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PubMed2002

Brain biopsy in Creutzfeldt-Jakob disease: evolution of pathological changes by prion protein immunohistochemistry.

The formation of protease-resistant prion protein (PrPsc) is considered to be an early event in the pathogenesis of Creutzfeldt-Jakob disease (CJD) and hence its demonstration in brain biopsies by immunohistochemistry is considered diagnostic. We analysed eight brain biopsies from the frontal cortex collected from different parts of India from cases diagnosed as CJD on clinical and pathological grounds for the expression of prion protein (PrP). The duration of illness in these cases varied from 2 months to 1 year. Immunohistochemistry was carried out on paraffin sections using two different clones (KG9 and 3F4) of monoclonal antibodies to PrP. Although all eight cases showed classical features of spongiform encephalopathy of varying severity, only five of the eight cases revealed PrP(sc) in the brain tissue. The immunolabelling was focal and all areas with spongiform change were not labelled. A temporal evolution in the staining pattern was evident - particulate diffuse labelling (synaptic type) in early stages (2 months), perivacuolar deposits in intermediate stages (5-6 months), and dense plaques in late stages (12 months).

Adult↗

PubMed2003

The evolution of the apparent diffusion coefficient in the pediatric brain at low and high diffusion weightings.

PURPOSE: To evaluate the evolution of the apparent diffusion coefficient (ADC) with age for different degrees of diffusion weighting using a clinically feasible approach. MATERIALS AND METHODS: Data was acquired using separate scans with b values in the range typically used for clinical studies (100-900 seconds/mm(2)) and higher b values (1800-3000 seconds/mm(2)). The ADC was calculated for each of the data sets by fitting the data to a monoexponential function. RESULTS: The results from 50 children aged three years and less showed some deviations from literature values derived using a full biexponential fit, with these differences reflecting the approximations inherent in this approach. The values obtained with this technique appear to be reproducible but the resulting "institutional values" are comparable to those from other centers only if identical measurement criteria are used. CONCLUSION: A significant decline in both components of the ADC during the first few months of life was observed; in addition, the attenuated slow ADC values seen in adult white matter were only present at birth in early myelinating regions. The subsequent development of the slow ADC in white matter suggests that it is associated with myelination or processes associated with axonal development.

Age Factors↗

PubMed1994

Spatial behavior in the Brazilian short-tailed opossum (Monodelphis domestica): comparison with the Norway rat (Rattus norvegicus) in the Morris water maze and radial arm maze.

The spatial behavior displayed in a swimming pool and radial arm maze by the Brazilian gray, short-tailed opossum (Monodelphis domestica) was compared with that of the laboratory rat (Rattus norvegicus). The performance of the opossums was clearly different from that of the rats in both tasks. The opossums failed to learn to find a hidden platform in the swimming pool (place task), but they did learn to swim to a visible platform. The opossums did learn working and reference memory components of the radial arm maze but showed different search strategies in this situation. The results are discussed with reference to possible species differences in motor behavior, ecology, brain structure and evolution.

Animals↗

PubMed2003

Power-law for axon diameters at branch point.

BACKGROUND: Axon calibers vary widely among different animals, neuron classes, and even within the same neuron. What determines the diameter of axon branches? RESULTS: We pursue the hypothesis that the axon caliber has evolved to minimize signal propagation delays, while keeping arbor volume to a minimum. For a general cost function, we show that the optimal diameters of mother and daughter branches at a bifurcation satisfy a power law. The derivation relies on the fact that the axon conduction speed scales as a power of axon diameter. Although available data are consistent with the law, there is a large spread in the data. Future experimental tests will determine whether this spread is due to biological variability or measurement error. CONCLUSIONS: Minimization of arbor volume and signal propagation delay may have been an important factor in the evolution of the brain.

Animals↗

PubMed2005

The evolution of homeobox genes: Implications for the study of brain development.

The homeobox gene superfamily includes many genes implicated in brain development in vertebrates; for example, the Otx, Emx, Dmbx, Gbx, En and Hox gene families. We describe the evolutionary history of the homeobox gene superfamily, as inferred from molecular phylogenetics and chromosomal mapping. Studies of amphioxus, a close relative of vertebrates, have proven particularly informative because it has a genome uncomplicated by recent lineage-specific gene duplications and because in situ hybridisation techniques exist for mapping gene positions and gene expression patterns. We describe an ancient subdivision into gene classes (ANTP, PRD, LIM, POU, SIN, TALE), each containing multiple gene families. The original ANTP class gene duplicated to give distinct NK-like and Hox/ParaHox-related genes, both of which underwent tandem duplication, before the expanding Hox gene cluster duplicated to give Hox and ParaHox clusters. A chromosomal breakage event probably occurred to separate the NK-like and extended Hox genes. Finally, there was additional and extensive gene duplication and gene loss in the vertebrate lineage. We argue that understanding evolutionary history is important for establishing consistent gene nomenclature, and for comparing gene expression patterns and gene functions between species and between gene families.

Animals↗

PubMed2003

Social neuroscience, empathy, brain integration, and neurodevelopmental disorders.

Paul MacLean has investigated integrated brain functioning through selected brain lesions in animals that disturb circuits necessary for complex behaviors, such as social displays. MacLean is unique in his comparative neurobehavioral approach that emphasizes the evolutionary origins of parenting and social behaviors and the implications of brain changes in the evolution from reptiles (social displays) to mammals (nursing, audiovocal communication, play) to man (self-awareness, intentionality, social context) that link affect and cognition. Subjectively, how "looking with feeling toward others," the basic element in empathy, evolved has been a central concern of his. Neuroimaging studies of social cognition, mother-infant communication, moral behavior, forgiveness, and trust are consistent with particular brain systems being activated in cooperative social behaviors. The identification of mirror neurons is pertinent to MacLean's model of isopraxis and studies of thalamocortical resonances may be pertinent to his neurobehavioral models. Studies of behavioral phenotypes in human neurodevelopmental disorders are consistent with MacLean's model of brain circuits being linked to complex behaviors during development. In autistic disorder, the behavioral phenotype involves disrupted social communication, deviant imaginative play, and motor stereotypies. In Lesch-Nyhan syndrome (LNS), self-injury occurs in individuals with normal sensory systems intact who require and request physical restraint to prevent self-injury; they ask for assistance from others to prevent them from harming themselves. Autism involves the lack of subjective awareness of others intentions and LNS involves a failure in self-regulation and self-control of self-injurious behavior. MacLean's models laid the groundwork for studies focused on understanding brain functioning in these conditions.

Animals↗

PubMed2004

Hypoxia-ischemic insult in neonatal rats induced slowly progressive brain damage related to memory impairment.

The present study was designed to determine potential associations between the brain damage induced by hypoxic-ischemic (HI) insult and spatial learning impairment in an eight-arm radial maze task. We first determined the pathological outcomes after 2, 5, 9, and 17 weeks of recovery following the HI insult. The results show that the brain damage progressed from 2 up to 17 weeks of recovery. To clarify the time course of the brain damage changes, we investigated the histological changes of the same individual with magnetic resonance imaging (MRI) after 5, 9, and 57 weeks of recovery following the HI insult. The MRI changes were similar to the histological changes, and the brain damages were exacerbated in the contralateral hemisphere after 57 weeks of recovery following the HI insult. To investigate whether alteration in brain function was correlated with MRI and histological changes, the rats were made to find their way through an eight-arm radial maze was performed at either 7th or 16th weeks of recovery. According to the results, the spatial learning impairments of rats in the maze starting at 16 weeks of recovery were more severe than those at 7 weeks of recovery, indicating that the impairments were progressive and depended on the degree of brain damage. The results of the present study are the first demonstration that the evolutional and specific brain damage following the HI insult is slowly and progressively exacerbated to the contralateral hemisphere and rats who experience the HI are at risk for showing a late impairment of brain function.

Age Factors↗

PubMedDate not supplied

[Comparative study of the fatty acid composition of glycerophosphatides from whole vertebrate brain and portions of it].

Fatty acids of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and monophosphoinositide were studied in the whole brain, in the forebrain and the brain stem in the frog Rana temporaria, tortoise Emys orbicularis, hen and cat. Every family of phospholipids (PL) possesses a characteristic fatty acid pattern irrespectively of the brain part. There are regular topologic differences in the fatty acid composition of PL, namely the relative amount of saturated and polyenoic acids is higher and that of monoenoic acids lower in the forebrain as compared to the brain stem. The increase in the relative size of the forebrain, occurring in the evolution of vertebrate brain, exerts a definite influence on the fatty acid composition of the total brain. Nevertheless this increase in the size of the forebrain does not solely determine the fatty acid composition of the total brain. Similar changes are occurring in all brain parts: the relative amount of saturated fatty acids of PL is increasing and that of unsaturated acids decreasing. The evolutionary deductions derived from the biochemical study of the total brain find confirmation in the investigation of the brain parts.

Animals↗

PubMed1990

Two different ways evolution makes neurons larger.

As evolution makes larger brains it also increases the size of many of the individual neurons that make up the brain. How neurons are made larger can give clues about design principles of the brain's circuits. One way of making a larger neuron is called conservative scaling. If evolution magnifies a particular type of neuron by a factor of two-that is, each dendrite is made twice as long-then the neuron is scaled conservatively if the magnified neuron has dendrites with 4 times the diameter of their unscaled counterparts. This type of scaling leaves the passive cable properties of the neuron unchanged and so maintains a balance in effectiveness between proximal and distal dendritic inputs. One might imagine that, for some types of circuits, maintaining such a balance would be necessary to use just the same neuronal interconnections in both large and small brains. We have compared dentate granule cells and CA1 pyramidal neurons in cat and human to establish how these cell types are, in fact, scaled. Both cell types are larger in human than in cat, even though their general form is conserved. Pyramidal neurons scale conservatively, but dentate granule cells do not. The CA1 circuits seem, then, to require conservation of the passive cable properties of their elements, whereas dentate does not. We suggest that the reason CA1 neurons scale conservatively is that, for this region, each individual synaptic input exerts a significant effect on the cell's output, whereas in dentate the neuronal output represents the average of a large number of anonymous individual inputs.

Animals↗

PubMed1998

Scientific meaning of meanings: quests for discoveries concerning our cultural ills.

This paper outlines pioneering concepts of fundamental physical and emotional features of the human brain which served as primary operators. These have developed during the past 10,000 years, giving rise to our present global megacultures and their various ancestral culture progenitors. Essential points are these: (1) Biological evolution endowed the human brain (quite inadvertently and unintentionally) with enormous latent powers for complex and sophisticated abstract ratiocinations. (2) Magnitudes of these latent powers grew exponentially with linear enlargements of brain size during the evolution of the genetic ancestors of Homo sapiens sapiens (Hss) during the past 3 million years, but these latent powers never materialized in utilized forms within the environmental contexts in which they evolved. (3) These sophisticated, abstract ratiocinations, both latent powers and operative forms in today's Hss brain, are divided between two major categories: utilitarian thinking and nonutilitarian thinking. (4) These two different types of thinking processes are carried out within separate, different regional combinations of neuronal biochemical entities within the same individual brain. (5) Sensitivities of abstract, sophisticated ratiocination processes within the human brain to influences from communication interactions with other human brains are exponentially greater in comparison with any other species of central nervous system in the earth's biosphere. This makes the brain population density the utmost critical factor, and determines the character of human thought within interacting populations of brains at a given time and place within a particular culture. (6) Abrupt increases of sedentary brain population densities, unnaturally greater by orders of magnitude than those that existed previously in biological evolutionary contexts, were engendered by the inauguration of agricultural practices 10,000 years ago. This enabled latent powers of the human brain used for complex and sophisticated abstract ratiocinations to become manifest in materialized forms of usage within relatively large groups of humans living i certain regions of the earth. (7) Thinking processes of the utilitarian category within brains living in such regions guided and dominated the development of sophisticated and complex social hierarchies and institutions, forms of communication, technologies, and cultures since that time. This dominating factor relegated thinking processes within the nonutilitarian categories of those brains to subservient roles during those developments. (8) Nonutilitarian abstracts ratiocinations possess a potential for proper adjudication and guidance of utilitarian abstract ratiocinations in the latter's development of culture. However, lack of the former's proper role in cultural developments since the beginning of the Holocene interglacial era has resulted in the imprisonment of Hss as aliens in an intellectual hell on a foreign planet.

Animals↗

PubMed2005

The evolution of the human mind and logic--mathematics structures.

The evolution of the human mind is discussed based on: (i) the fact that living beings interchange matter, energy and information with their environment, (ii) an ontological interpretation of the "reality" of the quantum world, of which logic-mathematics structures are considered constitutive parts, (iii) recent theories according to which living beings are considered as dynamic complex systems organized by information, and (iv) the fact that the evolution of living beings is guided by information about the environment and by intrinsic information on living systems (auto-organization). Assuming the evolution of vision as a model we observe that the driving forces that directed the evolution of the eyes, as dynamic complex systems, are the information about the environment supplied by sunlight and the intrinsic information-gaining mechanism of living organisms. Thus, there exists a convergence toward a visual system with the greatest ability to obtain light information, like the human eye, and also a divergence that leads to the development of specific qualities in some species. As in the case of vision the evolution of the human mind-brain cannot be a consequence of factors unrelated to the object of its own functioning. The human mind was structured for the acquisition from reality of the logic-mathematics structures that underlie the whole universe and consequently of an internal representation of the external world and of its own self. Thus, these structures are, together with the intrinsic capacity for auto-organization of the human brain, the predominant driving force of the human mind evolution. Both factors are complementary.

Biological Evolution↗

PubMed1999

Visual circuits of the avian telencephalon: evolutionary implications.

Birds and primates are vertebrates that possess the most advanced, efficient visual systems. Although lineages leading to these two classes were separated about 300 million years ago, there are striking similarities in their underlying neural mechanisms for visual processing. This paper discusses such similarities with special emphasis on the visual circuits in the avian telencephalon. These similarities include: (1) the existence of two parallel visual pathways and their distinct telencephalic targets, (2) anatomical and functional segregation within the visual pathways, (3) laminar organization of the telencephalic targets of the pathways (e.g. striate cortex in primates), and (4) possible interactions between multiple visual areas. Additional extensive analyses are necessary to determine whether these similarities are due to inheritance from a common ancestral stock or the consequences of convergent evolution based on adaptive response to similar selective pressures. Nevertheless, such a comparison is important to identify the general and specific principles of visual processing in amniotes (reptiles, birds, and mammals). Furthermore, these principles in turn will provide a critical foundation for understanding the evolution of the brain in amniotes.

Animals↗

PubMed1995

Magnetic resonance imaging of multiple brain abscesses of the bilateral basal ganglia.

A 64-year-old woman developed multiple brain abscesses of the basal ganglia associated with Klebsiella pneumoniae septicemia. Magnetic resonance (MR) images showed three different stages of the brain abscesses. The images of early cerebritis of this site mimicked lacunar infarctions or dilated Virchow-Robin spaces. The differentiation of the brain abscess from lacunae and dilated Virchow-Robin spaces is discussed, together with the evolution of the brain abscesses on MR images.

Basal Ganglia↗

PubMed2004

Interspecific allometry of the brain and brain regions in parrots (psittaciformes): comparisons with other birds and primates.

Despite significant progress in understanding the evolution of the mammalian brain, relatively little is known of the patterns of evolutionary change in the avian brain. In particular, statements regarding which avian taxa have relatively larger brains and brain regions are based on small sample sizes and statistical analyses are generally lacking. We tested whether psittaciforms (parrots, cockatoos and lorikeets) have larger brains and forebrains than other birds using both conventional and phylogenetically based methods. In addition, we compared the psittaciforms to primates to determine if cognitive similarities between the two groups were reflected by similarities in brain and telencephalic volumes. Overall, psittaciforms have relatively larger brains and telencephala than most other non-passerine orders. No significant difference in relative brain or telencephalic volume was detected between psittaciforms and passerines. Comparisons of other brain region sizes between psittaciforms and other birds, however, exhibited conflicting results depending upon whether body mass or a brain volume remainder (total brain volume - brain region volume) was used as a scaling variable. When compared to primates, psittaciforms possessed similar relative brain and telencephalic volumes. The only exception to this was that in some analyses psittaciforms had significantly larger telencephala than primates of similar brain volume. The results therefore provide empirical evidence for previous claims that psittaciforms possess relatively large brains and telencephala. Despite the variability in the results, it is clear that psittaciforms tend to possess large brains and telencephala relative to non-passerines and are similar to primates in this regard. Although it could be suggested that this reflects the advanced cognitive abilities of psittaciforms, similar studies performed in corvids and other avian taxa will be required before this claim can be made with any certainty.

Animals↗

PubMed2002

Cerebral evolution.

We suggest that the evolution of the large human brain could not have occurred on the savannahs of Africa. It depended on avoiding the trap of universal loss of brain capacity amongst all land species as they evolved larger bodies. The nutrition at the water's front would have given evolving humans the edge over other hominid species. They would have had access to a rich, plentiful and easily harvested food resource, rich in DHA, trace elements and anti-oxidants, for little energy expenditure. This does not deny the possibility that the men hunted for meat. However, a reliable and consistent nutrient dense food resource, rich in DHA would have been especially important for women during pregnancy and lactation and of course the children during the period of fetal and neonatal brain development and reproductive maturation.

Biological Evolution↗

PubMed2007

The ongoing adaptive evolution of ASPM and Microcephalin is not explained by increased intelligence.

Recent studies have made great strides towards identifying putative genetic events underlying the evolution of the human brain and its emergent cognitive capacities. One of the most intriguing findings is the recurrent identification of adaptive evolution in genes associated with primary microcephaly, a developmental disorder characterized by severe reduction in brain size and intelligence, reminiscent of the early hominid condition. This has led to the hypothesis that the adaptive evolution of these genes has contributed to the emergence of modern human cognition. As with other candidate loci, however, this hypothesis remains speculative due to the current lack of methodologies for characterizing the evolutionary function of these genes in humans. Two primary microcephaly genes, ASPM and Microcephalin, have been implicated not only in the adaptive evolution of the lineage leading to humans, but in ongoing selective sweeps in modern humans as well. The presence of both the putatively adaptive and neutral alleles at these loci provides a unique opportunity for using normal trait variation within humans to test the hypothesis that the recent selective sweeps are driven by an advantage in cognitive abilities. Here, we report a large-scale association study between the adaptive alleles of these genes and normal variation in several measures of IQ. Five independent samples were used, totaling 2393 subjects, including both family-based and population-based datasets. Our overall findings do not support a detectable association between the recent adaptive evolution of either ASPM or Microcephalin and changes in IQ. As we enter the post-genomic era, with the number of candidate loci underlying human evolution growing rapidly, our findings highlight the importance of direct experimental validation in elucidating their evolutionary role in shaping the human phenotype.

Adolescent↗

PubMed2004

[Evolution of language: attempt at synthesis].

There are at least three traits that distinguish modern Homo sapiens from his closest relatives: bipedal locomotion, the unusual size of his brain and the ability to use symbolic language. To this day the emergence and evolution of these traits have not been explained sufficiently. New research in anthropology, linguistics, cognitive science and other disciplines shows, that the evolution of the human language faculty is a complex field that was influenced by a wide variety of factors. This paper tries to show the width of these factors and to work out the demands that are to be met by a theory of language evolution. After the introduction, in Section 2 the evolutionary principles and their role in the evolution of symbolic communication will be reviewed. Section 3 gives an overview of the results and controversies of brain evolution research, while Section 4 introduces our current knowledge of the neuronal basis of language. In Section 5 the controversies that had the greatest impact on the field and development of ways to solve them are reviewed before Section 6 summarizes the most important preadaptations for the evolving language faculty.

Animals↗

PubMed2002

The Otx family.

Otx1 and Otx2, the murine homologs of the Drosophila orthodenticle gene, play a remarkable role in specification and regionalization of forebrain and midbrain. Recently, genetic approaches have indicated that OTD, OTX1 and OTX2 have retained reciprocal functional equivalence in evolution, whereas their regulatory control has been remarkably modified. This suggests that during the evolution of the vertebrate brain, regulatory changes modulating the transcriptional and translational control of pre-existing gene functions might have favored the establishment of new morphogenetic pathways.

Animals↗