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Results for “Contrastive learning”

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PubMed1991

The use of visual information by house flies, Musca domestica (Diptera: muscidae), foraging in resource patches.

House flies, Musca domestica, respond to visual contrasts on the substrate if a resource is associated with the contrasting patterns. Visible resource patch boundaries serve as a signal to flies that they are about to leave a rewarding patch. Searching flies respond to such visual information by walking along the resource patch boundary and turning back into the patch at its edge. This edge detection and response serve as a mechanism for flies with visual cues to stay in a rewarding patch and locate more resources within it. The intensity of their response correlates with the quality of the resource. In the absence of visual cues, patch shape affects foraging success; flies find more resources in circular than in linear resource distributions. The effects of visual cues, however, render patch shape unimportant. Various substrate contrasts are effective as resource information for flies: dark (e.g., green) figures on bright (e.g., white) backgrounds or bright figures on dark backgrounds. Responses to substrate contrasts measured in this study indicate that, over the short term, house flies can learn a visual cue associated with a food source.

Animals↗

PubMed1977

Men's reactions to their partners' elective abortions.

Sixty men who accompanied their wives or girlfriends when the latter came for elective abortions were surveyed to explore, broadly, men's experience of abortion. Portions of the survey relevant to health care revealed that most men felt involved in the abortion experience. They initially wished to play an active, but circumscribed, role in matters related to abortion; they wanted to accompany their partners in order to be supportive and considered themselves responsible, along with their partners, for preventing unwanted pregnancies and choosing abortion. In contrast, there was initially a lack of interest in participation in clinic functions or learning about abortion and contraception despite inadequate knowledge. However, as information and comfort with the setting were gained, it became apparent that greater responsiveness was there to be tapped. Permitting men increased participation in abortion services, both educational and psychological, is discussed as advantageous.

Abortion, Legal↗

PubMed1996

Distinctions between hippocampus of mouse and rat: protein F1/GAP-43 gene expression, promoter activity, and spatial memory.

We began these experiments as an attempt to replicate in the mouse the induction by kainate (KA) of F1/GAP-43 mRNA we observed in adult rat hippocampal granule cells [Mol. Brain Res., 33 (1995) 22-28]. However, even though KA induced behavioral seizures in the mouse similar to those in the rat, neither induction of F1/GAP-43 mRNA nor subsequent mossy fiber sprouting observed in the rat was detected in three different mouse strains. It was also surprising that the distribution of constitutive levels of F1/GAP-43 mRNA in mouse and rat hippocampus was qualitatively different. Indeed, F1/GAP-43 expression in CA3 pyramidal cells was significantly greater in rat than mouse, while F1/GAP-43 expression in CA1 cells of rat and mouse was equivalent using densitometric analysis. Thus, F1/GAP-43 expression in rat is quantitatively higher in CA3 and CA1 pyramidal cells. In mouse, expression was equivalent in these two subfields. In a transgenic mouse bearing a rat F1/GAP-43 promoter-reporter (lacZ) construct (line 252), in-vivo promoter activity of F1/GAP-43 was studied in hippocampal cells. Transgene expression in hippocampal pyramidal subfields, high in CA3, low in CA1 pyramidal cells, paralleled the distribution of rat F1/GAP-43 mRNA levels, not mouse. Differences in the constitutive F1/GAP-43 expression pattern in hippocampus between rat and mouse may therefore be determined by different recognition elements present on the F1/GAP-43 promoter. KA injected into the line 252 transgenic mouse did not activate the rat F1/GAP-43 promoter in mouse hippocampal granule cells. The absence of both F1/GAP-43 mRNA expression induction and promoter activation in mouse granule cells after KA is likely related to genera differences in transcriptional regulatory mechanisms, though post-transcriptional mechanisms cannot be excluded. Since the different hippocampal chemistry of F1/GAP-43 in rat and mouse likely extends to other molecular species, behaviors in rat and mouse that depend on hippocampal function might be different as well. We therefore evaluated spatial memory ability in a delayed matching-to-sample task. In contrast to rat, we were surprised to find no evidence of the ability to learn this task in three different mouse strains. Since interest in mouse genetics in relation to behavior and memory functions of hippocampus is growing, generalizations concerning hippocampal function from studies carried out on the mouse need to be made with caution considering the specific behavioral, pharmacological, and general molecular differences observed here. One can also be opportunistic and exploit the natural variations between these two genera to gain insight into the molecular mechanisms underlying information storage.

Animals↗

PubMed2005

Pulmonary applications of perfluorochemical liquids: ventilation and beyond.

In this review of liquid ventilation, concepts and applications are presented that summarise the pulmonary applications of perfluorochemical liquids. Beginning with the question of whether this alternative form of respiratory support is needed and ending with lessons learned from clinical trials, the various methods of liquid assisted ventilation are compared and contrasted, evidence for mechanoprotective and cytoprotective attributes of intrapulmonary perfluorochemical liquid are presented and alternative intrapulmonary applications, including their use as vehicles for drugs, for thermal control and as imaging agents are presented.

Clinical Trials as Topic↗

PubMed2003

Acamprosate does not induce a conditioned place preference and reveals no state-dependent effects in this paradigm.

To evaluate the putative rewarding properties of the anticraving substance acamprosate, male rats learned to associate injections of vehicle and acamprosate (200 mg/kg ip) with two visually contrasting compartments in a place conditioning paradigm. The degree of preference for the acamprosate-associated compartment was determined, in both a postconditioning test with undrugged animals and a consecutive test with drugged animals, to rule out the possibility that a putatively rewarding effect of acamprosate may have been masked by state-dependent effects. The animals did not show any preference for the substance-paired compartment, neither in the undrugged nor in the drugged state. In conclusion, acamprosate has no rewarding properties as shown in place preference. Therefore, it may prevent a relapse in detoxified alcoholics in a way other than by simply substituting the rewarding effects of ethanol. This adds to the therapeutic value of acamprosate in the treatment of drug craving.

Acamprosate↗

PubMed2003

Successive two-item same-different discrimination and concept learning by pigeons.

Four pigeons were trained in a successive same/different procedure involving the alternation of two stimuli per trial. Using a go/no-go procedure, two different or two identical color photographs were alternated, with a brief, dark, inter-stimulus interval, on a computer screen for 20s. Pigeons learned to discriminate between same (S+) and different (D-) sequences with moderate to large contrasts between successive pictures. Analyses of pecking behavior within single trials revealed this discrimination emerged at the earliest possible point in the sequence (i.e. by the presentation of the second item). Pigeons transferred to novel color and gray-scale pictures, and showed savings in tests with novel video stimuli. These results suggest that same/different discrimination and concept formation can be acquired with successively presented pairs of stimuli by pigeons. When combined with results using simultaneous same/different presentations, these findings further support a qualitative similarity among birds and primates in their capacity to judge certain types of stimulus relations.

Journal Article↗

PubMed2005

Testing for localized stimulus enhancement and object movement reenactment in pig-tailed macaques (Macaca nemestrina) and young children (Homo sapiens).

Four puzzle boxes were used to investigate localized stimulus enhancement and object movement reenactment (OMR) in 13 pig-tailed macaques (Macaca nemestrina) and 30 human infants (Homo sapiens). Participants received contrasting demonstrations on each box. A circular lid was gripped by its rim or handle and swiveled to the left or right. A flap door was pushed or flipped. A sliding lid was pushed to the left or right. A pin bolt was demonstrated being pushed down, or the participants were left to solve the puzzle for themselves. Despite the fact that the monkeys watched the demonstrations about 60% of the time, only a weak OMR effect was found on the sliding lid. In contrast, the children watched significantly more, and there was clear evidence of socially mediated learning on all of the boxes.

Age Factors↗

PubMed1996

Sleep and anxieties in Brazilian children: the role of cultural and environmental factors in child sleep disturbance.

To test the contextual hypothesis of sleep disturbance, disadvantaged urban Brazilian children's self-reported fears were correlated with parental reports of children's sleep disturbance. Fears of death at the hands of "death squads," environment-related worries and other fears reflecting Brazil's political, religious, and collective culture all correlated with sleep disturbance. Results are contrasted with findings of earlier studies on sleep and anxieties in samples of learning-disabled adolescents and victims of lightning.

Anxiety Disorders↗

PubMed2000

Aging mechanisms.

Aging (senescence) has long been a difficult issue to be experimentally analyzed because of stochastic processes, which contrast with the programmed events during early development. However, we have recently started to learn the molecular mechanisms that control aging. Studies of the mutant mouse, klotho, showing premature aging, raise a possibility that mammals have an "anti-aging hormone." A decrease of cell proliferation ability caused by the telomeres is also tightly linked to senescence. Frontier experimental studies of aging at the molecular level are leading to fascinating hypotheses that aging is the price we had to pay for the evolution of the sexual reproduction system that produces a variety of genetic information and complex body structures.

Aging↗

PubMed1986

Assessing the predictive validity of psychomotor tests as measures of biological age in mice.

Two experiments assessed the predictive validity of a psychomotor test battery in male C57BL/6J mice. First, performance was recorded for 66 mice in rotorod, tightrope, grip strength, exploratory activity, and runwheel activity tasks at 24 mo of age. Except in the rotorod task, performance was positively and significantly correlated to lifespan, i.e. better performance indicated longer lifespan. Body weight and body temperature were also significantly correlated with lifespan, while water consumption was negatively related. Using the five behavioral scores in a multiple regression analysis, about 40% of the variance in lifespan was explainable. When measures of body weight, body temperature, and water consumption were added to the regression equation, about 54% of the variance in lifespan could be explained. As revealed by factor analysis, a high degree of interrelationship existed among variables. In a second experiment, 54 mice were tested in the psychomotor battery every 8 weeks from 24 mo. Scores in the tightrope and both locomotor activity tasks revealed age-related declines, whether considering all individuals or only those surviving to 28 mo. Significant correlations between first and subsequent scores indicated stability of individual differences for tightrope and exploratory activity at most ages and for runwheel activity at 26 mo but not later. Rotorod and grip strength scores were not stable and suggested confounding by learning. Significant correlations with lifespan were obtained at some ages for all tests. In contrast to the first experiment, however, there were no significant correlations between lifespan and scores at 24-mo for any test and little correlation among scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗

PubMed1983

Onset spectra and formant transitions in the adult's and child's perception of place of articulation in stop consonants.

Stevens and Blumstein [Perspectives on the Study of Speech (Erlbaum, Hillsdale, NJ, 1981)] have proposed that the global shape of the CV syllable onset spectrum provides the listener with a primary and contextually invariant cue for place of stop consonant articulation. Contextually variable formant transitions are, in contrast, claimed to constitute secondary cues to place of articulation that, during development, are learned through their co-occurrence with the primary spectral ones. In the two experiments reported here, these claims about the relative importance of the onset spectrum and formant transition information were assessed by obtaining adults' and young children's identifications of synthetic stimuli in which these two potential cues specified different places of articulation. In general, the responses of both adults and children appeared to be determined by the formant transitions of the stimuli. These results provide little support for the claim that sensitivity to the global properties of the onset spectrum (as described by Stevens and Blumstein) underlie place of articulation perception or for Stevens and Blumstein's primary versus secondary cue distinction. Rather, these findings are consistent with the view that dynamic, time-varying information is important in the perception of place of articulation.

Adult↗

PubMed2000

Imaging cognition II: An empirical review of 275 PET and fMRI studies.

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/motion), language (written/spoken word recognition, spoken/no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration.

Adult↗

PubMed1995

Parse's theory in practice with a group in the community.

The author, a nurse guided by Parse's theory of human becoming, describes one way to focus on quality of life in person-centered practice with a group in the community, in contrast to traditional nursing practice with groups in which the focus is on problems, learning, and socially-defined responsibility. The author describes living true presence over a 10-week period in accord with Parse's practice method with a group of persons with genital herpes. Emerging patterns of health of the group are reported along with a loose agenda for community-based practice.

Female↗

PubMed2001

The processing of stereoscopic information in human visual cortex: psychophysical and electrophysiological evidence.

Three-dimensional depth perception relies in part on the binocular fusion of horizontally disparate stimuli presented to the left and right eye. The mammalian visual system offers a unique possibility to study electrophysiologically cortical neuronal mechanisms: since the input of the two eyes remains separated up to the level of the visual cortex, evoked potential components that are generated exclusively by cortical structures may be explored when dynamic random-dot stereograms (dRDS) are presented. In a series of independent studies, we determined the scalp topography of dRDS evoked brain activity in different groups of healthy subjects, and we found consistent results. Major differences between stereoscopic and contrast evoked brain activity are seen in the strength of the potential fields as well as in their topography. Our findings suggest that there are fewer neurons in the human visual cortex that are responsive to horizontal disparity, and that higher visual areas like V2 are more engaged with stereoscopic processing than the primary visual cortex. On the other hand, component latencies of evoked brain activity show no effect signifying that the binocular information flow to the visual cortex has a similar time course for both the processing of contrast information and of dRDS stimuli. We could also verify that healthy subjects can learn to perceive 3D structure contained in dRDS. Changes in perceptual ability as measured with psychophysical tests are paralleled by systematic alterations in the topography of stereoscopically evoked potential fields. Stereoscopic VEP recordings may also be of clinical use: in patients with selectively disturbed depth perception but normal visual acuity there is a high correlation between clinical symptoms, perceptual deficiency, and altered VEP amplitudes and latencies.

Brain Mapping↗

PubMed1992

Financing long-term care with limited resources: combining the resources of the public and private sectors.

Under Connecticut's recently implemented public/private partnership to finance long-term care, individuals will no longer need to impoverish themselves in order to receive Medicaid assistance. To encourage those people who can afford to buy a private long-term care insurance policy to do so, the state promises to shield one dollar in assets from Medicaid "spend-down" rules for every dollar a private policy pays out for Medicaid-covered services. This article describes the Partnership, shows how dwindling resources and budget constraints affected the development of this model, and then contrasts Connecticut's experience with that of other states and describes what can be learned from this demonstration.

Aged↗

PubMed2005

Splicing of a rare class of introns by the U12-dependent spliceosome.

Pre-mRNA splicing is catalyzed by two unique spliceosomes, designated U2- or U12-dependent. In contrast to the well-characterized U2-dependent spliceosome, much remains to be learned about the less abundant U12-type spliceosome. This review focuses on recent advances in elucidating the structure and function of the minor U12-dependent spliceosome. Interesting similarities and differences between the U12- and U2-dependent spliceosomes are also highlighted.

Amino Acid Sequence↗

PubMed1990

Effects of experimentally induced colds on aspects of memory.

Four experiments were carried out to investigate the effects of experimentally-induced colds on various aspects of memory of 27, 47, 39, and 30 adults. Free recall, digit span, and retrieval from semantic memory were unaffected by having a cold. Immediate recognition of important information from a story was impaired in subjects with colds, which suggests they were less able to follow the theme of the story. In contrast to this, volunteers with colds had better recognition of information from a story learned prior to the virus challenge.

Adult↗

PubMed2001

Gene therapy of scarring: a lesson learned from fetal scarless wound healing.

Cutaneous wounding in adult humans and higher vertebrate animals results in scar formation. In contrast, both human and animal fetuses, at early gestational ages, exhibit skin wound healing without scarring. This distinction suggests that the repair of adult wounds by skin regeneration, rather than by fibrosis, may be achieved if adult wounds can be modified to mimic the healing process of fetal wounds. The development of gene therapy offers the possibility to specifically enhance or block the gene expression of cytokines and extracellular molecules, and thus convert adult wound healing into a healing process more similar to tissue regeneration. This article reviews the characteristics of fetal wound repair focusing on cytokine profiles and the inflammatory response to dermal injury. Also included are new developments in gene transfer techniques as well as their application in wound healing. Finally, the authors propose possible strategies of wound gene therapy, to reduce wound scarring and to promote tissue regeneration.

Animals↗