PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Brain evolution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources
PubMed1989

Sound localization, use of binaural cues and the superior olivary complex in pigs.

Noise localization thresholds and the ability to localize pure tones at 60 degrees separation were determined for three domestic pigs using a conditioned avoidance procedure. The average threshold for localizing a brief noise burst was 4.5 degrees which is much more accurate than the thresholds of other hoofed mammals, such as horses, cattle and goats. The ability of pigs to localize low-frequency tones indicates that they can use the binaural phase-difference cue. However, they were unable to localize tones of 4 kHz and higher, indicating that, like other hoofed mammals, their ability to use binaural intensity cues is greatly restricted if not completely absent. An examination of the superior olivary complex of pigs revealed that in relative size, shape and cell density it is more like that of cats than that of other hoofed mammals.

Animals↗
PubMed1989

Projections from the sacculus to the cochlear nuclei in the Mongolian gerbil.

The projections of the saccule, an otolith end organ, to the cochlear nuclei were studied using both transganglionic transport and intracellular injection techniques. Labeled fibers and terminals were observed in the anterior and posterior portions of the ventral cochlear nucleus and the dorsal cochlear nucleus. Most terminals were present in the granule cell domain, especially in the subpeduncular corner between the anteroventral cochlear nucleus and the floccular peduncle of the cerebellum. It has been hypothesized that the cochlea in mammals may have developed phylogenetically from the saccule. The projections from the saccule to the cochlear nuclei were investigated in a mammalian species, the Mongolian gerbil, in an attempt to obtain initial information supporting or refuting this hypothesis. The presence of an otolith end organ projection to the cochlear nuclei in rodents should encourage comparative studies in additional aspects of the evolution of the auditory system.

Animals↗
PubMed1989

Central projections of the nervus terminalis in four species of amphibians.

The central projections of the nervus terminalis were investigated in two anuran and two urodele species by means of horseradish peroxidase injections into one nasal cavity. In anurans, the nervus terminalis projects to the medial septum, to the preoptic nucleus, to the nucleus of the anterior commissure and to the hypothalamus. In addition to these structures, the dorsal thalamus, the infundibulum and the mesencephalic tegmentum are innervated in urodeles. The structure containing the highest density of terminals in the amphibians investigated is the hypothalamus. In one anuran and one urodele species, the contralateral hypothalamus is primarily innervated, whereas in the other two species the majority of fibers remain ipsilateral. A comparison with other vertebrates shows that the terminalis system in urodeles has the greatest diversity of connections. Anurans, in contrast, lack some connections that are present in urodeles and fishes. These findings have implications for a possible relation of the nervus terminalis to an aquatic habitat.

Ambystoma mexicanum↗
PubMed1988

Presumptive relict reproductive behavior in small parrots.

Recent studies of experimentally elicited egg-care behaviors in three species of small, hole-nesting parrots, and of their evolutionary implications are reviewed. A suite of primarily nonthermal egg-care responses are adaptive for nesting in shallow terrestrial scrapes, rather than in cavities. These responses appear to be relics from times before hole-nesting began; as such, they may provide 'windows' into certain nonthermal aspects of terrestrial-nesting practices during ancestral stages. A suite of primarily thermal egg-care behaviors, elicited when nests are exposed to light and view, progress from mere initial curiosity, inspection, and manipulation of fostered eggs by nonbreeding parents, to more extensive manipulation and episodic concealment of a pair's own eggs by crouching over them, to crouching lengthily over eggs with some incubation but nighttime abandonment, to continuous 24-hour incubation. This progression may retrace certain aspects of major ancestral stages of thermal egg care. Stages of primary oocytes and follicles during ovarian development, and of maturing follicles during breeding cycles of some species, may retrace the phylogenetic progression of sizes of ancestral clutches and ripe follicles. These phenomena and the retention of many of the experimentally elicited egg-care responses are attributed largely to the highly conservative evolution of the central nervous system.

Animals↗
PubMed1983

The role of the corticospinal tract in the evolution of human digital dexterity.

A morphometric analysis of the corticospinal tract's relation to digital dexterity was performed on 21 species theoretically related to man's ancestral lineage. The results indicate that the Primate line is not unique among mammals with respect to the cortical control of digital dexterity. A comparative analysis suggests that two changes took place early in Primate evolution: a reduction in functional distance (i.e. number of synapses) between neocortex and spinal motor neurons innervating the digits, and an extension of direct neocortical influence beyond the cervical segments of the spinal cord. A further change progressed throughout Primate evolution, from the mid-Eocene to the present, in which the overall size of the corticospinal tract increased steadily as though consolidating the cortical influence over body musculature, especially that of the digits.

Animals↗
PubMed1993

Brainstem organization and branchiomeric nerves.

The branchiomeric portion of the vertebrate head represents a region of specialized function and, at the same time, a transition between head and body. Recent experimental work has called into question the 'visceral' nature of the branchiomeres, interpreting them instead within the framework of the segmentation of the body, as is seen clearly in rhombomeres. The vagus nerve is critical to our understanding of this region. It is usually viewed as a serial homologue of dorsal roots of spinal nerves, and the hypoglossal, with its several roots, has been seen as arising from associated ventral roots. The accessory is often considered to have been derived directly from the vagus, having become individuated in tetrapods in general and especially in amniotes. Work on amphibians is examined with respect to these issues, and within structuralist, functionalist and phylogenetic frameworks. The accessory in mammals and birds is a composite; the spinal motor nucleus, which can be traced at least to elasmobranchs, is distinctly different in origin from the more recently added bulbar portion, which is derived from the vagus. The spinal portion appears to have evolved independently of the system associated with branchially derived musculature. The hypoglossal is derived from ventral-column material, but it is not clearly associated with the vagus phylogenetically.

Amphibians↗
PubMed1996

Effect of mild hypothermia on cerebral energy metabolism during the evolution of hypoxic-ischemic brain damage in the immature rat.

BACKGROUND AND PURPOSE: Intraischemic hypothermia (34 degrees C and 31 degrees C) has a profound neuroprotective effect on the brain of the immature rat. Hypothermia immediately after hypoxia-ischemia is not beneficial. To determine the mechanisms by which mild to moderate hypothermia affects cerebral energy metabolism of the brain of the newborn rat pup, we examined alterations in cerebral glycolytic intermediates and high-energy phosphate compounds during intraischemic and postischemic hypothermia and correlated these findings with known neuropathologic injury. METHODS: Seven-day-old rat pups underwent unilateral common carotid artery ligation and exposure to hypoxia in 8% oxygen at either 37 degrees C, 34 degrees C, or 31 degrees C for 3.0 hours. Separate groups were exposed to hypoxia-ischemia at 37 degrees C for 3 hours but recovered at either 37 degrees C, 34 degrees C, or 31 degrees C. At 60, 120, and 180 minutes of intraischemic hypothermia and at 10, 30, 60, and 240 minutes of postischemic hypothermia, individual rat pups were quick-frozen in liquid nitrogen for later determination of cerebral concentrations of glucose, lactate, ATP, and phosphocreatine. RESULTS: Cerebral glucose was significantly higher and lactate significantly lower in the 31 degrees C animals during hypoxia-ischemia than either the 34 degrees C or 37 degrees C groups. Brain ATP concentrations were completely preserved during hypoxia-ischemia at 31 degrees C, whereas 34 degrees C of hypothermia had no effect on preserving high-energy phosphate compounds compared with those animals in the 37 degrees C group. Postischemic hypothermia of either 34 degrees C or 31 degrees C had no effect on the rate or extent of recovery of glycolytic intermediates or high-energy phosphate compounds compared with the normothermic 37 degrees C rat pups. CONCLUSIONS: Moderate hypothermia of 31 degrees C completely inhibits the depletion of ATP during hypoxia-ischemia, a mechanism that likely accounts for its neuroprotective effect. No preservation of ATP was seen, however, during intraischemic mild hypothermia of 34 degrees C despite the relatively profound neuroprotective effect of this degree of temperature reduction. Thus, the mechanisms by which mild hypothermia is neuroprotective are temperature dependent and may act at more than one point along the cascade of events eventually leading to hypoxic-ischemic brain damage in the immature rat.

Adenosine Triphosphate↗
PubMed1999

Interview with John Kaas.

Jon Kaas received a Ph.D. in Psychology with Irving Diamond at Duke University and completed a postdoctoral fellowship with Clinton Woolsey in neurophysiology at the University of Wisconsin, where he also collaborated with Ray Guillery. After 4 years as an Assistant Professor in Neurophysiology at Wisconsin, he moved to the Department of Psychology at Vanderbilt University where he is currently Centennial Professor. Awards include the Earl Sutherland Prize, Javits Neuroscience Investigator Award, Krieg Cortical Discoverer Award, and American Psychological Association Distinguished Scientific Contribution Award.

Animals↗
PubMed2004

Exact solution for the optimal neuronal layout problem.

Evolution perfected brain design by maximizing its functionality while minimizing costs associated with building and maintaining it. Assumption that brain functionality is specified by neuronal connectivity, implemented by costly biological wiring, leads to the following optimal design problem. For a given neuronal connectivity, find a spatial layout of neurons that minimizes the wiring cost. Unfortunately, this problem is difficult to solve because the number of possible layouts is often astronomically large. We argue that the wiring cost may scale as wire length squared, reducing the optimal layout problem to a constrained minimization of a quadratic form. For biologically plausible constraints, this problem has exact analytical solutions, which give reasonable approximations to actual layouts in the brain. These solutions make the inverse problem of inferring neuronal connectivity from neuronal layout more tractable.

Animals↗
PubMed2000

On meme--gene coevolution.

In this article we examine the effects of the emergence of a new replicator, memes, on the evolution of a pre-existing replicator, genes. Using a version of the NKCS model we examine the effects of increasing the rate of meme evolution in relation to the rate of gene evolution, for various degrees of interdependence between the two replicators. That is, the effects of memes' (suggested) more rapid rate of evolution in comparison to that of genes is investigated using a tunable model of coevolution. It is found that, for almost any degree of interdependence between the two replicators, as the rate of meme evolution increases, a phase transition-like dynamic occurs under which memes have a significantly detrimental effect on the evolution of genes, quickly resulting in the cessation of effective gene evolution. Conversely, the memes experience a sharp increase in benefit from increasing their rate of evolution. We then examine the effects of enabling genes to reduce the percentage of gene-detrimental evolutionary steps taken by memes. Here a critical region emerges as the comparative rate of meme evolution increases, such that if genes cannot effectively select memes a high percentage of the time, they suffer from meme evolution as if they had almost no selective capability.

Animals↗