Nuclear organization of some immunohistochemically identifiable neural systems in two species of the Euarchontoglires: A Lagomorph, Lepus capensis, and a Scandentia, Tupaia belangeri.

The present study describes the organization of the nuclei of the cholinergic, catecholaminergic, serotonergic and orexinergic systems in the brains of two members of Euarchontoglires, Lepus capensis and Tupaia belangeri. The aim of the present study was to investigate the nuclear complement of these neural systems in comparison to previous studies on Euarchontoglires and generally with other mammalian species. Brains were coronally sectioned and immunohistochemically stained with antibodies against choline acetyltransferase, tyrosine hydroxylase, serotonin and orexin-A.

Cellular location and major terminal networks of the orexinergic system in the brain of two megachiropterans.

The present study describes the distribution of orexin-A immunoreactive neurons and their terminal networks in the brains of two species of megachiropterans. In general the organization of the orexinergic system in the mammalian brain is conserved across species, but as one of two groups of mammals that fly and have a high metabolic rate, it was of interest to determine whether there were any specific differences in the organization of this system in the megachiropterans. Orexinergic neurons were limited in distribution to the hypothalamus, and formed three distinct clusters, or nuclei, a main cluster with a perifornical location, a zona incerta cluster in the dorsolateral hypothalamus and an optic tract cluster in the ventrolateral hypothalamus.

Cellular location and major terminal networks of the orexinergic system in the brains of five microchiropteran species.

The present study describes the distribution of Orexin-A immunoreactive cell bodies and terminal networks in the brains of five microchiropteran species. Given the specialized flight and echolocation abilities of the microchiropterans it was of interest to examine if any specific differences in a generally phylogenetically homogenous neural system could be found. The orexinergic neurons have been found within the hypothalamus of all species studied, and were represented by a large cluster that spanned the anterior, dorsomedial, perifornical and lateral hypothalamic regions, with a smaller cluster extending into the region of the medial zona incerta.

Visual acuity and heterogeneities of retinal ganglion cell densities and the tapetum lucidum of the African elephant (Loxodonta africana).

The eyes of three adult male African elephants were examined, the retinas were whole-mounted, stained and analyzed to determine visual acuity. A range of small to large ganglion cell types were observed across the retinas. We observed three regions of high ganglion cell density, one in the upper temporal quadrant, a visual or horizontal streak and a smaller region at the nasal end of the horizontal streak.

Nuclear organization of cholinergic, putative catecholaminergic and serotonergic systems in the brains of two megachiropteran species.

The nuclear organization of the cholinergic, putative catecholaminergic and serotonergic systems within the brains of the megachiropteran straw-coloured fruit bat (Eidolon helvum) and Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) were identified following immunohistochemistry for cholineacetyltransferase, tyrosine hydroxylase and serotonin. The aim of the present study was to investigate possible differences in the nuclear complement of the neuromodulatory systems of these species in comparison to previous studies on megachiropterans, microchiropterans and other mammals. The nuclear organization of these systems is identical to that described previously for megachiropterans and shows many similarities to other mammalian species, especially primates; for example, the putative catecholaminergic system in both species presented a very compact nucleus within the locus coeruleus (A6c) which is found only in megachiropterans and primates.

Nuclear organization of cholinergic, putative catecholaminergic and serotonergic systems in the brains of five microchiropteran species.

The current study describes, using immunohistochemical methods, the nuclear organization of the cholinergic, catecholaminergic and serotonergic systems within the brains of five microchiropteran species. For the vast majority of nuclei observed, direct homologies are evident in other mammalian species; however, there were several distinctions in the presence or absence of specific nuclei that provide important clues regarding the use of the brain in the analysis of chiropteran phylogenetic affinities. Within the five species studied, three specific differences (presence of a parabigeminal nucleus, dorsal caudal nucleus of the ventral tegmental area and the absence of the substantia nigra ventral) found in two species from two different families (Cardioderma cor; Megadermatidae, and Coleura afra; Emballonuridae), illustrates the diversity of microchiropteran phylogeny and the usefulness of brain characters in phylogenetic reconstruction.

Genetic contribution to individual variation in binocular rivalry rate.

Binocular rivalry occurs when conflicting images are presented in corresponding locations of the two eyes. Perception alternates between the images at a rate that is relatively stable within individuals but that varies widely between individuals. The determinants of this variation are unknown.

Retinal ganglion cell density of the black rhinoceros (Diceros bicornis): calculating visual resolution.

A single right retina from a black rhinoceros was whole mounted, stained and analyzed to determine the visual resolution of the rhinoceros, an animal with reputedly poor eyesight. A range of small (15-microm diameter) to large (100-microm diameter) ganglion cell types was seen across the retina. We observed two regions of high density of retinal ganglion cells at either end of a long, but thin, horizontal streak.

The changing face of perceptual rivalry.

Functional brain-imaging studies of house-face binocular rivalry and Rubin's vase-faces illusion have consistently reported face perception-dependent activity in the right fusiform gyrus. Here we use Rubin's illusion and report that activation of the left hemisphere by caloric vestibular stimulation increases the predominance of the faces percept in a substantial number of test subjects. While partially supporting the brain-imaging lateralization reports, our findings also challenge these studies by suggesting that neural mechanisms of Rubin's illusion cannot be limited to extrastriate perception-dependent processing.

Psilocybin links binocular rivalry switch rate to attention and subjective arousal levels in humans.

Rationale: Binocular rivalry occurs when different images are simultaneously presented to each eye. During continual viewing of this stimulus, the observer will experience repeated switches between visual awareness of the two images. Previous studies have suggested that a slow rate of perceptual switching may be associated with clinical and drug-induced psychosis.

Caloric vestibular stimulation reveals discrete neural mechanisms for coherence rivalry and eye rivalry: a meta-rivalry model.

Binocular rivalry is an extraordinary visual phenomenon that has engaged investigators for centuries. Since its first report, there has been vigorous debate over how the brain achieves the perceptual alternations that occur when conflicting images are presented simultaneously, one to each eye. Opposing high-level/stimulus-representation models and low-level/eye-based models have been proposed to explain the phenomenon, recently merging into an amalgam view.

Plaid motion rivalry: correlates with binocular rivalry and positive mood state.

Recently Hupé and Rubin (2003, Vision Research 43 531- 548) re-introduced the plaid as a form of perceptual rivalry by using two sets of drifting gratings behind a circular aperture to produce quasi-regular perceptual alternations between a coherent moving plaid of diamond-shaped intersections and the two sets of component 'sliding' gratings. We call this phenomenon plaid motion rivalry (PMR), and have compared its temporal dynamics with those of binocular rivalry in a sample of subjects covering a wide range of perceptual alternation rates. In support of the proposal that all rivalries may be mediated by a common switching mechanism, we found a high correlation between alternation rates induced by PMR and binocular rivalry.

Using psilocybin to investigate the relationship between attention, working memory, and the serotonin 1A and 2A receptors.

Increasing evidence suggests a link between attention, working memory, serotonin (5-HT), and prefrontal cortex activity. In an attempt to tease out the relationship between these elements, this study tested the effects of the hallucinogenic mixed 5-HT1A/2A receptor agonist psilocybin alone and after pretreatment with the 5-HT2A antagonist ketanserin. Eight healthy human volunteers were tested on a multiple-object tracking task and spatial working memory task under the four conditions: placebo, psilocybin (215 microg/kg), ketanserin (50 mg), and psilocybin and ketanserin.

Optical imaging of functional organization of V1 and V2 in marmoset visual cortex.

Using optical imaging of intrinsic cortical signals, we examined the functional organization of visual cortical areas V1 and V2 of the marmoset (Callithrix jacchus). Previous studies have reported that adult marmosets do not have ocular dominance columns (ODCs); however, recent studies have called this into question. Using optical imaging methods, we examined whether ODCs could be detected in adult marmosets.

The properties of CpG islands in the putative promoter regions of human immunoglobulin (Ig) genes.

CpG island is a GC-rich motif occurred in gene promoter region, which can play important roles in gene silencing and imprinting. Here, we present a set of discriminant functions that can recognize the structural and compositional features of CpG islands in the putative promoter regions (PPRs) of human and mouse immunoglobulin (Ig) genes. We showed that the PPRs of both human and mouse Ig genes irrespective of gene chromosomal localization are apparently CpG island poor, with a low percentage of the CpG islands overlapped with the transcription start site (TSS).

Modulating the rate and rhythmicity of perceptual rivalry alternations with the mixed 5-HT2A and 5-HT1A agonist psilocybin.

Binocular rivalry occurs when different images are presented simultaneously to corresponding points within the left and right eyes. Under these conditions, the observer's perception will alternate between the two perceptual alternatives. Motivated by the reported link between the rate of perceptual alternations, symptoms of psychosis and an incidental observation that the rhythmicity of perceptual alternations during binocular rivalry was greatly increased 10 h after the consumption of LSD, this study aimed to investigate the pharmacology underlying binocular rivalry and to explore the connection between the timing of perceptual switching and psychosis.

Laughter abolishes binocular rivalry.

Background: Binocular rivalry is an increasingly popular technique for the study of consciousness, which changes quasi-regularly during rivalry, despite the unchanging sensory stimuli presented to each eye. For example, if a small patch of horizontal stripes is presented constantly to the fovea of one eye and a small patch of vertical stripes is similarly presented constantly to the fovea of the other eye, most subjects experience an alternation between stimuli rather than a simultaneous mixed percept of both.

Methods: Binocular rivalry was induced, superimposed on normal viewing, using liquid crystal shutters and a short persistence monitor, which produced a one degree circular patch of horizontal gratings to the right eye and an identical patch of vertical gratings in the same location for the left eye.

Bi-sensory, striped representations: comparative insights from owl and platypus.

Bi-sensory striped arrays are described in owl and platypus that share some similarities with the other variant of bi-sensory striped array found in primate and carnivore striate cortex: ocular dominance columns. Like ocular dominance columns, the owl and platypus striped systems each involve two different topographic arrays that are cut into parallel stripes, and interdigitated, so that higher-order neurons can integrate across both arrays. Unlike ocular dominance stripes, which have a separate array for each eye, the striped array in the middle third of the owl tectum has a separate array for each cerebral hemisphere.

Psilocybin impairs high-level but not low-level motion perception.

The hallucinogenic serotonin(1A&2A) agonist psilocybin is known for its ability to induce illusions of motion in otherwise stationary objects or textured surfaces. This study investigated the effect of psilocybin on local and global motion processing in nine human volunteers. Using a forced choice direction of motion discrimination task we show that psilocybin selectively impairs coherence sensitivity for random dot patterns, likely mediated by high-level global motion detectors, but not contrast sensitivity for drifting gratings, believed to be mediated by low-level detectors.