Cortical asymmetries at different spatial hierarchies relate to phonological processing ability

Neural basis of language familiarity effects on voice recognition: An fNIRS study

Recognizing talkers' identity via speech is an important social skill in interpersonal interaction. Behavioral evidence has shown that listeners can identify better the voices of their native language than those of a non-native language, which is known as the language familiarity effect (LFE). However, its underlying neural mechanisms remain unclear. This study therefore investigated how the LFE occurs at the neural level by employing functional near-infrared spectroscopy (fNIRS). Late unbalanced bilinguals were first asked to learn to associate strangers' voices with their identities and then tested for recognizing the talkers' identities based on their voices speaking a language either highly familiar (i.e., native language Chinese), or moderately familiar (i.e., second language English), or completely unfamiliar (i.e., Ewe) to participants. Participants identified talkers the most accurately in Chinese and the least accurately in Ewe. Talker identification was quicker in Chinese than in English and Ewe but reaction time did not differ between the two non-native languages. At the neural level, recognizing voices speaking Chinese relative to English/Ewe produced less activity in the inferior frontal gyrus, precentral/postcentral gyrus, supramarginal gyrus, and superior temporal sulcus/gyrus while no difference was found between English and Ewe, indicating facilitation of voice identification by the automatic phonological encoding in the native language. These findings shed new light on the interrelations between language ability and voice recognition, revealing that the brain activation pattern of the LFE depends on the automaticity of language processing.

A volumetric asymmetry study of gray matter in individuals with and without dyslexia

Brain imaging work aimed at increased classification of dyslexia has underscored an important relationship between anterior (i.e., the inferior frontal gyrus; IFG) and posterior (i.e., superior temporal gyrus and supramarginal gyrus) brain regions. The extent to which the three components of the inferior frontal gyrus, namely the pars orbitalis, triangularis, and opercularis, are differentially related to the posterior regions, namely the superior temporal gyrus and supramarginal gyrus, needs further elucidation. Information about the nature of the anterior-posterior connections would facilitate our understanding of the neural underpinnings associated with dyslexia. Adult participants (N = 38; 16 with dyslexia) took part in an MRI study, whereby high-resolution structural scans were obtained. Volumetric asymmetry of the three regions of the IFG, the superior temporal gyrus, and the supramarginal gyrus was extracted. Significant differences were found for each of the three IFG regions, such that skilled readers had a greater leftward asymmetry of the orbitalis and triangularis, and greater rightward asymmetry of the opercularis, when compared to individuals with dyslexia. Furthermore, the pars triangularis was significantly associated with leftward asymmetry of the superior temporal gyrus for skilled but not dyslexic participants. For individuals with dyslexia, the cortical asymmetry of the IFG, and the corresponding connections with other reading-related brain regions, is inherently different from skilled readers. We discuss our findings in the context of the print-to-speech framework to further our understanding of the neural underpinnings associated with dyslexia.

Sensory temporal sampling in time: an integrated model of the TSF and neural noise hypothesis as an etiological pathway for dyslexia

Much progress has been made in research on the causal mechanisms of developmental dyslexia. In recent years, the "temporal sampling" account of dyslexia has evolved considerably, with contributions from neurogenetics and novel imaging methods resulting in a much more complex etiological view of the disorder. The original temporal sampling framework implicates disrupted neural entrainment to speech as a causal factor for atypical phonological representations. Yet, empirical findings have not provided clear evidence of a low-level etiology for this endophenotype. In contrast, the neural noise hypothesis presents a theoretical view of the manifestation of dyslexia from the level of genes to behavior. However, its relative novelty (published in 2017) means that empirical research focused on specific predictions is sparse. The current paper reviews dyslexia research using a dual framework from the temporal sampling and neural noise hypotheses and discusses the complementary nature of these two views of dyslexia. We present an argument for an integrated model of sensory temporal sampling as an etiological pathway for dyslexia. Finally, we conclude with a brief discussion of outstanding questions.

Evolution of Human Brain Left-Right Asymmetry: Old Genes with New Functions

The human brain is generally anatomically symmetrical, boasting mirror-like brain regions in the left and right hemispheres. Despite this symmetry, fine-scale structural asymmetries are prevalent and are believed to be responsible for distinct functional divisions within the brain. Prior studies propose that these asymmetric structures are predominantly primate specific or even unique to humans, suggesting that the genes contributing to the structural asymmetry of the human brain might have evolved recently. In our study, we identified approximately 1,500 traits associated with human brain asymmetry by collecting paired brain magnetic resonance imaging features from the UK Biobank. Each trait is measured in a specific region of one hemisphere and mirrored in the corresponding region of the other hemisphere. Conducting genome-wide association studies on these traits, we identified over 1,000 quantitative trait loci. Around these index single nucleotide polymorphisms, we found approximately 200 genes that are enriched in brain-related Gene Ontology terms and are predominantly upregulated in brain tissues. Interestingly, most of these genes are evolutionarily old, originating just prior to the emergence of Bilateria (bilaterally symmetrical animals) and Euteleostomi (bony vertebrates with a brain), at a significantly higher ratio than expected. Further analyses of these genes reveal a brain-specific upregulation in humans relative to other mammalian species. This suggests that the structural asymmetry of the human brain has been shaped by evolutionarily ancient genes that have assumed new functions over time.

Structural Covariance of the Duplicated Heschl's Gyrus: A Sulcal/Gyral Template Morphology Approach

Heschl's gyrus (HG) can occur as a single gyrus or with a completely duplicated posterior HG that has been related to a variety of abilities and disorders. Voxel-based studies typically involve the normalization of these qualitatively different HG types, thus making it difficult to evaluate the contribution of sulcal/gyral variability to voxel-based effects and perhaps obscuring some effects. To examine the structural covariance of single and duplicated HG, templates were created for the left single and duplicated HG. Structural covariance analysis with a Jacobian measure of volumetric displacement demonstrated consistent spatial covariance with homologous structure in the right hemisphere across qualitatively different HG morphology. These results suggest that HG duplication is aptly named with respect to cortical structure variation and demonstrate a multi-template approach for studying qualitatively unique brain function and structure linked to perceptual and cognitive functions.

HIGHLIGHTS

Qualitatively unique sulcal/gyral features can affect voxel-based analyses.Heschl's gyrus is highly variable across people.Morphology-specific templates were created to study Heschl's gyrus structural covariance.Single and duplicated Heschl's gyrus exhibited a similar pattern of covariance.

Dyslexia: Causes and Concomitant Impairments

In recent decades, theories have been presented to explain the nature of dyslexia, but the causes of dyslexia remained unclear. Although the investigation of the causes of dyslexia presupposes a clear understanding of the concept of cause, such an understanding is missing. The present paper proposes the absence of at least one necessary condition or the absence of all sufficient conditions as causes for impaired reading. The causes of impaired reading include: an incorrect fixation location, too short a fixation time, the attempt to recognize too many letters simultaneously, too large saccade amplitudes, and too short verbal reaction times. It is assumed that a longer required fixation time in dyslexic readers results from a functional impairment of areas V1, V2, and V3 that require more time to complete temporal summation. These areas and areas that receive input from them, such as the fusiform gyrus, are assumed to be impaired in their ability to simultaneously process a string of letters. When these impairments are compensated by a new reading strategy, reading ability improves immediately.

Longitudinal resting-state functional connectivity changes in the insular subdivisions of abstinent individuals with opioid use disorder

The insular cortex plays a critical role in reward circuitry involved with drug craving in substance use disorders. This study aimed to investigate whether opioid use disorder exhibit functional alterations in the insular circuitry after abstinence. Sixty-one opioid use disorder underwent resting-state and 3D-T1-weighted magnetic resonance imaging and completed craving questionnaires at baseline and after 8 months of abstinence. Changes in resting-state functional connectivity in the insular cortex and their correlations with craving were analyzed. Craving was reduced at follow-up compared with baseline. Compared with that at baseline, there was significantly increased resting-state functional connectivity between the right insular cortex and the superior frontal gyrus/anterior cingulate gyrus (family-wise error corrected) at follow-up. Changes in the functional connectivity of the right dorsal anterior insula/posterior insula with the bilateral superior frontal gyrus were negatively correlated with changes in craving. Our results demonstrated the presence of changes in functional connectivity of the insula in opioid use disorder after protracted abstinence, providing novel evidence of a correlation between craving changes and changes in the neurocircuitry of insular cortex subdivision after abstinence. This study reveals the possibility of neuroplasticity after protracted abstinence, providing insight for future abstinence therapies and rehabilitation procedures for patients with substance use disorders.

Introducing Structural Symmetry and Asymmetry Implications in Development of Recent Pharmacy and Medicine

Structural symmetry, anti-symmetry, or asymmetry represent a foundational property that, for chemical compounds, often determines their chemical and biological activity [...]