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E Brenner

Publications and source records attributed to E Brenner.

At least 91 records · Page 5Linked to original sources
PubMed1992

Development of visually guided behaviour requires oriented contours.

Kittens do not learn to use visual information to guide their behaviour if they are deprived of the optic flow that accompanies their own movements. We show that the optic flow that is required for developing visually guided behaviour is derived from changes in contour orientations, rather than from velocity patterns. We used several tests to assess visually guided behaviour. The performance of kittens that had only been allowed to see isolated dots of light was indistinguishable from that of kittens that had received no visual exposure at all. Kittens that had seen streaks of light performed better on several tasks. We discuss this finding with relation to the visual pathways that are presumably involved.

Animals↗
PubMed1992

[The lateral articular surface of the medial cuneiform bone facing the intermediate cuneiform bone].

300 medial cuneiform bones were examined to explore the different forms of the joint surface on the lateral side of the bone facing the intermediate cuneiform bone. This joint surface consists of two parts, a proximal one and a dorsal one. The proximal part is orientated dorsoplantarally. At its proximal margin there exists a tight contact with the proximal joint surface for the navicular bone. The dorsal part is sited at the dorsal margin of the lateral side of the bone. Different forms of fusion of these part could be seen. In 62.67% they show tight confluence. In 17.67% the fusion is limited to a slight contact. In the rest, 19.67%, there exists no contact between these two parts. These forms correlate to the proximal height of the bone. A large proximal height extends the degree of separation of the dorsal joint surfaces (consisting of the dorsal section of the proximal part and the whole dorsal of the joint surface for the intermediate cuneiform bone as well as the joint surface for the second metatarsal bone). Therefore these joint surfaces are split to their components.

Humans↗
PubMed1991

Epidemiological basis for clinical diagnosis of childhood malaria in endemic zone in West Africa.

It is difficult to distinguish childhood malaria from other common febrile disorders by parasite count alone, because of the wide variation in tolerance of parasitaemia among individuals. We postulated that the proportion of febrile episodes among young children that can be attributed to parasitaemia varies according to simple clinical criteria. We studied 1114 children aged 2-9 years, who attended a dispensary in the Republic of Niger, with a case-control approach; each of 557 febrile children was matched with a non-febrile control by sex, age, ethnic group, and day of presentation. Febrile episodes were classified according to three clinical criteria: the presence of a likely non-malarial cause; the duration (less than 3 or more than 3 days before presentation); and the intensity (below 39 degrees C or 39 degrees C and above). There was no evidence for an association between febrile episodes and parasite count during the dry, low-transmission, season. During the rainy, high-transmission, season, by contrast, there was a highly significant relation (p less than 0.0001) between the likelihood of fever and the parasite count; each clinical criterion strengthened the association. There was no association between parasitaemia and low intensity fevers, with an obvious cause, that started 3 or more days before presentation, even in the rainy season; however, the relative risk of a fever that met all three criteria developing in those with vs those without parasitaemia was 27.5. The proportion of febrile cases attributable to detectable parasitaemia (population attributable risk) ranged from 0 to 0.92. Our results suggest that simple clinical criteria may be valuable in the selection of febrile patients for antimalarial treatment. In this geographic area, high fever of short duration and with no other obvious cause that occurs during the rainy season is most likely to be malaria.

Animals↗
PubMed1991

Judging object motion during smooth pursuit eye movements: the role of optic flow.

We tend to following moving objects with our eyes. To estimate their velocities, therefore, we must take account of our eye movements. During smooth pursuit, velocity judgements can be led astray by moving the background. Do we misjudge an object's velocity when the background moves because the additional shift of the background's image on the retina is interpreted as the result of additional motion of the observer rather than as motion of the background? In the present experiment, the traditional configuration of target and background was supplemented with a "floor of tiles" drawn in perspective directly under the "background". The motion of this new simulated plane was used to specify whether the additional retinal shift represents actual motion in the background, rotation of the observer's eyes, or observer locomotion parallel to the target. Moving the background clearly influenced the perceived velocity of the target. However, "specifying" whether the observer or the background had moved did not affect the outcome. For observer locomotion parallel to the target, the change in target velocity that is predicted by the optic flow depends on the perceived distance of the target. Nevertheless, presenting the target at different distances (by presenting different images of the two eyes) did not affect the subjects' settings. The results show that our judgement of objects' velocities does not depend on an assessment of our own movements on the basis of a global analysis of the optic flow.

Humans↗
PubMed1990

Striking absence of long-lasting effects of early color deprivation on monkey vision.

A monkey (Macaca fascicularis) spent its first three months under far red illumination that made color vision impossible. It developed normal spectral sensitivity. In the present study we examined two aspects of color vision that presumably reflect cortical connectivity. In the first part of this article we show that chromatic induction was also unaffected: a blue surrounding made a gray target appear to be yellow to the monkey. At five months of age, the deprived monkey did not readily use color to recognize objects, although it was able to do so if necessary. In the second part of this article we show that, as an adult, the monkey was quite willing to use color to categorize objects. We conclude that early color deprivation does not result in long lasting deficits in color vision.

Aging↗
PubMed1990

Centrifugal motion bias in the cat's lateral suprasylvian visual cortex is independent of early flow field exposure.

1. Neurones in the postero-medial part of the cat's lateral suprasylvian visual cortex (area PMLS) show an overall preference for centrifugal motion, suggesting that the PMLS may be specialized in the analysis of expanding optic flow fields associated with forward locomotion. 2. We examined whether the visual experience young kittens normally receive during forward locomotion guides the development of the centrifugal preference in the PMLS. 3. Seven kittens were reared in the dark and exposed to either expanding or contracting flow fields for at least 100 h during their 4th-11th weeks of life. Specific experience was achieved by exposing kittens either to flow field patterns generated on a screen or by actually moving them forward or backward in a carousel. 4. Our results show that although the development of directional selectivity in the PMLS requires visual experience, the centrifugal bias is independent of specific visual exposure. The preference for centrifugal motion among PMLS cells was just as evident in kittens exposed to contracting as in kittens exposed to expanding flow fields. 5. We conclude that the preference for centrifugal motion in the PMLS is not the result of anisotropic stimulation kittens receive during locomotion in early ontogeny, but is probably innately determined as a phylogenetic adaptation.

Animals↗
PubMed1988

Hypohaptoglobinaemia as an epidemiological and clinical indicator for malaria. Results of two studies in a hyperendemic region in West Africa.

Hypohaptoglobinaemia is a common phenomenon in tropical countries, where it is probably due to malaria-induced haemolysis. Two studies were carried out in a hyperendemic zone of West Africa to test its specificity and usefulness as an epidemiological indicator for measuring malaria endemicity. The first study evaluated the prevalence of hypohaptoglobinaemia before and after courses of antimalarial chemotherapy of varying duration. The second monitored haptoglobin levels in an untreated population during a whole year to compare its seasonal variations with those of several classic indicators of malaria. These studies suggest that in regions where malaria is endemic the prevalence of hypohaptoglobinaemia could be as useful an indicator as the parasitic index but would be much easier to establish and to monitor.

Adolescent↗
PubMed1988

Event related potentials recorded from rats performing a reaction-time task.

We recorded evoked potentials during performance of a reaction-time task, in which rats had to release a lever quickly in response to either a visual or an auditory stimulus for a food reward. We found two distinct peaks in their cortical evoked potentials. The first peak appeared at a fixed time after the stimulus, irrespective of the time it took the rat to release the lever. Its amplitude decreased with increasing reaction time. The second peak's latency was always longer when the rat took more time to release the lever, but its amplitude did not change. We believe that the first peak's amplitude is determined by the rat's "attention" to the stimulus, whereas the second peak's latency is related to the rat's "intention" to release the lever.

Animals↗
PubMed1987

Central noradrenaline depletion during development and its effect on behaviour.

Although early depletion of noradrenaline is known to affect the morphological development of various structures in the brain, it is not clear what implications this has for adult behaviour. In the present study, 6-hydroxydopamine (6OHDA) was injected into the lateral ventricles of 12 day old rats, permanently destroying most of the noradrenergic innervation of the spinal cord and of all the brain areas examined except for the pons/medulla, and reducing the dopamine content of the cerebral cortex considerably. The noradrenaline content of the heart, as well as general developmental parameters such as food intake and body weight, were unaffected. Despite the extensive noradrenaline depletion during development, these rats' spatial memory--as determined in a radial maze task--was no worse than that of controls. In a lever-pressing task the 6OHDA treated rats made no more errors than did controls, but performed more slowly. The results indicate that at least some aspects of learning, memory and sensory-motor ability can develop normally when the noradrenergic innervation of the brain is largely destroyed.

Animals↗
PubMed1987

No increase in reaction-time after lesion of the dorsal noradrenergic bundle.

In this study we examined whether lesions of rats' dorsal noradrenergic bundles affect their reaction times to temporally unpredictable stimuli. Injection of 6-hydroxydopamine into rats' dorsal bundles drastically reduced the noradrenaline content of their cerebral cortex. Nevertheless, 6OHDA treated rats could still react as quickly as controls. Moreover, the treatment did not affect the efficiency with which rats performed the task, even when they were forced to respond very quickly.

Animals↗
PubMed1987

Effect of noradrenergic denervation on task-related visual evoked potentials in rats.

The present study examines whether destruction of the noradrenergic innervation of the forebrain interferes with the processing of sensory information in a manner that results in impaired selective attention. Electro-cortical responses to task-relevant and irrelevant stimuli were found to be sensitive indicators of the rat's attention to the stimuli. The amplitude of the response to the task-relevant stimulus increased as the rat's performance improved. The response to irrelevant flashes of light depended on the predictability of the flashes and on the rat's level of arousal. Noradrenergic denervation (with the selective neurotoxin DSP4) did not affect either the behavioural response to a visual stimulus which the rat had been trained to respond to for a food reward, or the late positive potential evoked by this stimulus. Neither did it affect the response to continuous (temporally predictable) flashes of light that were irrelevant to the task. Although the response to unpredictable flashes was also largely unaffected, we did find an additional late component in this response after DSP4 treatment. These results show that the noradrenergic innervation of the occipital cortex does not always regulate the extent to which visual stimuli are processed, but that noradrenergic neurotransmission may be activated in order to diminish excessive processing of unexpected stimuli.

Animals↗
PubMed1986

Visual and auditory evoked potentials in different areas of rat cerebral cortex.

Visual and auditory evoked potentials were studied in the occipital, temporal, prefrontal and cingulate areas of the rat cerebral cortex. We found that both prefrontal and cingulate areas can respond to more than one sensory modality. The latencies of the response to light and sound, though slightly longer in these associative areas than in the two primary cortical regions, were still within the range of early sensory evoked responses (i.e. less than 50 ms).

Acoustic Stimulation↗
PubMed1986

6-Hydroxydopamine treatment does not affect the young rat's ability to modify its response when changing from food to water deprivation.

In this study we examined whether depletion of forebrain noradrenaline would affect latent learning as predicted on the basis of the role attributed to the dorsal noradrenergic bundle in attention. Either 6-hydroxydopamine (6-OHDA) or saline was injected into the lateral ventricles of male Wistar pups on postnatal day 12. Immediately after weaning the rats were food deprived and trained to choose the left arm of a Y-maze which contained food while the right arm provided access to water. Once they had learnt to enter the left arm they were allowed access to food but not to water for one day and then tested again. All the rats quickly adjusted their behavioural response to the fact that they were deprived of water. The 6-OHDA-treated rats' behaviour did not differ significantly from that of the controls.

Adaptation, Psychological↗
PubMed1985

Growth and plasticity of rat cerebral cortex after central noradrenaline depletion.

Male Wistar rats (aged 31 to 33 days) received bilateral intraventricular injections of saline or 6-hydroxydopamine and were subjected to either "standard" or "enriched" rearing conditions for 42 days. The treatment reduced cerebral cortical noradrenaline by 80% and decreased the growth of the cerebral cortex. It did not, however, prevent experience in an enriched environment from enhancing the growth of the cerebral cortex.

Animal Husbandry↗
PubMed1985

Early colour deprivation in a monkey (Macaca fascicularis).

Various forms of selective visual deprivation are known to affect the development of the monkey visual system. In the present study a monkey was born and spent the first three months of its life under red illumination. Despite this colour deprivation, the young monkey learnt to distinguish between colours. Furthermore, the monkeys' increment threshold spectral sensitivity was not affected by the deprivation.

Adaptation, Ocular↗