Quantitative analysis of the teleost brain: evolutionary and adaptive features of encephalization. II. Primary brain subdivisions

1. Frequently there is an opposition between olfactory and visual senses. Fresh water fishes are generally macrosomatic and microptic, marine fishes (especially coral reef fishes) are microsmatic and macroptic while piscivorous pelagic fishes are macrosmatic and macroptic. 2. The importance of the cerebellum is a function of both the fish's activity level and its body size. 3. There is a marked opposition between the diencephalon and the medulla oblongata and a greater one between the non-olfactory-telencephalon (NOT) and the medulla oblongata (MA). Although it is not possible to give an accurate evolutionary significance, the ratio of NOT/MA is low in primitive teleostean fishes and high in more derived species (Acanthuridae and Tetraodontiformes).     

Neural development in metatherian and eutherian mammals: variation and constraint.

A model for predicting the timing of neurogenesis in mammals (Finlay and Darlington [1995] Science 268:1578-1584) is here extended to an additional five metatherian species and to a variety of other events in neural development. The timing of both the outgrowth of axonal processes and the establishment and segregation of connections proves to be as highly predictable as neurogenesis. Expressed on a logarithmic scale, late developmental events are as predictable as early ones. The fundamental order of events is the same in eutherian and metatherian animals, but there is a curvilinear relation between the event scales of the two; for metatherians, later events are slowed relative to earlier events. Furthermore, in metatherians, the timing of developmental events is more variable than in eutherians. The slowing of late developmental events in metatherians is associated with their considerably longer time to weaning compared with eutherians.     

Quantitative analysis of the teleost brain: evolutionary and adaptive characteristics of encephalization. III. Multivariate analysis of the cephalic index]

A multivariate analysis of 9 brain indices from 83 teleost species showed a marked opposition between the non-olfactory telencephalon (and diencephalon) and the medulla oblongata (phylogenetic characters) and between the olfactory bulbs and the optic tectum (adaptive characters). Results of three different classifying algorithms allowed determination of 6 stable groupings and 9 intermediate ones, some with systematic importance and some purely adaptive. For this reason brain organization criteria must be used with precaution for systematic purposes. Nevertheless, the position of Brotula multibarbata showed that this fish is an evolved acanthopterygian.     

Mosaic evolution and adaptive brain component alteration under domestication seen on the background of evolutionary theory

Brain sizes and brain component sizes of five domesticated pigeon breeds including homing (racing) pigeons are compared with rock doves (Columba livia) based on an allometric approach to test the influence of domestication on brain and brain component size. Net brain volume, the volumes of cerebellum and telencephalon as a whole are significantly smaller in almost all domestic pigeons. Inside the telencephalon, mesopallium, nidopallium (+ entopallium + arcopallium) and septum are smaller as well. The hippocampus is significantly larger, particularly in homing pigeons. This finding is in contrast to the predictions of the 'regression hypothesis' of brain alteration under domestication. Among the domestic pigeons homing pigeons have significantly larger olfactory bulbs. These data are interpreted as representing a functional adaptation to homing that is based on spatial cognition and sensory integration. We argue that domestication as seen in domestic pigeons is not principally different from evolution in the wild, but represents a heuristic model to understand the evolutionary process in terms of adaptation and optimization.     

Gradients in cytoarchitectural landscapes of the isocortex: Diprotodont marsupials in comparison to eutherian mammals

Although it has been claimed that marsupials possess a lower density of isocortical neurons compared with other mammals, little is known about cross‐cortical variation in neuron distributions in this diverse taxonomic group. We quantified upper‐layer (layers II–IV) and lower‐layer (layers V–VI) neuron numbers per unit of cortical surface area in three diprotodont marsupial species (two macropodiformes, the red kangaroo and the parma wallaby, and a vombatiform, the koala) and compared these results to eutherian mammals (e.g., xenarthrans, rodents, primates). In contrast to the notion that the marsupial isocortex contains a low density of neurons, we found that neuron numbers per unit of cortical surface area in several marsupial species overlap with those found in eutherian mammals. Furthermore, neuron numbers vary systematically across the isocortex of the marsupial mammals examined. Neuron numbers under a unit of cortical surface area are low toward the frontal cortex and high toward the caudo‐medial (occipital) pole. Upper‐layer neurons (i.e., layers II–IV) account for most of the variation in neuron numbers across the isocortex. The variation in neuron numbers across the rostral to the caudal pole resembles primates. These findings suggest that diprotodont marsupials and eutherian mammals share a similar cortical architecture despite their distant evolutionary divergence.     

Ecomorphology of orbit orientation and the adaptive significance of binocular vision in primates and other mammals

Primates are characterized by forward-facing, or convergent, orbits and associated binocular field overlap. Hypotheses explaining the adaptive significance of these traits often relate to ecological factors, such as arboreality, nocturnal visual predation, or saltatory locomotion in a complex nocturnal, arboreal environment. This study re-examines the ecological factors that are associated with high orbit convergence in mammals. Orbit orientation data were collected for 321 extant taxa from sixteen orders of metatherian (marsupial) and eutherian mammals. These taxa were coded for activity pattern, degree of faunivory, and substrate preference. Results demonstrate that nocturnal and cathemeral mammals have significantly more convergent orbits than diurnal taxa, both within and across orders. Faunivorous eutherians (both nocturnal and diurnal) have higher mean orbit convergence than opportunistically foraging or non-faunivorous taxa. However, substrate preference is not associated with higher orbit convergence and, by extension, greater binocular visual field overlap. These results are consistent with the hypothesis that mammalian predators evolved higher orbit convergence, binocular vision, and stereopsis to counter camouflage in prey inhabiting a nocturnal environment. Strepsirhine primates have a range of orbit convergence values similar to nocturnal or cathemeral predatory non-primate mammals. These data are entirely consistent with the nocturnal visual predation hypothesis of primate origins.     

Afferent connections of the nucleus posterior thalami in the rat, with some evolutionary and functional considerations

The afferents to the nucleus posterior thalami were investigated in the rat using the methods of retrograde and anterograde transport of horseradish peroxidase (HRP). The main afferents arise from the following structures: sensorimotor cortex, zona incerta, thalamic ventrobasal complex, pretectum, intermediate and deep layers of the superior colliculus, nucleus suprageniculatus, nucleus ruber and perirubral area, mesencephalic reticular formation, nucleus interstitialis of Cajal, nucleus tegmenti pedunculopontinus, nucleus reticularis pontis, sensorial and spinal tract trigeminal nuclei. There is some confusion about the anatomical localization and appellation of the posterior thalamic region among mammals. In most of them, however, the pattern of afferents to this area appears to be relatively homogeneous. We conclude that the projections to the thalamic posterior nucleus of the rat are similar to those reported in other mammals. This nucleus has been suspected of playing a role in the processing of somaesthetic or visual informations. On the basis of the multimodal nature of its afferents, a specific role of this nucleus is excluded. Instead, a non-specific function of modulation or integration is suggested.     

Comparative anatomical study of the tegmentomammillary projections in some mammals: A horseradish peroxidase study

Mammillary projections from each subnuclei of Gudden's tegmental nuclei were investigated by retrograde transport of horseradish peroxidase (HRP) in the cat, rat, guinea pig, golden hamster and house shrew (Suncus murinus, Insectivora).

The dorsal tegmental nucleus of Gudden (TD) is composed of the pars dorsalis (TDD) and the pars ventralis (TDV) in the cat, rat, guinea pig, and golden hamster, but the TD of the house shrew can not be divided. The ventral tegmental nucleus of Gudden (TV) is composed of the pars principalis (TVP) and the pars suprafascicularis (TVS) in the golden hamster and house shrew, but the TVS is not recognized in the cat, rat and guinea pig.

The TDV projects to the lateral mammillary nucleus, and the TVP projects to the medial mammillary nucleus ipsilaterally in the cat, rat, guinea pig and golden hamster. The TVS of the golden hamster projects to the medial mammillary nucleus. The TVP and TVS of the house shrew project to the medial mammillary nucleus, and the TVS also to the lateral mammillary nucleus.

In addition, the pars compacta of the nucleus centralis superior projects to the medial mammillary nucleus in the rat, guinea pig and golden hamster. However, the TDD sends no fibers to the mammillary nuclei in these 5 species of mammals.     

Maternal effects in mammals: Broadening our understanding of offspring programming

The perinatal period is a sensitive time in mammalian development that can have long-lasting consequences on offspring phenotype via maternal effects. Maternal effects have been most intensively studied with respect to two major conditions: maternal diet and maternal stress. In this review, we shift the focus by discussing five major additional maternal cues and their influence on offspring phenotype: maternal androgen levels, photoperiod (melatonin), microbiome, immune regulation, and milk composition. We present the key findings for each of these topics in mammals, their mechanisms of action, and how they interact with each other and with the maternal influences of diet and stress. We explore their impacts in the contexts of both predictive adaptive responses and the developmental origins of disease, identify knowledge gaps and research opportunities in the field, and place a particular emphasis on the application and consideration of these effects in non-model species and natural ecological systems.     

When to get mad: adaptive significance of rage in animals

The wide distribution of rage in animals suggests that rage should have an adaptive significance. In the present work, the function of rage is explored under an evolutionary perspective. I try to assess the selective advantage conferred to the individual presenting rage compared to one that does not. In this work, I considered animals under the 'strategist' perspective rather than the 'stimulus-reactor' one. I suggest that rage has a highly adaptive significance both as: (1) an emotion to prepare antagonistic actions and (2) as a communicative act. I suggest therefore that, as a communicative act, rage can be explored through the theory of games. In three crucial scenarios, I investigate, using the theory of games framework, when, and how, there is a selective advantage for individuals expressing, bluffing and simulating rage.     

Coronal organ of ascidians and the evolutionary significance of secondary sensory cells in chordates

A new mechanoreceptor organ, the coronal organ, in the oral siphon of some ascidians belonging to the order Pleurogona has recently been described. In contrast to the known mechanoreceptor organs of ascidian atrium that consist of sensory neurons sending their own axons to the cerebral ganglion, coronal sensory cells are secondary mechanoreceptors, i.e., axonless cells forming afferent and efferent synapses with neurites of neurons located in the ganglion. Moreover, coronal cells exhibit an apical apparatus composed of a cilium accompanied or flanked by rod-like microvilli (stereovilli). Because of the resemblance of these cells to vertebrate hair cells, their ectodermal origin and location in a linear array bordering the bases of the oral tentacles and velum, the coronal organ has been proposed as a homologue to the vertebrate acousticolateralis system. Here we describe the morphology of the coronal organs of six ascidians belonging to the suborders Phlebobranchia and Aplousobranchia (order Enterogona). The sensory cells are ciliated, lack typical stereovilli, and at their bases form synapses with neurites. In two species, the sensory cells are accompanied by large cells involved in synthesis and secretion of protein. We hypothesize that the coronal organ with its secondary sensory cells represents a plesiomorphic feature of ascidians. We compare the coronal organ with other chordate sensory organs formed of secondary sensory cells, i.e., the ventral lip receptors of appendicularians, the oral secondary sensory cells of cephalochordates, and the acousticolateralis system of vertebrates, and we discuss their homologies at different levels of organization.     

On the probable absense of retino-hypothalamic connections in five mammals and an amphibian

Attempts have been made in the Rat, Rabbit, Hedgehog, Ferret and Xenopus toad to trace degenerating fibers into the hypothalamus after division of one optic nerve. No evidence was found of a retion-hypothalamic connection. This finding is not in accordance with the results reported by several others who made comparable experiments; and it is suggested that confusion may have arisen because neuro-secretory nerve fibers taken for degenerating hypothalamic pathways.     

Synaptic plasticity in the cerebral cortex of mice: effects of radiation and anesthesia

In the neuropil of layers II and III of the frontal cortex of adult mice, as seen in the electron microscope, sodium pentobarbital anesthesia alone results in a significant decrease in synaptic profile length at 1 day after anesthetization, followed by a return to normal or above normal levels after 2-28 days, while the number of synaptic profiles per unit cross section (profile incidence) is not altered; irradiation with 5-500 rad plateau argon particles significantly inhibits the profile shortening effect of anesthesia at 1 day after exposure, but this inhibition is not dose related; an inverse dose relationship in profile incidence appears at 2 days following irradiation with argon particles; at 1 to 2 hours after 150 or 220 rad x-irradiation, profile incidence is significantly reduced while the length is increased, effects that appear to be dose related and unaffected by adrenalectomy.     

On the binding of monoamine oxidase inhibitors to some sites distinct from the MAO active site, and effects thereby elicited

Many inhibitors of monoamine oxidase, particularly those developed during the past three decades, are often referred to as being "selective" for one or other isoform of the enzyme. However true this may be, selectivity within the EC 1.4.3.4 family does not preclude the possibility of interactions of these drugs with other proteins unrelated to monoamine oxidase. Indeed, evidence exists which either suggests or demonstrates directly that many of these inhibitors do interact with, and affect the behaviour of, other enzymes, receptor systems and uptake pumps, with potentially interesting consequences, desirable or otherwise, for the patient or the pharmacologist. An overview of many such interactions, and speculation upon some of the possible consequences, are provided in this review.     

Probability effects in the stop-signal paradigm: the insula and the significance of failed inhibition

In the present randomized, mixed-trial event-related fMRI study, we examined the neural mechanisms underlying inhibitory control using a stop-signal paradigm in which stop-signal frequency was manipulated parametrically across blocks. As hypothesized, presenting stop signals less frequently was accompanied by a stronger set to respond to the go stimuli as subjects were faster in responding to go stimuli on no stop-signal trials and made more commission errors (i.e., were less successful in inhibiting the go response) on stop-signal trials. When response inhibition was successful, having to inhibit responses more frequently compared to less frequently was associated with greater activation in occipital areas. This presumably reflects enhanced visual attention to the stop signal. When response inhibition failed, greater activity was observed in bilateral insula when stop signals were presented less compared to more frequently. The insula may thus play a role in processing the significance of inhibitory failure.     

On the pathogenesis and therapy of dementia of the Alzheimer type: some neuropathological, biochemical, genetic and pharmacotherapeutic considerations

The extensive literature on dementia of Alzheimer type (DAT) testifies to the enormous progress achieved in the clinical and biochemical delineation of this disease. Newly developed laboratory and imaging techniques are also being applied to the diagnosis of DAT. Nevertheless, unequivoval diagnosis still relies primarily on morphological data from biopsy or autopsy. An overview is presented of major morphological changes occurring at different levels of organization in the central nervous system (CNS) in DAT. Currently formulated etiopathogenic hypotheses of DAT are reviewed and discussed in the context of morphological alterations. Some of the recombinant DNA methods, that are currently available for gene analysis, are described. Some approaches for studying Alzheimer specific genes using the above methods have been suggested. Finally, a critical overview of the current pharmacotherapeutic armamentarium used in DAT and senile dementia is presented. The efficacy, side effects, and the main mechanisms of action of the two categories of drug therapy -supposed etiopathogenic and symptomatic- are presented.