Frasnelli Elisa
Center for Mind/Brain Sciences, University of Trento Rovereto, Italy.
Front Psychol. 2013 Dec 11;4:939. doi: 10.3389/fpsyg.2013.00939.
Traditionally, only humans were thought to exhibit brain and behavioral asymmetries, but several studies have revealed that most vertebrates are also lateralized. Recently, evidence of left-right asymmetries in invertebrates has begun to emerge, suggesting that lateralization of the nervous system may be a feature of simpler brains as well as more complex ones. Here I present some examples in invertebrates of sensory and motor asymmetries, as well as asymmetries in the nervous system. I illustrate two cases where an asymmetric brain is crucial for the development of some cognitive abilities. The first case is the nematode Caenorhabditis elegans, which has asymmetric odor sensory neurons and taste perception neurons. In this worm left/right asymmetries are responsible for the sensing of a substantial number of salt ions, and lateralized responses to salt allow the worm to discriminate between distinct salt ions. The second case is the fruit fly Drosophila melanogaster, where the presence of asymmetry in a particular structure of the brain is important in the formation or retrieval of long-term memory. Moreover, I distinguish two distinct patterns of lateralization that occur in both vertebrates and invertebrates: individual-level and population-level lateralization. Theoretical models on the evolution of lateralization suggest that the alignment of lateralization at the population level may have evolved as an evolutionary stable strategy in which individually asymmetrical organisms must coordinate their behavior with that of other asymmetrical organisms. This implies that lateralization at the population-level is more likely to have evolved in social rather than in solitary species. I evaluate this new hypothesis with a specific focus on insects showing different level of sociality. In particular, I present a series of studies on antennal asymmetries in honeybees and other related species of bees, showing how insects may be extremely useful to test the evolutionary hypothesis.
传统上，人们认为只有人类会表现出大脑和行为的不对称性，但多项研究表明，大多数脊椎动物也存在偏侧化现象。最近，无脊椎动物左右不对称的证据开始出现，这表明神经系统的偏侧化可能是简单大脑以及复杂大脑的一个特征。在此，我将介绍一些无脊椎动物中感觉和运动不对称以及神经系统不对称的例子。我将阐述两个案例，其中不对称的大脑对于某些认知能力的发展至关重要。第一个案例是线虫秀丽隐杆线虫，它具有不对称的嗅觉感觉神经元和味觉感知神经元。在这种线虫中，左右不对称负责感知大量盐离子，对盐的偏侧化反应使线虫能够区分不同的盐离子。第二个案例是果蝇黑腹果蝇，大脑特定结构中不对称的存在对于长期记忆的形成或提取很重要。此外，我区分了脊椎动物和无脊椎动物中出现的两种不同的偏侧化模式：个体水平和群体水平的偏侧化。关于偏侧化进化的理论模型表明，群体水平上偏侧化的一致性可能是作为一种进化稳定策略进化而来的，在这种策略中，个体不对称的生物体必须与其他不对称生物体协调其行为。这意味着群体水平的偏侧化更有可能在社会性物种而非独居物种中进化。我以特别关注表现出不同社会性水平的昆虫为重点来评估这一新假设。特别是，我展示了一系列关于蜜蜂和其他相关蜜蜂物种触角不对称的研究，表明昆虫对于检验进化假设可能非常有用。
