The Study of Brain Asymmetry

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Life Sciences".

Deadline for manuscript submissions: closed (31 October 2023) | Viewed by 6858

Special Issue Editor

Nalecz Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, 02-109 Warsaw, Poland
Interests: signal processing and analysis; EEG connectivity; nonlinear dynamics

Special Issue Information

Dear Colleagues,

There are anatomical and functional differences between both hemispheres of human brain. Brain asymmetry has also been observed in other animals, including zebrafish, pigeon, rat, and others. In 1861 Paul Broca discovered that one very important function, language processing, is lateralized to the left hemisphere of the human brain. Damage to two brain areas localized in the left hemisphere, Broca's area and Wernicke's area, may result in the loss of the ability to formulate coherent appropriate sentences and loss of language comprehension. Other areas, such as the fusiform face area, specializing in visual-spatial and facial recognition, are localized in the right hemisphere. Moreover, the left hemisphere is responsible for the processing of pleasurable experiences and for decision-making processes, while the right hemisphere is involved in the processing of negative emotions, vigilance, arousal, and self-reflection. The motor functions are also lateralized. The left hemisphere acts on the right side of the body, and vice-versa. Left-handedness can result from the motor cortex asymmetry. The corpus callosum is responsible for the communication between both hemispheres. Sometimes this structure is cut to treat epilepsy. An abnormal brain asymmetry has been observed in various disorders, including Alzheimer’s disease, schizophrenia, depression, posttraumatic stress disorder, autism, and dyslexia. Stress in childhood or chronic stress, as well as an elevated activation of the right frontal cortex in healthy persons, are considered risk factors for emotion-related disorders. In patients with depression and with negative symptoms of schizophrenia, mainly the alpha activity in the left frontal lobe is decreased. Meanwhile, positive symptoms of schizophrenia like auditory hallucinations and delusions are associated with increased activity of the right hemisphere. In patients with Alzheimer's disease the leftward cerebral dominance is reduced, while the brain activity of patients with autism and dyslexia is characterized by a lack of hemispheric asymmetry. Thus, the study of brain asymmetry can be helpful in the diagnosis of various neurological and psychiatric disorders.

Dr. Elzbieta Olejarczyk
Guest Editor

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Keywords

  • brain asymmetry
  • lateralization
  • leftward cerebral dominance
  • Broca’s area
  • Wernicke’s area
  • fusiform face area
  • corpus callosum
  • motor cortex
  • language processing
  • facial recognition
  • visual-spatial recognition
  • decision-making
  • vigilance
  • arousal
  • self-reflection
  • handedness
  • epilepsy
  • Alzheimer’s disease
  • schizophrenia
  • depression
  • posttraumatic stress disorder
  • autism
  • dyslexia
  • stress
  • emotion-related disorders

Published Papers (5 papers)

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Research

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9 pages, 1289 KiB  
Article
Exploring Hemispheric Lateralization and Second Language Class Performance in 10 y.o. Students
by Valeriia Demareva
Symmetry 2023, 15(12), 2147; https://doi.org/10.3390/sym15122147 - 03 Dec 2023
Viewed by 705
Abstract
This study investigated the relationship between functional hemispheric asymmetry at various brain levels and the performance of fourth-grade students in English as a second language classroom activities. Specifically, the study explored the impact of leftward and rightward asymmetry patterns on total classroom scores, [...] Read more.
This study investigated the relationship between functional hemispheric asymmetry at various brain levels and the performance of fourth-grade students in English as a second language classroom activities. Specifically, the study explored the impact of leftward and rightward asymmetry patterns on total classroom scores, considering lessons with a two-week interval and pre-lesson and post-lesson measurements. The sample comprised 27 right-handed students from an English-intensive school program. To assess functional hemispheric asymmetry before and after two English classes, computer laterometry based on a ‘two-source’ lead–lag dichotic paradigm was employed. Results revealed that leftward asymmetry in lability (brainstem-related) and excitability (primary auditory cortex-related) predicted higher total scores in classroom activities. The interaction between leftward lability and excitability asymmetries was a significant predictor of improved performance. These findings suggest that multiple regions of the left hemisphere are involved in supporting various linguistic tasks and emphasize the dynamic nature of functional hemispheric asymmetry. No significant relationship was observed between rightward asymmetry and classroom scores. However, future research may explore specific language tasks and sex-related differences in lateralization. The study underscores the importance of considering individual cognitive profiles in language learning and teaching, potentially improving language acquisition outcomes. Full article
(This article belongs to the Special Issue The Study of Brain Asymmetry)
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16 pages, 1311 KiB  
Article
Studies of EEG Asymmetry and Depression: To Normalise or Not?
by Christopher F. Sharpley, Wayne M. Arnold, Ian D. Evans, Vicki Bitsika, Emmanuel Jesulola and Linda L. Agnew
Symmetry 2023, 15(9), 1689; https://doi.org/10.3390/sym15091689 - 02 Sep 2023
Cited by 2 | Viewed by 881
Abstract
A brief review of 50 studies from the last 10 years indicated that it is often accepted practice to apply log transformation processes to raw EEG data. This practice is based upon the assumptions that (a) EEG data do not resemble a normal [...] Read more.
A brief review of 50 studies from the last 10 years indicated that it is often accepted practice to apply log transformation processes to raw EEG data. This practice is based upon the assumptions that (a) EEG data do not resemble a normal distribution, (b) applying a transformation will produce an acceptably normal distribution, (c) the logarithmic transformation is the most valid form of transformation for these data, and (d) the statistical procedures intended to be used are not robust to non-normality. To test those assumptions, EEG data from 100 community participants were analysed for their normality by reference to their skewness and kurtosis, the Kolmogorov–Smirnov and Shapiro–Wilk statistics, and shapes of histograms. Where non-normality was observed, several transformations were applied, and the data again tested for normality to identify the most appropriate method. To test the effects of normalisation from all these processes, Pearson and Spearman correlations between the raw and normalised EEG alpha asymmetry data and depression were calculated to detect any variation in the significance of the resultant statistic. Full article
(This article belongs to the Special Issue The Study of Brain Asymmetry)
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11 pages, 1986 KiB  
Communication
Asymmetric Pattern of Correlations of Leucine Aminopeptidase Activity between Left or Right Frontal Cortex versus Diverse Left or Right Regions of Rat Brains
by Manuel Ramírez-Sánchez, Isabel Prieto, Ana Belén Segarra, Inmaculada Banegas, Magdalena Martínez-Cañamero, Germán Domínguez-Vías, Raquel Durán, Francisco Vives and Francisco Alba
Symmetry 2023, 15(7), 1320; https://doi.org/10.3390/sym15071320 - 28 Jun 2023
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Abstract
Previous studies demonstrated an asymmetry of left predominance for mean values of soluble leucine aminopeptidase (LeuAP) activity in the frontal cortex (FC) and hypothalamus of adult male rats, fluorimetrically analyzed by the hydrolysis of Leu-β-naphthylamide as a substrate. No asymmetries were observed in [...] Read more.
Previous studies demonstrated an asymmetry of left predominance for mean values of soluble leucine aminopeptidase (LeuAP) activity in the frontal cortex (FC) and hypothalamus of adult male rats, fluorimetrically analyzed by the hydrolysis of Leu-β-naphthylamide as a substrate. No asymmetries were observed in nine other left (L) and right (R) regions obtained from rostro-caudally sectioned coronal slices. Neither had inter-hemispheric differences observed for lactate dehydrogenase (LDH), analyzed simultaneously in the same brain regions (L and R) of the same animals. However, the level of intra-hemispheric or inter-hemispheric correlation of LeuAP or LDH between such brain regions has not been analyzed. In order to obtain additional suggestions on the functional heterogeneity between regions of LeuAP and LDH, in the present investigation, the level of intra-hemispheric and inter-hemispheric correlations of the frontal cortex with the rest of the regions studied is described: (A) between the left frontal cortex (LFC) and the rest of the left regions; (B) between the right frontal cortex (RFC) and the rest of the right regions; (C) between the left frontal cortex and all of the right regions; and (D) between the right frontal cortex and all of the left regions. All of the correlations obtained were positive. The intra-hemispheric analysis showed a greater heterogeneity of values in the correlations observed between RFC and the rest of the right regions than between LFC and the rest of the left regions. Greater heterogeneity is observed when comparing RFC correlations with left regions than when comparing LFC correlations with right regions. In conclusion, the greatest heterogeneity (suggesting a greater functional variability) was observed in the right intra-hemispheric analysis and in the inter-hemispheric analysis between the RFC and the left hemisphere. The results for LDH showed a great homogeneity between regions both in the intra- and inter-hemispheric studies. Full article
(This article belongs to the Special Issue The Study of Brain Asymmetry)
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11 pages, 348 KiB  
Article
Brain Functional Connectivity Asymmetry: Left Hemisphere Is More Modular
by Lucia Jajcay, David Tomeček, Jiří Horáček, Filip Španiel and Jaroslav Hlinka
Symmetry 2022, 14(4), 833; https://doi.org/10.3390/sym14040833 - 18 Apr 2022
Cited by 3 | Viewed by 2544
Abstract
Graph-theoretical approaches are increasingly used to study the brain and may enhance our understanding of its asymmetries. In this paper, we hypothesize that the structure of the left hemisphere is, on average, more modular. To this end, we analyzed resting-state functional magnetic resonance [...] Read more.
Graph-theoretical approaches are increasingly used to study the brain and may enhance our understanding of its asymmetries. In this paper, we hypothesize that the structure of the left hemisphere is, on average, more modular. To this end, we analyzed resting-state functional magnetic resonance imaging data of 90 healthy subjects. We computed functional connectivity by Pearson’s correlation coefficient, turned the matrix into an unweighted graph by keeping a certain percentage of the strongest connections, and quantified modularity separately for the subgraph formed by each hemisphere. Our results show that the left hemisphere is more modular. The result is consistent across a range of binarization thresholds, regardless of whether the two hemispheres are thresholded together or separately. This illustrates that graph-theoretical analysis can provide a robust characterization of lateralization of brain functional connectivity. Full article
(This article belongs to the Special Issue The Study of Brain Asymmetry)
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Review

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20 pages, 393 KiB  
Review
Dynamical Asymmetries, the Bayes’ Theorem, Entanglement, and Intentionality in the Brain Functional Activity
by David Bernal-Casas and Giuseppe Vitiello
Symmetry 2023, 15(12), 2184; https://doi.org/10.3390/sym15122184 - 11 Dec 2023
Viewed by 880
Abstract
We discuss the asymmetries of dynamical origin that are relevant to functional brain activity. The brain is permanently open to its environment, and its dissipative dynamics is characterized indeed by the asymmetries under time translation transformations and time-reversal transformations, which manifest themselves in [...] Read more.
We discuss the asymmetries of dynamical origin that are relevant to functional brain activity. The brain is permanently open to its environment, and its dissipative dynamics is characterized indeed by the asymmetries under time translation transformations and time-reversal transformations, which manifest themselves in the irreversible “arrow of time”. Another asymmetry of dynamical origin arises from the breakdown of the rotational symmetry of molecular electric dipoles, triggered by incoming stimuli, which manifests in long-range dipole-dipole correlations favoring neuronal correlations. In the dissipative model, neurons, glial cells, and other biological components are classical structures. The dipole vibrational fields are quantum variables. We review the quantum field theory model of the brain proposed by Ricciardi and Umezawa and its subsequent extension to dissipative dynamics. We then show that Bayes’ theorem in probability theory is intrinsic to the structure of the brain states and discuss its strict relation with entanglement phenomena and free energy minimization. The brain estimates the action with a higher Bayes probability to be taken to produce the aimed effect. Bayes’ rule provides the formal basis of the intentionality in brain activity, which we also discuss in relation to mind and consciousness. Full article
(This article belongs to the Special Issue The Study of Brain Asymmetry)
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