Brain Behavior and Evolution最新文献

Humans display larger and more complex parietal lobes, when compared with other primates. The superior parietal lobule is a region still poorly known in terms of comparative and evolutionary neuroanatomy, although at least its medial region, the precuneus, is apparently expanded in our species. In this article, I review twenty years of personal research on the morphology and evolution of this cortical element. The precuneus is particularly variable among adult humans, mostly in its dorsal and anterior areas. This large individual variability seems already settled at birth. During aging, this cortical region is particularly sensitive to atrophy and neurodegeneration. Its ventral areas are embedded in a complicated topological environment, suggesting spatial, metabolic, and vascular constraints. Human and non-human primates share a similar organization of the superior parietal lobule, although with different proportions. Even when compared with extinct hominids, the precuneus in modern humans looks more expanded. These changes are expected to be associated with some cognitive variations, possibly involving visuospatial integration, body cognition, mental imaging, and self-construction.

We reanalyzed data from Sobrero et al. (2016) to measure dorsal dentate gyrus (dDG) folding or gyrification in Octodon degus and O. lunatus as a morphological proxy for neurogenesis and macrostructural plasticity in hippocampal or extracortical regions. Using Zilles' (ZGI) and Vogeley's (VGI) indices, we quantified dDG gyrification across hemispheres in populations differing in habitat complexity and social behaviour. Left dDG gyrification (ZGIL) showed a preliminary association with social group size, while right dDG gyrification (VGIR) was predicted by population differences. Octodon lunatus from shrub-dense environments exhibited greater dDG folding than O. degus from open habitats, supporting an influence of habitat conditions in shaping hippocampal morphology. Although not statistically significant, hemispheric asymmetries were suggested, a trend consistent with previously reported right-lateralized DG cell numbers in O. lunatus and habitat-sociality effects on DG cell counts in O. degus from El Salitre. Overall, our results support dDG gyrification as an informative marker of neural plasticity shaped by habitat conditions, emphasizing the importance of wild models in brain-ecology research.

Introduction Over the last century, sea surface temperatures have increased by more than 0.5˚C, with predictions suggesting an increase of 1-4˚C by 2100. Oceanic warming poses significant challenges to marine species, particularly those with physiological and developmental processes that are tightly linked to environmental conditions. In cartilaginous fishes, including sharks, the brain grows continually throughout life, supported by the capacity for lifelong neurogenesis. This feature suggests that the nervous system - both peripheral (sensory) and central (brain) - of sharks may be highly plastic and able to adapt dynamically to a changing environment. Methods We investigated the effects of elevated rearing temperature on brain development in the epaulette shark (Hemiscyllium ocellatum), a species known for its tolerance of environmental fluctuations in intertidal habitats. Eggs (n = 12) were sourced from a breeding stock at the New England Aquarium and reared in either ambient (27°C) or elevated (31°C, 4°C above ambient) seawater temperatures until two months post-hatch. Using histological analyses, we compared the relative volume of the nose (olfactory rosette), total brain, and major brain regions between treatment groups. Results Despite this species' natural exposure to temperature variability, Generalized Linear Models revealed that elevated temperature significantly altered the volume of the olfactory sensory epithelium, olfactory bulbs, and medulla oblongata after accounting for overall brain size. Analyses of proportional brain region volumes also showed that elevated temperature was associated with reduced olfactory bulb size and increased subpallial volume relative to total brain size. These changes may suggest potential changes in cognitive capacity related to olfactory processing as well as sensory and / or motor functions at elevated temperatures. Conclusions While short-term studies, such as this one, cannot capture long-term adaptive potential, understanding the impacts of elevated temperature on brain phenotypes provides critical insights into how elasmobranchs may cope with changing ocean conditions. Such knowledge will be vital for predicting the resilience of these ecologically important species to future environmental stressors.

Background: The mammalian auditory cortex can be parcellated into multiple functional subfields, with each subfield making a distinct contribution to sound processing. For example, primary fields consisting of primary auditory cortex and anterior auditory field are the first to receive information from the thalamus, and the neurons in each of these fields have different properties in terms of latency and response duration. Non-primary auditory fields consist of secondary auditory cortex, which is involved in object recognition and emotional conditioning, while dorsal auditory fields are more responsive during locomotion and spatial tasks. What is currently unknown is how the structure of each auditory cortical subfield relates to function. Thus, it is imperative to understand how anatomical substrates that make up each field contribute to function.

Summary: In this review, we suggest that myelin may serve as a structural anchor for the organization of auditory cortical subfields. Myelination patterns among mammals that have been studied (primates, carnivores, rodents, and bats) show that primary auditory cortical fields are more heavily myelinated than non-primary auditory cortical fields, and upper cortical layers are less myelinated than middle and deep layers. Myelin also demonstrates experience-dependent plasticity and can be measured with a variety of invasive and noninvasive methods, and demyelination has been linked to cognitive decline. Conversely, the archicortex is lightly myelinated, and we speculate that because myelin inhibits axonal and synaptic plasticity, it would not be advantageous for the archicortex to be myelin-dense, as it has greater requirements for flexibility for learning and memory.

Key messages: This is the first review, to our knowledge, that uses a comprehensive comparative approach across mammals to determine the distribution of myelin across auditory cortical subfields. We argue that a detailed map of the myeloarchitecture of the auditory cortex must be directly aligned to the functional maps of the auditory cortex to account for individual variability and identify subfields accurately. Furthermore, myelin maps need to be compared with other anatomical markers as well to improve our understanding of the role of myelin. Finally, a detailed histological myelin map can serve as a ground truth for comparisons to noninvasive measures of myelin.

Introduction: Wet dog shake (WDS) is a motion in mammals and birds, consisting in vigorous and rapid rotations of the head and trunk around the spinal axis, which allows them to dry themselves. WDS requires fine balance control. To date, motor control in WDS has not been studied.

Methods: Here, for the first time, we investigated the trunk and limbs muscle EMG activity and correlated it with the kinematics of body movement and ground reactions force during WDS in rats.

Results: Strict reciprocity was revealed between the forelimb muscle on the right and left sides despite bipedal hindlimb position. Reciprocal activity was observed between the lumbar and the thoracic segments. The hindlimb muscle activity exhibited two distinct muscle synergies with strict reciprocity and atypical co-activity of flexors and extensors, which were previously observed in paw shaking behavior. These two synergies correlate with the two muscle groups of the pelvic fins of fish. The absence of typical postural responses of the hindlimb was revealed.

Conclusions: (1) It is likely that WDS and paw shaking share a common nervous control. (2) The absence of typical postural responses may indicate that body balance in WDS is maintained by perfectly matched frequency and strength of the trunk muscle contractions. (3) In the hypothesis about the origin of WDS, based on the revealed characteristics, we compare it with the S-start response behavior in fish.

Introduction: Zebrin II (ZII) is a glycolytic enzyme that is expressed in cerebellar Purkinje cells. In both mammals and birds, ZII is expressed heterogeneously, such that there are sagittal stripes of Purkinje cells with a high ZII expression (ZII+) alternating with stripes of Purkinje cells with little or no expression (ZII-). To date, ZII expression studies examined at least one species from most of the major branches of the avian phylogeny including Paleognatha (tinamous, kiwi), Galloanseres (chicken), Columbaves (pigeon), and Elementaves (hummingbird). In this regard, the most glaring omission is that a species from Telluraves, a clade that contains 75% of all avian species, has not been studied.

Methods: In this paper, we examined ZII expression in the zebra finch Taeniopygia castanotis (order Passeriformes). Given that Telluraves have evolved sophisticated hindlimb movements associated with the jump to arboreality, we hypothesized that ZII expression would differ in those areas of the cerebellum that have a strong representation of the hindlimbs, namely folia II-V and IX.

Results: Contrary to our prediction, we found that the pattern of ZII expression in the cerebellum is highly similar to that observed in other bird species. In folium I, all Purkinje cells are ZII+. In the rest of the anterior lobe (folia II-V) there are 4 pairs of ZII+/- stripes. In the posterior lobe, folia VI-VII all Purkinje cells are ZII+, in folia VIII-IXcd there are 5-7 pairs of ZII+/- stripes, and in folium X all Purkinje cells are ZII+. Moreover, the expression of ZII+ in Purkinje cell terminals in the cerebellar and vestibular nuclei was similar to that observed in other species.

Conclusion: These data indicate that the pattern of heterogeneous expression of ZII in cerebellar Purkinje is likely conserved across the entirety of the avian phylogenetic tree.

Introduction: Cervical and lumbar enlargements involving several spinal segments are present in the spinal cord of tetrapods, reflecting the heavy motor and sensory innervation of limbs. Such spinal enlargements are not apparent in teleost fishes. However, teleosts possess paired pectoral and pelvic fins that are homologous to forelimbs and hindlimbs, respectively, and modest spinal enlargements might be present in teleosts as well.

Methods: In the present study, therefore, we have investigated the innervation of different fins by spinal nerves in zebrafish. We then investigated the changes in transverse sectional areas of the spinal cord and gray matter, referring to the levels of spinal cord innervating different fins.

Results: These analyses revealed that enlargements of the spinal cord and gray matter are indeed present for pectoral and pelvic fins that are paired appendages like limbs in tetrapods. In addition, enlargements are also present for the dorsal, anal, and caudal fins.

Conclusion: The present study thus suggests that spinal enlargements are present also in teleosts, although they are modest and can only be detected by analyses at the histological level. The present study also indicates that enlargements can be formed not only for paired fins that are homologous to limbs of tetrapods but also for unpaired fins. That is, spinal enlargements are present for all appendages or fins in teleosts.

Introduction: The detection of novelty is a cognitive ability that is fundamental to survival. Following detection, a decision must be made to either approach (neophilia) or avoid (neophobia) the novel stimulus. The tendency to choose one strategy over the other is referred to as an animal's neotic preference. To date, the bulk of research reports that mammals are neophilic, while birds tend to be neophobic. These data, however, are differentiated not only by the class of animal (i.e., Mammalia vs. Aves), but also by the testing methods used, namely the context in which testing occurs.

Method: To disentangle these factors, we assessed the reaction to novelty in two commonly used domesticated species, rats and pigeons, within two different contexts, a novel testing arena (common for mammals) and within the home cage (common for birds).

Results: Here, we show that both rats and pigeons show neophobia in the home cage and neophilia in a testing arena, demonstrating that some degree of the differences previously reported are likely due to testing protocols. Moreover, individual scores in one testing protocol did not predict testing scores in the other.

Conclusion: These results limit the ability to: (a) compare findings across these paradigms and (b) conceive of neotic preference as a single stable trait across multiple (especially novel) contexts.

Introduction: The inner ear is a complex three-dimensional structure responsible for the detection of sound, balance, and acceleration. Detailed knowledge about the development of the inner ear of gnathostomes (jawed vertebrates) comes from studies in bony fishes and tetrapods, but comparable information about this process in chondrichthyans, the oldest gnathostome radiation, is lacking. This study describes for the first time the embryonic development of the inner ear and its innervation in the catshark Scyliorhinus canicula.

Methods: By using molecular markers of proliferating cells, migrating neuroblasts, and early differentiating neurons and genes expressed in placode-derived sensory neurons (NeuroD) and inner ear sensory patches (Sox2), we have established the spatiotemporal developmental pattern of the catshark inner ear also observed with micro-CT, and we have characterized developing sensory patches and described the establishment of the inner ear innervation.

Results: The development of the catshark inner ear takes place by invagination of the otic placode, as revealed by the expression of NeuroD at very early stages. From the very simple initial epithelial structure, the otic epithelium gradually grows and subdivides to form a complex three-dimensional labyrinth already recognizable at early stage 32. At this stage, the anterior semicircular canal and the horizontal semicircular canal of the catshark meet and fuse over the utricular concurrently with the beginning of the maturation of the inner ear sensory organs. We also show that the endolymphatic duct is formed as consequence of the invagination process; that the primary neurons of the statoacoustic ganglion originate by delamination from the otic epithelium, as in other vertebrates; that inner ear innervation starts when fibers immunoreactive to DCX link the otic cup to the brain at stage 20; and that the innervation pattern is completed at stage 32.

Conclusion: Present results provide cytological data on developmental changes that may be helpful for comparison with the development of this sensory system in other vertebrates and thus to gain knowledge on the evolution of the development of the inner ear.

Introduction: This study analyzes the expression of the transcription factor orthopedia (Otp) in the alar hypothalamus and its evolutionary relationship with the amygdaloid complex.

Methods: Immunofluorescence analysis was used in several representative vertebrates, including sarcopterygians (mice, chickens, turtles, anuran amphibians, and lungfish) and actinopterygian fish (teleosts and polypteriforms).

Results: We reveal highly conserved Otp expression in all species used, supporting its critical role in hypothalamic regional specification and in the development of neuroendocrine cells and the amygdaloid complex. Our results show that hypothalamic radial migration of Otp contributes to amygdaloid populations, particularly in those with subpallial origin, in a highly conserved manner from basal actinopterygians.

Conclusion: Differences between sarcopterygians and actinopterygians in the Otp expression patterns in cells migrated to the pallial amygdala highlight an evolutionary divergence, particularly in the complexity and cellular composition of this region, tracing its evolutionary emergence by using the studied species as reference. Moreover, present results emphasize the evolutionary and functional importance of hypothalamic-amygdaloid interactions.