network (DMN) and to examine whether altered hippocampal-neocortical functional connectivity correlates with memory impairment. A secondary aim was to explore if these connectivity changes are present 6 months after ECT.

METHODS

In-patients with severe depression (n = 35) received bitemporal ECT. Functional connectivity of the hippocampus was probed with resting-state fMRI before the first ECT-session, after the end of ECT, and at a six-month follow-up. Memory was assessed with the Verbal Learning Test - Delayed Recall. Seed-based connectivity analyses established connectivity of four hippocampal seeds, covering the anterior and posterior parts of the right and left hippocampus.

RESULTS

Compared to baseline, three of four hippocampal seeds became less connected to the core nodes of the posterior DMN in the week after ECT with Cohen's d ranging from -0.9 to -1.1. At the group level, patients showed post-ECT memory impairment, but individual changes in delayed recall were not correlated with the reduction in hippocampus-DMN connectivity. At six-month follow-up, no significant hippocampus-DMN reductions in connectivity were evident relative to pre-ECT, and memory scores had returned to baseline.

CONCLUSION

ECT leads to a temporary disruption of functional hippocampus-DMN connectivity in patients with severe depression, but the change in connectivity strength is not related to the individual memory impairment.

Comparative analysis of brain language templates with primary language areas detected from presurgical fMRI of brain tumor patients

INTRODUCTION

Functional brain templates are often used in the analysis of clinical functional MRI (fMRI) studies. However, these templates are mostly built based on anatomy or fMRI of healthy subjects, which have not been fully vetted in clinical cohorts. Our aim was to evaluate language templates by comparing with primary language areas (PLAs) detected from presurgical fMRI of brain tumor patients.

METHODS

Four language templates (A-D) based on anatomy, task-based fMRI, resting-state fMRI, and meta-analysis, respectively, were compared with PLAs detected by fMRI with word generation and sentence completion paradigms. For each template, the fraction of PLA activations enclosed by the template (positive inclusion fraction, [PIF]), the fraction of activations within the template but that did not belong to PLAs (false inclusion fraction, [FIF]), and their Dice similarity coefficient (DSC) with PLA activations were calculated.

RESULTS

For anterior PLAs, Template A had the greatest PIF (median, 0.95), whereas Template D had both the lowest FIF (median, 0.074), and the highest DSC (median, 0.30), which were all significant compared to other templates. For posterior PLAs, Templates B and D had similar PIF (median, 0.91 and 0.90, respectively) and DSC (both medians, 0.059), which were all significantly higher than that of Template C. Templates B and C had significantly lower FIF (median, 0.061 and 0.054, respectively) compared to Template D.

CONCLUSION

This study demonstrated significant differences between language templates in their inclusiveness of and spatial agreement with the PLAs detected in the presurgical fMRI of the patient cohort. These findings may help guide the selection of language templates tailored to their applications in clinical fMRI studies.

Structural changes in eloquent cortex secondary to glioma in sensorimotor area

This study aims to investigate the structural reorganization in the sensorimotor area of the brain in patients with gliomas, distinguishing between those with impaired and unimpaired strength. Using voxel-based morphometry (VBM) and region of interest (ROI) analysis, gray matter volumes (GMV) were compared in the contralesional primary motor gyrus, primary sensory gyrus, premotor area, bilateral supplementary motor area, and medial Brodmann area 8 (BA8). The results revealed that in patients with right hemisphere gliomas, the right medial BA8 volume was significantly larger in the impaired group than in the unimpaired group, with both groups exceeding the volume in 16 healthy controls (HCs). In patients with left hemisphere gliomas, the right supplementary motor area (SMA) was more pronounced in the impaired group compared to the unimpaired group, and both groups were greater than HCs. Additionally, the volumes of the right medial BA8 in both the impaired group were greater than HCs. Contralateral expansions in the gray matter of hand- and trunk-related cortices of the premotor area, precentral gyrus, and postcentral gyrus were observed compared to HCs. Furthermore, a negative correlation was found between hand Medical Research Council (MRC) score and volumes of the contralateral SMA and bilateral medial BA8. Notably, our findings reveal consistent results across both analytical approaches in identifying significant structural reorganizations within the sensorimotor cortex. These consistent findings underscore the adaptive neuroplastic responses to glioma presence, highlighting potential areas of interest for further neurosurgical planning and rehabilitation strategies.

Unveiling the cognitive network organization through cognitive performance

The evaluation of cognitive functions interactions has become increasingly implemented in the cognition exploration. In the present study, we propose to examine the organization of the cognitive network in healthy participants through the analysis of behavioral performances in several cognitive domains. Specifically, we aim to explore cognitive interactions profiles, in terms of cognitive network, and as a function of participants' handedness. To this end, we proposed several behavioral tasks evaluating language, memory, executive functions, and social cognition performances in 175 young healthy right-handed and left-handed participants and we analyzed cognitive scores, from a network perspective, using graph theory. Our results highlight the existence of intricate interactions between cognitive functions both within and beyond the same cognitive domain. Language functions are interrelated with executive functions and memory in healthy cognitive functioning and assume a central role in the cognitive network. Interestingly, for similar high performance, our findings unveiled differential organizations within the cognitive network between right-handed and left-handed participants, with variations observed both at a global and nodal level. This original integrative network approach to the study of cognition provides new insights into cognitive interactions and modulations. It allows a more global understanding and consideration of cognitive functioning, from which complex behaviors emerge.

Considerations for implanting speech brain computer interfaces based on functional magnetic resonance imaging

Objective.Brain-computer interfaces (BCIs) have the potential to reinstate lost communication faculties. Results from speech decoding studies indicate that a usable speech BCI based on activity in the sensorimotor cortex (SMC) can be achieved using subdurally implanted electrodes. However, the optimal characteristics for a successful speech implant are largely unknown. We address this topic in a high field blood oxygenation level dependent functional magnetic resonance imaging (fMRI) study, by assessing the decodability of spoken words as a function of hemisphere, gyrus, sulcal depth, and position along the ventral/dorsal-axis.Approach.Twelve subjects conducted a 7T fMRI experiment in which they pronounced 6 different pseudo-words over 6 runs. We divided the SMC by hemisphere, gyrus, sulcal depth, and position along the ventral/dorsal axis. Classification was performed on in these SMC areas using multiclass support vector machine (SVM).Main results.Significant classification was possible from the SMC, but no preference for the left or right hemisphere, nor for the precentral or postcentral gyrus for optimal word classification was detected. Classification while using information from the cortical surface was slightly better than when using information from deep in the central sulcus and was highest within the ventral 50% of SMC. Confusion matrices where highly similar across the entire SMC. An SVM-searchlight analysis revealed significant classification in the superior temporal gyrus and left planum temporale in addition to the SMC.Significance.The current results support a unilateral implant using surface electrodes, covering the ventral 50% of the SMC. The added value of depth electrodes is unclear. We did not observe evidence for variations in the qualitative nature of information across SMC. The current results need to be confirmed in paralyzed patients performing attempted speech.

A lateralized motor network in order to understand adaptation to visuomotor rotation

Objective.The functional asymmetry between the two brain hemispheres in language and spatial processing is well documented. However, a description of difference in control between the two hemispheres in motor function is not well established. Our primary objective in this study was to examine the distribution of control in the motor hierarchy and its variation across hemispheres.Approach.We developed a computation model termed the bilateral control network and implemented the same in a neural network framework to be used to replicate certain experimental results. The network consists of a simple arm model capable of making movements in 2D space and a motor hierarchy with separate elements coding target location, estimated position of arm, direction, and distance to be moved by the arm, and the motor command sent to the arm. The main assumption made here is the division of direction and distance coding between the two hemispheres with distance coded in the non-dominant and direction coded in the dominant hemisphere.Main results.With this assumption, the network was able to show main results observed in visuomotor adaptation studies. Importantly it showed decrease in error exhibited by the untrained arm while the other arm underwent training compared to the corresponding naïve arm's performance-transfer of motor learning from trained to the untrained arm. It also showed how this varied depending on the performance variable used-with distance as the measure, the non-dominant arm showed transfer and with direction, dominant arm showed transfer.Significance.Our results indicate the possibility of shared control between the two hemispheres. If indeed found true, this result could have major significance in motor rehabilitation as treatment strategies will need to be designed in order to account for this and can no longer be confined to the arm contralateral to the affected hemisphere.

Gender differences in the functional language networks at birth: a resting-state fNIRS study

Numerous studies reported inconsistent results concerning gender influences on the functional organization of the brain for language in children and adults. However, data for the gender differences in the functional language networks at birth are sparse. Therefore, we investigated gender differences in resting-state functional connectivity in the language-related brain regions in newborns using functional near-infrared spectroscopy. The results revealed that female newborns demonstrated significantly stronger functional connectivities between the superior temporal gyri and middle temporal gyri, the superior temporal gyri and the Broca's area in the right hemisphere, as well as between the right superior temporal gyri and left Broca's area. Nevertheless, statistical analysis failed to reveal functional lateralization of the language-related brain areas in resting state in both groups. Together, these results suggest that the onset of language system might start earlier in females, because stronger functional connectivities in the right brain in female neonates were probably shaped by the processing of prosodic information, which mainly constitutes newborns' first experiences of speech in the womb. More exposure to segmental information after birth may lead to strengthened functional connectivities in the language system in both groups, resulting in a stronger leftward lateralization in males and a more balanced or leftward dominance in females.

Mapping brain function in adults and young children during naturalistic viewing with high-density diffuse optical tomography

Human studies of early brain development have been limited by extant neuroimaging methods. MRI scanners present logistical challenges for imaging young children, while alternative modalities like functional near-infrared spectroscopy have traditionally been limited by image quality due to sparse sampling. In addition, conventional tasks for brain mapping elicit low task engagement, high head motion, and considerable participant attrition in pediatric populations. As a result, typical and atypical developmental trajectories of processes such as language acquisition remain understudied during sensitive periods over the first years of life. We evaluate high-density diffuse optical tomography (HD-DOT) imaging combined with movie stimuli for high resolution optical neuroimaging in awake children ranging from 1 to 7 years of age. We built an HD-DOT system with design features geared towards enhancing both image quality and child comfort. Furthermore, we characterized a library of animated movie clips as a stimulus set for brain mapping and we optimized associated data analysis pipelines. Together, these tools could map cortical responses to movies and contained features such as speech in both adults and awake young children. This study lays the groundwork for future research to investigate response variability in larger pediatric samples and atypical trajectories of early brain development in clinical populations.

Detection of Language Lateralization Using Spectral Analysis of EEG

PURPOSE

Language lateralization relies on expensive equipment and can be difficult to tolerate. We assessed if lateralized brain responses to a language task can be detected with spectral analysis of electroencephalography (EEG).

METHODS

Twenty right-handed, neurotypical adults (28 ± 10 years; five males) performed a verb generation task and two control tasks (word listening and repetition). We measured changes in EEG activity elicited by tasks (the event-related spectral perturbation [ERSP]) in the theta, alpha, beta, and gamma frequency bands in two language (superior temporal and inferior frontal [ST and IF]) and one control (occipital [Occ]) region bilaterally. We tested whether language tasks elicited (1) changes in spectral power from baseline (significant ERSP) at any region or (2) asymmetric ERSPs between matched left and right regions.

RESULTS

Left IF beta power (-0.37±0.53, t = -3.12, P = 0.006) and gamma power in all regions decreased during verb generation. Asymmetric ERSPs (right > left) occurred between the (1) IF regions in the beta band (right vs. left difference of 0.23±0.37, t(19) = -2.80, P = 0.0114) and (2) ST regions in the alpha band (right vs. left difference of 0.48±0.63, t(19) = -3.36, P = 0.003). No changes from baseline or hemispheric asymmetries were noted in language regions during control tasks. On the individual level, 16 (80%) participants showed decreased left IF beta power from baseline, and 16 showed ST alpha asymmetry. Eighteen participants (90%) showed one of these two findings.

CONCLUSIONS

Spectral EEG analysis detects lateralized responses during language tasks in frontal and temporal regions. Spectral EEG analysis could be developed into a readily available language lateralization modality.

Hemispheric asymmetry of hand and tool perception in left- and right-handers with known language dominance

Regions in the brain that are selective for images of hands and tools have been suggested to be lateralised to the left hemisphere of right-handed individuals. In left-handers, many functions related to tool use or tool pantomime may also depend more on the left hemisphere. This result seems surprising, given that the dominant hand of these individuals is controlled by the right hemisphere. One explanation is that the left hemisphere is dominant for speech and language in the majority of left-handers, suggesting a supraordinate control system for complex motor sequencing that is required for skilled tool use, as well as for speech. In the present study, we examine if this left-hemispheric specialisation extends to perception of hands and tools in left- and right-handed individuals. We, crucially, also include a group of left-handers with right-hemispheric language dominance to examine their asymmetry biases. The results suggest that tools lateralise to the left hemisphere in most right-handed individuals with left-hemispheric language dominance. Tools also lateralise to the language dominant hemisphere in right-hemispheric language dominant left-handers, but the result for left-hemispheric language dominant left-handers are more varied, and no clear bias towards one hemisphere is found. Hands did not show a group-level asymmetry pattern in any of the groups. These results suggest a more complex picture regarding hemispheric overlap of hand and tool representations, and that visual appearance of tools may be driven in part by both language dominance and the hemisphere which controls the motor-dominant hand.