Brain Asymmetry Research Articles

Lateral Asymmetry of Brain and Behaviour in the Zebra Finch, Taeniopygia guttata

Lateralisation of eye use indicates differential specialisation of the brain hemispheres. We tested eye use by zebra finches to view a model predator, a monitor lizard, and compared this to eye use to view a non-threatening visual stimulus, a jar. We used a modified method of scoring eye preference of zebra finches, since they often alternate fixation of a stimulus with the lateral, monocular visual field of one eye and then the other, known as biocular alternating fixation. We found a significant and consistent preference to view the lizard using the left lateral visual field, and no significant eye preference to view the jar. This finding is consistent with specialisation of the left eye system, and right hemisphere, to attend and respond to predators, as found in two other avian species and also in non-avian vertebrates. Our results were considered together with hemispheric differences in the zebra finch for processing, producing, and learning song, and with evidence of right-eye preference in visual searching and courtship behaviour. We conclude that the zebra finch brain has the same general pattern of asymmetry for visual processing as found in other vertebrates and suggest that, contrary to earlier indications from research on lateralisation of song, this may also be the case for auditory processing.

Effect of baseline brain activity on response to low-frequency rTMS/intensive occupational therapy in poststroke patients with upper limb hemiparesis: a near-infrared spectroscopy study

Background: The beneficial effects of the combination therapy of low-frequency repetitive transcranial magnetic stimulation of nonlesional hemisphere and intensive occupational therapy (LF-rTMS/OT) on upper limb hemiparesis have been well established in poststroke patients. However, there is no information on the effect of brain activity on LF-rTMS/OT treatment outcome.Method: A total of 59 poststroke patients with upper limb hemiparesis received 15-day LF-rTMS/OT. Motor function of the affected upper limb was evaluated before and after the treatment. We also conducted functional near-infrared spectroscopy (fNIRS) before the treatment and calculated the laterality index (LI) based on the change in oxy-hemoglobin in the primary sensorimotor cortex and supplementary motor cortex. The correlation between LI before LF-rTMS/OT and observed improvement in upper limb motor function was analyzed.Results: Motor recovery was significantly more pronounced in patients with unaffected hemisphere dominance in both hemispheres (LI of −1 to 0) than in those with affected hemisphere dominance in the lesional hemisphere (LI of 0 to 1). There was a significant negative correlation between LI and improvement in upper limb motor function.Discussion: The results demonstrated that patients with a shift in brain activity to the noninjured cerebral cortex exhibited better motor recovery following LF-rTMS/OT. The findings suggest that evaluation of brain asymmetry before LF-rTMS/OT with fNIRS can help predict the response to LF-rTMS/OT.

Evidence for Right-Sided Horses Being More Optimistic than Left-Sided Horses.

Simple SummaryBehaviour that indicates stress or poor welfare in horses can be very subtle and, especially for the lay person, difficult to assess. Furthermore, the absence of such behaviour does not necessarily indicate a healthy mental state. Therefore, this study aimed to investigate whether a preference for the left or right forelimb in different tasks (motor laterality) or for left or right sensory organs (sensory laterality) indicates a positive mental state (positive cognitive bias—optimism) or negative mental state (negative cognitive bias—pessimism). This study demonstrates that horses that use the right forelimb more often when starting to move off from a standing position (initial forelimb use) are more likely to expect a neutral stimulus to be positive and to be in an optimistic mental state than horses that use the left forelimb. This knowledge about the horses’ mental state can help us to improve their welfare by minimizing negative events. Furthermore, evaluation of the mental state of animals by determining motor laterality is quicker and easier than conventional tests for cognitive bias that include a long period of training.An individual’s positive or negative perspective when judging an ambiguous stimulus (cognitive bias) can be helpful when assessing animal welfare. Emotionality, as expressed in approach or withdrawal behaviour, is linked to brain asymmetry. The predisposition to process information in the left or right brain hemisphere is displayed in motor laterality. The quality of the information being processed is indicated by the sensory laterality. Consequently, it would be quicker and more repeatable to use motor or sensory laterality to evaluate cognitive bias than to perform the conventional judgment bias test. Therefore, the relationship between cognitive bias and motor or sensory laterality was tested. The horses (n = 17) were trained in a discrimination task involving a box that was placed in either a “positive” or “negative” location. To test for cognitive bias, the box was then placed in the middle, between the trained positive and negative location, in an ambiguous location, and the latency to approach the box was evaluated. Results indicated that horses that were more likely to use the right forelimb when moving off from a standing position were more likely to approach the ambiguous box with a shorter latency (generalized linear mixed model, p < 0.01), and therefore displayed a positive cognitive bias (optimistic).

Correction to: Emotion recognition based on physiological signals using brain asymmetry index and echo state network

The authors quite agree that the AsI model is first developed by Panagiotis Petrantonakis from references [11] and [18] in their thesis.

Associations of age and sex with brain volumes and asymmetry in 2\u20135-week-old infants

Information on normal brain structure and development facilitates the recognition of abnormal developmental trajectories and thus needs to be studied in more detail. We imaged 68 healthy infants aged 2–5 weeks with high-resolution structural MRI (magnetic resonance imaging) and investigated hemispheric asymmetry as well as the associations of various total and lobar brain volumes with infant age and sex. We found similar hemispheric asymmetry in both sexes, seen as larger volumes of the right temporal lobe, and of the left parietal and occipital lobes. The degree of asymmetry did not vary with age. Regardless of controlling for gestational age, gray and white matter had different age-related growth patterns. This is a reflection of gray matter growth being greater in the first years, while white matter growth extends into early adulthood. Sex-dependent differences were seen in gray matter as larger regional absolute volumes in males and as larger regional relative volumes in females. Our results are in line with previous studies and expand our understanding of infant brain development.

Characteristics for Functional Brain Asymmetry of Children With Pseudobulbar Dysartria

The article raises important problem of the causes of functional brain asymmetry and interhemispheric interaction of children with pseudobulbar dysarthria. The left hemisphere is dominant in relation to speech function for the absolute majority of people. Therefore, the physiological process for forming distribution of functions between hemispheres in ontogeny is important not only from the point of the correct speech development as the highest mental function but also reflects on the wide spectrum of psyche features, perception and cognitive processes, adaptive capabilities of the organism, control over involuntary behavior. There are 40 children with a normal speech development and with a clinical diagnosis of ‘pseudobulbar dysarthria’, determine a lateral phenotype, calculate coefficients of functional asymmetry, and the most common types of violations identify of higher cortical functions. Confirmed information on the prevalence for the right hemispheric dominance among children with speech disorders. The most common types of violations in higher cortical functions are the failure of phonemic analysis and auditory memory.&#x0D; Keywords: functional asymmetry, interhemispheric actions, children, pseudobulbar dysarthria

Individual Differences and Hemispheric Asymmetries for Language and Spatial Attention.

Language and spatial processing are cognitive functions that are asymmetrically distributed across both cerebral hemispheres. In the present study, we compare left- and right-handers on word comprehension using a divided visual field paradigm and spatial attention using a landmark task. We investigate hemispheric asymmetries by assessing the participants’ behavioral metrics; response accuracy, reaction time and their laterality index. The data showed that right-handers benefitted more from left-hemispheric lateralization for language comprehension and right-hemispheric lateralization for spatial attention than left-handers. Furthermore, left-handers demonstrated a more variable distribution across both hemispheres, supporting a less focal profile of functional brain organization. Taken together, the results underline that handedness distinctively modulates hemispheric processing and behavioral performance during verbal and nonverbal tasks. In particular, typical lateralization is most prevalent for right-handers whereas atypical lateralization is more evident for left-handers. These insights contribute to the understanding of individual variation of brain asymmetries and the mechanisms related to changes in cerebral dominance.

Left/right asymmetric collective migration of parapineal cells is mediated by focal FGF signaling activity in leading cells

The ability of cells to collectively interpret surrounding environmental signals underpins their capacity to coordinate their migration in various contexts, including embryonic development and cancer metastasis. One tractable model for studying collective migration is the parapineal, a left-sided group of neurons that arises from bilaterally positioned precursors that undergo a collective migration to the left side of the brain. In zebrafish, the migration of these cells requires Fgf8 and, in this study, we resolve how FGF signaling correlates with-and impacts the migratory dynamics of-the parapineal cell collective. The temporal and spatial dynamics of an FGF reporter transgene reveal that FGF signaling is activated in only few parapineal cells usually located at the leading edge of the parapineal during its migration. Overexpressing a constitutively active Fgf receptor compromises parapineal migration in wild-type embryos, while it partially restores both parapineal migration and mosaic expression of the FGF reporter transgene in fgf8-/- mutant embryos. Focal activation of FGF signaling in few parapineal cells is sufficient to promote the migration of the whole parapineal collective. Finally, we show that asymmetric Nodal signaling contributes to the restriction and leftwards bias of FGF pathway activation. Our data indicate that the first overt morphological asymmetry in the zebrafish brain is promoted by FGF pathway activation in cells that lead the collective migration of the parapineal to the left. This study shows that cell-state differences in FGF signaling in front versus rear cells is required to promote migration in a model of FGF-dependent collective migration.

Asymmetrical Commissural Control of the Subdominant Hemisphere in Pigeons

Functional brain asymmetries depend both on hemisphere-specific factors and lateralized commissural interactions, but their detailed neural mechanisms are mostly unknown. Because birds are visually lateralized, we tested pigeons monocularly in a color discrimination task while recording from single visuomotor forebrain neuron. All birds learned faster and responded quickly with the right eye and left hemisphere. This asymmetry depended on three factors. First, Go-stimulus onset resulted in a higher left hemispheric proportion of excited relative to inhibited neurons such that, second, left-sided visuomotor neurons could trigger the animal's response faster. Third, the left hemisphere was able to adjust the timing of individual activity patterns of right hemispheric neurons via asymmetrical commissural interactions, such that the right hemisphere came too late to control the response. These results imply that hemispheric dominance in birds is realized by both lateralized activation of forebrain motor areas and shifts of the contralateral spike time.

Brain asymmetry in directing attention during dichotic listening test: An fNIRS study

ABSTRACTIn a classical dichotic listening paradigm, besides auditory brain asymmetry, cognitive functions such as attention and conflict resolution play a major role. The aim of this study is to reveal the possible haemodynamic mechanisms of higher attentional performance in prefrontal cortex during dichotic listening test. Twenty-six healthy participants underwent a dichotic listening task in three sessions; non-forced attention, attention focused to right ear, and attention focused to left ear. In each session, haemodynamic activity of prefrontal brain area was recorded using functional near-infrared spectroscopy (fNIRS). Effects of focused attention and performance level of the task on oxy-, deoxy-, and total haemoglobin levels were investigated. Oxy- and total haemoglobin levels in right prefrontal regions during forced-right and forced-left sessions were significantly higher than levels of the non-forced session. This might be an indicator of inhibition and orienting attentional functions of right inferior frontal gyrus. High performers had significantly higher deoxyhaemoglobin levels in the forced-left session compared to the non-forced session, while low performers’ deoxyhaemoglobin levels did not differ among these sessions. Observing this difference only in the forced-left session but not in the forced-right session might suggest conflict resolution in top-down and bottom-up processes during the forced-left session for right-handed participants.

LGI1 expression and human brain asymmetry: insights from patients with LGI1-antibody encephalitis

BackgroundWhile brain asymmetry has been a fascinating issue in neuroscience, the critical mechanism remains to be elucidated. Based on some index cases with asymmetric 18F-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) uptake in leucine-rich glioma-inactivated 1 (LGI1)-antibody encephalitis, we hypothesized LGI1 expression could be asymmetrically distributed in the human brain.MethodsWe enrolled 13 patients who were diagnosed with LGI1-antibody encephalitis between June 2012 and January 2018 at Seoul National University Hospital. Their pretreatment 18F-FDG-PET images were analyzed to find asymmetry between the left and right hemispheres. Guided by these observations, expression of LGI1 in the human hippocampus and the globus pallidus of both cerebral hemispheres was studied in nine post-mortem human brains.ResultsEleven of the 13 LGI1-antibody encephalitis patients (84.6%) showed asymmetrical FDG high uptake in the hippocampus: nine (81.8%) on the left hippocampus and two (18.2%) on the right. In the basal ganglia, seven patients (53.8%) showed asymmetry: four (57.1%) on the left and three (42.9%) on the right. The asymmetry was not evident in the laterality of faciobrachial dystonic seizures, brain MRI, and EEG. When the expression of LGI1 protein was analyzed in nine post-mortem human brains by western blotting, LGI1 expression was higher on eight left globus pallidus samples (88.89%, P = 0.019) and on four left hippocampal samples (44.44%, P = 0.652), compared to their right hemisphere samples.ConclusionsImaging parameters from patients with LGI1-antibody encephalitis and studies of LGI1 protein expression suggest that LGI1 is asymmetrically distributed in the human brain. These observations have implications for our understanding of human brain development.

Subtle left-right asymmetry of gene expression profiles in embryonic and foetal human brains

Left-right laterality is an important aspect of human –and in fact all vertebrate– brain organization for which the genetic basis is poorly understood. Using RNA sequencing data we contrasted gene expression in left- and right-sided samples from several structures of the anterior central nervous systems of post mortem human embryos and foetuses. While few individual genes stood out as significantly lateralized, most structures showed evidence of laterality of their overall transcriptomic profiles. These left-right differences showed overlap with age-dependent changes in expression, indicating lateralized maturation rates, but not consistently in left-right orientation over all structures. Brain asymmetry may therefore originate in multiple locations, or if there is a single origin, it is earlier than 5 weeks post conception, with structure-specific lateralized processes already underway by this age. This pattern is broadly consistent with the weak correlations reported between various aspects of adult brain laterality, such as language dominance and handedness.

Along-tract analysis of the arcuate fasciculus using the Laplacian operator to evaluate different tractography methods

PurposeWe propose a new along-tract algorithm to compare different tractography algorithms in tract curvature mapping and along-tract analysis of the arcuate fasciculus (AF). In particular, we quantified along-tract diffusion parameters and AF spatial distribution evaluating hemispheric asymmetries in a group of healthy subjects. MethodsThe AF was bilaterally reconstructed in a group of 29 healthy subjects using the probabilistic ball-and-sticks model, and both deterministic and probabilistic constrained spherical deconvolution. We chose cortical ROIs as tractography targets and the developed along-tract algorithm used the Laplacian operator to parameterize the volume of the tract, allowing along-tract analysis and tract curvature mapping independent of the tractography algorithm used. ResultsThe Laplacian parameterization successfully described the tract geometry underlying hemispheric asymmetries in the AF curvature. Using the probabilistic tractography methods, we found more tracts branching towards cortical terminations in the left hemisphere. This influenced the left AF curvature and its diffusion parameters, which were significantly different with respect to the right. In particular, we detected projections towards the middle temporal and inferior frontal gyri bilaterally, and towards the superior temporal and precentral gyri in the left hemisphere, with a significantly increased volume and connectivity. ConclusionsThe approach we propose is useful to evaluate brain asymmetries, assessing the volume, the diffusion properties and the quantitative spatial localization of the AF.

Emotion recognition based on physiological signals using brain asymmetry index and echo state network

This paper proposes a method to evaluate the degree of emotion being motivated in continuous music videos based on asymmetry index (AsI). By collecting two groups of electroencephalogram (EEG) signals from 6 channels (Fp1, Fp2, Fz and AF3, AF4, Fz) in the left and right hemispheres, multidimensional directed information is used to measure the mutual information shared between two frontal lobes, and then, we get AsI to estimate the degree of emotional induction. In order to evaluate the effect of AsI processing on physiological emotion recognition, 32-channel EEG signals, 2-channel EEG signals and 2-channel EMG signals are selected for each subject from the DEAP dataset, and different sub-bands are extracted using wavelet packet transform. k-means algorithm is used to cluster the wavelet packet coefficients of each sub-band, and the probability distribution of the coefficients under each cluster is calculated. Finally, the probability distribution value of each sample is sent as the original features into echo state network for unsupervised intrinsic plasticity training; the reservoir state nodes are selected as the final feature vector and fed into the support vector machine. The experimental results show that the proposed algorithm can achieve an average recognition rate of 70.5% when the subjects are independent. Compared with the case without AsI, the recognition rate is increased by 8.73%. On the other hand, the ESN is adopted for the original physiological feature refinement which can significantly reduce feature dimensions and be more beneficial to the emotion classification. Therefore, this study can effectively improve the performance of human–machine interface systems based on emotion recognition.

Frontal brain asymmetries as effective parameters to assess the quality of audiovisual stimuli perception in adult and young cochlear implant users.

SUMMARYHow is music perceived by cochlear implant (CI) users? This question arises as “the next step” given the impressive performance obtained by these patients in language perception. Furthermore, how can music perception be evaluated beyond self-report rating, in order to obtain measurable data? To address this question, estimation of the frontal electroencephalographic (EEG) alpha activity imbalance, acquired through a 19-channel EEG cap, appears to be a suitable instrument to measure the approach/withdrawal (AW index) reaction to external stimuli. Specifically, a greater value of AW indicates an increased propensity to stimulus approach, and vice versa a lower one a tendency to withdraw from the stimulus. Additionally, due to prelingually and postlingually deafened pathology acquisition, children and adults, respectively, would probably differ in music perception. The aim of the present study was to investigate children and adult CI users, in unilateral (UCI) and bilateral (BCI) implantation conditions, during three experimental situations of music exposure (normal, distorted and mute). Additionally, a study of functional connectivity patterns within cerebral networks was performed to investigate functioning patterns in different experimental populations. As a general result, congruency among patterns between BCI patients and control (CTRL) subjects was seen, characterised by lowest values for the distorted condition (vs. normal and mute conditions) in the AW index and in the connectivity analysis. Additionally, the normal and distorted conditions were significantly different in CI and CTRL adults, and in CTRL children, but not in CI children. These results suggest a higher capacity of discrimination and approach motivation towards normal music in CTRL and BCI subjects, but not for UCI patients. Therefore, for perception of music CTRL and BCI participants appear more similar than UCI subjects, as estimated by measurable and not self-reported parameters.

Tracing the structural origins of atypical language representation: consequences of prenatal mirror-imaged brain asymmetries in a dizygotic twin couple

We investigated the predictive value of prenatal superior temporal sulcus (STS) depth asymmetry in a special case of a female dizygotic twin that showed inverted prenatal asymmetry of this structure. For this purpose, we performed a follow-up investigation in this former fetus at the age of seven, where we assessed the functional language lateralization using task-based and resting-state functional magnetic resonance imaging (fMRI). As control group we employed her twin brother, who showed a typical folding pattern prenatally, as well as a complementary set of four age-matched children that had fetal MRI of their brains and typical STS depth asymmetry. We could show that the twin with the atypical fetal asymmetry of the STS also showed significantly differing rightward language lateralization in the frontal and temporal lobes. Additionally, resting-state data suggest a stronger connectivity between inferior frontal gyri in this case. The twin showed normal cognitive development. This result gives a first glimpse into the STS’ atypical asymmetry being a very early morphological marker for later language lateralization.

Neuropeptidase activity in the frontal cortex of Wistar-Kyoto and spontaneously hypertensive rats treated with vasoactive drugs: a bilateral study.

Background and objective:Hypertension can lead to mood disorders that may worsen or ameliorate depending on the type of antihypertensive prescribed. Depression is associated with modifications in basal brain asymmetry particularly that of the frontal cortex, which is involved in blood pressure control. Furthermore, different vasoactive drugs may change the brain's asymmetry in a manner that contributes to cognition status. We studied the bilateral activity of several neuropeptidases in frontal cortex as a reflect of the functional status of certain neuropeptides involved in mood.Methods:Using arylamide derivatives as substrates, we fluorometrically analysed the activity of these enzymes in the left and right frontal cortex of control untreated Wistar–Kyoto (WKY) and spontaneously hypertensive rats (SHRs) and compared their activities with WKY or SHR treated with the antihypertensive drugs captopril (CAP) and propranolol (PRO) or with the hypertensive N (G)-nitro-l-arginine methyl ester. SBP was also measured in all WKY and SHR groups.Results:Untreated WKY, WKY treated with CAP or PRO and SHR treated with CAP exhibited normotensive values of SBP. However, WKY treated with N (G)-nitro-l-arginine methyl ester as well as untreated SHR and SHR treated with PRO and N(G)-nitro-l-arginine methyl ester demonstrated hypertensive values of SBP. Changes in the bilateral distribution of neuropeptidases were depending on the strain, the enzyme analysed and the drug used. Normotensive WKY groups (WKY, CAP, PRO) revealed intrahemispheric correlations mainly in the left hemisphere. In contrast, WKY treated with N(G)-nitro-l-arginine methyl ester and SHR groups demonstrated intrahemispheric correlations mainly in the right hemisphere. Interhemispheric correlations were mostly observed in WKY as well as in SHR groups with antihypertensive treatments (CAP, PRO).Conclusion:Our results suggest specific brain bilateral patterns of neuropeptidase activities in WKY that change in SHR. This observation may be related to the cognitive disorders that have been described in these animals and that change under antihypertensive or hypertensive drug's treatments.

Lateralized expression of left-right axis formation genes is shared by adult brains of lefty and righty scale-eating cichlids

Variation in the laterality often exists within species and can be maintained by frequency-dependent selection. Although the molecular developmental mechanisms underlying the left-right axis formation have been investigated, the genomic mechanisms underlying variation in laterality remain largely unknown. The scale-eating cichlid Perissodus microlepis in Lake Tanganyika exhibit lateralized predation; lefty individuals with the mouth opening toward the right preferentially attack on the prey's left trunk, while righty individuals with the opposite opening attacks on the right trunk. Here, we performed RNA-sequencing and subsequent confirmation with quantitative-PCR in the telencephalon, optic tectum, and hindbrain of the cichlid and identified five genes (pkd1b, ntn1b, ansn, pde6g, and rbp4l1) that were differentially expressed between the hemispheres regardless of the laterality. Surprisingly, pkd1b and ntn1b are involved in nodal and netrin signalling, respectively, which are important for left–right asymmetry formation during early embryogenesis. This result indicates that nodal- and netrin-related signals may also play important roles in the maintenance of asymmetry in adult brain. By contrast, no genes showed reversal of lateral differences between lefty and righty individuals in any brain regions examined, suggesting that laterality in the scale-eating cichlid does not simply result from inversion of the left–right asymmetry of gene expression.

Functional brain asymmetry and cognitive strategies in sports single combats

Functional brain asymmetry and cognitive strategies in sports single combats

Functional brain asymmetry and cognitive strategies in sports single combats

Issues of individual typological classification on the basis of human brain hemisphere organization, which is the basis for optimizing professional orientation, sports selection and individual approach in the process of long-term training. Objective. Study of the relationship of functional brain asymmetry with cognitive strategies of athletes in martial arts. Methods. Testing, experimental studies, statistical methods. Results. The study involved 79 highly skilled athletes specializing in Greco-Roman and free-style wrestling. The group of research methods included determination of functional hemispheric asymmetry of the brain using the field-dependent test (the version of Color & Word Test). To study the state of cognitive processes of verbal stimuli perception the method of Establishment of regularities was used. Characteristics of visual perception of nonverbal stimuli and operational thinking were evaluated by the method of Perceptual Speed. It was found that the functional asymmetry of the brain in highly skilled athletes is reflected in the higher field dependence on the influence of external stimuli (adaptive cognitive strategy of perception and processing of information), whereas the presence of symmetry of the brain in athletes is reflected in the higher field independency of the influence of information from external environment (autonomous cognitive strategy of perception and processing of information). The results indicate that autonomous cognitive strategy is characterized by greater possibilities for the manifestation of cognitive functions, in particular, the better ability to quickly and qualitatively perceive and process external information, as compared to athletes with functional asymmetry of the cerebral hemispheres.