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At least 559 records · Page 31Linked to original sources
PubMed2005

Prefrontal white matter volume is disproportionately larger in humans than in other primates.

Determining how the human brain differs from nonhuman primate brains is central to understanding human behavioral evolution. There is currently dispute over whether the prefrontal cortex, which mediates evolutionarily interesting behaviors, has increased disproportionately. Using magnetic resonance imaging brain scans from 11 primate species, we measured gray, white and total volumes for both prefrontal and the entire cerebrum on each specimen (n = 46). In relative terms, prefrontal white matter shows the largest difference between human and nonhuman, whereas gray matter shows no significant difference. This suggests that connectional elaboration (as gauged by white matter volume) played a key role in human brain evolution.

Animals↗
PubMed2001

Extent of tumor-brain interface: a new tool to predict evolution of malignant gliomas.

OBJECT: Tumor size is one of the features commonly used in oncology to predict disease evolution. However, for most primary brain tumors it is not predictive of outcome. Taking advantage of a gene therapy trial in which recurrences of glioblastoma were targeted with suicide genes, the authors developed a new parameter: the extent of tumor-brain interface--also called surface of tumor volume (STV)--to better describe three-dimensional conformation and the relationship between tumors and the surrounding normal tissue. Correlations between the STV and the usual clinical parameters were analyzed. METHODS: Between 1995 and 1998, 16 patients presenting with recurrent glioblastomas were enrolled in this study. Preoperative magnetic resonance images were analyzed on a separate workstation; the interface between tumor and normal brain tissue was measured on each 3-mm-thick section to assess STV. The mean STV was 29.2 cm2, and the mean tumor volume (TV) was 23.8 cm3. The STV was significantly correlated with survival (Spearman test: r = -0.54, p = 0.03), but TV was not (Spearman test: r = -0.39, p = 0.15). A separate analysis of responding and nonresponding patients showed that, as expected, STV was negatively correlated with survival among nonresponding patients (p = 0.04), but that among responding patients there was a positive tendency between STV and survival. CONCLUSIONS: These findings indicate that STV may be a useful tool for predicting the evolution of malignant glioma. Moreover, in future gene therapy trials in which such in situ approaches are used, increasing density and improved distribution of transfer cells should be taken into consideration as an important issue for efficacy.

Adult↗
PubMed2004

Mechanisms of hypoxic-ischemic injury in the term infant.

The pathogenesis of hypoxic-ischemic brain injury in the term infant is multifactorial and complex. Over the past decade the investigative emphasis has turned to cellular and molecular mechanisms of injury, and it has been increasingly recognized that the neonatal brain differs vastly from the adult brain in terms of response to hypoxia-ischemia. This review will discuss the initiation and evolution of brain injury in the term neonate, and the inherent biochemical and physiologic qualities of the neonatal brain that make its response to hypoxia-ischemia unique. Attention will be given to specific areas of investigation including excitotoxicity, oxidative stress, and inflammation. The coalescence of these entities to a final common pathway of hypoxic-ischemic brain injury will be emphasized.

Brain↗
PubMed1998

Hebb and Darwin.

It is proposed that vertebrate brains, especially those of mammals, operate according to an algorithm subsumable as "synaptic Darwinism". The key postulate is that genes and synapses follow the same rules, because they act as autocatalytic, hypercyclic, units of selection. Synapses replicate by quantally strengthening, and mutate by connecting new cells. Because synapses relate pre- and post-synaptic firing, they perform a translation operation. Furthermore the product of this operation, conjoint firing, favors replication (by Hebb's Rule). The result is that variants are selected and patterns of connection automatically adopt optimal configurations. These configurations are determined by scalar neuromodulatory "reward" signals applied globally to layers of neurons, which reduce spike frequency adaptation and enhance Hebbian replication. Global or local control of mutation rates provides further improvements in the Darwinian algorithm. All the processes and circuits postulated have plausible, and often obvious, implementations. The result is that brains evolve and adapt like large ecosystems.

Animals↗
PubMed1979

Phylogenetic and regional variations in brain gangliosides of tetrapods.

1. Ganglioside patterns were analyzed from four neural tissues (medulla, midbrain, forebrain and retina) in a representative from each of the four tetrapod classes. 2. Regional variations in ganglioside patterns were noted within some species, but differences were greater across phylogenetic lines. 3. These results suggest that evolutionary history plays a greater role than neural differentiation in the expression of brain ganglioside patterns.

Animals↗
PubMed2005

Bigger is not always better: when brains get smaller.

Many studies assume that an increase in brain size is beneficial. However, the costs of producing and maintaining a brain are high, and we argue that brain size should be secondarily reduced by natural selection whenever the costs outweigh the benefits. Our results confirm this by showing that brain size is subject to bidirectional selection. Relative to the ancestral state, brain size in bats has been reduced in fast flyers, while it has increased in manoeuvrable flyers adapted to flight in complex habitats. This study emphasizes that brain reduction and enlargement are equally important, and they should both be considered when investigating brain size evolution.

Animals↗
PubMedDate not supplied

[Self-stimulation of phylogenetically new and ancient hypothalamic structures when reinforcement schedules are changed].

The following two types of reaction are exhibited by self-stimulating rats following a transition from the regimen of preference (free) to that of fixed series of stimuli: I. increased frequency of pressings with simultaneous shortening of their duration, approaching the duration of fixed series; II. reduced frequency of pressings with their longer duration. Of the two studied hypothalamic areas, the former type of reaction is exhibited predominantly in the self-stimulation points located in the lateral hypothalamic area, while the latter type - in the lateral preoptic area. Different strategy of the animals' behaviour observed during the change of reinforcement routines is discussed with regard to different levels of integration of emotionally-positive mechanisms of brain structures of phylogenetically different age.

Animals↗