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Results for “Transfer learning”

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At least 1,441 records · Page 80Linked to original sources
PubMed1997

Immunological induction of flavour aversion in mice. II. Passive/adoptive transfer and pharmacological inhibition.

Mice immunized with ovalbumin develop a strong aversion to ingesting sweetened egg white dilutions or ovalbumin solutions. In immunized animals, gavage or voluntary ingestion of ovalbumin triggers an increase of vascular permeability in the intestine; pretreatment with a mixture of histamine and serotonin antagonists blocked this reaction, but not the aversion; dexamethasone inhibited both the aversion and the increase in permeability. The aversion was transferred to normal recipient mice with high-titre anti-Ova sera obtained with complete Freund's adjuvant, but not with lower-titre serum pools of mice immunized with the help of Al(OH)3 adjuvant. However, the aversion was also (adoptively) transferred with whole spleen cells from immune donors. This later condition is inefficient to transfer the formation of high titres of specific antibodies.

Adoptive Transfer↗
PubMed1998

In utero gene transfer reveals survival effects of nerve growth factor on rat brain cholinergic neurones during development.

Nerve growth factor (NGF) is a maintenance factor for cholinergic neurones in the brain, but its properties as a developmental survival factor are largely unknown. The low accessibility of the developing mammalian brain to experimental manipulation makes it difficult to increase NGF levels during the early phases of brain development. In the present study we have used an in utero, ex-vivo gene transfer approach to explore NGF actions during development of the cholinergic system in the rat brain. Significantly increased numbers of cholinergic neurones were found only in the mesopontine complex in animals receiving NGF-secreting transplants, whereas the cholinergic neurones in the basal forebrain and striatum were not clearly affected. The present results suggest that overexpression of NGF during development may promote the survival of distinct populations of central cholinergic neurones into adulthood.

Animals↗
PubMed1999

Categorization of complex visual images by rhesus monkeys. Part 1: behavioural study.

In order to study how visual categories are coded by the activities of single neurons, it is necessary to first demonstrate that the animal subjects can categorize the visual stimuli employed in the single-unit recordings. Thus, rhesus monkeys were trained in a visual categorization task designed to minimize rote learning of individual exemplars and to allow testing of transfer from old to novel exemplars of the category. The stimuli were presented during controlled fixation. The monkeys learned to distinguish complex colour images of trees from other objects and generalized from old to novel exemplars. An extensive series of tests with probe stimuli showed that simple form, colour and texture features had insufficient stimulus control to account for the categorization performance. Scrambling the images impaired categorization performance, suggesting that the configuration of stimulus components controlled the categorization. The animals also learned a fish/non-fish categorization, but more slowly than a tree/non-tree categorization. These results indicate that rhesus monkeys can learn to categorize socially neutral, complex, natural visual images and suggest that this categorization is based on a combination of low-level features.

Animals↗
PubMedDate not supplied

Aging, encoding fluency, and metacognitive monitoring.

Encoding fluency (how rapidly one generates a mediator for a new association) may be a cue used to judge one's own learning. To evaluate age differences in utilization of this cue, older and younger adults were instructed to use interactive imagery to study paired associates, pressing a button to indicate when an image had been formed for a given pair. A judgment of learning (JOL) was also made immediately after each pair had been studied. Hence, at least two cues pertaining to encoding fluency-whether an image had been formed (a diagnostic cue) and the latency of formation (a nondiagnostic one)-were available when making JOLs. Age equivalence was found in JOL accuracy, and JOLs for both age groups were positively related to imagery formation and were negatively related to the latency of image formation. Moreover, subjectively judged latency correlated higher with JOLs than actual (objective) latency, supporting the hypothesis that perceived fluency is a cue used in constructing JOLs.

Adolescent↗
PubMed2001

Training of providers in embryo transfer: what is the minimum number of transfers required for proficiency?

BACKGROUND: Embryo transfer represents one of the most critical procedures in the practice of assisted reproduction. The objective of this study was to identify retrospectively the minimum number of embryo transfers required to train providers properly in this skill. METHODS AND RESULTS: The study group consisted of 204 patients who received embryo transfers between January 1996 and March 2000 in a university-based programme of assisted reproduction. The main outcome measure was clinical pregnancies per embryo transfer. Five Fellow trainees performed a total of 204 embryo transfers for an overall pregnancy rate of 45.5% per embryo transfer (93/204). In comparison, the programme pregnancy rate per transfer for experienced providers was 47.3% (560/1179). A chronological graph of each individual trainee's experience for the first 50 embryo transfers performed suggested a lower initial pregnancy rate for three of the five trainees. To determine whether a learning curve might exist, results of the first 25 transfers were compared as a subgroup with the second 25 transfers. Pregnancy rates were lower for the 1-25 transfer subgroup than in the 26-50 subgroup for three of the five Fellow trainees, although the difference was not statistically significant. CONCLUSION: Clinical pregnancy rates of Fellows-in-training were indistinguishable statistically from those of experienced staff by 50 transfers.

Adult↗
PubMed2006

Strong-field atomic phase matching.

We interpret a learning-control experiment with the goal of optimizing multiphoton population transfer in atomic sodium in the strong-field limit. Despite multiple experimental constraints, a learning algorithm discovers optimal pulses that can be understood in terms of a simple dynamic picture of the atom-field interaction. We show that the shaped pulses counteract the dynamic Stark-induced stimulated emission that would otherwise impede the efficient use of a pi pulse to invert a multiphoton transition.

Journal Article↗
PubMed2006

An asymmetry between memory encoding and retrieval. Revelation, generation, and transfer-appropriate processing.

Transfer-appropriate-processing accounts of memory emphasize the similarity of encoding and retrieval processes, and imply that experimental manipulations should have similar effects on encoding and retrieval. Exceptions to this expectation are thus of great interest, but extant exceptions (produced by studies using divided attention, alcohol, and benzodiazepines) are debatable, single dissociations between encoding and retrieval. The present experiments demonstrate a reversed dissociation, in which the same variable produced opposite effects when implemented at encoding and retrieval. At encoding, participants either solved anagrams of study words or read intact study words. At retrieval, participants likewise solved anagrams or read intact words prior to making recognition memory judgments. Compared with reading intact words, solving anagrams at encoding enhanced later recognition accuracy, whereas solving anagrams at test impaired accuracy. These results were obtained with old/new decisions (Experiment 1) and with confidence ratings (Experiment 2).

Adult↗