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[The self-organization of the brain as the integration of the processes of different spatial and time scales].
The article is devoted to analysis of theoretical aspects of brain functioning. The base of authors philosophy is some general principles, which one can see on macro- and microlevels of brain functioning organization.
A human-specific gene in microglia.
Recent studies have shown multiple differences between humans and apes in sialic acid (Sia) biology, including Siglecs (Sia-recognizing-Ig-superfamily lectins). Comparisons with the chimpanzee genome indicate that human SIGLEC11 emerged through human-specific gene conversion by an adjacent pseudogene. Conversion involved 5 cent untranslated sequences and the Sia-recognition domain. This human protein shows reduced binding relative to the ancestral form but recognizes oligosialic acids, which are enriched in the brain. SIGLEC11 is expressed in human but not in chimpanzee brain microglia. Further studies will determine if this event was related to the evolution of Homo.
Sequential colour mapping system of brain potentials.
We present a colour mapping system for the visualization of both the spatial scalp distribution and the temporal evolution of brain potentials. The system is applicable to recordings of auditory, visual and somatosensory potentials. It uses a Tektronix 4113 colour terminal connected to a Solar 16 (SEMS) mini-computer. The brain potentials are recorded on up to 16 scalp electrodes. The gain and the baseline are corrected separately on each channel. At each point of the scalp the potential is reconstructed by a linear interpolation of the measured potentials of the four nearest electrodes. Simultaneously n2 (1 less than n less than 8) colour maps can be presented on the screen. This allows the study of the temporal evolution of full scalp evoked potentials. The user chooses the two extreme latencies defining the time window to be explored and the latencies of the maps are regularly time-spaced within this window. In a typical case, in which four maps are desired, the latencies of the maps can be chosen independently. The 16-colour palette is predetermined but the user has three possibilities to establish the correspondence between the electrical potential and the colours. Examples are shown in the visual and somatosensory stimulation modalities. The advantages and limitations of such a representation are discussed.
Selection processes in living systems: role in cognitive construction and recovery from brain damage.
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Human brain functions and the foundations of science.
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The periodicity of collagen in the brain sheath of a polychaete.
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Models for the human brain.
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[The brain: its problems and its resources].
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[Studies of the brain of Solenodon paradoxus, Brandt 1833 (Insectivora, Solenodontidae). Form of the brain and determination of the neocortex index].
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Serial recording of median nerve stimulated subcortical somatosensory evoked potentials (SEPs) in developing brain death.
Subcortical somatosensory evoked potentials (SEPs) to median nerve stimulation were recorded serially in 35 patients during the evolution towards brain death and in brain death. Neuropathological alterations of the central nervous system down to the C1/C2 spinal cord segment in brain death are well known. SEP components supposed to be generated above this level should be lost in brain death, while components generated below should not be altered. Erb's point, scalp and neck potentials were recorded at C3/4, or over the spinous process C7, using an Fz reference. In 10 patients additional montages, including spinous process C2-Fz, a non-cephalic reference (Fz-contralateral shoulder) and a posterior to anterior neck montage (spinous process C7-jugulum) were used. The cephalic referenced N9 and N11 peaks remained unchanged until brain death. N9 and N11 decreased in parallel in amplitude and increased in latency after systemic effects like hypoxia or hypothermia occurred. The cephalic referenced 'N14' decreased in amplitude and increased in latency after the clinical brain death syndrome was observed, while N13 in the posterior to anterior neck montage remained unchanged. The alteration of 'N14' went parallel to the decrease of the P14 amplitude. The subcortical SEPs in the cephalic referenced lead are supposed to be a peak composed by a horizontally orientated dorsal horn generated N13 and a rostrally orientated P14 arising at the level of the foramen magnum. The deterioration of the non-cephalic referenced P14 and of its cephalic referenced reflection 'N14' seems to provide an additional objective criterion for the diagnosis of brain death.
Comparative morphology of central neuropils in the brain of arthropods and its evolutionary and functional implications.
Most insects and decapod crustaceans possess an assemblage of midline neuropils, the central complex. Recent phylogenetic studies show a sister-group relationship between hexapods and decapods, suggesting that central complexes in both groups are homologous structures derived from a basal ancestral neuropil. This ancestral archetype of the central complex (lacking the protocerebral bridge) might be represented in the chilopods. Until recently, diplopods were regarded as closely related to chilopods and united within the taxon "Myriapoda". The entire lack of a midline neuropil in diplopods, however, renders the monophyletic origin of the class Myriapoda unlikely. In this study we used a palette of immunocytochemical and neuroanatomical methods to investigate mid-line neuropils in hitherto poorly examined arthropod groups. Of special interest for resolving arthropod phylogeny are onychophorans, who are believed to be an evolutionary ancient group that resembles the ancestors of modern arthropods. Striking similarities in central brain neuroarchitecture of the onychophoran Euperipatoides rowellii and of a chelicerate species, however, suggest a close phylogenetic relationship between these two groups. Our findings imply that onychophorans either represent the oldest form of the chelicerates or that extant onychophorans have developed from chelicerate-like ancestors by neoteny.
The long reach of evolution and development. Effects on the Alzheimer brain.
Genes that cause late-onset neurodegenerative disease may have the property of evolvability. Their tendency to collect mutations may have contributed to the rapid evolution of the brain.
[Evolution of structural changes arising in the brain of revied animals].
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GFAP-immunopositive structures in spiny dogfish, Squalus acanthias, and little skate, Raia erinacea, brains: differences have evolutionary implications.
GFAP expression patterns were compared between the brains of a spiny dogfish (Squalus acanthias) and a little skate (Raia erinacea). After anesthesia, the animals were perfused with paraformaldehyde. Serial vibratome sections were immunostained against GFAP using the avidin-biotin method. Spiny dogfish brain contained mainly uniformly-distributed, radially arranged ependymoglia. From GFAP distribution, the layered organization in both the telencephalon and the tectum were visible. In the cerebellum, the molecular and granular layers displayed conspicuously different glial structures; in the former a Bergmann glia-like population was found. No true astrocytes (i.e., stellate-shaped cells) were found. Radial glial endfeet lined all meningeal surfaces. Radial fibers also seemed to form endfeet and en passant contacts on the vessels. Plexuses of fine perivascular glial fibers also contributed to the perivascular glia. Compared with spiny dogfish brain, GFAP expression in the little skate brain was confined. Radial glia were limited to a few areas, e.g., segments of the ventricular surface of the telencephalon, and the midline of the diencephalon and mesencephalon. Scarce astrocytes occurred in every brain part, but only the optic chiasm, and the junction of the tegmentum and optic tectum contained large numbers of astrocytes. Astrocytes formed the meningeal glia limitans and the perivascular glia. No GFAP-immunopositive Bergmann glia-like structure was found. Astrocytes seen in the little skate were clearly different from the mammalian and avian ones; they had a different process system - extra large forms were frequently seen, and the meningeal and perivascular cells were spread along the surface instead of forming endfeet by processes. The differences between Squalus and Raia astroglia were much like those found between reptiles versus mammals and birds. It suggests independent and parallel glial evolutionary processes in amniotes and chondrichthyans, seemingly correlated with the thickening of the brain wall, and the growing complexity of the brain. There is no strict correlation, however, between the replacement of radial ependymoglia with astrocytes, and the local thickness of the brain wall.
Arousal mechanisms: speedy flies don't sleep at night.
Alertness and behavioral performance depend on an animal's level of arousal. In vertebrates, reinforcement and maintenance of arousal in the cortex are ensured by diffuse inputs from neurons releasing biogenic amine neuromodulators. Fruit flies similarly use dopamine for arousal control, indicating an ancient evolutionary origin of this essential feature of the functioning brain.
Emotional endophenotypes in evolutionary psychiatry.
Evolutionary psychiatry emerged from the conceptual successes of sociobiology and evolutionary psychology. It will need to avoid the many mistakes that biology-free Evolutionary Psychology has been prey to. It should not ignore the wealth of information that exists between the phenotypic expression of symptoms and the genotypic sources of core brain/mind processes that are disrupted in psychiatric disorders. Syndromal-conceptual thinking has become a barrier to illuminating the biological sources of psychiatric disorders. Endophenoytpic-biomarker approaches now offer robust alternatives for generating linkages between psychiatrically relevant psychological changes and the neurobiological infrastructure of disordered mentation. Here I summarize recent advances in endophenotypic thinking in biological psychiatry, and suggest that various core emotional-affective processes may be among the most important endophenotypes that need to be clarified at both neurobiological and genetic levels of analysis. To this end, I discuss strategies to link basic emotional processes that are commonly imbalanced in psychiatric disorders to neuroanatomical, neurochemical, neurophysiology, and molecular genetic levels of analysis. Conjoint animal behavioral-genetic and gene expression, microarray analyses can clarify a variety of key emotional endophenotypes and thereby provide a coherent infrastructure for psychiatric systematics. To further clarify the neurobiological dimensions of psychiatric disorders, we must also focus on psychosocial and environmental stress vectors that converge to create imbalanced emotional and motivational brain activities of psychiatric significance.