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PubMed1977

An assessment of hemispheric specialization in monkeys.

Split-brain monkeys learned several sets of visual discriminations with each hemisphere. Some stimuli, such as photographs of monkey's faces, were intended to favor mechanisms similar to those of man's nondominant hemisphere, while other tasks, requiring sequential comparison of visual stimuli, should favor mechanisms similar to ones in the dominant hemisphere of man. The tests uniformly demonstrated hemispheric equivalence for solving all types of problems, regardless of handedness, sex, or side of surgical retraction. A review of the literature also offers little support for the concept of hemispheric specialization in infra-human mammals although a few leads still need to be explored before abandoning the hope of finding the roots of human cerebral dominance in monkeys.

Animals↗

PubMed2001

Distribution of the orphan nuclear receptor Nurr1 in medaka (Oryzias latipes): cues to the definition of homologous cell groups in the vertebrate brain.

The orphan nuclear receptor Nurr1 has been extensively studied in mammals and shown to contribute to the differentiation of several cell phenotypes in the nervous and endocrine systems. In this study, the gene homologous to the mammalian Nurr1 (NR4A2) was isolated in the teleost fish medaka (Oryzias latipes), and the distribution of its transcripts was analyzed within brains of embryos and adults. Nurr1 has a widespread distribution in the medaka brain. Large amounts of Nurr1 transcripts were found in the intermediate nucleus of the ventral telencephalon, preoptic magnocellular nucleus, ventral habenula, nucleus of the periventricular posterior tuberculum, and nuclei of glossopharyngeal and vagus nerves. To search for homologous cell groups between teleost fish and tetrapods brains, the co-localization of Nurr1 and tyrosine hydroxylase (TH) transcripts was analyzed. Neither Nurr1 nor TH expression was detected in the ventral midbrain, but both transcripts were present in the periventricular nucleus of the posterior tuberculum. This observation supports the hypothesis that this nucleus is homologous to dopaminergic mesencephalic nuclei of mammals. The presence of Nurr1 in the preoptic magnocellular nucleus of medaka and paraventricular hypothalamic nucleus of mammals reinforces the hypothesis of homology between these areas. TH and Nurr1 transcripts are also co-localized, among others, in the nucleus of the paraventricular organ and nucleus of the vagus nerve. This work suggests that the differentiating role of Nurr1 in the central nervous system is conserved in gnathostomes.

Animals↗

PubMed1992

Identification of cholecystokinin/gastrin peptides in frog and turtle. Evidence that cholecystokinin is phylogenetically older than gastrin.

Peptides homologous to mammalian cholecystokinin (CCK) and gastrin in brain, antrum, and small intestine of an amphibian (the bullfrog, Rana catesbeiana) and a reptile (the turtle, Pseudomys scripta) were characterized. All tissues contained peptides reacting with antisera specific for the carboxyamidated C-terminal tetrapeptide common for CCK and gastrin. Extracts of all tissues, except the turtle antrum, also reacted with an antiserum specific for mammalian sulfated CCK, while no extract contained peptides reacting with an antiserum specific for mammalian gastrin. Both species contained predominantly small acidic forms in the brain and larger less acidic forms in the antrum and intestine. The antral peptides of both species were identified. The largest frog gastrin was a 47-residue peptide: DLLASLTHEQ KQLIMSQLLP ELLSELSNAE DHLHPMRDRD YAGWMDF.NH2. The largest turtle gastrin was a 52-residue peptide: DLLEALSQDQ KLLMAKFLPH IYAELANREG NWHEDAALRP LHDHDYPGWM DF.NH2. They display 51% similarity. Having Tyr in position 7 from the C-terminus, both resemble structurally mammalian CCK rather than gastrin, which suggests that CCK is phylogenetically older than gastrin. The turtle antral peptide contains a Tyr followed by Pro as in chicken gastrin. Thus, apparently at the stage of reptiles, a route different from the mammalian was taken in order to evolve a specific gastrin function.

Amino Acid Sequence↗

PubMed1995

Rise and fall of modular orthodoxy.

The premise of cortical modularity is based on strong dissociations caused by focal lesions. These dissociations are rare, and their explanatory power and theoretical importance are vastly overrated. The effects of brain lesions must be considered in their totality, rather than in idiosyncratic selectivity. These effects are more consistent with a continuous, graded functional neocortical geometry, than with a modular neocortex. Distinction must be drawn between strong intrinsic modularity, and weak emergent modularity. Strong intrinsic modularity is more characteristic of the thalamus than of the cortex. The advent of neocortex may have represented an evolutionary escape from strong modularity as the dominant principle of neural organization, and a shift toward a more interactive principle of neural organization dominated by emergent properties. The latter may take the form of weak modularity, reflective of cognitive skill routinization. The extent of weak, emergent modularization may be asymmetric, more pronounced in the left hemisphere, while the right hemisphere is essentially amodular.

Agnosia↗

PubMed2006

Lateralized righting behavior in the tortoise (Testudo hermanni).

Lateralization of brain and behaviour at the population level has been documented in all vertebrate classes. Research was mostly carried out on mammalian and avian species, the least investigated class with this regards being the Reptilia, with studies concentrating on lateralized aggressive behaviour in lizards. No research has been carried out on lateralization in the Chelonian order. We investigated the presence of motor asymmetries in the tortoise Testudo hermanni, using the righting response (i.e. the animal is positioned upside-down and the left/right side to which it uprights is observed), a procedure already employed to assess behavioural lateralization in amphibians. The ability of righting has a particularly high adaptive value in tortoises, as in case of overturning, and consequent exposure to sunrays, changes in body temperature and difficulties in respiration could occur leading to serious conditions. Thirty-four tortoises underwent a series of righting tests in a standardized apparatus, 15 tortoises were also retested 10 months later. A bias at the individual as well as at the population level was found for preferentially turning on the right side. Consistency of responses at retest was also observed. The results are discussed with reference to the implications for the evolution of brain lateralization in vertebrates.

Age Factors↗

PubMed2002

The distribution and morphological characteristics of cholinergic cells in the brain of monotremes as revealed by ChAT immunohistochemistry.

The present study employs choline acetyltransferase (ChAT) immunohistochemistry to identify the cholinergic neuronal population in the central nervous system of the monotremes. Two of the three extant species of monotreme were studied: the platypus (Ornithorhynchus anatinus) and the short-beaked echidna (Tachyglossus aculeatus). The distribution of cholinergic cells in the brain of these two species was virtually identical. Distinct groups of cholinergic cells were observed in the striatum, basal forebrain, habenula, pontomesencephalon, cranial nerve motor nuclei, and spinal cord. In contrast to other tetrapods studied with this technique, we failed to find evidence for cholinergic cells in the hypothalamus, the parabigeminal nucleus (or nucleus isthmus), or the cerebral cortex. The lack of hypothalamic cholinergic neurons creates a hiatus in the continuous antero-posterior aggregation of cholinergic neurons seen in other tetrapods. This hiatus might be functionally related to the phenomenology of monotreme sleep and to the ontogeny of sleep in mammals, as juvenile placental mammals exhibit a similar combination of sleep elements to that found in adult monotremes.

Animals↗

PubMed1981

Exploring the dorsal surface of hominoid brain endocasts by stereoplotter and discriminant analysis.

One of the more vexing problems with hominoid endocasts has been to secure reliable information that goes beyond their volumes. One method is explored here, where a large number (N = 171) of radial distances from a homologous internal central point to the dorsal endocast surface are measured in a polar coordinate system. From two pilot studies, one with a hominoid sample of N = 64, and the other with an enlarged sample of N = 92, the following results can be mentioned tentatively: (1) there are residual data that differ taxonomically in different cortical regions once overall endocast size is corrected in allometric fashion; (2) the major cortical regions where these differences appear most strongly are in the lower parietal lobule, anterior occipital zone, and the dorsoanterior region of the frontal lobe; (3) the method shows excellent promise in objectively and quantitatively depicting taxa-specific shape differences in functionally understood cortical regions through multivariate statistical analyses.

Animals↗

PubMed1984

Molecular regulators of brain function: a new view.

A working hypothesis is proposed based on two mutually dependent concepts: neurons may be functionally regulated not only by presently known neurotransmitters but by many kinds of informational substances. Known informational substances are considered in categories corresponding to major regulators of the central nervous system, including transmitters, peptides, hormones, "factors" and various proteins. Many new informational substances are being discovered by the application of DNA technology. Alongside neuronal circuitry that forms the basis for conventional neuroanatomy and neurophysiology, and that operates through conventional synaptic junctions, is a system here called parasynaptic, i.e. in "parallel with" synapse-linked circuitry. In the parasynaptic system, informational substances reach specific target cell receptors by diffusion from release points through extracellular fluids. The parasynaptic system has the same degree of selectivity as synaptic circuitry but possesses, in addition, a domain of versatility and plasticity lacking in "hardwired" circuitry; the latter is, however, also influenced by highly potent informational substances in the ambient extracellular fluid.

Animals↗

PubMed2000

Central complex in the brain of crayfish and its possible homology with that of insects.

A small, medial heterolateral neuropil in the brain of crustaceans has long been regarded as the central body of the crustacean brain. Its simplicity and the absence of clear layers within its neuropil have led to the question of its homology with the more complex central body that occupies an approximately equivalent position in the brain of insects. We have labelled neurons in the central body of the Australian freshwater crayfish Cherax destructor by the extracellular application of dextrans and by treating the brain with antibodies to anti-CCAP, anti-locustatachykinin, anti-perisulfakinin, anti-proctolin, anti-dip-allatostatin AI, anti-PEA-head-peptide, anti-serotonin, and anti-rabbit anti-substance P, all of which label neurons in the insect brain. The dextran and immunocytochemical labelling have revealed a neural complex associated with the crayfish central body that is very similar in overall anatomical architecture to the subset of neuropils that are incorporated in the central complex of the insects, and in particular to that of the locust. Similarities between the crayfish and locust central complexes extend to the number and position of the neuropils, the location of the cell body clusters of the neurons that belong to the central complex, the numbers of tracts that link some of the constituent neuropils together, and the form and immunoreactivity of many of the individual neuron classes. These similarities are taken as evidence to support a possible homology between the crustacean central complex and that of the insects.

Animals↗

PubMed2004

Causes and consequences of limited attention.

This review focuses on the evolutionary causes and consequences of limited attention, defined as the restricted rate of information processing by the brain. The available data suggest, first, that limited attention is a major cognitive constraint determining animals' search for cryptic food, and, second, that limited attention reduces animals' ability to detect predators while involved in challenging tasks such as searching for cryptic food. These two effects of limited attention probably decrease animal fitness. Furthermore, a simulated evolutionary study provides empirical support for the prediction that focused attention by predators selects for prey polymorphism. The neurobiological mechanisms underlying limited attention have been widely studied. A recent incorporation of that mechanistic knowledge into an ecological model suggests that limited attention is an optimal strategy that balances effective yet economical search for cryptic objects. The review concludes with a set of testable predictions aimed to expand the currently limited empirical knowledge on the evolutionary ecology of limited attention.

Animals↗

PubMed2001

Anatomy and three-dimensional reconstructions of the brain of the white whale (Delphinapterus leucas) from magnetic resonance images.

Magnetic resonance imaging offers a means of observing the internal structure of the brain where traditional procedures of embedding, sectioning, staining, mounting, and microscopic examination of thousands of sections are not practical. Furthermore, internal structures can be analyzed in their precise quantitative spatial interrelationships, which is difficult to accomplish after the spatial distortions often accompanying histological processing. For these reasons, magnetic resonance imaging makes specimens that were traditionally difficult to analyze, more accessible. In the present study, images of the brain of a white whale (Beluga) Delphinapterus leucas were scanned in the coronal plane at 119 antero-posterior levels. From these scans, a computer-generated three-dimensional model was constructed using the programs VoxelView and VoxelMath (Vital Images, Inc.). This model, wherein details of internal and external morphology are represented in three-dimensional space, was then resectioned in orthogonal planes to produce corresponding series of "virtual" sections in the horizontal and sagittal planes. Sections in all three planes display the sizes and positions of such structures as the corpus callosum, internal capsule, cerebral peduncles, cerebral ventricles, certain thalamic nuclear groups, caudate nucleus, ventral striatum, pontine nuclei, cerebellar cortex and white matter, and all cerebral cortical sulci and gyri.

Animals↗

PubMed1982

[Importance of the bacteriologic study in brain abscess. Comparison of the evolution of bacteriologic and therapeutic results in a series of 102 cases].

Progresses in bacteriological study have been analyzed on 102 cases of intracranial infections between 1968 and 1980: sterile cultures decrease from 56% to 11,5%, rate of isolation of anaerobic and association of aero-anaerobic bacteria increase respectively from 10 to 40% and from 2 to 17,1%. Clinical results progress in close relation; the mortality rate decrease from 11,5% to 8,3% as well as morbidity rate from 33% to 19,4%. Moreover clinical results are worse when the bacteriological study fails to isolate any germ: mortality 15,7% and sequellae 53,5%. The best results are observed in the group of anaerobic infections: mortality 4% and sequellae 26,6%. Lastly, the interest of the systematic research of particular bacteria such as capnophilic or microaerophilic bacteria or mycobacterium tuberculosis (2 cases) is underlined. This work emphasizes the importance of the bacteriological study for the management of intracranial infections and the improvement of the clinical results.

Bacteriological Techniques↗

PubMed1985

Late evolutionary appearance of 'peripheral-type' binding sites for benzodiazepines.

Four classes of non-mammalian vertebrates were examined for the presence of both 'brain-specific' and 'peripheral-type' binding sites for benzodiazepines in the central nervous system. 'Brain-specific' binding sites for benzodiazepines were found in the central nervous systems of all non-mammalian vertebrates studied. However, in contrast to mammals, either very low or undetectable levels of 'peripheral-type' binding sites for benzodiazepines were observed in the central nervous systems of these non-mammalian vertebrates. Furthermore, the density of 'peripheral-type' binding sites for benzodiazepines in non-mammalian vertebrate heart was less than or equal to 2% of that found in mammalian cardiac tissue. These findings suggest a very late evolutionary appearance of 'peripheral-type' binding sites for benzodiazepines, implying that these sites may have (a) highly specialized function(s) in both peripheral tissues and the central nervous system.

Animals↗

PubMed2001

Adult neurogenesis and neuronal regeneration in the central nervous system of teleost fish.

In contrast to mammals, teleost fish exhibit an enormous potential to produce new neurons in the adult central nervous system and to replace damaged neurons by newly generated ones. In the gymnotiform fish Apteronotus leptorhynchus, on average, 100,000 cells, corresponding to roughly 0.2% of the total population of cells in the adult brain, are in S-phase within any 2-h period. As in all other teleosts examined thus far, many of these cells are produced in specific proliferation zones located at or near the surface of ventricular, paraventricular, and cisternal systems, or in areas that are likely derived from proliferation zones located at ventricular surfaces during embryonic development. The majority of cells born in such proliferation zones migrate within the first few weeks following their generation to specific target areas. In the cerebellum, where approximately 75% of all brain cells are born during adulthood, cells originate from the molecular layers of the corpus cerebelli and the valvula cerebelli partes lateralis and medialis, as well as from the eminentia granularis pars medialis. From these proliferation zones, the young cells migrate to the associated granule cell layers or to the eminentia granularis pars posterior, respectively. In the course of their migration, the young cells appear to be guided by radial glial fibers. Upon arrival at their target region, approximately 50% of the young cerebellar cells undergo apoptosis. The remaining cells survive for the rest of the fish's life, thus contributing to permanent brain growth. At least some cells differentiate into granule cell neurons. The potential to produce new neurons, together with the ability to guide the young cells to their target areas by radial glial fibers and to eliminate damaged cells through apoptosis, also forms the basis for the enormous regenerative capability of the central nervous system of Apteronotus, as demonstrated in the cerebellum and spinal cord. A factor involved in the cerebellar regeneration appears to be somatostatin, as the expression of this neuropeptide is up-regulated in a specific spatio-temporal fashion following mechanical lesions. Besides its involvement in neuronal regeneration adult neurogenesis in Apteronotus, and possibly teleost fish in general, appears to play a role in providing central neurons to match the growing number of sensory and motor elements in the periphery, and to establish the neural substrate to accommodate behavioral plasticity.

Aging↗

PubMed2003

Inter-sequence and inter-imaging unit variability of diffusion tensor MR imaging histogram-derived metrics of the brain in healthy volunteers.

BACKGROUND AND PURPOSE: Diffusion tensor MR imaging has the potential to improve our ability to monitor several neurologic conditions. As a preliminary step to the assessment of the role of diffusion tensor MR imaging in the context of longitudinal and multicenter studies, we evaluated the effect of sequence-, imaging unit-, and imaging-reimaging-induced variations on diffusion tensor MR imaging quantities derived from histogram analysis of a large portion of the central brain of healthy volunteers. METHODS: Each of eight healthy volunteers underwent imaging on two MR imaging units using three different pulsed gradient spin-echo single shot echo-planar pulse sequences (each of them having a different diffusion gradient scheme). Four additional healthy participants underwent imaging twice on the same imaging unit to assess imaging-reimaging variability. RESULTS: For mean diffusivity histograms, the differences between inter-sequence and inter-imaging unit coefficients of variation were significant for all the considered quantities with P values ranging from.003 to <.001. Also, the inter-imaging unit coefficient of variation for average fractional anisotropy was significantly higher than the corresponding inter-sequence coefficient of variation (P =.002). In general, inter-sequence mean diffusivity histogram-derived metrics (coefficients of variation ranging from 1.72% to 5.56%) were more reproducible than were fractional anisotropy histogram-derived metrics (coefficients of variation ranging from 5.45% to 7.34%). Imaging-reimaging variability was found to fall in the range of inter-sequence coefficients of variation for all the considered quantities. CONCLUSION: This study shows that inter-sequence, imaging-reimaging, and inter-imaging unit variabilities of diffusion tensor MR imaging-derived measurements are relatively low, suggesting that diffusion tensor MR imaging might provide additional measures of outcome with which to assess the evolution of brain structural damage in large scale studies of various neurologic conditions.

Analysis of Variance↗

PubMed1983

Quantitative brain organisation in anteaters (Edentata-Tubilidentata).

We can state that the encephalization and the quantitative organisation of the brain in edentates sensu lato exhibit a certain degree of common patterning but also differences between groups that have long been separated. Orycteropus in Africa and the dasypodids in South America can be considered relatively primitive if evolutionary progress is linked essentially with encephalization and neocorticalization. But again, as pointed out by Pirlot (1980), the concept of primitiveness needs careful reconsideration. To this end, more genera from the classical edentate group ought to be worked upon. In particular, the South American bradypodid Choloepus would be of great interest, as well as the African pangolin (Manis). Above all, more data are needed on the behaviour of all those ill-toothed mammals, especially in connection with their olfaction and their balance control as well as with the relative use they make of vision and audition. This project is now at an early stage in Montreal.

Animals↗

PubMed1996

Statistical approach to shape from shading: reconstruction of three-dimensional face surfaces from single two-dimensional images.

The human visual system is proficient in perceiving three-dimensional shape from the shading patterns in a two-dimensional image. How it does this is not well understood and continues to be a question of fundamental and practical interest. In this paper we present a new quantitative approach to shape-from-shading that may provide some answers. We suggest that the brain, through evolution or prior experience, has discovered that objects can be classified into lower-dimensional object-classes as to their shape. Extraction of shape from shading is then equivalent to the much simpler problem of parameter estimation in a low-dimensional space. We carry out this proposal for an important class of three-dimensional (3D) objects: human heads. From an ensemble of several hundred laser-scanned 3D heads, we use principal component analysis to derive a low-dimensional parameterization of head shape space. An algorithm for solving shape-from-shading using this representation is presented. It works well even on real images where it is able to recover the 3D surface for a given person, maintaining facial detail and identity, from a single 2D image of his face. This algorithm has applications in face recognition and animation.

Brain↗

PubMed1995

Species differences in estrogen receptor and progesterone receptor-mRNA expression in the brain of sexual and unisexual whiptail lizards.

Circulating concentrations of gonadal steroid hormones and reproductive behavior in female vertebrates vary as a function of ovarian state. Steroids secreted by the ovary, specifically estrogen and progesterone, influence the expression of behaviors associated with reproduction by intracellular sex steroid receptors located in specific regions of the brain. Using in situ hybridization, we analyzed estrogen receptor and progesterone receptor messenger RNA expression in several brain regions of ovariectomized, vitellogenic, and postovulatory individuals from two species of whiptail lizards (Cnemidophorus uniparens and C. inornatus). Although these species are genetically very similar, they differ in two aspects of their reproductive biology: (i) the unisexual C. uniparens alternate between expressing female-typical and male-like pseudosexual behaviors while female C. inornatus normally express only female receptive behavior, and (ii) circulating estradiol concentrations in reproductively active female C. uniparens are approximately five-fold lower than in reproductively active female C. inornatus. We found that the regulation of sex steroid receptor gene expression was region specific, with receptor-mRNA expression being increased, unchanged, or decreased during vitellogenesis depending on the area. Furthermore, several species differences in the amount of sex steroid receptor-mRNA were found that may be relevant to the species differences in circulating estrogen concentrations and sexual behavior.

Animals↗