![]() In particular, these developmental steps are influenced by environmental experiences, which regulate the fine-tuning of neural networks via processes that are referred to as ontogenetic plasticity. During ongoing development, hemispheric specialization increases for specific functions and subsystems interact to shape the final functional organization of a brain. The basic lateralized organization of a brain is already established through genetically controlled embryonic events. The relative impact of genetic and nongenetic factors varies between different developmental phases and neuronal structures. This review combines data from human and animal research (especially on birds) and outlines a multi-level model for asymmetry formation. ![]() Current genetic psychology collects data on genes relevant to brain lateralizations, while animal research provides information on the cellular mechanisms mediating the effects of not only genetic but also environmental factors. Although there is little doubt that asymmetries arise through genetic and nongenetic factors, an overarching model to explain the development of functional lateralization patterns is still lacking. Through quantifying the variation in arm truncation, this study provides a new foundation to explore behavioral compensation for arm loss in cephalopods.Īsymmetries in the functional and structural organization of the nervous system are widespread in the animal kingdom and especially characterize the human brain. Overall, we show that arm injuries in our sampling of three intertidal species are frequent and asymmetrical, and that when injured, octopus on average lose a considerable proportion of their arm. rubescens also exhibited the steepest scaling patterns, and showed a positive correlation between body size and number of truncated arms. The mean percent of arm that was truncated was 28.1 % overall but varied between species and by sex and was highest in O. rubescens, posterior arms (pairs 3 and 4) were more truncated. bimaculoides had a greater proportion of their anterior arms (pairs 1 and 2) truncated, while in O. We found a significant left side bias for greater proportion of arm truncation for all species and sexes except in O. Truncated arms were found in 59.8 % of specimens examined, with individuals bearing one to as many as seven injured arms. We then compared the frequency and proportion of arm losses between different body locations. Here, we used scaling relationships specific to the arms of three sympatric octopus species of the genus Octopus, to calculate the proportion of arm truncation. These numerous appendages, which explore the environment, handle food, and defend the animal against predators, are highly susceptible to truncation or loss. ![]() Octopuses have eight radially symmetrical arms that surround the base of a bilaterally symmetrical body. Throughout this review, we highlight the value of functional neuroimaging and developmental approaches to shed light on the mechanisms underlying human handedness. ![]() Thirdly, findings on primates’ hand preferences for communicative gestures accounts for a link between gestural laterality and a left-hemispheric specialization for intentional communication and language. Secondly, lateralization for actions directed to living targets (to self or conspecifics) seems to be in relationship with the brain lateralization for emotion processing. These could have emerged under selective pressures notably related to the animal locomotion and social styles. Firstly, lateralization for the manipulation of inanimate objects has been associated with genetic and ontogenetic factors, with specific brain regions’ activity, and with morphological limb specializations. In this review, we highlight the great contribution of comparative research to the understanding of human handedness’ evolutionary and developmental pathways, by distinguishing animal forelimb asymmetries for functionally different actions-i.e., potentially depending on different hemispheric specializations. Since then, many studies have evidenced lateralized functions in a wide range of species, including both vertebrates and invertebrates. Until the 1990s, the notion of brain lateralization-the division of labor between the two hemispheres-and its more visible behavioral manifestation, handedness, remained fiercely defined as a human specific trait.
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