Survival with asymmetrical brain: advantages and disadvantages of cerebral lateralization. Behav Brain Sci

Department of Psychology and B.R.A.I.N. Centre for Neuroscience, University of Trieste, 34123 Trieste, Italy.
Behavioral and Brain Sciences (Impact Factor: 20.77). 09/2005; 28(4):575-89; discussion 589-633. DOI: 10.1017/S0140525X05000105
Source: PubMed


Recent evidence in natural and semi-natural settings has revealed a variety of left-right perceptual asymmetries among vertebrates. These include preferential use of the left or right visual hemifield during activities such as searching for food, agonistic responses, or escape from predators in animals as different as fish, amphibians, reptiles, birds, and mammals. There are obvious disadvantages in showing such directional asymmetries because relevant stimuli may be located to the animal's left or right at random; there is no a priori association between the meaning of a stimulus (e.g., its being a predator or a food item) and its being located to the animal's left or right. Moreover, other organisms (e.g., predators) could exploit the predictability of behavior that arises from population-level lateral biases. It might be argued that lateralization of function enhances cognitive capacity and efficiency of the brain, thus counteracting the ecological disadvantages of lateral biases in behavior. However, such an increase in brain efficiency could be obtained by each individual being lateralized without any need to align the direction of the asymmetry in the majority of the individuals of the population. Here we argue that the alignment of the direction of behavioral asymmetries at the population level arises as an "evolutionarily stable strategy" under "social" pressures occurring when individually asymmetrical organisms must coordinate their behavior with the behavior of other asymmetrical organisms of the same or different species.

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    • "Birds are visually lateralized with a left hemispheric superiority for visual discrimination of form details (Güntürkün and Kesch, 1987;Güntürkün, 1997a;Vallortigara and Rogers, 2005;Manns and Ströckens, 2014). In pigeons, this functional asymmetry is especially obvious when the animals memorize (vonFersen and Güntürkün, 1990) or categorize stimuli (Yamazaki et al., 2007) that can only be discerned by attending to small pictorial features. "
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    ABSTRACT: Birds show remarkable visual abilities that surpass most of our visual psychophysiological abilities. In this study, we investigated visual associative areas of the tectofugal visual system in pigeons. Similar to the condition in mammals, ascending visual pathways in birds are subdivided into parallel form/color vs. motion streams at the thalamic and primary telencephalic level. However, we know practically nothing about the functional organization of those telencephalic areas that receive input from the primary visual telencephalic fields. The current study therefore had two objectives: First, to reveal whether these visual associative areas of the tectofugal system are activated during visual discrimination tasks; second, to test whether separated form/color vs. motion pathways can be discerned among these association fields. To this end, we trained pigeons to discriminate either form/color or motion stimuli and used the immediate early gene protein ZENK to capture the activity of the visual associative areas during the task. We could indeed identify several visual associative telencephalic structures by activity pattern changes during discriminations. However, none of these areas displayed a difference between form/color vs. motion sessions. The presence of such a distinction in thalamo-telencephalic, but not in further downstream visual association areas opens the possibility that these separate streams converge very early in birds, which possibly minimizes long-range connections due to the evolutionary pressure towards miniaturized brains.
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    • "The most prominent manifestation of lateralised behaviour in humans is that of handedness (i.e., the predominant use of one hand), with roughly 90% of people using their right hand for most activities (Annett, 1985;Porac and Coren, 1981). Studies of lateralised behaviour patterns in other species (e.g., amphibians, rodents, cats, primates, marsupials, whales) now suggest that cerebral functional asymmetry is not unique to humans, but, rather, may be a fundamental feature of all vertebrate, and even some invertebrate, brains (for reviews seeFrasnelli et al., 2012;MacNeilage et al., 2009;Rogers, 2002;Rogers et al., 2013;Vallortigara et al., 2010;Vallortigara and Rogers, 2005). What is less clear is whether non-human species exhibit lateralisation in their limb use in a manner that approximates human handedness or whether the prefered use of a specific hand, paw or similar appendage is related to other aspects of brain asymmetry (see reviews byCorballis, 2009;Rogers, 2009;Versace and Vallortigara, 2015). "
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    • "Given that laterally asymmetrical movements are ubiquitous among biological organisms, they are likely to have been adaptive and/or inevitable (Vallortigara and Rogers, 2005). It is impossible for a bilaterally symmetrical organism to maneuver through a two-or three-dimensional space until one side of the body leads, because the forces that cause the movements of the body are generated within the body (Glezer (1987) put forward this perspective as a comment on MacNeilage et al. (1987)). "
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    ABSTRACT: Laterally asymmetrical movements are ubiquitous among organisms. A bilaterally symmetrical organism cannot maneuver through a two- or three-dimensional space unless and until one side of its body leads, because the forces that cause the movements of the body are generated within the body. One question follows: are there any costs or benefits of laterally asymmetrical movements? We test whether directionally consistent laterally asymmetrical movements at different levels of organization of movements (at the individual, and not the population level) can work synergistically. We show-by means of a hypothetical system resembling a humanoid robot-that a laterally asymmetrical movement at a lower level of organization of movements can stimulate laterally asymmetrical movements that are directionally consistent at consecutive higher levels. We show-by comparing two hypothetical systems, incorporating laterally symmetrical and asymmetrical movements, respectively-that the asymmetrical system outperforms the symmetrical system by optimizing space and time and that this space-time advantage increases with the increasing complexity of the task. Together, these results suggest that laterally asymmetrical movements can self-organize as a consequence of space-time optimization.
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