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

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 24736

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Special Issue Editor

Dr. Francisco José Germain Martínez

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Guest Editor

Department of Systems Biology, Alcalá de Henares University, 28871 Madrid, Spain
Interests: medicine neuroscience biochemistry; genetics and molecular biology
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue of Symmetry shows various examples of how, behind an apparent symmetry in the nervous system, some of the processing of nervous information, especially sensory information, is carried out asymmetrically between both cerebral hemispheres. Until the second half of the twentieth century, it was thought that both cerebral hemispheres were the same. The discovery that the planum temporale had different sizes in both cerebral hemispheres showed anatomical differences between them and began the search for other anatomical and functional differences that would help to understand the global functioning of the nervous system. In fact, an increasing knowledge of these differences is allowing us to understand the nervous processing of different systems in an integrated way, rather than as isolated systems. Perhaps the most typical example is found in auditory processing of language, although in other sensory systems such as visual it is also observed.

The objective of this work is to develop the bases that help to understand the processing of nervous information, specifically the way in which anatomical and functional asymmetry contributes to a better global functioning, either by a division of functions or by an optimization of the same.

We encourage authors to send works carried out in different systems, with different strategies and methodological techniques in order to contribute to the construction of a more complete and global image of neural processing.

Prof. Dr. Francisco José Germain Martínez
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

neuronal asymmetry
sensory system
somatosensory system
motor systems
neuroscience
cognitive science

Published Papers (11 papers)

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Research

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12 pages, 1722 KiB

Open AccessArticle

Influence of Facial Symmetry and Physical Appearance in Patients Perception of Medical Students: A Gender Differences Study

by Francisco Sánchez-Ferrer, María Dolores Grima-Murcia, Ana Pilar Nso-Roca and Eduardo Fernández-Jover

Symmetry 2023, 15(4), 787; https://doi.org/10.3390/sym15040787 - 23 Mar 2023

Viewed by 1420

Abstract

Background: Studies have shown that symmetry plays an aesthetic role and has a positive effect on the perception of human faces. Our work hypothesizes that facial symmetry positively correlates with physical attractiveness and, thus, with higher visual evaluations of future doctors. Materials and methods: Observational study of 46 students (26 women and 20 men), comparing subjective indicators, symmetry of their facial features, and students’ academic performance. Results: We found no correlation between these subjective results and an objective factor of symmetry facial recognition. User evaluators’ subjective assessments of students’ physical appearance showed significant gender differences for almost all the domains assessed. Moreover, these variables were correlated to each other: women were perceived more positively than men. There were also correlations in the variables related to academic performance but no gender differences. We did not observe any relationship between subjective variables related to physical appearance and objective ones related to academic performance. Conclusion: Facial symmetry was not correlated with positive physical appearance and, therefore, with a better evaluation of future doctors by patients. Users perceive women physicians more positively, despite there being no difference at an academic level. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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20 pages, 1790 KiB

Open AccessArticle

Concordance of Lateralization Index for Brain Asymmetry Applied to Identify a Reliable Language Task

by Kayako Matsuo, Norio Yasui-Furukori, Kazutaka Shimoda, Yasushi Kaji and Kazufumi Akiyama

Symmetry 2023, 15(1), 193; https://doi.org/10.3390/sym15010193 - 9 Jan 2023

Viewed by 1376

Abstract

How can we determine which language task is relevant for examining functional hemispheric asymmetry? A problem in measuring brain asymmetry using functional magnetic resonance imaging lies in the uncertain reliability of the computed index regarding the “true” asymmetry degree. Strictly speaking, the results from the Wada test or direct cortical stimulation cannot be an exact “ground truth”, specifically for the degree of asymmetry. Therefore, we developed a method to evaluate task performance using reproducibility independent of the phenomenon of functional lateralization. Kendall’s coefficient of concordance (W) was used as the statistical measure. The underlying idea was that although various algorithms to compute the lateralization index show considerably different index values for the same data, a superior language task would reproduce similar individual ranking sequences across the algorithms; the high reproducibility of rankings across various index types would indicate a reliable task to investigate functional asymmetry regardless of index computation algorithms. Consequently, we found specificity for brain locations; a verb-generation task demonstrated the highest concordance across index types along with sufficiently high index values in the inferior frontal gyrus, whereas a narration–listening task demonstrated the highest concordance in the posterior temporo-parietal junction area. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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19 pages, 4843 KiB

Open AccessArticle

Modulation of Asymmetry in Auditory Perception through a Bilateral Auditory Intervention

by Beatriz Estalayo-Gutiérrez, María José Álvarez-Pasquín and Francisco Germain

Symmetry 2022, 14(12), 2490; https://doi.org/10.3390/sym14122490 - 24 Nov 2022

Viewed by 971

Abstract

The objective of this work was to analyze the modulating effect of an auditory intervention (AI) on the threshold and symmetry of auditory perception in people with different emotional states. The effects of AI were compared 3 months after using threshold audiometry (air conduction). The studied groups were emotional well-being (EWB) (n = 50, 14 with AI, 36 without AI); anxiety (ANX) (n = 31, 10 with AI, 21 without AI); and mixed group (MIX) (n = 45, 19 with AI, 26 without AI). The EWB group with AI lost the advantage of the left ear due to the hearing gain of the right ear, whereas in EWB without AI, no changes were observed. The ANX group with AI showed a non-significant improvement in both ears, maintaining the left interaural advantage. Interestingly, in the group without AI, the interaural difference was lost. The MIX group did not show interaural differences either with or without AI. However, the AI group showed a lower left ear threshold than that of the right ear, in contrast to the non-AI group. In conclusion, the application of this AI manages to decrease the prioritization of high frequencies, in addition to balance hearing between ears, which could decrease activation in states of anxiety. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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9 pages, 267 KiB

Open AccessArticle

Step Length Asymmetry Predicts Rehabilitation Length in Subacute Post Stroke Patients

by Isabella Schwartz, Yonah Ofran, Naama Karniel, Martin Seyres and Sigal Portnoy

Symmetry 2022, 14(10), 1995; https://doi.org/10.3390/sym14101995 - 23 Sep 2022

Viewed by 1271

Abstract

Background: During the rehabilitation of individuals post stroke, evaluations are performed in order to discern the patient’s prognosis and optimize the treatment plan. However, these tests do not focus on gait symmetry, which might be a predictor for rehabilitation outcomes. We aimed to correlate gait symmetry measures of subacute post stroke patients with rehabilitation outcome and find the symmetry measure that best predicts the variability of the rehabilitation duration. A secondary aim was to compare these measures between patients with right and left brain lesions. Methods: We recruited 30 subacute post stroke patients (14 with right side lesion). We collected the following measures: National Institutes of Health Stroke Scale (NIHSS), Functional Independence Measure (FIM), the 10 m walk test (10MWT), Functional Ambulation Categories (FAC), spatial-temporal gait measures, and gait symmetry and variability. Results: We found moderate correlations between the step length symmetry and the length of rehabilitation, NIHSS, FIM, FAC and 10MWT. The symmetry index of the step length predicted the length of the rehabilitation period as it explained 32.1% of its variance (p = 0.001). Discussion: We conclude that a simple test of the step length symmetry might be informative in predicting rehabilitation length in subacute post stroke patients. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

18 pages, 4094 KiB

Open AccessArticle

Modulation of Auditory Perception Laterality under Anxiety and Depression Conditions

by Beatriz Estalayo-Gutiérrez, María José Álvarez-Pasquín and Francisco Germain

Symmetry 2022, 14(1), 24; https://doi.org/10.3390/sym14010024 - 24 Dec 2021

Cited by 2 | Viewed by 2392

Abstract

The objective of this work is to confirm the asymmetry in non-linguistic auditory perception, as well as the influence of anxiety-depressive disorders on it. Eighty-six people were recruited in the emotional well-being group, fifty-six in the anxiety group, fourteen in the depression group, and seventy-seven in the mixed group. In each group, audiograms were obtained from both ears and the differences were statistically analyzed. Differences in hearing sensitivity were found between both ears in the general population, such differences increased in people with anxiety-depressive disorders. When faced with anxiety-depressive disorders, the right ear suffered greater hearing loss than the left, showing peaks of hyper-hearing at the frequency of 4000 Hz in the anxiety subgroup, and hearing loss in the depression subgroup. In relation to anxiety, the appearance of the 4:8 pattern was observed in the right ear when the person had suffered acute stress in the 2 days prior to the audiometry, and in both ears if they had suffered stress in the 3–30 days before said stress. In conclusion, the advantage of the left ear in auditory perception was increased with these disorders, showing a hyperaudition peak in anxiety and a hearing loss in depression. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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11 pages, 1146 KiB

Open AccessArticle

Transcranial Direct Current Stimulation over the Right Inferior Parietal Cortex Reduces Transposition Errors in a Syllabic Reordering Task

by Vanessa Costa, Giuseppe Giglia, Simona Talamanca, Chiara Finocchiaro, Giuseppe Cosentino, Brigida Fierro and Filippo Brighina

Symmetry 2021, 13(11), 2077; https://doi.org/10.3390/sym13112077 - 3 Nov 2021

Cited by 1 | Viewed by 2538

Abstract

Evidence derived from functional imaging and brain-lesion studies has shown a strong left lateralization for language, and a complementary right hemisphere dominance for visuospatial abilities. Nevertheless, the symmetrical functional division of the two hemispheres gives no reason for the complexity of the cognitive operations involved in carrying out a linguistic task. In fact, a growing number of neuroimaging and neurostimulation studies suggest a possible right hemisphere involvement in language processing. The objective of this work was to verify the contribution of the left and right parietal areas in a phonological task. We applied anodal transcranial direct current stimulation (tDCS) to the right or left inferior parietal lobe, during a syllabic reordering task. After having learnt a combination of images of real objects and trisyllabic pseudowords with a simple consonant–vowel (CV) syllabic structure (e.g., tu-ru-cu), participants were shown the same images paired to two different pseudowords: one correct but with transposed syllables, and one alternative, never before seen. The participant’s task was to orally produce the chosen pseudoword, after having rearranged the order of its syllables. Two types of error were considered: transposition (correct pseudoword but incorrectly reordered) and identity (incorrect pseudoword). The results showed that right anodal stimulation significantly reduced the number of transposition errors, whereas left anodal stimulation significantly reduced the number of identity errors. These results suggested that both left and right inferior parietal areas were differentially involved in a syllabic reordering task, and, crucially, they demonstrated that visuospatial processes served by the right inferior parietal area could be competent for establishing the correct syllabic order within a word. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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12 pages, 1607 KiB

Open AccessFeature PaperArticle

Ocular Asymmetry in Electrooculographic Responses

by Haitao Liu, Fei Liao and Pedro de la Villa

Symmetry 2021, 13(10), 1809; https://doi.org/10.3390/sym13101809 - 28 Sep 2021

Cited by 1 | Viewed by 1893

Abstract

Between the cornea and the posterior pole of the eye, there is a transepithelial potential capable of being registered through an electrooculogram (EOG). It is questionable whether electrooculographic responses are similar in both eyes despite ocular dominance in human beings. We studied the effect of different electrooculographic stimulation parameters, in terms of directionality, linear and angular velocity, contrast, and state of adaptation to light/dark, that may induce possible interocular differences in visual function. The study was carried out with electroencephalography-type surface electrodes placed in the medial, lateral, superior, and inferior positions of both human eyes to record the eye movements. We found a greater amplitude of the EOG response in the left eye than to the right eye for light bars moving from right to left (p < 0.01; t-test). The EOG response amplitude was similar in both eyes for light bars moving in vertical directions, but greater than horizontal or rotational stimuli. We conclude that vertical stimuli should be used for EOG functional evaluation of eye movements, since horizontal stimuli generate significant interocular differences. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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16 pages, 3788 KiB

Open AccessArticle

Binaural Background Noise Enhances Neuromagnetic Responses from Auditory Cortex

by Dawei Shen, Claude Alain and Bernhard Ross

Symmetry 2021, 13(9), 1748; https://doi.org/10.3390/sym13091748 - 19 Sep 2021

Cited by 2 | Viewed by 1754

Abstract

The presence of binaural low-level background noise has been shown to enhance the transient evoked N1 response at about 100 ms after sound onset. This increase in N1 amplitude is thought to reflect noise-mediated efferent feedback facilitation from the auditory cortex to lower auditory centers. To test this hypothesis, we recorded auditory-evoked fields using magnetoencephalography while participants were presented with binaural harmonic complex tones embedded in binaural or monaural background noise at signal-to-noise ratios of 25 dB (low noise) or 5 dB (higher noise). Half of the stimuli contained a gap in the middle of the sound. The source activities were measured in bilateral auditory cortices. The onset and gap N1 response increased with low binaural noise, but high binaural and low monaural noise did not affect the N1 amplitudes. P1 and P2 onset and gap responses were consistently attenuated by background noise, and noise level and binaural/monaural presentation showed distinct effects. Moreover, the evoked gamma synchronization was also reduced by background noise, and it showed a lateralized reduction for monaural noise. The effects of noise on the N1 amplitude follow a bell-shaped characteristic that could reflect an optimal representation of acoustic information for transient events embedded in noise. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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14 pages, 7386 KiB

Open AccessEditor’s ChoiceArticle

Brain Symmetry Analysis during the Use of a BCI Based on Motor Imagery for the Control of a Lower-Limb Exoskeleton

by Laura Ferrero, Mario Ortiz, Vicente Quiles, Eduardo Iáñez, José A. Flores and José M. Azorín

Symmetry 2021, 13(9), 1746; https://doi.org/10.3390/sym13091746 - 19 Sep 2021

Cited by 8 | Viewed by 3292

Abstract

Brain–Computer Interfaces (BCI) are systems that allow external devices to be controlled by means of brain activity. There are different such technologies, and electroencephalography (EEG) is an example. One of the most common EEG control methods is based on detecting changes in sensorimotor rhythms (SMRs) during motor imagery (MI). The aim of this study was to assess the laterality of cortical function when performing MI of the lower limb. Brain signals from five subjects were analyzed in two conditions, during exoskeleton-assisted gait and while static. Three different EEG electrode configurations were evaluated: covering both hemispheres, covering the non-dominant hemisphere and covering the dominant hemisphere. In addition, the evolution of performance and laterality with practice was assessed. Although sightly superior results were achieved with information from all electrodes, differences between electrode configurations were not statistically significant. Regarding the evolution during the experimental sessions, the performance of the BCI generally evolved positively the higher the experience was. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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Review

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10 pages, 862 KiB

Open AccessReview

Asymmetric Lateralization during Pain Processing

by Carolina Roza and Anabel Martinez-Padilla

Symmetry 2021, 13(12), 2416; https://doi.org/10.3390/sym13122416 - 14 Dec 2021

Cited by 6 | Viewed by 2823

Abstract

Pain is defined as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”. This complex perception arises from the coordinated activity of several brain areas processing either sensory–discriminative or affective–motivational components. Functional studies performed in healthy volunteers revealed that affective–emotional components of pain are processed bilaterally but present a clear lateralization towards the right hemisphere, regardless of the site of stimulation. Studies at the cellular level performed in experimental animal models of pain have shown that neuronal activity in the right amygdala is clearly pronociceptive, whilst activation of neurons in the left amygdala might even exert antinociceptive effects. A shift in lateralization becomes evident during the development of chronic pain; thus, in patients with neuropathic pain symptoms, there is increased activity in ipsilateral brain areas related with pain. These observations extend the asymmetrical left–right lateralization within the nervous system and provide a new hypothesis for the pathophysiology of chronic forms of pain. In this article, we will review experimental data from preclinical and human studies on functional lateralization in the brain during pain processing, which will help to explain the affective disorders associated with persistent, chronic pain. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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Other

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18 pages, 927 KiB

Open AccessBrief Report

EEG Power Band Asymmetries in Children with and without Classical Ensemble Music Training

by Gabriel Byczynski, Kylie Schibli, Gary Goldfield, Gerry Leisman and Amedeo D’Angiulli

Symmetry 2022, 14(3), 538; https://doi.org/10.3390/sym14030538 - 7 Mar 2022

Cited by 3 | Viewed by 2965

Abstract

Much evidence shows that music training influences the development of functional brain organization and cerebral asymmetry in an auditory-motor integrative neural system also associated with language and speech. Such overlap suggests that music training could be used for interventions in disadvantaged populations. Accordingly, we investigated neurofunctional changes associated with the influence of socially based classical ensemble music (CEM) training on executive auditory functions of children from low socioeconomic status (LSES), as compared to untrained counterparts. We conducted a novel ROI-focused reanalysis of stimulus-locked event-related electroencephalographic (EEG) band power data previously recorded from fifteen LSES children (9–10 years), with and without CEM, while performing a series of auditory Go/No-Go trials (involving 1100 Hz or 2000 Hz tones). An analysis of collapsed Alpha2, Beta1, Beta2, Delta, and Theta EEG bands showed significant differences in increased and decreased left asymmetry between the CEM and the Comparison group in key frontal and central electrodes typically associated with learning music. Overall, in Go trials, the CEM group responded more quickly and accurately. Linear regression analyses revealed both positive and negative correlations between left hemispheric asymmetry and behavioral measures of PPVT score, auditory sensitivity, Go accuracy, and reaction times. The pattern of results suggests that tone frequency and EEG asymmetries may be attributable to a shift to left lateralization as a byproduct of CEM. Our findings suggest that left hemispheric laterality associated with ensemble music training may improve the efficiency of productive language processing and, accordingly, may be considered as a supportive intervention for LSES children and youth. Full article

(This article belongs to the Special Issue Neuroscience, Neurophysiology and Asymmetry)

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