Laterality最新文献

The last decade of laterality research has been bolstered by a significant broadening in theoretical framing and investigative approaches. Comparative research contributions continue to strengthen the position that ancient functional and anatomical brain biases are preserved in modern humans. However, how they unfold over developmental time and contribute to cognitive abilities is still unclear. To make further advances, we must position human brains and behaviors within an evolutionary framework. This includes viewing motor-sensory behavior as an integral part of a developing cognitive system.

In my comment on the target article of Ocklenburg et al. [Laterality 2020: Entering the next decade. Laterality, 1-33. doi:10.1080/1357650X.2020.1804396], I point out the relevance of studies in non-human species within natural settings for understanding the ecological pressures, which shape the direction and degree of brain asymmetries. I therefore outline some major research projects, which are not included in the paper of Ocklenburg et al. and which require comparative animal research.

In this comment to Ocklenburg et al.'s paper I stressed the contribution that computational ethology can provide to the accurate tracking of lateralized behaviour in a variety of species; I also discussed how current interest in so-called «minimal cognition» may help to disentangle shared and species-specific mechanisms of brain and behavioural asymmetries.

In our recent opinion paper "Laterality 2020: entering the next decade", we highlighted trends that we thought are likely to shape laterality research in the 2020s. Our opinion paper inspired 11 commentaries by experts from several disciplines which discussed a wide range of topics complementing the 10 trends we identified in the opinion paper. In this reply, we summarize and discuss the 11 commentaries by clustering them into 3 different main topics. The topic that was covered by the largest number of commentaries was the role of comparative and evolutionary approaches in laterality research. Moreover, several comments focused on the ontogenesis of hemispheric asymmetries and the importance of reliability and validity in laterality research. Embracing the technical advances, research trends and controversies laid out in the commentaries will significantly improve our understanding of several of the core questions of laterality research.

It is commonly assumed that cerebral asymmetry is unidimensional, but evidence increasingly suggests that different brain circuits are independently lateralized. This might explain why the search for a laterality gene has provided multiple candidates, each with weak linkage. An alternative possibility is that there is a single genetically invariant source of lateralization, perhaps cytoplasmic, and subject to many influences, some genetic, some epigenetic, and some random. This could further explain why laterality is associated with a variety of disorders, such as dyslexia, schizophrenia, stress disorders, and depression.

Ocklenburg et al. (2020, Laterality 2020: Entering the next decade. Laterality) provided the field of laterality research with a stimulating research perspective for the coming decade, based on the current state of the art in both animal and human laterality research. Although this is paper takes many different approaches of laterality into account, we emphasize that the eco-evolutionary approach needs more attention. This concerns the question why organisms are lateralized in the first place, in other words, how does lateralization enhance the Darwinian fitness of the individual. We argue that laterality can be distinguished along four dimensions, and that each of them requires different ultimate explanations. Studying these functional and evolutionary explanations requires the development of ecologically relevant tests, adapted to the species at hand. It also requires experimental manipulation of laterality, testing the effect in (semi)-natural conditions on fitness parameters. Tools for such manipulation of laterality urgently require a better understanding of the developmental plasticity of lateralization, extending the field of evo-devo to that of eco-evo-devo. We also warn against seeing the minority in the distribution of direction or strength of lateralization as being a pathology as such minorities in biology can often be explained as adaptations by natural frequency dependent selection.

With this comment, I comment on the key ideas of the opinion paper by Ocklenburg et al. The authors describe trends in lateralization research for the next decade. With my commentary, I take the liberty of pointing out that it is first more important to focus on the relevant questions to be answered in the context of lateralization research before calling out research trends. Furthermore, the focus of lateralization research in humans should be more on the human brain and human behaviour because the human brain is highly specialized despite many similarities with other species' brains.

This is a commentary on a paper by Ocklenburg et al. ([2020]. Laterality 2020: entering the next decade. Laterality). I discuss measurement and task selection issues that should not be neglected as we make our way through the next decade. I also comment further on a few pointed issues relevant to open science and meta-analysis.

Non-shared environmental variance (NSEV) accounts for 76% of variance in genetic modelling of handedness. However, it is very misleading to suggest that NSEV, "highlights the importance of non-genetic factors for the ontogenesis of hemispheric asymmetries". NSEV is poorly named, is calculated only by subtraction, and provides no direct evidence for environmental effects in the sense of the external environment. Miller suggested that it would be better named as "residual effect". Mitchell has suggested that much or indeed most of NSEV is "developmental variance" and should be included under the heading of nature rather than nurture, and in handedness, "largely reflect[s] the outcome of randomness in brain development". Overall only a very small proportion of NSEV in handedness is likely to be related to external environmental factors in the usual sense of the term.