Brain Lateralization: A Comparative Perspective

Abstract

Comparative studies on brain asymmetry date back to the 19th century but then largely disappeared due to the assumption that lateralization is uniquely human. Since the reemergence of this field in the 1970s, we learned that left-right differences of brain and behavior exist throughout the animal kingdom and pay off in terms of sensory, cognitive, and motor efficiency. Ontogenetically, lateralization starts in many species with asymmetrical expression patterns of genes within the Nodal cascade that set up the scene for later complex interactions of genetic, environmental, and epigenetic factors. These take effect during different time points of ontogeny and create asymmetries of neural networks in diverse species. As a result, depending on task demands, left- or right-hemispheric loops of feedforward or feedback projections are then activated and can temporarily dominate a neural process. In addition, asymmetries of commissural transfer can shape lateralized processes in each hemisphere. It is still unclear if interhemispheric interactions depend on an inhibition/excitation dichotomy or instead adjust the contralateral temporal neural structure to delay the other hemisphere or synchronize with it during joint action. As outlined in our review, novel animal models and approaches could be established in the last decades, and they already produced a substantial increase of knowledge. Since there is practically no realm of human perception, cognition, emotion, or action that is not affected by our lateralized neural organization, insights from these comparative studies are crucial to understand the functions and pathologies of our asymmetric brain.

A large-scale estimate on the relationship between language and motor lateralization

“…One of the best known functional hemispheric asymmetries is the lateralization of the human language system 1 . A number of studies have demonstrated that about 85–90% of the population shows a left-hemispheric dominance in several language-related tasks 2 – 6 .…”

Light‐dependent development of the tectorotundal projection in pigeons

“…The growing number of examples for left‐right differences in brain and behaviour in animal species of very different complexity characterizes asymmetries (or lateralization) as a general organization principle of the nervous system in the animal kingdom (Güntürkün, Ströckens, & Ocklenburg, 2020; Vallortigara & Rogers, 2005). The emergence of cerebral asymmetries and thus processing differences between the two brain sides illustrate how gene–environment interactions sculpt the functional architecture of the brain.…”

Does Asymmetrical Gonopodium Morphology Predict Lateralized Behavior in the Fish Xenophallus umbratilis?

“…We are still learning about behavioral handedness in these cases (Vallortigara and Rogers, 2005;Gunturkun et al, 2020). Clearly, such information may be critical to understanding why such behavioral biases evolved in the first place.…”