[Evolution and development of capacities of the human brain in the course of human history].
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Anthropology↗
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Interspecies Organoids Reveal Human-Specific Molecular Features of Dopaminergic Neuron Development and Vulnerability.
The disproportionate expansion of telencephalic structures during human evolution involved tradeoffs that imposed greater connectivity and metabolic demands on midbrain dopaminergic neurons. Despite the central role of dopaminergic neurons in human-enriched disorders, molecular specializations associated with human-specific features and vulnerabilities of the dopaminergic system remain unexplored. Here, we establish a phylogeny-in-a-dish approach to examine gene regulatory evolution by differentiating pools of human, chimpanzee, orangutan, and macaque pluripotent stem cells into ventral midbrain organoids capable of forming long-range projections, spontaneous activity, and dopamine release. We identify human-specific gene expression changes related to axonal transport of mitochondria and reactive oxygen species buffering and candidate cis- and trans-regulatory mechanisms underlying gene expression divergence. Our findings are consistent with a model of evolved neuroprotection in response to tradeoffs related to brain expansion and could contribute to the discovery of therapeutic targets and strategies for treating disorders involving the dopaminergic system.
Brain evolution↗
Expression of thyroid transcription factor-1 (TTF-1) gene in the ventral forebrain and endostyle of the agnathan vertebrate, Lampetra japonica.
The Thyroid transcription factor-1 (TTF-1) gene belongs to the Nkx-2.1 subfamily and encodes a transcription factor containing an NK-2-type homeodomain. In our study, we isolated and characterized cDNA clones for the TTF-1/Nkx-2.1 orthologue (LjTTF-1) from the agnathan vertebrate Lampetra japonica. Spatial and temporal expression patterns assessed by in situ hybridization revealed the expression of LjTTF-1 in the anterior nerve cord and anteroventral region of the pharynx. The neural expression was subsequently restricted to the ventral diencephalon. The pharyngeal expression, on the other hand, extended posteriorly to the fourth pharyngeal-pouch level and was finally localized in the endostyle anlage. In the differentiated endostyle of ammocoete larvae, the expression of LjTTF-1 was chiefly detected in type 2a, 2b, and 2c cells, which develop adjacent to glandular cells. These expression patterns of LjTTF-1 support the idea that this gene family plays an important role in the development of the rostral brain and endostyle equivalent organs. Furthermore, histological comparisons between TTF-1/Nkx-2.1 expression in the endostyles of ammocoetes and ascidians suggested the possibility that the organogenetic architecture of the endostyle is conserved among chordates.
Amino Acid Sequence↗
Persistence of the nervus terminalis in adult bats: a morphological and phylogenetical approach.
The presence of the terminalis system in adult bats is demonstrated by light microscopical investigation of several species of Microchiroptera. In late embryonic and fetal stages of the mouse-eared bat (Myotis myotis) the compact central terminalis ganglion gradually differentiates into a three-dimensional network of cord-like ganglia and fiber bundles. Rostrally the terminalis system is in immediate contact with the medial-most fila olfactoria; caudally terminalis rootlets attach near the border between the olfactory bulb and the septum of the brain. With respect to the findings presented here it seems likely that all mammals develop a terminalis system in early ontogenesis and retain it until the adult stage. However, considerable differences concerning the number of persisting neurons may be found among some mammalian orders.
Animals↗
X-linked imprinting: effects on brain and behaviour.
Imprinted genes are monoallelically expressed in a parent-of-origin-dependent manner and can affect brain and behavioural phenotypes. The X chromosome is enriched for genes affecting neurodevelopment and is donated asymmetrically to male and female progeny. Hence, X-linked imprinted genes could potentially influence sexually dimorphic neurobiology. Consequently, investigations into such loci may provide new insights into the biological basis of behavioural differences between the sexes and into why men and women show different vulnerabilities to certain mental disorders. In this review, we summarise recent advances in our knowledge of X-linked imprinted genes and the brain substrates that they may act upon. In addition, we suggest strategies for identifying novel X-linked imprinted genes and their downstream effects and discuss evolutionary theories regarding the origin and maintenance of X-linked imprinting.
Animals↗
Frontal cerebral perfusion after antidepressant drug treatment versus ECT in elderly patients with major depression: a 12-month follow-up control study.
BACKGROUND: Little is known about the evolution of brain perfusion alterations in patients with major depression, and still less about the changes in functional neuroimage produced by different antidepressant biological treatments. METHOD: Between January 2001 and December 2003, long-term follow-up frontal brain perfusion was compared in 2 subgroups of elderly patients (>or= 60 years) treated for severe unipolar major depression (DSM-IV): one subgroup of 16 patients administered electroconvulsive therapy, and another of 26 patients receiving pharmacologic treatment. All patients were remitters. A medication-free brain single photon emission computed tomography was performed in baseline conditions and after a minimum period of 12 months of euthymia. Twenty-eight age- and sex-matched healthy controls were also assessed. RESULTS: No significant differences were found between the 2 subgroups in frontal uptake ratios after a 12-month follow-up period of euthymia. During the acute episode, patients presented significant anterior hypofrontality; 12 months later the hypofrontality had disappeared. CONCLUSION: The long-term evolution of frontal perfusion in elderly major depressives who respond to antidepressant biological treatment is essentially the same in those who receive electroconvulsive therapy and in those who receive medication.
Aged↗
Localization and characterization of gonadotropin-releasing hormones in the brain, gonads, and plasma of a dipnoi (lungfish, Protopterus annectens).
Two molecular forms of GnRH (chicken GnRH II and a second variant) are present in the brains of species from all the major vertebrate groups. Their differential distribution in the brain and temporal expression during development suggests that have different functional roles. We investigated the nature of GnRH molecular forms in the brain, plasma, testis, and ovary of adult and juvenile lungfish (Protopterus annectens), using high performance liquid chromatography and radioimmunoassay with specific GnRH antisera. In the brain of adult and juvenile lungfish, two peptides with identical chromatographic and immunologic properties to mammalian GnRH and chicken GnRH II were detected. Chicken GnRH II predominated in both the adult and juvenile brain, and the percentage of chicken GnRH II relative to mammalian GnRH was greater in the juvenile brain. In the plasma, only mammalian GnRH was present. Immunoreactive GnRH was not detected in the testis and ovary. Chicken GnRH II and mammalian GnRH were found in the cells of the preoptic nucleus and in the ganglion of the nervus terminalis. Fibers were seen in the ventral hypothalamus, and chicken GnRH II immunoreactivity was detected within the neural lobe of the pituitary. The finding of chicken GnRH II in a sarcopterygian fish adds further support to our hypothesis that this ubiquitous structural variant is highly conserved and likely to have an important functional role. Mammalian GnRH, previously described in several early-evolved actinopterygian fish, also has a fairly widespread distribution and early evolutionary origin. The immunocytochemical distribution of mammalian GnRH and chicken GnRH II fibers in the lungfish brain suggests that both forms are hypophysiotropic. In addition, the presence of mammalian GnRH in the plasma of the lungfish suggests that this molecular form of GnRH has a hypophysiotropic function reaching target organs (pituitary and gonads) via the general circulation.
Animals↗
Evolution of neuroendocrine mechanisms that regulate sexual behavior.
Whiptail lizards provide a unique system to study evolution of brain mechanisms because both ancestral (sexual) and descendant (parthenogenetic) species exist. Parthenogenetic whiptails enable us to avoid the two major confounds in sex differences research - males and females that differ both genetically and hormonally. Parthenogens are females that reproduce clonally, yet display alternately female-like and male-like pseudosexual behavior. Thus, the neural circuitry underlying male and female sexual behavior can be examined within the 'same' brain (same genome), enabling us to see how neuroendocrine mechanisms controlling mounting behavior change. In ancestral males, testicular androgens control sexual behavior, whereas male-like pseudocopulatory behavior is controlled by ovarian progesterone in parthenogens, revealing that progesterone is important in regulating sexual behavior in male vertebrates, including mammals.
Animals↗
Twenty-day cerebral and umbilical Doppler monitoring on a growth retarded and hypoxic fetus.
In one growth retarded and hypoxic fetus, the cerebral and umbilical hemodynamic changes were assessed (by Doppler), daily over 20 days. The fetal brain was investigated by magnetic resonance imaging (MRI) close to the delivery, and because the fetus died at delivery we performed an anatomical study of the fetal brain. The evolution of the fetal hemodynamics (day by day) was interpreted according to the MRI findings and the clinical findings. During the period of observation (under sustained hypoxia) the fetal deterioration was characterized by: (a) the progressive development of the oligohydramnios (190d), (b) the disappearance of the vascular reactivity (eight successive cerebral resistance index (RI) constant at 194d), (c) the occurrence of fetal heart rate decelerations (199d), and finally (d) the increase of the cerebral vascular resistances with reduction of the brain perfusion (204d). The anatomical study of the brain showed a periventricular congestion however the histology revealed hypoxic lesions like gliosis and a marked vasodilation of the anterior and middle cerebral arteries. Finally in addition to single Doppler measurements performed 1 week before delivery (for prediction of fetal outcome), one can suggest to use the 'loss of fluctuation of the cerebral RI' to identify the beginning of the period of very high risk for the fetus. Such hypothesis may have to be confirmed on a larger number of pathological pregnancies.
Adult↗
Neuro-evolutionary patterning of sociality.
Evolutionary shifts in species-typical group size ('sociality') probably reflect natural selection on motivational processes such as social arousal, approach-avoidance, reward, stress/anxiety and dominance. Using four songbird species that differ selectively in sociality (one territorial, one modestly gregarious, and two highly gregarious species), we here examined immediate early gene (IEG) responses of relevant brain regions following exposure to a same-sex conspecific. The paradigm limited behavioural performance, thus species differences should reflect divergence in motivational and/or perceptual processes. Within the extended medial amygdala (which is involved in appetitive approach, social arousal and avoidance), we observed species differences in IEG response that are negatively graded in relation to sociality. In addition, brain areas that are involved in social stress and dominance-related behaviour (ventrolateral septum, anterior hypothalamus and lateral subdivision of the ventromedial hypothalamus) exhibited IEG responses that dichotomously distinguish the territorial species from the three gregarious species. The IEG responses of areas involved in reward (nucleus accumbens and ventral pallidum) and general stress processes (e.g. paraventricular hypothalamus, lateral bed nucleus of the stria terminalis and most areas of the lateral septum) do not correlate with sociality, indicating that social evolution has been accompanied by selection on a relatively discrete suite of motivational systems.
Analysis of Variance↗
The social nature of primate cognition.
The hypothesis that the enlarged brain size of the primates was selected for by social, rather than purely ecological, factors has been strongly influential in studies of primate cognition and behaviour over the past two decades. However, the Machiavellian intelligence hypothesis, also known as the social brain hypothesis, tends to emphasize certain traits and behaviours, like exploitation and deception, at the expense of others, such as tolerance and behavioural coordination, and therefore presents only one view of how social life may shape cognition. This review outlines work from other relevant disciplines, including evolutionary economics, cognitive science and neurophysiology, to illustrate how these can be used to build a more general theoretical framework, incorporating notions of embodied and distributed cognition, in which to situate questions concerning the evolution of primate social cognition.
Animals↗
The brain of the Remipedia (Crustacea) and an alternative hypothesis on their phylogenetic relationships.
Remipedia are rare and ancient mandibulate arthropods inhabiting almost inaccessible submerged cave systems. Their phylogenetic position is still enigmatic and the subject of extremely controversial debates. To contribute arguments to this discussion, we analyzed the brain of Godzilliognomus frondosus Yager, 1989 (Remipedia, Godzilliidae) and provide a detailed 3D reconstruction of its anatomy. This reconstruction yielded the surprising finding that in comparison with the brain of other crustaceans such as representatives of the Branchiopoda and Maxillopoda the brain of G. frondosus is highly organized and well differentiated. It is matched in complexity only by the brain of "higher" crustaceans (Malacostraca) and Hexapoda. A phylogenetic analysis limited to brain anatomy across the Mandibulata strongly contradicts the prevailing hypothesis that the Remipedia are a basal, ancestral crustacean group but instead argues in favor of a remipede-malacostracan-hexapod clade and most likely a sister-group relationship of Remipedia and Malacostraca.
Animals↗
A theoretical model of selective cooling using intracarotid cold saline infusion in the human brain.
A three-dimensional mathematical model was developed to examine the transient and steady-state temperature distribution in the human brain during selective brain cooling (SBC) by unilateral intracarotid freezing-cold saline infusion. To determine the combined effect of hemodilution and hypothermia from the cold saline infusion, data from studies investigating the effect of these two parameters on cerebral blood flow (CBF) were pooled, and an analytic expression describing the combined effect of the two factors was derived. The Pennes bioheat equation used the thermal properties of the different cranial layers and the effect of cold saline infusion on CBF to propagate the evolution of brain temperature. A healthy brain and a brain with stroke (ischemic core and penumbra) were modeled. CBF and metabolic rate data were reduced to simulate the core and penumbra. Simulations using different saline flow rates were performed. The results suggested that a flow rate of 30 ml/min is sufficient to induce moderate hypothermia within 10 min in the ipsilateral hemisphere. The brain with stroke cooled to lower temperatures than the healthy brain, mainly because the stroke limited the total intracarotid blood flow. Gray matter cooled twice as fast as white matter. The continuously falling hematocrit was the main time-limiting factor, restricting the SBC to a maximum of 3 h. The study demonstrated that SBC by intracarotid saline infusion is feasible in humans and may be the fastest method of hypothermia induction.
Blood Flow Velocity↗
Reconstructing the behaviors of extinct species: an excursion into comparative paleoneurology.
How can the behavior of an extinct species be reconstructed-say a dinosaur such as Allosaurus? Despite the relatively abundant fossilized remains of this and other dinosaurs, the incompleteness of the fossil record has permitted room for considerable speculation, mythology, and perhaps a bit of unsettling reflection on what factors contributed to the eventual fate of these remarkably successful animals. Among the speculations is how these 'bigger-than-life' creatures behaved, a topic that itself can attain equal diversity and grandeur. With recent advancements in measuring the relatedness of living organisms, how genetics contribute to brain development and how this relates to behavior, combined with the availability of newly discovered high quality fossils and imaging methods to exploit their secrets, novel insights into how extinct creatures such as Allosaurus intermingled with its many relatives over 100 million years ago are beginning to emerge.
Animals↗
The neural basis of predicate-argument structure.
Neural correlates exist for a basic component of logical formulae, PREDICATE(x). Vision and audition research in primates and humans shows two independent neural pathways; one locates objects in body-centered space, the other attributes properties, such as colour, to objects. In vision these are the dorsal and ventral pathways. In audition, similarly separable "where" and "what" pathways exist. PREDICATE(x) is a schematic representation of the brain's integration of the two processes of delivery by the senses of the location of an arbitrary referent object, mapped in parietal cortex, and analysis of the properties of the referent by perceptual subsystems. The brain computes actions using a few "deictic" variables pointing to objects. Parallels exist between such nonlinguistic variables and linguistic deictic devices. Indexicality and reference have linguistic and nonlinguistic (e.g., visual) versions, sharing the concept of attention. The individual variables of logical formulae are interpreted as corresponding to these mental variables. In computing action, the deictic variables are linked with "semantic" information about the objects, corresponding to logical predicates. Mental scene descriptions are necessary for practical tasks of primates, and preexist language phylogenetically. The type of scene descriptions used by nonhuman primates would be reused for more complex cognitive, ultimately linguistic, purposes. The provision by the brain's sensory/perceptual systems of about four variables for temporary assignment to objects, and the separate processes of perceptual categorization of the objects so identified, constitute a pre-adaptive platform on which an early system for the linguistic description of scenes developed.
Afferent Pathways↗
The origin of the vertebrate brain.
The need for a "model" of the development of the head and the nervous system is examined. The purpose of such a model is to facilitate the testing of the probability of the correctness of anatomic and developmental ideas from a number of areas. Without such a model this information presents only a jumble of discordant facts. The proposed model suggests the following: 1. The nervous system of amphioxus tells us little, or nothing, about the ancestral vertebrate system. 2. The gap between the neural tube stage, established in the chordate, and the complex central nervous system typical of the vertebrate is partly closed by the identification of two stages. 3. The first of these stages assumes that the original anterior end of the nervous system corresponded with the anterior end of the notochord: thus it was at the anterior end of the present mesencephalon. Outgrowth of the anterior mesencephalic wall, totally sensory in nature, moved the neuropore anteriorly. This outgrowth is correlated with the gradual conversion of a velar mouth to a biting mouth by forward and downward extension of the head. 4. As a result of the anterior and downward expansion of the anterior wall of the mesencephalon, the cephalic flexure and infundibulum were produced. The primitive eye changed its relationship to the brain from attaching anterolateral to laterally; its point of attachment shifted from dorsal to the neuropore to ventral to the neuropore. 5. The nasohypophyseal field in the neural tube ancestor was closely associated with the anterior wall of the brain below the neuropore, and nerve fibers growing from this epithelium extended to the brain below (posterior?) to the optic stalk. With outgrowth, the fibers now entered the brain substance anterior to the optic stalk and dorsal (?) to the neuropore. 6. The second stage, which is well known from the literature, is the outgrowth of the telencephalic lobes from the dorsolateral and anterior wall of the "diencephalon." 7. Among the vertebrates further elaboration of the system can be documented.
Animals↗
Comparative approaches in evolutionary psychology: molecular neuroscience meets the mind.
Evolutionary psychologists often overlook a wealth of information existing between the proximate genotypic level and the ultimate phenotypic level. This commonly ignored level of biological organization is the ongoing activity of neurobiological systems. In this paper, we extend our previous arguments concerning strategic weaknesses of evolutionary psychology by advocating a foundational view that focuses on similarities in brain, behavior, and various basic psychological features across mammalian species. Such an approach offers the potential to link the emerging discipline of evolutionary psychology to its parent scientific disciplines such as biochemistry, physiology, molecular genetics, developmental biology and the neuroscientific analysis of animal behavior. We detail an example of this through our impending work using gene microarray technology to characterize gene expression patterns in rats during aggressive and playful social interactions. Through a focus on functional homologies and the experimental analysis of conserved, subcortical emotional and motivational brain systems, neuroevolutionary psychobiology can reveal ancient features of the human mind that are still shared with other animals. Claims regarding evolved, uniquely human, psychological constructs should be constrained by the rigorous evidentiary standards that are routine in other sciences.
Adaptation, Psychological↗
Astrocytic complexity distinguishes the human brain.
One of the most distinguishing features of the adult human brain is the complexity and diversity of its cortical astrocytes. Human protoplasmic astrocytes manifest a threefold larger diameter and have tenfold more primary processes than those of rodents. In all mammals, protoplasmic astrocytes are organized into spatially non-overlapping domains that encompass both neurons and vasculature. Yet unique to humans and primates are additional populations of layer 1 interlaminar astrocytes that extend long (millimeter) fibers, and layer 5-6 polarized astrocytes that also project distinctive long processes. We propose that human cortical evolution has been accompanied by increasing complexity in the form and function of astrocytes, which reflects an expansion of their functional roles in synaptic modulation and cortical circuitry.
Adult↗