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Biomedical subjects

R E Lubow

Publications and source records attributed to R E Lubow.

At least 37 records · Page 2Linked to original sources
PubMed1997

Visual search as a function of type of prior experience with target and distractor.

In a visual search task, participants identified the presence of a unique shape against a background of homogeneous distractors. Types of prior experience with the target, the distractor, or both were examined. In 2 experiments, a preexposure (PE) phase was followed by a test phase. The test display consisted of a target that was either target or distractor in PE or novel. Distractors were either targets or distractors in PE or novel. Reaction time was fastest for novel targets with familiar distractors, irrespective of the source of familiarity, and slowest for novel targets with novel distractors. Results are discussed in terms of attentional explanations of latent inhibition (LI) and perceptual learning and of visual search phenomena, such as novel popout. LI, previously attributed only to a deficit in the stimulus preexposed group, may also be due to enhanced performance in the nonpreexposed group.

Association↗
PubMed1996

Latent inhibition effects reflected in event-related brain potentials in healthy controls and schizophrenics.

The present study examined the effects of pre-exposure of an irrelevant stimulus on reaction time and the contingent negative variation (CNV) in healthy controls and schizophrenic patients. In Phase I, subjects were either pre-exposed (PE) or not pre-exposed (NPE) to repeated presentations of an auditory probe stimulus (white noise), while engaged in counting auditory nonsense syllables. In Phase II, all subjects were required to produce a rapid motor response to a visual imperative stimulus that was preceded by the previously irrelevant auditory stimulus. During Phase II in controls, for PE as compared to NPE subjects, the build-up of CNV across trials was delayed. In schizophrenics, for both PE and NPE subjects, there was no pre-exposure effect on the CNV component. These findings indicate that ERPs may be useful in explicating the normal latent inhibition effect (poor associative learning to a stimulus after it has been passively pre-exposed) and its disruption in schizophrenia.

Adult↗
PubMed1995

Latent inhibition in conditioned taste aversion: the roles of stimulus frequency and duration and the amount of fluid ingested during preexposure.

Two experiments examined the effects of total stimulus preexposure on latent inhibition (LI) in a conditioned taste aversion procedure with rats. Experiment 1 varied the frequency and duration of saccharin preexposures. LI was an increasing function of the product of frequency x duration. Experiment 2 kept saccharin exposure time constant but varied the amount of saccharin consumed by manipulating number of hours of fluid deprivation prior to exposure. Deprivation schedule conditions affected the amounts consumed which, in turn, modulated LI magnitude, at least with a 1-day acquisition-test interval, as in Experiment 1. The data clearly indicate that LI is a function of total amount of contact with the preexposed saccharin solution. In addition, half of the subjects in Experiment 2 were tested 21 days after the conditioning event. LI was not present in any group tested at this interval. These data were discussed in regard to the controversy regarding whether LI represents a failure to acquire the CS-US association or a failure to retrieve that association.

Animals↗
PubMed1995

Latent inhibition in humans: data, theory, and implications for schizophrenia.

Learning about the consequences of a stimulus is retarded if that stimulus has been experienced without reinforcement. A literature review of this latent inhibition (LI) effect indicates that LI is similar in human and other species, although in adult humans it often requires a masking or distracter task. The discrepancy in conditions for producing LI can be accounted for by developmental differences in the automatic processing of unattended stimuli. In adults, automatic processes are subject to a controlled information-processing override. Masking prevents controlled processing of the preexposed stimuli so that they remain unattended. The role of masking in attenuating LI in schizotypal/schizophrenic groups is assessed. It is proposed that schizophrenia is related to an inability to use occasion-setting properties of context or to switch from controlled to automatic processing of inconsequential events.

Adult↗
PubMed1994

English and Hebrew letter report by English- and Hebrew-reading subjects: evidence for stimulus control, not hemispheric asymmetry.

Three experiments were conducted using tachistoscopic circular displays of English and/or Hebrew letters that were equidistant from a fixation point. It was found that: (1) Irrespective of native language, English or Hebrew, subjects initiate their reports of English letters from the upper left quadrant and of Hebrew letters from the upper right quadrant of the display. In addition, subsequent letter reports come mostly from the same quadrant. (2) Although Experiments 1 and 2 indicated that direction of reporting might be a function of display language, Experiment 3 provided data to show that direction of reporting was a function of the position of the first response and not the display letter language that engaged that response, nor the display language of adjacent letters. It was suggested that the typical asymmetries reported in the literature, such as right visual field superiority for word stimuli, are the result of a particular set of stimulus conditions (e.g., hemifield presentations) and response requirements (e.g., reaction time and correct recognition). When stimulus conditions and response requirements are made compatible with previously overlearned behaviors, the potential influences of cerebral asymmetries are overshadowed by external stimulus control.

Adult↗
PubMed1994

Attention reduces perceived brightness contrast.

The effects of attention on brightness perception was investigated in four experiments. In the first three, subjects estimated the brightness of a briefly presented small grey square by selecting a number that corresponded to one of four possible squares varying on a lightness-darkness dimension. In the last experiment, subjects matched the brightness of two peripheral squares, one attended and one unattended. When the stimulus appeared on a white background (Experiments 1, 2, and 4a) it was judged as brighter when attention was directed to its location than when attention was diverted to another location. When the stimulus appeared on a dark background (Experiments 3 and 4b), the opposite pattern of results was obtained: the attended stimulus was judged as darker than the unattended one. These results show that attention reduces the perceived contrast between the stimulus and its background, suggesting that attention enables subjects to provide a more veridical judgement of stimulus brightness by limiting processing resources to the square itself, at the expense of the surrounding background. As attention produced a directional brightness effect rather than just an improvement in report accuracy, the results can be attributed to early perceptual processing effects, hence providing support for early selection views of attention.

Adult↗
PubMed1993

Amphetamine-produced attenuation of latent inhibition is modulated by stimulus preexposure duration: implications for schizophrenia.

The relationship between amphetamine-produced dopamine overreactivity and attention to irrelevant stimuli is reflected in an attenuated latent inhibition (LI) effect. This occurs in both animal and human subjects. The present study examines the manner in which this effect in rats is modulated by the duration of stimulus preexposure. A factorial design was used with three levels of stimulus preexposure duration and either amphetamine or saline administration. In addition, there were corresponding groups that did not receive stimulus preexposure. It was found that although amphetamine did indeed abolish LI at short exposure intervals (30 sec), the LI effect was normal for long stimulus preexposure durations (150 sec). The data were discussed in terms of the affects of amphetamine on the processing of irrelevant stimuli and the relationship of such a dysfunctional attentional process to schizophrenia.

Animals↗
PubMed1993

Latent inhibition deficits in hyperactive children.

Latent inhibition (LI), the retardation of associative learning as a function of prior stimulus exposure, is believed to reflect normal attentional processes. Previous research has demonstrated an attenuated LI effect in acute schizophrenics as well as normal subjects who rate high on schizotypal scales. The present study examined LI in two age groups (66.1 and 77.4 months) of hyperactive and normal children. The younger normal children exhibited LI while the older ones did not. Neither of the hyperactive groups displayed LI. The loss of LI in the hyperactive subjects was explained by proposing that these children are deficient in processing non-salient, irrelevant stimuli.

Attention↗
PubMed1993

Latent inhibition and recall/recognition of irrelevant stimuli as a function of pre-exposure duration in high and low psychotic-prone normal subjects.

Learning to ignore non-relevant stimuli (coloured geometric shapes) was evaluated in high and low psychotic-prone normal subjects in two experiments. In the first, subjects were tested in a latent inhibition paradigm in a 2 x 2 x 3 factorial design (high vs. low psychotic proneness, as measured by MMPI subscales; pre-exposure of the stimuli such that they were non-relevant before the test but relevant in the test vs. absence of such pre-exposure; three levels of pre-exposure duration: 3-, 6- and 15-min). Low psychotic-prone subjects showed the latent inhibition effect (poorer learning as a result of pre-exposure to the non-relevant stimuli as compared to no pre-exposure) at 6- and 15-min durations, but not at 3-min. High psychotic-prone subjects failed to show latent inhibition at 3- and 6-min durations, but did show the effect at 15-min. The second experiment employed a 2 x 3 design (high vs. low psychotic proneness; three levels of pre-exposure duration of the same stimuli used in Expt 1). High psychotic-prone normal subjects recalled and recognized more previously non-relevant stimuli than low psychotic-prone subjects, particularly after 6-min pre-exposure to those stimuli. The data of the two experiments suggest that the attenuation of latent inhibition in high psychotic-prone subjects as compared to low psychotic-prone subjects is a result of the increased attention to non-relevant information.

Adult↗
PubMed1991

Why is the driver rarely motion sick? The role of controllability in motion sickness.

The central hypothesis of the work is that the dimension of control-no control plays an important role in motion sickness. Although it is generally agreed that having control over a moving vehicle greatly reduces the likelihood of motion sickness, few studies have addressed this issue directly, and the theoretical explanation for this phenomenon is not completely clear. In this study, we equated groups differing in controllability for head movement, vision, activity, and predictability, which have often been suggested in the literature as explanations for the driver's immunity to motion sickness. Twenty-two pairs of yoked subjects were exposed to nauseogenic rotation. One subject of each pair had control over the rotation and head movements, while the other was exposed passively to the same motion stimulus. Subjects who had control reported significantly fewer motion sickness symptoms and less of a decrement in their well-being, as compared to the yoked subject without control. The results are discussed in relation to Reason's sensory rearrangement theory and the concept of feed-forward mechanisms in motion perception.

Adult↗
PubMed1989

Conditioned taste aversion in humans using motion-induced sickness as the US.

The purpose of the experiment was to demonstrate conditioned taste aversion (CTA) and latent inhibition (LI) of CTA in humans using rotation-induced motion sickness as the unconditioned stimulus. To accomplish this, flavour familiarity (familiar vs unfamiliar) and rotation (rotation vs no rotation) were manipulated in a 2 X 2 factorial design. Subjects consumed either a familiarly flavoured carbonated beverage or a novel one after which half of each group was rotated or not rotated. Two hours later the subjects were re-presented with the flavoured drink that they had previously drunk. The groups receiving rotation consumed less of the drink that the non-rotated groups, thus demonstrating CTA. The rotated group pre-exposed to the novel flavoured drink consumed less than the rotated group pre-exposed to the familiar drink, thus demonstrating LI. The effectiveness of the rotation procedure in producing motion sickness was confirmed by self-reports of general feelings and by symptom rating scales. In addition, it was found that, at the time of consuming the test drink the rotation groups' motion-sickness symptom scores were reduced to the level of the nonrotated groups. Applications of these data to the prophylactic treatment of chemotherapy-induced food aversions were discussed.

Adolescent↗
PubMed1988

Disruption of latent inhibition by acute administration of low doses of amphetamine.

In the latent inhibition (LI) paradigm, nonreinforced preexposure to a stimulus retards subsequent conditioning to that stimulus. Three experiments investigated the effects of acute amphetamine administration on LI in rats. Experiments 1 and 3 used a conditioned emotional response (CER) procedure and Experiment 2 used two-way active avoidance procedure. Experiments 1 and 2 showed that, in both the CER and avoidance procedures, 1.5 mg/kg dl-amphetamine administered either in the preexposure or the conditioning stage alone did not disrupt LI. In contrast, amphetamine administered in both of the stages abolished LI. Experiment 3 showed that the abolition of LI was obtained when the preexposure and conditioning were given 24 hr apart but not when the two stages were given in one session.

Animals↗
PubMed1985

The effects of early handling on latent inhibition in male and female rats.

Latent inhibition (LI) is a behavioral paradigm in which repeated exposure to stimuli not followed by meaningful consequences renders these stimuli ineffective for subsequent learning. The development of LI is considered to reflect learning not to attend to, ignore, or tune out irrelevant stimuli. The present study investigated the differences in the development of LI between handled and nonhandled males and females. Infantile handled (Days 1-22) and nonhandled, male and female Wistar rats were tested in maturity in the LI paradigm. The LI procedure consisted of two stages: pre-exposure, where animals received 60 presentations of the to-be-conditioned stimulus (tone) and test, where the animals acquired a two-way active avoidance response with the tone serving as the warning signal. Handled animals reached higher percentage of avoidance responses as compared with nonhandled animals. Latent inhibition was obtained in both the handled and the nonhandled females, but only the handled males showed the LI effect. Nonhandled males failed to develop LI. The results indicate that the effects of handling are evident in learning tasks that do not involve motivational-emotional variables, i.e., learning to ignore irrelevant stimuli; handling differentially affects males and females, with a much greater impact on males and the nonhandling procedure has significant deleterious consequences on adult behavior.

Animals↗
PubMed1985

The abolition of the partial reinforcement extinction effect (PREE) by amphetamine.

The effects of amphetamine administration on the partial reinforcement extinction effect (PREE) at one trial a day, were examined. Two groups of rats were trained to run in a straight alley. The continuously reinforced (CRF) group received food reward on every trial. The partially reinforced (PRF) group was rewarded on a quasirandom 50% schedule. All animals were then tested in extinction. dl-Amphetamine 1.5 mg/kg was administered in a 2 X 2 design, i.e., drug-no drug in acquisition and drug-no drug in extinction. The PREE, i.e., increased resistance to extinction exhibited by PRF animals as compared to CRF animals, was obtained in animals that received saline in acquisition, independently of drug treatment in extinction. In contrast, amphetamine administered in acquisition abolished the PREE irrespective of drug treatment in extinction. In addition, amphetamine administered in extinction alone increased resistance to extinction in PRF animals.

Amphetamine↗
PubMed1984

Abolition of the expression but not the acquisition of latent inhibition by chronic amphetamine in rats.

The animal amphetamine model of schizophrenia has been based primarily on stereotyped behavior. The present study sought to demonstrate an amphetamine-induced deficit in attentional processes. To this end, the effects of acute and chronic (14 days) 1.5 mg/kg dl-amphetamine administration on the ability of rats to ignore irrelevant stimuli were examined using the paradigm of latent inhibition (LI) in a conditioned emotional response (CER) procedure. The procedure consisted of three stages: pre-exposure, in which the to-be-conditioned stimulus, tone, was presented without being followed by reinforcement; acquisition, in which the pre-exposed tone was paired with shock; and test, in which LI was indexed by animals' suppression of licking during tone presentation. Experiment 1 showed that chronic but not acute treatment abolished LI. Experiment 2 showed that animals receiving chronic amphetamine pretreatment but pre-exposed and conditioned without the drug, exhibited normal LI. In Experiment 3, animals which received chronic amphetamine pretreatment and were pre-exposed under the drug but conditioned without it, also showed normal LI. The implications of these results for the animal amphetamine model of schizophrenia are discussed.

Amphetamine↗
PubMed1975

Behavioral decrement following stimulus preexposure: effects of number of preexposures, presence of a second stimulus, and interstimulus interval in children and adults.

This article presents an analysis of the similarities between the stimulus familiarization effect and latent inhibition. Just as latent inhibition has been readily demonstrated in infrahumans, and only with considerable difficulty in adult humans, the experiments reported here obtained a significant interaction between the stimulus familiarity effect and age. Children exhibited increased reaction time to preexposed stimuli as opposed to nonpreexposed stimuli, but adults did not show this effect. In addition, a number of variables were shown to affect the amount of decrement. The decrement increased as a function of the number of preexposures and decreased with the addition of a second stimulus placed in a conditioning relationship to the to-be-tested stimulus during preexposure. However, an increased in the interstimulus interval was only marginally effective in increasing the inhibitory effects of preexposure. The data were discussed in relation to a conditioned attention explanation for these phenomena of behavioral decrement.

Adult↗
PubMed1974

High-order concept formation in the pigeon.

After 30 days of operant training, with pecking responses to aerial photographs containing man-made objects reinforced with food, and no food reinforcement for pecking on photographs not containing man-made objects, a discrimination to the two classes of photographs was obtained. The discriminative response generalized to photographs with which the pigeons had no previous experience. This study demonstrates that pigeons are capable of forming relatively high-order concepts. Some possible stimulus properties controlling the discrimination are discussed.

Journal Article↗