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Results for “Generalization, Stimulus”

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At least 1,243 records · Page 69Linked to original sources
PubMed1991

Stimulability as a factor in the phonological generalization of misarticulating preschool children.

The relationship among six functionally misarticulating preschool children's phoneme-specific stimulability skills, the choice of treatment targets (i.e., stimulable or nonstimulable sounds), and generalization of correct sound production was explored in this prospective study. Each subject [age range of 4:11 (years:months) to 5:6] was taught to produce [r] and one other sound that was absent from his or her phonetic inventory using a contrasting-minimal-pairs production approach. A multiple baseline across behaviors single-subject research design provided experimental control. For 86% of the 28 monitored sounds, generalization was consistent with pretreatment stimulability skills; production of stimulable sounds tended to improve regardless of treatment target. These results suggest that nonstimulable sounds are likely to require direct treatment; thus, generalization probe responses may be maximized by treating nonstimulable sounds rather than stimulable sounds.

Articulation Disorders↗
PubMed2001

The hypothalamic-pituitary-adrenal response to critical illness.

The maintenance of life depends on the capacity of the organism to sustain its equilibrium via allostasis'-the ability to achieve stability through change. Life-threatening disease induces acute adaptive responses specific to the stimulus and generalized responses when the disturbances are prolonged. These changes are associated with increased activity of the hypothalamic-pituitary-adrenal axis and may have survival value in preparing the body for fight or flight'. There is a shift towards an increase in glucocorticoid production and away from mineralocorticoid and androgen production, as well as an increase in the biological effects of glucocorticoids through an increased cortisol free fraction and an increased glucocorticoid receptor sensitivity. During the prolonged phase, there is a dissociation between high plasma cortisol and low adrenocorticotropin hormone levels, suggesting non-adrenocorticotropin hormone-mediated mechanisms for the regulation of the adrenal cortex. This hypercortisolism is in contrast to the very low dehydroepiandrosterone sulphate level, indicating an imbalance between the immunostimulatory and immunosuppressive adrenocortical hormones. The question is whether the total serum cortisol concentration represents sufficient glucocorticoid biological activity during the prolonged phase of critical illness.

Animals↗
PubMed2000

A case of post-anoxic encephalopathy with initial massive myoclonic status followed by alternating Jacksonian seizures.

To contrast stimulus-sensitive generalized myoclonus with ensuing multifocal localized myoclonus in a patient with post-anoxic coma, we stressed the clinical as well as electroencephalographical differences between his initial generalized and subsequent focal myoclonus. While generalized myoclonus was presumably of extracortical origin and responsive to valproic acid, alternating Jacksonian seizures were definitely cortical and suppressed with phenytoin. These two different types of myoclonus should not be confused in post-anoxic coma.

Aged↗
PubMed2001

A model for potential tumor immunotherapy based on knowledge of immune mechanisms responsible for spontaneous abortion.

Attempts to treat various cancers by immunotherapy have been tried for about 50 years. Most studies have focused on improving cytotoxic T lymphocyte (CTL) responses against various tumors. Immunotherapy has been both active and passive, and results have been modest at best. Spontaneous abortion (SAB) of pregnancies could in some ways resemble remission of a tumor. Both tumors and conceptusses are faced with a similar problem -- how to grow in a host in a vascular rich area, and yet escape immune surveillance despite both entities being an allogenic stimulus. In general, the fetus is far more immunogenic than a spontaneous tumor, and yet abortuses seem to avoid CTL responses but are sometimes invaded by natural killer (NK) cells. There are data suggesting that SAB will occur if there is inhibition of production of an immunosuppressive protein called progesterone-induced blocking factor (PIBF). This protein inhibits NK cell cytolysis and influences TH2 cytokine dominance over TH1. If some tumors avoid NK cell destruction through a PIBF mechanism, perhaps an active rejection of these tumors could be achieved by inhibiting PIBF production by treating with a progesterone receptor antagonist. Passive immunization could also be considered by conjugative radionuclide or toxic chemical to a PIBF antibody which may be tumor specific since PIBF is not produced in normal tissue. The first step should be to see if PIBF can be detected in the peripheral circulation in patients with certain tumors.

Abortion, Spontaneous↗
PubMed1997

The effects of the degree of surgical trauma and glucose load on concentration of thyrotropin, growth hormone and prolactin under enflurane anaesthesia.

Sixty patients undergoing gynecological surgery under enflurane nitrous-oxide anesthesia were studied. The goal was to investigate the effects of the degree of surgical trauma and glucose load on the pattern of TSH, GH and PRL secretion before, during and following surgery. For this purpose the patients were divided into four groups according to the severity of the operation and the type of fluid administered. The groups were as follows: group 1, major surgery--glucose solution; group II, major surgery--lactated Ringer solution; group III, minor surgery--glucose solution; group IV, minor surgery--no intravenous fluids. The three hormone concentrations, 45 min after the start of anesthesia, increased in all groups. The highest values for GH and PRL concentration were observed in group IV. This increase was followed by a decrease 24 h and 5 days after induction, at the end of the study, except in group IV where TSH and GH levels fell back to normal values more slowly. These results lead to the following conclusions: a) Enflurane does not suppress hormonal stress response to surgical trauma; b) A similar pattern is obtained for pituitary response, indicating that a general pituitary stimulus takes place in these situations; c) Glucose load plays an important role in pituitary hormonal response to surgical stress; d) There is no direct relationship between the degree of surgical trauma and the hormone levels in patients under enflurane anaesthesia.

Adult↗
PubMed1994

Shape from shading. I: Surface curvature and orientation.

The human visual system makes effective use of shading alone in recovering the shape of objects. Pictures of sculptures are readily interpreted--a situation where shading provides virtually the sole cue to shape. However, shading has been considered a poor cue to depth in comparison with retinal disparity and kinetic cues. Curvature discrimination thresholds were measured with the use of a surface-alignment task for a range of surface curvatures from 0.16 cm-1 to 1.06 cm-1. Weber fractions were around 0.1, demonstrating considerable precision in this task. Weber fractions did not vary substantially as a function of surface curvature. Rotation of the light source around the line of sight had no effect on curvature discrimination but rotation towards the viewer increased discrimination thresholds. In contrast, slant discrimination declined with rotation of the light-source vector towards the viewpoint. When a band-limited random grey-level texture was mapped onto the sphere, curvature discrimination thresholds increased gradually as a function of texture contrast, even though texture and shading provided consistent cues to depth. Adding texture also increased slant discrimination thresholds, demonstrating that texture can act as a source of noise in shape-from-shading tasks. The psychophysical findings have been used to evaluate whether current algorithms for shape from shading in computer vision could serve as models of human three-dimensional shape analysis and to highlight low-level intramodular interactions between depth cues. It is demonstrated that, in the case of surfaces defined by shading, curvature descriptions are primary and do not depend upon the prior encoding of surface orientation, and Koenderink's local-shape index is suggested as an alternative intermediate representation of surface shape in the human visual system.

Attention↗
PubMed1996

Generalization to novel images in upright and inverted faces.

An image of a face depends not only on its shape, but also on the viewpoint, illumination conditions, and facial expression. A face recognition system must overcome the changes in face appearance induced by these factors. Two related questions were investigated: the capacity of the human visual system to generalize the recognition of faces to novel images, and the level at which this generalization occurs. This problem was approached by comparing the identification and generalization capacity for upright and inverted faces. For upright faces, remarkably good generalization to novel conditions was found. For inverted faces, the generalization to novel views was significantly worse for both new illumination and viewpoint, although the performance on the training images was similar to that on the upright condition. The results indicate that at least some of the processes that support generalization across viewpoint and illumination are neither universal (because subjects did not generalize as easily for inverted faces as for upright ones) nor strictly object specific (because in upright faces nearly perfect generalization was possible from a single view, by itself insufficient for building a complete object-specific model). It is proposed that generalization in face recognition occurs at an intermediate level that is applicable to a class of objects, and that at this level upright and inverted faces initially constitute distinct object classes.

Adolescent↗
PubMed1999

Spectral sensitivity of the domestic fowl (Gallus g. domesticus).

1. The spectral sensitivity of 7 broiler fowl was determined in a behavioural test. 2. Initially the birds were trained to receive a food reward by pecking at a clear, Perspex panel behind which was a light stimulus (circular, diameter = 9 mm), originating from a tungsten-halogen lamp. Subsequently, they were trained to choose between 2 panels only 1 of which was lit; the assignation of light and dark on each panel was randomly ascribed between trials. The colour of the lit panel was determined by the wavelength of the light transmitted through one of 13 closely defined narrow bandwidth filters between 326<lambda<694 nm. The flux of photons and hence the intensity of the stimulus received by the bird could be controlled by changing the voltage across the lamp. The photon flux was gradually reduced until the birds failed to detect accurately the lit panel. Success was defined as a choice of the lit panel 9 or more times in a sequence of 10 trials, providing that the sequence contained at least 4 changes in the position of the stimulus. 3. Generally, the birds showed a peak sensitivity between 540<lambda<577 nm. The results agree with electrophysiological data between 507<lambda<694 nm and psychophysical data between 500<lambda<700 nm but our data showed higher sensitivities between 380<lambda<507 nm compared with electro-physiological findings. 4. Our findings confirm that broilers can 'see' into the UV(A) range and that their spectral sensitivity is different to the human. The implication of this is that the measurement of light intensity in poultry housing using the lux unit does not accurately describe the intensity perceived by fowl. 5. Experimenters using colour, for example differently coloured lighting or food, need to account for this different sensitivity when interpreting their results.

Animals↗
PubMed1979

Signal detection analysis of conditioning data.

Signal detection analysis of learning and conditioning data provides for a greater distinction to be made between learning and performance through the use of the two signal detection parameters, d' and B. The use of the two parameters permits alternative interpretation of several types of data sets discussed. This analytic technique may be used with either discrete trial or free-response data. The present article reveiws applications of signal detection parameters in the literature, and provides for their extension to other uses.

Conditioning, Classical↗