Asymmetry in the Central Nervous System: Functional Implications

The processing of several brain functions is asymmetrically distributed between homotopic hemispheric areas, as initially shown for the language and, with the advent of modern imaging techniques, for many other functions. Accordingly, local asymmetric cortical lesions may result in very specific functional loss. Paradoxically, the cognitive effects of unilateral lesions can be rescued by a second contralateral one, as elegantly demonstrated by Lomber and Payne in 1996. In their seminal paper, the hemineglect induced by silencing the suprasylvian cortex could be rescued by the deactivation of the contralateral homotopic region. In this instance, the initial deficit could not be attributed to the local injury, but to the unbalance created between the two hemispheres. Beyond this extreme experimental evidence, recent literature suggests that asymmetry in the trigeminal sensory inputs related to occlusal factors may lead to deficits in cognitive functions by affecting the balance of the brain ascending modulatory systems.

The goal of this Research Topic is to focus on the neurophysiological and molecular mechanisms underlying balance maintenance and/or balance disruption, as well as on their outcome in behavioral and adaptive terms, exploring the effects of nerve and brain stimulation, prosthesis application, natural sensorimotor activation and central and peripheral injuries (as, for example, stroke and neurectomy) in both physiological and pathophysiological models, humans and animals.

The achievement of this goal will provide a novel conceptual framework explaining the multifaceted contributions of brain (a)symmetry and interhemispheric functional balance/imbalance to brain functions, in both physiological and pathological conditions

This Research Topic welcomes original studies, reviews, or comments on structural, functional, and molecular brain asymmetries (particularly in relation to specific brain functions) and on the impact of unilateral modulation/lesion of the central/peripheral nervous system on cognition, emotion, sensation, motor behavior, learning, and plasticity, as well as on the underlying neurophysiological and molecular mechanisms. Studies on modifications elicited by asymmetric lesions, by changes in peripheral inputs, and by physiological perturbations of brain activity on behavior, gene expression, connectivity, and neural excitability are of great interest.