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Biomedical subjects

R W Byrne

Publications and source records attributed to R W Byrne.

16 recordsLinked to original sources
PubMed2004

Foraging behaviour in domestic pigs (Sus scrofa): remembering and prioritizing food sites of different value.

This experiment investigated whether domestic pigs can remember the locations of food sites of different relative value, and how a restricted retrieval choice affects their foraging behaviour. Nine juvenile female pigs were trained to relocate two food sites out of a possible eight in a spatial memory task. The two baited sites contained different amounts of food and an obstacle was added to the smaller amount to increase handling time. On each trial, a pig searched for the two baited sites (search visit). Once it had found and eaten the bait, it returned for a second (relocation) visit, in which the two same sites were baited. Baited sites were changed between trials. All subjects learnt the task. When allowed to retrieve both baits, the subjects showed no preference for retrieving a particular one first (experiment 1). When they were allowed to retrieve only one bait, a significant overall preference for retrieving the larger amount emerged across subjects (experiment 2). To test whether this preference reflected an avoidance of the obstacle with the smaller bait, 15 choice-restricted control trials were conducted. In control trials obstacles were present with both baits. Pigs continued to retrieve the larger bait, indicating they had discriminated between the two food sites on the basis of quantity or profitability and adjusted their behaviour accordingly when the relocation choice was restricted. This suggests for the first time that domestic pigs have the ability to discriminate between food sites of different relative value and to remember their respective locations.

Animals↗
PubMed2003

Imitation as behaviour parsing.

Non-human great apes appear to be able to acquire elaborate skills partly by imitation, raising the possibility of the transfer of skill by imitation in animals that have only rudimentary mentalizing capacities: in contrast to the frequent assumption that imitation depends on prior understanding of others' intentions. Attempts to understand the apes' behaviour have led to the development of a purely mechanistic model of imitation, the 'behaviour parsing' model, in which the statistical regularities that are inevitable in planned behaviour are used to decipher the organization of another agent's behaviour, and thence to imitate parts of it. Behaviour can thereby be understood statistically in terms of its correlations (circumstances of use, effects on the environment) without understanding of intentions or the everyday physics of cause-and-effect. Thus, imitation of complex, novel behaviour may not require mentalizing, but conversely behaviour parsing may be a necessary preliminary to attributing intention and cause.

Animals↗
PubMed2000

Hand preferences in unimanual and bimanual feeding by wild vervet monkeys (Cercopithecus aethiops).

Lateral preference was examined in spontaneous feeding actions in 2 troops of wild vervet monkeys (Cercopithecus aethiops). Processing of 4 foods (termites, leaf shoots, sugarcane, and fruit) was studied. Actions included unimanual reaching to moving objects, operating from an unstable posture, and coordinated bimanual processing. Between 19 and 31 subjects were available, according to the task. In 2 tasks, laterality of 2 independent stages was measured separately, giving 6 measures in all. On 4 of these measures, most monkeys were ambipreferent, and only a few showed significant hand preferences. Only for termite feeding and detaching material from fruits did the majority show significant lateralization; no tasks elicited exclusive use of 1 hand. Preference appeared labile, because in 2 tasks, population trends reversed with increasing age. No population trends to left or right were found; instead, these monkeys showed ambilaterality, with lateralization associated with task complexity.

Animals↗
PubMed1999

The presence of transcription factors in chicken albumin, yolk and blastoderm.

Embryonic development is determined by preset intrinsic programs and extrinsic signals. To explore the possibility that transcription factors are present at the onset of development, preparations of yolk, albumin, and blastoderm from unfertilized and fertilized white Leghorn chicken eggs were screened by a panel of 16 transcription factor antibodies with Western blot techniques. Yolk was positive for 13 transcription factors, whereas blastoderm was positive for 10, and albumin was positive for 5. In yolk, several transcription factors, GATA-2, E2F-1, MyoD, and TFIID, were developmentally regulated. These results indicate that intracellular yolk and extracellular albumin contain transcription factors which presumably influence early chick embryonic development from prefertilization to the late blastoderm stage. Thus, the utility of preset maternal transcription factors within yolk and albumin complement maternally derived mRNA to determine the early development of the zygote.

Albumins↗
PubMed1998

Learning by imitation: a hierarchical approach.

To explain social learning without invoking the cognitively complex concept of imitation, many learning mechanisms have been proposed. Borrowing an idea used routinely in cognitive psychology, we argue that most of these alternatives can be subsumed under a single process, priming, in which input increases the activation of stored internal representations. Imitation itself has generally been seen as a "special faculty." This has diverted much research towards the all-or-none question of whether an animal can imitate, with disappointingly inconclusive results. In the great apes, however, voluntary, learned behaviour is organized hierarchically. This means that imitation can occur at various levels, of which we single out two clearly distinct ones: the "action level," a rather detailed and linear specification of sequential acts, and the "program level," a broader description of subroutine structure and the hierarchical layout of a behavioural "program." Program level imitation is a high-level, constructive mechanism, adapted for the efficient learning of complex skills and thus not evident in the simple manipulations used to test for imitation in the laboratory. As examples, we describe the food-preparation techniques of wild mountain gorillas and the imitative behaviour of orangutans undergoing "rehabilitation" to the wild. Representing and manipulating relations between objects seems to be one basic building block in their hierarchical programs. There is evidence that great apes suffer from a stricter capacity limit than humans in the hierarchical depth of planning. We re-interpret some chimpanzee behaviour previously described as "emulation" and suggest that all great apes may be able to imitate at the program level. Action level imitation is seldom observed in great ape skill learning, and may have a largely social role, even in humans.

Animals↗
PubMed1997

Can spider monkeys (Ateles geoffroyi) discriminate vocalizations of familiar individuals and strangers?

In a field experiment, tape-recorded vocalizations of spider monkeys (Ateles geoffroyi) were played back to investigate whether individuals were able to discriminate between group members and strangers. Monkeys responded remarkably similarly in the two cases, with no significant difference found between the numbers of calls given by an individual, or the types of call given. However, a group was more likely to give some vocal reaction when hearing a stranger's call than when hearing one from an individual of their own community. Further, the only instances in which agonistic territorial behaviours occurred were in reaction to strangers' playbacks. No significant effects on the response given were produced by the sex of the caller, the location and time of day of the broadcast, the size of the subgroup hearing the call or the activity in which they were involved. These results are discussed with respect to acoustic, social and ecological factors that may lead to the apparent lack of vocal discrimination of strangers within the community range.

Animals↗
PubMed1995

Operative resection of 100 spinal lipomas in infants less than 1 year of age.

A retrospective analysis of 100 children followed at Children's Memorial Hospital, Chicago, who underwent surgery for a spinal lipoma was performed. The mean follow-up was 5 years. We found that an operation performed during the 1st year of life with the goal of untethering the spinal cord and debulking the spinal lipoma was safe and effective, whereas a cosmetic (nonuntethering) procedure always led to delayed postoperative deterioration (symptomatic tethered cord). Of the infants that presented with motor, urologic or orthopedic symptoms, 39% improved, 58% stabilized, while 3% worsened as a result of surgery. No asymptomatic infant deteriorated postoperatively and 93% of these children remained symptom-free at follow-up (mean follow-up was 44 months). The overall outcome of infants after untethering procedures in this study was significantly better than the natural history of spinal lipomas. Several risk factors were identified that may predispose children to delayed postoperative deterioration: an initial cosmetic procedure; the presence of preoperative symptoms, and the presence of a lipomyelomeningocele.

Abnormalities, Multiple↗
PubMed1994

Intramedullary abscess: a report of two cases and a review of the literature.

Two cases of chronic spinal cord abscess are reported, and the relevant literature is reviewed with emphasis on the last 20 cases. Presentation, cause, modern diagnostic testing, operative findings, treatment choices, and prognosis are all discussed. Significant changes in the presentation, management, and outcome in these more recent cases are emphasized.

Abscess↗
PubMed1993

Chemical composition of baboon plant foods: implications for the interpretation of intra- and interspecific differences in diet.

Information on the chemical composition of baboon foods from the Laikipia Plateau, Kenya, is presented. Despite some differences in methods, results of analyses performed on the same foods at different sites were found to be extremely consistent, encouraging the view that meaningful intra- and interspecific comparisons of diet selection are feasible. Contrary to assumptions in the literature, no relationship between the abundance of food types and their chemical composition was found, nor was the foliage eaten by the baboons found to be a low-quality or high-fibre item in comparison with fruits and storage organs. Emphasis is placed on the need for caution in the use of simplistic dietary taxonomies which imply phytochemical and ecological homogeneity within broad food categories. Comparisons between three species revealed marked differences in the chemical composition of their diets; in particular, baboon diets were found to be higher in protein and lower in fibre than those of either lowland gorillas or Malaysian leaf monkeys, and differences in condensed tannin levels were also found. The relationship between these differences and the socio-ecology of the three species is discussed.

Alkaloids↗
PubMed1991

Dietary and foraging strategies of baboons.

As large-bodied savannah primates, baboons have long been of special interest to students of human evolution: many different populations have been studied and dietary comparisons among them are becoming possible. Baboons' foraging strategies can be shown to combine high degrees of flexibility and breadth with selectivity. In this paper we develop and test multivariate models of the basis of diet selection for populations of montane and savannah baboons. Food selection is positively related to protein and lipid content and negatively to fibre, phenolics and alkaloids. Seasonal changes in dietary criteria predicted by these rules are tested and confirmed. Although nutritional bottlenecks occur at intervals, a comparison between long-term nutrient intakes in four different populations indicates convergence on lower degrees of variation than exist in superficial foodstuff profiles.

Acclimatization↗
PubMed1991

Hand preferences in the skilled gathering tasks of mountain gorillas (Gorilla g. berengei).

Manual dexterity of 44 wild gorillas of all ages and both sexes was investigated on six naturally acquired feeding tasks of varied logical structure, which included multi-stage and bimanually coordinated procedures. At least 400 min observation of feeding per animal, and analysis at the level of bouts rather than individual actions, can be expected to produce statistically robust results; 22 years background data allowed effects of genealogy and injury to be investigated. Five tasks elicited very strong hand preferences in most animals (weakest on the simplest task), while one was usually performed with a strategy in which left and right hands were used symmetrically; the preferences were fully established at 3 years old. Preferences were highly correlated within each of two sets of tasks, but between the two sets there was no correlation across animals in direction or strength of preference. No population trends towards left or right handers were found in either set of tasks, or both sets pooled; distributions were U-shaped and approximately symmetric, with a slight bias towards right-handed fine manipulation in one set of tasks. Processing efficiency was only slightly greater with the preferred hand, and similar in left- and right-handed animals. Neither direction nor strength of hand preference showed a tendency to run in families, but females showed greater strength of preference. Major injury masked strong hand preference, but injuries could not account for the overall distribution of preference; instead this may reflect inbreeding. Feedback acting on initially random hand choices, and imitation at the "program" level rather than slavish copying of acts, are proposed to account for the results.

Aging↗
PubMed1989

The construction and assessment of mental maps.

In investigations into the manner in which people store spatial information, experimental subjects are often asked to estimate the distances and bearings between various landmarks. Methodology is described for constructing the mental map underlying a subject's matrix of distances, and the mental map underlying a subject's matrix of bearings. Also presented are methods of comparing matrices of distances or bearings, and the mental maps constructed from them, with the geographical map; this enables an assessment of differences between them. Some statistical models of disorientation are considered, and a method of choosing between them is described.

Attention↗
PubMed1986

Aggression toward large carnivores by wild chimpanzees of Mahale Mountains National Park, Tanzania.

In the Mahale Mountains National Park of Tanzania, a group of about 33 chimpanzees were observed to surround a leopard den containing a mother and at least one cub and to drag out and kill the cub. This is the first report of chimpanzees or any other primate species killing their potential predator's offspring. The incident suggests that chimpanzees, without any weapons, can manage to defend themselves against a carnivore of at least up to leopard size, and implicates how the early hominids may have reacted against their potential predators.

Aggression↗