Brain, Behavior and Evolution

Brains are very plastic both in response to phenotypic diversity and to larger evolutionary trends. Differences between taxa cannot be easily attributed to either factors. Comparative morphological data on higher taxonomic levels is scarce especially in ray-finned fishes. Here we show the great diversity of brain areas of more than 150 species of ray-finned fishes by volumetric measurements using block face imaging. We found that differences among families or orders are more likely due to environmental needs than to systematic position...

Here, we present the first evidence for brain adaptation in pigs tolerant to the human presence, as a behavioral trait favoring domestication. The study was carried out on minipiglets from population bred in the Institute of Cytology and Genetics (Novosibirsk, Russia). We compared the behavior, metabolism of monoaminergic neurotransmitter systems and functional activity of the hypothalamic-pituitary-adrenal system, as well as neurotrophic markers in the brain of minipigs differing by tolerance to human presence (HT and LT - High and Low Tolerance)...

The hippocampus plays an important role in spatial navigation and spatial learning across a variety of vertebrate species. Sex and seasonal differences in space use and behavior are known to affect hippocampal volume. Similarly, territoriality and differences in home range size are known to affect the volume of the reptile hippocampal homologues, the medial and dorsal cortices (MC, DC). However, studies have almost exclusively investigated males and little is known about sex or seasonal differences in MC and/or DC volumes in lizards...

Local circuit neurons are present in the thalamus of all vertebrates where they are considered inhibitory. They play an important role in computation and influence the transmission of information from the thalamus to the telencephalon. In mammals, the percentage of local circuit neurons in the dorsal lateral geniculate nucleus remains relatively constant across a variety of species. In contrast, the numbers of local circuit neurons in the ventral division of the medial geniculate body in mammals vary significantly depending on the species examined...

Pteropodidae is the only phytophagous bat family that predominantly depends on visual and olfactory cues for orientation and foraging. During daytime, pteropodids of different species roost in sites with varying light exposure. Pteropodids have larger eyes relative to body size than insectivorous bats. Retinal topography has been studied in less than 10% of the approximately 200 pteropodid species, a behavioural estimation of spatial resolution is available only for Pteropus giganteus, and little is known about the relationship between their roost site preference and visual ecology...

Brain size evolution in hominins constitutes a crucial evolutionary trend, yet the underlying mechanisms behind those changes are not well understood. Here, climate change is considered as an environmental factor using four paleoclimate records testing temperature, humidity, and precipitation against changes to brain size in 298 Homo specimens over the past fifty thousand years. Across regional and global paleoclimate records, brain size in Homo averaged significantly lower during periods of climate warming as compared to cooler periods...

The amygdala is a complex brain structure in the vertebrate telencephalon, essential for regulating social behaviors, emotions and (social) cognition. In contrast to the vast majority of neuron types described in the many nuclei of the mammalian amygdala, little is known about the neuronal diversity in non-mammals, making reconstruction of its evolution particularly difficult. Here, we characterize glutamatergic neuron types in the amygdala of the urodele amphibian Pleurodeles waltl. Our single-cell RNA sequencing data indicate the existence of at least ten distinct types and subtypes of glutamatergic neurons in the salamander amygdala...

Endocranial casts are capable of capturing the general brain form in extinct mammals due to the high fidelity of the endocranial cavity and the brain in this clade. Camelids, the clade including extant camels, llamas, and alpacas, today display high levels of gyrification and brain complexity. The evolutionary history of the camelid brain has been described as involving unique neocortical growth dynamics which may have led to its current state. However, these inferences are based on their fossil endocast record from approximately ~40 Mya (Eocene) to ~11 Mya (Miocene), with a gap in this record for the last ~10 million years...

Mudskippers are intertidal burrowing fish with unique living habits. So far, studies on the cytoarchitecture of brain in fish with such behaviors remain limited. Therefore, documenting the neuroanatomy of this animal is of interest because of its unique characteristics. In this study, we examined the cytoarchitecture of the mudskipper (Boleophthalmus pectinirostris) brain and investigated whether it has any peculiarities in its brain structures. In general, the basic composition, morphology and organization of the mudskipper brain do not vary markedly from other teleosts...

Crocodilians (alligators, crocodiles and gharials) are the closet living relatives to birds, and as such, represent a key clade to understand the evolution of the avian brain. However, many aspects of crocodilians neurobiology remain unknown. In this paper we address an important knowledge gap as there are no published studies of cerebellar connections in any crocodilian species. We used injections of retrograde tracers into the cerebellum of the American Alligator (Alligator mississippiensis) to describe for the first time the origin of climbing and mossy fiber inputs...

The amygdala is a central node in functional networks regulating emotions, social behavior and social cognition. It develops in the telencephalon and includes pallial and subpallial parts, but these are extremely complex with multiple subdivisions, cell types and connections. The homology of the amygdala in non-mammals is highly controversial, especially for the pallial part, and we are still far from understanding general principles on its organization that are common to different groups. Here we review data on the adult functional architecture and developmental genoarchitecture of the amygdala in different amniotes (mammals and sauropsids), which are helping to disentangle and to better understand this complex structure...

The 2022 meetings of the J.B. Johnston Club for Evolutionary Neuroscience and Karger Workshop in Evolutionary Neuroscience will be held immediately before the annual meeting of the Society for Neuroscience on Thursday, November 10 (the Karger Workshop), and Friday, November 11 (the regular JBJC meeting). Both meetings will take place at the Horton Grand Hotel, San Diego CA, USA. This year's Karger Workshop in Evolutionary Neuroscience, made possible by the continuing support of Karger Publishers, is organized by Daphne Soares with assistance by Grace Capshaw...

In Atlantic salmon (Salmo salar) seasonal photoperiod is shown to regulate the onset of sexual maturation, yet which brain region(s) are involved and how light information impacts the neuroendocrine system are still not fully understood in teleosts. Detailed knowledge about the photoperiodic regulation of maturation in fish is still missing. In birds, it is shown that gonadotrophin releasing hormone (GNRH) is located in the same neurons as vertebrate ancient (VA) opsin suggesting a direct photoreceptive regulation for onset of sexual maturity...

The amygdala, a complex array of nuclei in the forebrain, controls emotions and emotion-related behaviors in vertebrates. Current research aims to understand the amygdala's evolution in ray-finned fish such as zebrafish because of the region's relevance for social behavior and human psychiatric disorders. Clear-cut molecular definitions of the amygdala and its evolutionary-developmental relationship to the one of mammals are critical for zebrafish models of affective disorders and autism. In this review, I argue that the prosomeric model and a focus on the olfactory system's organization provide ideal tools for discovering deep ancestral relationships between the emotional systems of zebrafish and mammals...

The neuromeric/prosomeric model has been rejuvenated by Puelles and Rubenstein (1993). Here, its application to the (teleostean) fish brain is detailed beginning with a historical account. The second part addresses three main issues with particular interest for fish neuroanatomy and looks at the impact of the neuromeric model on their understanding. The first one is the occurence of four early migrating forebrain areas (M1 through M4) in teleosts and their comparative interpretation. The second issue addresses the complex development and neuroanatomy of the teleostean alar and basal hypothalamus...

The subgenual organ complex in the leg of Polyneoptera (Insecta) consist of several chordotonal organs specialised to detect mechanical stimuli from substrate vibrations and airborne sound. In stick insects (Phasmatodea), the subgenual organ complex contains the subgenual organ and the distal organ located distally to the subgenual organ. The subgenual organ is a highly sensitive detector for substrate vibrations. The distal organ has a characteristic linear organisation of sensilla, and is likely also to respond to substrate vibrations...

Birds and mammals have independently evolved complex behavioral and cognitive capabilities yet have markedly different brain structures. An open question is to what extent, despite these differences in anatomy, birds and mammals have evolved similar neural solutions to complex motor control and at what level of organization these similarities might lie. Courtship song in songbirds, a learned motor skill that is similar to the fine motor skills of many mammals including human speech, provides a powerful system in which to study the links connecting the development and evolution of cells, circuits, and behavior...

The amygdaloid complex plays a crucial role in socio-emotional conduct, learning, survival, and reproductive behaviors. It is constituted by a set of nuclei presenting a great cellular heterogeneity and embryonic origin diversity (pallial, subpallial and even extra-telencephalic). In the last two decades, the tetrapartite pallial paradigm defined the pallial portion of the amygdala as a derivative of the lateroventral pallium. However, the pallial conception is currently being reanalyzed and one of these new proposals is to consider the mouse pallial amygdala as a radial histogenetic domain independent from the rest of the pallial subdomains...

Several areas of the vertebrate brain are involved in facilitating and inhibiting the production of sexual behaviors and displays. In the laboratory, a higher rate of sexual displays is correlated with a larger ventral posterior amygdala (VPA), an area of the brain involved in the expression of sexual display behaviors, as well as larger VPA neuronal somas. However, it remains unclear if individuals in the field reflect similar patterns, as there are likely many more selective pressures in the field that may also modulate the VPA architecture...

The scientific context of the special issue dedicated to Luis Puelles and Agustin Gonzalez is given in this short epilogue.