[Typhoid vaccine as a general non-specific stimulus in ophthalmology].
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Endophthalmitis↗
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Results for “Generalization, Stimulus”
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Scalar timing in temporal generalization in children with short and long stimulus durations.
This experiment investigated temporal generalization performance in children aged 3, 5, and 8 years by using auditory stimulus durations where the standard was 0.4 s or 4.0 s, and non-standard stimuli were spaced linearly around the standard. At all ages, generalization gradients superimposed well when plotted on the same relative scale, indicating conformity to scalar timing. Whatever the standard duration used, the principal developmental changes were the increasing steepness of the generalization gradient with increasing age and a shift from symmetrical gradients, in the 3- and 5-year-olds, to adult-like asymmetrical gradients in the 8-year-olds.
Child↗
On the experimental analysis of naming and the formation of stimulus classes.
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Association Learning↗
Studies on the discriminative stimulus properties of apomorphine in rhesus monkeys.
Four rhesus monkeys were trained to discriminate the effect of apomorphine (0.1 mg/kg IM) from that of saline injections. The discriminative stimulus (DS) effect of apomorphine generalized to the dopamine D2 receptor agonist quinpirole. The D1 dopamine receptor agonist SKF 38393 elicited responses only on the saline-appropriate lever. Stimulus generalization of the dopamine autoreceptor agonist 3-PPP exhibited stereospecificity favoring the (+) over the (-) isomer. d-Amphetamine, phencyclidine, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), and clonidine did not share the DS effect of apomorphine. The D2-selective antagonists sulpiride and metoclopramide reversed both the DS effect and the response rate reduction produced by the training dose of apomorphine. Chlorpromazine and the D1 antagonist Sch 23390 also antagonized the DS effect, but the antagonism was accompanied by a further rate reduction. Haloperidol and clozapine antagonized the DS effect incompletely. The DS effect produced by apomorphine in this study appears to be mediated predominantly by post-synaptic D2 receptor activation, with contribution also from the D1 receptor.
Animals↗
Temporal specificity of perceptual learning in an auditory discrimination task.
Although temporal processing is used in a wide range of sensory and motor tasks, there is little evidence as to whether a single centralized clock or a distributed system underlies timing in the range of tens to hundreds of milliseconds. We investigated this question by studying whether learning on an auditory interval discrimination task generalizes across stimulus types, intervals, and frequencies. The degree to which improvements in timing carry over to different stimulus features constrains the neural mechanisms underlying timing. Human subjects trained on a 100- or 200-msec interval discrimination task showed an improvement in temporal resolution. This learning generalized to a perceptually distinct duration stimulus, as well as to the trained interval presented with tones at untrained spectral frequencies. The improvement in performance did not generalize to untrained intervals. To determine if spectral generalization was dependent on the importance of frequency information in the task, subjects were simultaneously trained on two different intervals identified by frequency. As a whole, our results indicate that the brain uses circuits that are dedicated to specific time spans, and that each circuit processes stimuli across nontemporal stimulus features. The patterns of generalization additionally indicate that temporal learning does not rely on changes in early, subcortical processing, because the nontemporal features are encoded by different channels at early stages.
Adult↗
Differences in taste responses to Polycose and common sugars in the rat as revealed by behavioral and electrophysiological studies.
Behavioral and electrophysiological experiments were performed to examine the suggestion that rats have two types of carbohydrate taste receptors, one for polysaccharides (e.g., Polycose) and one for common sugars (e.g., sucrose). Qualitative difference between the tastes of Polycose and sugars including sucrose, maltose, glucose, and fructose was surveyed by means of a conditioned taste aversion paradigm in which the number of licks for 20 s to each taste stimulus was measured. Aversive conditioning to Polycose did not generalize to sugars, while aversive conditioning to sucrose generalized to other sugars, but not to Polycose. In the electrophysiological study, taste responses of the whole chorda tympani were recorded. A proteolytic enzyme, pronase E, suppressed nerve responses to both Polycose and sugars to less than 50%. A novel anti-sweet peptide, gurmarin, strongly suppressed responses to sugars, but had essentially no effect on Polycose responses. On the other hand, KHCO3 enhanced responses to sugars to about 300%, but had little effect on Polycose responses. These results have confirmed the notion that rats can differentiate the tastes between Polycose and common sugars and that rats have two types of carbohydrate receptors.
Animals↗
Alterations of salt taste perception in the developing rat.
Behavioral correlates of changing neurophysiological taste sensitivities during development were assessed with a conditioned taste aversion procedure. Young rats (age 25-30 days) avoided 0.1M monochloride salts and 1.0M sucrose reliably less than adults (age 90-105 days), but the two groups did not differ when the conditioned stimulus (CS) was 0.1M citric acid. Analyses of generalization gradients revealed that young rats were unable to discriminate among the tastes of NaCl, NH4Cl, and KCl, whereas adults readily made such discriminations. Both age groups had similar generalization gradients when the CS was 1.0M sucrose or 0.1M citric acid. These data indicate that quantitative and qualitative aspects of salt taste perception alter with age. Furthermore, the behavioral changes noted in the present study correspond closely with previous findings from developmental studies of neurophysiological taste responses.
Aging↗
Neuronal correlates of parametric working memory in the prefrontal cortex.
Humans and monkeys have similar abilities to discriminate the difference in frequency between two mechanical vibrations applied sequentially to the fingertips. A key component of this sensory task is that the second stimulus is compared with the trace left by the first (base) stimulus, which must involve working memory. Where and how is this trace held in the brain? This question was investigated by recording from single neurons in the prefrontal cortex of monkeys while they performed the somatosensory discrimination task. Here we describe neurons in the inferior convexity of the prefrontal cortex whose discharge rates varied, during the delay period between the two stimuli, as a monotonic function of the base stimulus frequency. We describe this as 'monotonic stimulus encoding', and we suggest that the result may generalize: monotonic stimulus encoding may be the basic representation of one-dimensional sensory stimulus quantities in working memory. Thus we predict that other behavioural tasks that require ordinal comparisons between scalar analogue stimuli would give rise to monotonic responses similar to those reported here.
Animals↗
Improving social interaction in chronic psychotic using discriminated avoidance ("nagging"): experimental analysis and generalization.
Three social-interaction behaviors of a withdrawn chronic schizophrenic were increased using a discriminated avoidance ("nagging") procedure. The three behaviors were: (a) voice volume loud enough so that two-thirds of his speech was intellibible at a distance of 3m; (b) duration of speech of at least 15 sec; (c) placement of hands and elbows on the armrests of the chair in which he was sitting. "Nagging" consisted of verbal prompts to improve performance when the behaviors did not meet their criteria. A combined withdrawal and multiple-baseline design was used to evaluate the effectiveness of the procedure, and the contingency was sequentially applied to each of the three behaviors in each of four different interactions to determine the degree of stimulus and response generalization. Results indicated that the contingency was the effective element in increasing the patient's appropriate performance, and that there was a high degree of stimulus generalization and a moderate degree of response generalization. After the patient's discharge from the hospital, the durability of improvement across time and setting was determined in followup sessions conducted at a day treatment center and at a residential care home. Volume and duration generalized well to the new settings, while arm placement extinguished immediately.
Adult↗
Stereoselective stimulus effects of 3-methylflunitrazepam and pentobarbital.
Rats trained to discriminate 3.0 mg/kg of diazepam from saline in a two-lever operant choice task were challenged with the racemic mixture and optical isomers of 3- methylflunitrazepam or pentobarbital. Generalization of the diazepam stimulus was found to occur to (+/-)- and S(+)-3- methylflunitrazepam , with the S(+)-isomer being twice as active as the racemate. Diazepam stimulus generalization also occurred to (+/-)-, S(-)-, and R(+)-pentobarbital, with the S(-)-isomer being approximately twice as active as (+/-)- or R(+)-pentobarbital. In addition, the administration of the imidazobenzodiazepine Ro 15-1788, a selective benzodiazepine receptor antagonist, prior to benzodiazepine or barbiturate administration competitively antagonized the discriminative stimulus properties of the benzodiazepines but was completely ineffective in attenuating the discriminative stimulus effect of the barbiturates. The results of this study suggest that benzodiazepines exert their stimulus effects by a stereoselective interaction at a benzodiazepine receptor and that stereochemical factors are important in evaluating the stimulus properties of benzodiazepines or barbiturates.
Animals↗
Sensitization induced receptive field plasticity in the auditory cortex is independent of CS-modality.
Sensitization training with an auditory stimulus produces a general increase in response magnitude across the entire receptive field (RF) of neurons in the primary auditory cortex of the guinea pig (Bakin, J.S. and Weinberger, N.M., Brain Res., 536 (1990) 271-286). To determine if this effect reflects an auditory system-specific process or is caused by a process independent of the training stimulus modality, RFs in primary auditory cortex were characterized before and immediately after adult guinea pigs were given sensitization training with either an auditory or a visual training stimulus. General increases in auditory response magnitude across the RF were observed in 7 out of 7 auditory sensitization cases and 4 out of 5 visual sensitization cases. There were no statistical differences between the effects of auditory and visual sensitization training. These findings indicate that the general increases observed following sensitization training are the result of processes independent of CS modality, in contrast to the highly specific RF modifications that are caused by classical conditioning. The findings suggest that the 2 forms of RF plasticity, CS-specific re-tuning due to associative conditioning and polymodal general increases in gain due to non-associative sensitization, may reflect neural mechanisms involved in selective attention and vigilance, respectively.
Acoustic Stimulation↗
Stimulus control induced by benzodiazepine antagonist Ro 15-1788 in the rat.
The imidazodiazepine Ro 15-1788 is a proposed benzodiazepine receptor antagonist. Recently however, behavioural effects of Ro 15-1788 have been demonstrated. In the present study, rats (n = 12) were trained to discriminate Ro 15-1788 (10 mg/kg, IP, t = 15 min) from vehicle in a two-lever food-reinforced procedure. All rats showed a reliable discrimination (mean injection-appropriate lever responding greater than 85%) after about 60 daily training sessions. Drug stimulus control was evidenced by an orderly generalization gradient obtained with 0.01-30 mg/kg Ro 15-1788 (ED50 for stimulus generalization: 0.12 mg/kg). Since even low doses of Ro 15-1788 have discriminative effects in the rat, it is concluded that Ro 15-1788 may have potent behavioural activity.
Animals↗
Individual differences in infant visual attention: four-month-olds' discrimination and generalization of global and local stimulus properties.
Cognitive performance and development is negatively correlated with fixation duration patterns during infancy, and evidence suggests that long-looking infants may process visual information more slowly than short-looking infants. 3 experiments described here tested the possibility that these differences may be due to differential sensitivity to global and local visual information. Infants were administered discrimination and generalization tasks involving global and local information at varying levels of familiarization time. Results indicated that 4-month-olds process visual information in a global-to-local sequence. Both long- and short-looking infants were sensitive to both types of information, although long lookers required additional familiarization time to match the performance of short lookers. Finally, apparent "generalization" of global information at brief familiarization levels was traced to insensitivity to local stimulus properties. The results do not support the hypothesis that long- and short-looking infants are differentially sensitive to global versus local visual information at 4 months of age.
Attention↗
The essential role of stimulus temporal patterning in enabling perceptual learning.
Little is known about how temporal stimulus factors influence perceptual learning. Here we demonstrate an essential role of stimulus temporal patterning in enabling perceptual learning by showing that 'unlearnable' contrast and motion-direction discrimination (resulting from random interleaving of stimuli) can be readily learned when stimuli are practiced in a fixed temporal pattern. This temporal patterning does not facilitate learning by reducing stimulus uncertainty; further, learning enabled by temporal patterning can later generalize to randomly presented stimuli.
Analysis of Variance↗
Contextual control of equivalence-based transformation of functions.
The transformation of functions refers to the untrained acquisition of stimulus functions among members of stimulus equivalence classes or relational frames. Although it is widely assumed that contextual control over the transformation of fuctions must exist, this has not yet been conclusively demonstrated in laboratory studies. Four experiments are reported in which (a) stimulus equivalence classes were established, (b) a conditional stimulus function was trained for one member of each of the classes, and (c) multiple-exemplar procedures were used to train and test for contextual control over the transformation of the stimulus function within the classes and to assess whether it generalized to new equivalence classes. Although a significant amount of training was required, the procedures ultimately resulted in the contextual control of function transformation for 9 of 10 participants and generalized contextual control for 4 of 5 participants.
Adult↗
Tell me, what did you see? The stimulus on computers.
Most psychology experiments start with a stimulus, and, for an increasing number of studies, the stimulus is presented on a computer monitor. Usually, that monitor is a CRT, although other technologies are becoming available. The monitor is a sampling device; the sampling occurs in four dimensions: spatial, temporal, luminance, and chromatic. This paper reviews some of the important issues in each of these sampling dimensions and gives some recommendations for how to use the monitor effectively to present the stimulus. In general, the position is taken that to understand what the stimulus actually is requires a clear specification of the physical properties of the stimulus, since the actual experience of the stimulus is determined both by the physical variables and by the psychophysical variables of how the stimulus is handled by our sensory systems.
Behavioral Sciences↗
The effect of fixed duration stimulus magnitude upon reaction time to a response terminated stimulus.
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Generalization, Stimulus↗
Chlorpromazine and lithium. (Effects on stimulus significance).
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Animals↗