Stimulus control by same-versus-different relations among multiple visual stimuli.

The authors devised a go/no-go discrimination learning task that allowed but did not require pigeons to report (a) from which of 2 different sets a collection of visual items was drawn and (b) the relations between or among the items as being the same as or different from one another. The results of 2 experiments using this task disclosed stimulus control by the particular items in the arrays and by the same- different relations exemplified by those items. Relational and item control depended on how many items were in the arrays. Same-different discrimination was evident with 2-item displays, but it was much stronger with 6 or more items. These findings help to define the substrates of advanced conceptual behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differences in the associability of relevant and irrelevant stimuli.

Pigeons in two experiments were first trained with a set of simple discriminations of the form AX+ CX?, BY+ DY? where A, B, C, and D were relevant, and belonged to one dimension, and X and Y were irrelevant and belonged to a different dimension. They were then tested with a discrimination of the form AX+ AY? BX?. The experiments revealed that the discrimination between AX+ and BX? was acquired more readily than between AX+ and AY?, which indicates that the original training resulted in the associability of the relevant stimuli being greater than that of the irrelevant stimuli. Experiment 2 revealed that the status of other stimuli from the two dimensions influenced these changes in associability. The associability of X and Y was enhanced by making other stimuli from the same dimension relevant, and the associability of A and B was reduced by making other stimuli from the same dimension irrelevant. The associability of the stimuli is attributed to the attention they are paid. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of selective excitotoxic lesions of the nucleus accumbens core, anterior cingulate cortex, and central nucleus of the amygdala on autoshaping performance in rats.

The nucleus accumbens core (AcbC), anterior cingulate cortex (ACC), and central nucleus of the amygdala (CeA) are required for normal acquisition of tasks based on stimulus-reward associations. However, it is not known whether they are involved purely in the learning process or are required for behavioral expression of a learned response. Rats were trained preoperatively on a Pavlovian autoshaping task in which pairing a visual conditioned stimulus (CS+) with food causes subjects to approach the CS+ while not approaching an impaired stimulus (CS-). Subjects then received lesions of the AcbC, ACC, or CeA before being retested. AcbC lesions severely impaired performance; lesioned subjects approached the CS + significantly less often than controls, failing to discriminate between the CS + and CS-. ACC lesions also impaired performance but did not abolish discrimination entirely. CeA lesions had no effect on performance. Thus, the CeA is required for learning, but not expression, of a conditioned approach response, implying that it makes a specific contribution to the learning of stimulus-reward associations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Summation of reinforcement rates when conditioned stimuli are presented in compound.

Three experiments used delay conditioning of magazine approach in rats to examine the summation of responding when two conditioned stimuli (CSs) are presented together as a compound. The duration of each CS varied randomly from trial-to-trial around a mean that differed between the CSs. This meant that the rats' response rate to each CS was systematically related to the reinforcement rate of that CS, but remained steady as time elapsed during the CS (Harris & Carpenter, 2011; Harris, Gharaei, & Pincham, 2011). When the rats were presented with a compound of two CSs that had been conditioned separately, they responded more during the compound than during either of the CSs individually. More significantly, however, in all three experiments, the rats responded to the compound at the same rate as they responded to a third CS that had been reinforced at a rate equal to the sum of the reinforcement rates of the two CSs in compound. We discuss the implications of this finding for associative models (e.g., Rescorla & Wagner, 1972) and rate-based models (Gallistel & Gibbon, 2000) of conditioning. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Attentional capture by a salient distractor in visual search: The effect of target-distractor similarity.

Models of attentional selection are based on either stimulus-driven or goal-directed processes. Support for the latter comes from a study showing that a salient singleton in a search display can be ignored when the target has a different defining feature (Kumada, 1999). We show that this finding holds only when the target and the nonsalient distractors are highly dissimilar from one another. When the target and the distractors are made more similar, whilst ensuring that the target still pops out of the display, the salient distractor can no longer be ignored. This outcome is consistent with predictions from stimulus-driven accounts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of the anterior cingulate cortex in the control over behavior by Pavlovian conditioned stimuli in rats.

To investigate the contribution of the anterior cingulate cortex (ACC) to stimulus-reward learning, rats with lesions of peri- and postgenual ACC were tested on a variety of Pavlovian conditioning tasks. Lesioned rats learned to approach a food alcove during a stimulus predicting food, and responded normally for conditioned reinforcement. They also exhibited normal conditioned freezing and Pavlovian-instrumental transfer, yet were impaired at autoshaping. To resolve this apparent discrepancy, a further task was developed in which approach to the food alcove was under the control of 2 stimuli, only 1 of which was followed by reward. Lesioned rats were impaired, approaching during both stimuli. It is suggested that the ACC is not critical for stimulus-reward learning per se, but is required to discriminate multiple stimuli on the basis of their association with reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reduced trials and reliability of visual-acuity thresholds obtained by the method of constant stimuli.

To determine the effect of a reduction in trials per stimulus upon reliability of visual-acuity thresholds computed by the method of constant stimuli, visual-acuity thresholds were determined for 15 Ss, using a Landolt ring. Thresholds were computed using 5 stimulus values and 5, 10, 20, 30, 40, and 50 presentations per stimulus. Retest reliabilities of .92 and higher were obtained for as few as 10 trials per stimulus. It is concluded that "1… . classical… investigators probably tended to utilize more judgments than are necessary… 2… . for purposes of estimating absolute thresholds, the Müller-Urban constant method with five stimulus sizes appears to yield satisfactorily reliable thresholds… when as few as 10 trials per stimulus and 4-choice response categories are used." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eyeblink conditioning in the rabbit (Oryctolagus cuniculus) with stimulation of the mystacial vibrissae as a conditioned stimulus.

Eyeblink conditioning is a well-understood paradigm for the study of learning and memory and has been successfully employed with the use of auditory and visual conditioned stimuli (CSs). In this study, vibrotactile stimulation of the mystacial vibrissae was examined as an alternative CS in the rabbit ( Oryctolagus cuniculus). The technique is described and acquisition of eyeblink conditioning (EBC) with stimulation of a single row of vibrissae in a delay paradigm is reported. Extinction of EBC with presentation of the CS alone is demonstrated, as well as reacquisition with stimulation of a single whisker. Finally, control experiments ensure that the CS has no auditory components. Ipsilateral presentation of the CS and airpuff is a more effective combination for training than contralateral presentations. Vibrotactile stimulation of the vibrissae as a CS will enable further examination of the neural correlates of learning in a well-characterized sensory system. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential Effects of 8-OH-DPAT on Two Forms of Appetitive Pavlovian Conditioning in the Rat.

Rats were trained on an appetitive Pavlovian conditioning task in which the conditioned stimulus (CS) was either localized (a light in the food tray) or nonlocalized (an increase in the general level of illumination). The conditioned response (CR) of approaching the site of food delivery in the presence of the CS was monitored. Presession treatment with the 5-HT1A agonist 8-OH-DPAT (subcutaneous injections at a dose of 0.15 mg/kg) retarded acquisition of the CR, but only when the localized CS was used. The results confirm the general proposal that serotonergic processes are involved in learning. The selective effect of the drug is not to be explained in terms of its motor effects and is consistent with the specific suggestion that systemic administration of 8-OH-DPAT is especially effective in disrupting learning tasks mediated by hippocampal mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination of computer-graphic stimuli by mice: A method for the behavioral characterization of transgenic and gene-knockout models.

An automated method is described for the behavioral testing of mice in an apparatus that allows computer-graphic stimulus material to be presented. Mice responded to these stimuli by making a nose-poke toward a computer monitor that was equipped with a touchscreen attachment for detecting responses. It was found that C57BLJ/6 mice were able to solve single-pair visual discriminations as well as 3-pair concurrent visual discriminations. The finding that mice are capable of complex visual discriminations introduces the possibility of testing mice on nonspatial tasks that are similar to those used with rats, monkeys, and humans. Furthermore, the method seems particularly well suited to the comprehensive behavioral assessment of transgenic and gene-knockout models. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validity and boundary conditions of automatic response activation in the Simon task.

Three experiments were conducted to determine whether spatial stimulus-response compatibility effects are caused by automatic response activation by stimulus properties or by interference between codes during translation of stimulus into response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, responses are faster at the response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

First came the trees, then the forest: Developmental changes during childhood in the processing of visual local-global patterns according to the meaningfulness of the stimuli.

This study investigated how global and local perceptual processes evolve during childhood according to the meaningfulness of the stimuli. Children had to decide whether visually presented pairs of items were identical or not. Items consisted of global forms made up of local forms. Both global and local forms could represent either objects or nonobjects. In dissimilar pairs, items differed at one level (target level), while the other level included similar forms on both sides (irrelevant level). The results indicate an evolution from local preference at 4 years of age to adult-like global preference at 9 years of age. Moreover, as previously reported in adults, regardless of age, identification impaired performance when the irrelevant level was made of objects and the target level was made of nonobjects (interference). However, in younger children, this interference existed even when objects were present at all levels, suggesting that the strategy used to perform the comparison task also varied according to age. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anterograde amnesia for Pavlovian fear conditioning and the role of one trial overshadowing: Effects of preconditioning exposures to morphine in rat.

Four experiments studied anterograde deficits in Pavlovian fear conditioning following prolonged exposure to the μ-opioid receptor agonist morphine. Injections of morphine produced temporally graded anterograde amnesia characterized by deficits in contextual and conditioned-stimulus (CS) conditioning 1 or 7 days and selective impairment in CS conditioning 21 days after last injection. This anterograde deficit in conditioning did not recover across a retention interval, was absent when rats were tested immediately after conditioning, and required the presence of an auditory CS. These results suggest that anterograde deficits in Pavlovian fear conditioning emerged from differences in susceptibility to 1-trial overshadowing of context by CS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Early success in using the relation between stimuli and rewards to deduce an abstract rule: Perceived physical connection is key.

Are spatial proximity (0.10-12.5 cm), temporal proximity (0-, 2-, and 5-s gaps), and/or perceived connectedness of stimulus and reward key to infants' ability to deduce an abstract nonmatching rule from reward feedback? In this investigation, 3 conditions of the delayed nonmatching to sample task were administered to infants 9, 12, and 15 months old, and 5 more conditions were administered just to 12-month-olds. Results showed that connectedness is key. In its presence, neither close spatial or temporal proximity was needed. In the absence of the perception that stimulus and reward were components of a single thing, even close spatial and temporal proximity were insufficient for infants in the 1st year to grasp the rule-based association between stimuli and rewards. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Conditioning of ictal and interictal behaviors in rats by amygdala kindling: Context as the conditional stimulus.

The authors showed that conditional effects of the stimulation environment modulate both the ictal and interictal behaviors of rats subjected to amygdala kindling. Rats received 53 stimulations to the left basolateral amygdala in 1 conditional stimulus (CS) context (CS+) and 53 sham stimulations (the stimulation lead was attached but no current was delivered) in another context (CS-), quasirandomly over 54 days. Three kinds of conditional effects were observed, First, after several stimulations, less ambulatory activity, more freezing, and less rearing reliably occurred in the CS + context than in the CS context. Second, after 45 stimulations, all of the rats chose the CS - context over the CS + context in a conditioned place preference test. Third, when the rats were finally stimulated in the CS- context, their motor seizures were less severe: Latencies were longer, motor seizures were shorter, convulsive patterns were of a lower class, and there were fewer falls. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Operant and Pavlovian control of visual stimulus orienting and food-related behaviors in rats with lesions of the amygdala central nucleus.

The effects of superimposing operant reward and omission contingencies on 2 Pavlovian conditioned responses evoked by a visual conditioned stimulus paired with food were examined in rats with lesions of the amygdala central nucleus (CN). In sham-lesioned rats, the frequency of an orienting response, rearing, was increased by reward contingencies and decreased by omission contingencies, compared with yoked Pavlovian controls. In contrast, in CN-lesioned rats, rearing was not affected by either operant contingency and occurred at lower levels with Pavlovian procedures alone than in sham-lesioned rats. Nevertheless, CN-lesioned and sham-lesioned rats showed similar increases in the frequency of conditioned food-cup behavior with reward contingencies, similar decreases with omission contingencies, and similar levels of that response with Pavlovian procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of activation and sensory stimuli in recovery from lateral hypothalamic damage in the cat: Erratum to Wolgin and Teitelbaum.

Reports an error in the original article by David L. Wolgin and Philip Teitelbaum (Journal of Comparative and Physiological Psychology, 1978, Vol. 92, No. 3, pp. 474-500). On page 488, the last three sentences of the first paragraph in the right column should be two sentences. The corrected sentences are provided. (The following abstract of this article originally appeared in record 1979-12945-001.) Analyzed the early stages of recovery from lateral hypothalamic lesions in 30 adult cats. In addition to aphagia and adipsia, neurological examination revealed deficits suggestive of deficient endogenous arousal, including somnolence, catalepsy, akinesia, and sensory neglect. Manipulations (tail pinch and injection of amphetamine) that counteracted these deficits also restored feeding. During recovery from aphagia, feeding gradually became activated by sensory stimuli (sight, feel, and smell) associated with food. These data suggest that activation is an important component in the control of normal feeding. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fractionating the preview benefit in search: Dual-task decomposition of visual marking by timing and modality.

Providing participants with a preview of half the distractors in a visual search task facilitates performance. The present study examined the effects of secondary tasks on the preview benefit in search. Participants had to attend to a visual or an auditory stream of digits that began either (a) at the onset of the preview or (b) after the preview. Secondary tasks that onset with the preview disrupted the preview benefit irrespective of their modality. Only visual secondary tasks disrupted the benefit in the delayed condition. These selective interference effects suggest that the preview benefit can be fractionated into 2 components: an initialization component that involves modality-independent resources and a maintenance component that depends on visual resources. Results are discussed in relation to theoretical accounts of the preview benefit in search. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses to olfactory stimuli in spotted hyenas (Crocuta crocuta): I. Investigation of environmental odors and the function of rolling.

Olfaction is crucial to spotted hyenas (Crocuta crocuta), yet there are no controlled studies of their reactions to odors. In Experiment 1, the authors examined responses of captive hyenas to various environmental (prey, nonprey animal, and plant) odors. Subjects approached and sniffed all odors equally but preferentially licked prey odors, scent marked next to odors, and rolled in animal-based odors. In Experiment 2, the authors examined the function of rolling by applying odors to the pelts of captive hyenas. When hyenas wore carrion, they gained positive social attention (increased investigation and allogrooming) from pen mates, but when they wore camphor, the normal social greeting ceremony was curtailed. Thus, olfactory stimuli elicit specific responses, influence where behavior is directed, and can be used to affect social interaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)