Subdividing Stress Groups into Eustress and Distress Groups Using Laterality Index Calculated from Brain Hemodynamic Response

A stress group should be subdivided into eustress (low-stress) and distress (high-stress) groups to better evaluate personal cognitive abilities and mental/physical health. However, it is challenging because of the inconsistent pattern in brain activation. We aimed to ascertain the necessity of subdividing the stress groups. The stress group was screened by salivary alpha-amylase (sAA) and then, the brain’s hemodynamic reactions were measured by functional near-infrared spectroscopy (fNIRS) based on the near-infrared biosensor. We compared the two stress subgroups categorized by sAA using a newly designed emotional stimulus-response paradigm with an international affective picture system (IAPS) to enhance hemodynamic signals induced by the target effect. We calculated the laterality index for stress (LIS) from the measured signals to identify the dominantly activated cortex in both the subgroups. Both the stress groups exhibited brain activity in the right frontal cortex. Specifically, the eustress group exhibited the largest brain activity, whereas the distress group exhibited recessive brain activity, regardless of positive or negative stimuli. LIS values were larger in the order of the eustress, control, and distress groups; this indicates that the stress group can be divided into eustress and distress groups. We built a foundation for subdividing stress groups into eustress and distress groups using fNIRS.

Tractography of the arcuate fasciculus in healthy right-handed and left-handed multilingual subjects and its relation to language lateralization on functional MRI

Functional MRI (fMRI) enables evaluation of language cortical organization and plays a central role in surgical planning. Diffusion Tensor Imaging (DTI) or Tractography, allows evaluation of the white matter fibers involved in language. Unlike fMRI, DTI does not rely on the patient’s cooperation. In monolinguals, there is a significant correlation between the lateralization of language on fMRI and on DTI. Our objective is to delineate the arcuate fasciculus (AF) in right- and left-handed trilinguals and determine if the AF laterality on DTI is correlated to language lateralization on fMRI. 15 right and 15 left-handed trilingual volunteers underwent fMRI and DTI. Laterality Index was determined on fMRI (fMRI-LI). Mean Diffusivity, Fractional Anisotropy (FA), Number of Fibers, Fiber Length, Fiber Volume and Laterality Index (DTI-LI) of the AF were calculated on DTI. 28 of the 30 subjects presented a bilateral AF. Most subjects (52%) were found to have a bilateral language lateralization of the AF on DTI. Only 4 subjects had bilateral lateralization of language on fMRI. The right AF demonstrated lower diffusivity than the left AF in the total participants, the right-handed, and the left-handed subjects. FA, Volume and Length of the AF were not significantly different between the two hemispheres. No correlation was found between the DTI-LI of the AF and the fMRI-LI. A prominent role of the right AF and a bilateral structural organization of the AF was present in our multilingual population regardless of their handedness. While in prior studies DTI was able to determine language lateralization in monolingual subjects, this was not possible in trilingual highly educated subjects.

Sex-Related Differences in White Matter Asymmetry and Its Implications for Verbal Working Memory in Psychosis High-Risk State

Objective: Sexual dimorphism has been investigated in schizophrenia, although sex-specific differences among individuals who are at clinical high-risk (CHR) for developing psychosis have been inconclusive. This study aims to characterize sexual dimorphism of language areas in the brain by investigating the asymmetry of four white matter tracts relevant to verbal working memory in CHR patients compared to healthy controls (HC). HC typically show a leftward asymmetry of these tracts. Moreover, structural abnormalities in asymmetry and verbal working memory dysfunctions have been associated with neurodevelopmental abnormalities and are considered core features of schizophrenia.Methods: Twenty-nine subjects with CHR (17 female/12 male) for developing psychosis and twenty-one HC (11 female/10 male) matched for age, sex, and education were included in the study. Two-tensor unscented Kalman filter tractography, followed by an automated, atlas-guided fiber clustering approach, were used to identify four fiber tracts related to verbal working memory: the superior longitudinal fasciculi (SLF) I, II and III, and the superior occipitofrontal fasciculus (SOFF). Using fractional anisotropy (FA) of tissue as the primary measure, we calculated the laterality index for each tract.Results: There was a significantly greater right>left asymmetry of the SLF-III in CHR females compared to HC females, but no hemispheric difference between CHR vs. HC males. Moreover, the laterality index of SLF-III for CHR females correlated negatively with Backward Digit Span performance, suggesting a greater rightward asymmetry was associated with poorer working memory functioning.Conclusion: This study suggests increased rightward asymmetry of the SLF-III in CHR females. This finding of sexual dimorphism in white matter asymmetry in a language-related area of the brain in CHR highlights the need for a deeper understanding of the role of sex in the high-risk state. Future work investigating early sex-specific pathophysiological mechanisms, may lead to the development of novel personalized treatment strategies aimed at preventing transition to a more chronic and difficult-to-treat disorder.

Influence of Alignment Strategies and Consonant Acoustic Features on Laterality Index in Dichotic Testing in Indian Languages

Background The right ear advantage (REA) observed for dichotic CV (DCV) testing in Indian languages is seen to be smaller compared with the observations in several studies in English and other languages. Purpose The present study aims to explore whether the differences in the temporal alignment of consonant–vowel (CV) stimuli used for the dichotic task is a contributing factor that can explain the smaller REAs observed in Indian languages. Research Design The study compared the laterality index (LI) values between DCV test results obtained using CV stimuli that were temporally aligned at the acoustic onset versus the burst onset, with 0 milliseconds lag between the right and left ears. Study Sample A total of 50 right-handed individuals (native speakers of Kannada language) in the age range of 17 to 30 years with normal hearing sensitivity participated in the study. Data Collection and Analysis The participants' responses to the two sets of DCV stimuli were recorded and compared. LI was calculated for the overall scores as well as for specific voiced and unvoiced segment combinations. To test the reliability of the findings, 10 of the participants were re-tested using the same stimuli and the data were checked for reliability. Results The overall LI was 15.1% for the stimuli temporally aligned at the burst onset, whereas it was 5.7% for the stimuli temporally aligned at the acoustic onset. The difference in LI was not significant between the alignment conditions for unvoiced–unvoiced and voiced–voiced CV combinations, but this difference was significant for the unvoiced–voiced and voiced–unvoiced CV combinations. Comparing test and re-test scores showed good reliability. Conclusion The results support our hypothesis that smaller REA observed in DCV task in Indian languages was due to the temporal alignment of CV stimuli. In the acoustic-onset-aligned condition, presenting pairs contrasting in the voicing feature tends to cancel out a relative ear advantage.

Tractography of the Arcuate Fasciculus in Healthy Right-Handed and Left-Handed Multilingual Subjects and Its Relation to Language Lateralization on Functional MRI

Purpose Functional MRI (fMRI) enables evaluation of language cortical organization and plays a central role in surgical planning. Diffusion Tensor Imaging (DTI) or Tractography, allows evaluation of the white matter fibers involved in language. Unlike fMRI, DTI does not rely on the patient's cooperation. In monolinguals, there is a good correlation between the lateralization of language on fMRI and on DTI. Our objective is to delineate the arcuate fasciculus (AF) in right- and left-handed trilinguals and determine if the AF laterality on DTI is correlated to language lateralization on fMRI.Methods 15 right and 15 left-handed trilingual volunteers underwent fMRI and DTI. Laterality Index was determined on fMRI (fMRI-LI). Mean Diffusivity, Fractional Anisotropy (FA), Number of Fibers, Fiber Length, Fiber Volume and Laterality Index (DTI-LI) of the AF were calculated on DTI.Results 28 of the 30 subjects presented a bilateral AF. Most subjects (52%) were found to have a bilateral language lateralization of the AF on DTI. Only 4 subjects had bilateral lateralization of language on fMRI. The right AF demonstrated lower diffusivity than the left AF in the total participants, the right-handed, and the left-handed subjects. FA, Volume and Length of the AF were not significantly different between the two hemispheres. No correlation was found between the DTI-LI of the AF and the fMRI-LI.Conclusion A prominent role of the right AF and a bilateral structural organization of the AF was present in our multilingual population regardless of their handedness. While in prior studies DTI was able to determine language lateralization in monolingual subjects, this was not possible in trilingual highly educated subjects.

Laterality of Blood Perfusion in the Lower Extremities after Drinking Saline at Different Temperatures

Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of skin blood flux after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities.Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed.Results: The results indicated that after drinking saline at different temperatures, the laterality index of skin blood flux at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. The results of wavelet analysis showed that the laterality index changes of skin blood flux were mainly reflected in the frequency interval V (0.4-1.6 Hz). Stimulation at 4 °C and 10 °C resulted in a decrease in the dominant frequency (DF) of the electrogastrogram and an increased root mean square of successive differences (RMSSD) of the RR interval. There was a weak negative correlation between the laterality index of frequency interval I or II and root mean square of successive differences.Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.

Laterality of Blood Perfusion in the Lower Extremities after Drinking Saline at Different Temperatures

Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of SkBF after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities.Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed.Results: The results indicated that after drinking saline at different temperatures, the laterality index of SkBF at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. Stimulation at 4 °C and 10 °C resulted in a decrease in the DF of the EGG and an increased RMSSD of the RR interval. Although this laterality is mainly contributed to by frequency interval V, there was a weak negative correlation between the laterality index of frequency interval I or II and RMSSD.Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.

Laterality of Blood Perfusion in the Lower Extremities after Drinking Saline at Different Temperatures

Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of SkBF after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities.Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed.Results: The results indicated that after drinking saline at different temperatures, the laterality index of SkBF at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. Stimulation at 4 °C and 10 °C resulted in a decrease in the DF of the EGG and an increased RMSSD of the RR interval. Although this laterality is mainly contributed to by frequency interval V, there was a weak negative correlation between the laterality index of frequency interval I or II and RMSSD.Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.

Laterality of Blood Perfusion in the Lower Extremities after Drinking Saline at Different Temperatures

Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of SkBF after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities.Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed.Results: The results indicated that after drinking saline at different temperatures, the laterality index of SkBF at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. Stimulation at 4 °C and 10 °C resulted in a decrease in the DF of the EGG and an increased RMSSD of the RR interval. Although this laterality is mainly contributed to by frequency interval V, there was a weak negative correlation between the laterality index of frequency interval I or II and RMSSD.Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.