Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene. This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech. It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing. Here we use functional magnetic resonance imaging with a sample of 155 subjects to measure asymmetrical activation induced by speech production in the frontal lobes, by face processing in the temporal lobes, and by spatial processing in the parietal lobes. Left-frontal, right-temporal, and right-parietal dominance were all intercorrelated, suggesting that right-cerebral biases may be at least in part complementary to the left-hemispheric dominance for language. However, handedness and parietal asymmetry for spatial processing were uncorrelated, implying independent lateralizing processes, one producing a leftward bias most closely associated with handedness, and the other a rightward bias most closely associated with spatial attention.

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Most people are right-handed and left-cerebrally dominant for language. This pattern of asymmetry, as well as departures from it, have been reasonably accommodated in terms of a postulated gene with two alleles, one disposing to this common pattern and the other leaving the direction of handedness and language asymmetry to chance. There are some leads as to the location of the gene or genes concerned, but no clear resolution; one possibility is that the chance factor is achieved by epigenetic cancelling of the lateralizing gene rather than through a chance allele. Neurological evidence suggests that the neural basis of manual praxis, including pantomime and tool use, is more closely associated with cerebral asymmetry for language than with handedness, and is homologous with the so-called "mirror system" in the primate brain, which is specialized for manual grasping. The evidence reviewed supports the theory that language itself evolved within the praxic system, and became lateralized in humans, and perhaps to a lesser extent in our common ancestry with the great apes. WIREs Cogn Sci 2012, 3:1-17. doi: 10.1002/wcs.158 For further resources related to this article, please visit the WIREs website.

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Hemispheric asymmetry is commonly viewed as a dual system, unique to humans, with the two sides of the human brain in complementary roles. To the contrary, modern research shows that cerebral and behavioral asymmetries are widespread in the animal kingdom, and that the concept of duality is an oversimplification. The brain has many networks serving different functions; these are differentially lateralized, and involve many genes. Unlike the asymmetries of the internal organs, brain asymmetry is variable, with a significant minority of the population showing reversed asymmetries or the absence of asymmetry. This variability may underlie the divisions of labor and the specializations that sustain social life. (JINS, 2017, 23, 710-718)

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BACKGROUND: Epidemiological evidence from population-based surveys suggest that the psychological well-being of adolescents has been severely affected by the COVID-19 pandemic itself, as well as by the safety measures implemented. The rationale of the study was to investigate the influence of the pandemic on psychiatric emergency service use, psychiatric admissions rates, emotional well-being, suicidality and self-harm behaviour in help-seeking children and adolescents. METHODS: Retrospective cohort study of electronic patient records before and during the COVID-19 pandemic from the emergency out-patient facility of the department of child and adolescent psychiatry and psychotherapy of the Psychiatric University Hospital Zürich. The frequency of all emergency service contacts from 1 January 2019 to 31 June 2021 were described and the frequency of records compared in half-year intervals. Emotional well-being, behavioural problems, suicidality and self-harm were estimated based on the mental state examination notes of electronic patient records from the 1 March to the 30 April for the years 2019, 2020 and 2021. RESULTS: After an initial decline in emergency contacts at the beginning of the first lockdown, the use of the centralised emergency service increased during the subsequent months and has since stabilised at a significantly higher level than before the pandemic. Comparison of emergency contacts in the first half of 2019 with the first half of 2021 shows that the number of emergency phone contacts nearly doubled, emergency outpatient assessments increased by 40%, emergency bridging interventions increased by 230%, and inpatient admissions of minors to adult psychiatric inpatient units more than doubled because of lack of service capacity in child and adolescent psychiatry. The proportion of adolescents who reported suicidal ideation increased significantly by 15%, from 69% to 84%, and the proportion of adolescents who reported self-harm behaviour increased by 17%, from 31% to 48%. CONCLUSION: We found a significant increase in psychiatric service use, as well as in reported serious mental health symptoms such as suicidality and self-harm behaviour in help-seeking children and adolescents in the course of the pandemic. The child and adolescent psychiatric healthcare system is overburdened and down-referral of adolescents in need of ongoing therapy is becoming increasingly difficult. We recommend prioritising preventive and therapeutic measures to support the mental health of our children and adolescents alongside the somatic management of the COVID-19 pandemic.