Dorsal noradrenergic bundle and selective attention in the rat.

Tested the role for the dorsal noradrenergic bundle (DNB) in selective attention and stimulus filtering in 4 experiments with 138 male Wistar rats. The DNB was damaged by stereotaxically guided injection of 4 μg of the neurotoxin 6-hydroxydopamine (6-OHDA). The latent inhibition effect was blocked by 6-OHDA-induced depletion of forebrain noradrenaline, whereas nonreversal shift performance was better in noradrenaline-depleted Ss than controls. Data indicate that Ss with DNB lesions are impaired in ignoring irrelevant stimuli. In situations in which control Ss did not learn to ignore irrelevant stimuli, no lesion-induced difference was found. Thus, controls and DNB lesioned Ss learned equally about each of 2 dimensions of a multiple-redundant discrimination task. This was assessed both by interpolated trials with only 1 dimension present and by shifts in which only 1 of the previous 2 dimensions remained relevant. It is concluded that the DNB lesion does not increase stimulus sampling globally but that it impairs performance only in those cases in which normal rats learn to ignore irrelevant stimuli. (53 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual sampling after lesions of the superior colliculus in rats.

In 2 experiments with 20 male black-hooded rats, Ss with bilateral lesions of the superior colliculus showed significantly poorer relearning of a horizontal/vertical stripe discrimination than control Ss. In Exp I, all Ss showed disruption of performance when a stimulus–response (S–R) separation was introduced by raising the stimuli above the site of responding. However, colliculectomized Ss were much more disturbed by the S–R separation than were control Ss. In Exp II, all Ss showed lower performance levels when conflicting patterns were introduced into the upper portion of the stimulus doors, but this time Ss with collicular lesions were less disturbed than controls. It is suggested (a) that when the stimulus and response sites are discontinuous, rats must make an appropriate orienting response to effectively sample the visual stimuli and (b) that lesions of the superior colliculus alter performance by interfering with this orienting behavior. The impairment in relearning is attributed to the absence of preoperative overtraining on the discrimination task. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stimulus selection and irrelevant stimuli in discrimination learning by pigeons.

Studied discrimination learning in 2 experiments with 32 and 16 White Carneaux pigeons. Exp. I confirmed that Ss trained in a free-operant situation produce a sharper gradient of generalization around a specific irrelevant stimulus if they are given true discrimination (TD) training than if given pseudodiscrimination (PD) training. An additional pair of groups, however, showed that this difference could be eliminated if, after initial training but before the test for generalization, both TD and PD Ss were given TD training on an entirely independent set of stimuli. This suggests that the normally flat PD gradient may represent a test effect: control by the specific irrelevant stimulus is masked by other more powerful irrelevant stimuli that are only suppressed by TD training. Exp. II demonstrated that in a discrete-trial situation, PD training results in a sharper gradient than does TD training, suggesting that the other unidentified irrelevant stimuli are present only in free-operant situations. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impact of group consensus and social support on stimulus meaning: Mediation of conformity by cognitive restructuring.

Three experiments with a total of 163 undergraduates tested the hypothesis that a person reinterprets the meaning of the stimulus object when facing unpopular responses from a unanimous group and that this change in meaning leads to a shift in response toward the group's position. In Exp I, several opinion items were presented, and either Ss observed unpopular responses, supposedly made earlier by a unanimous group (UG) or by a group having 1 dissenter (social support), or they observed no response at all (control). Ss merely gave their interpretation of the meaning of a key word or phrase in each opinion statement—they did not give their own opinions. Results show that UG Ss gave more uncommon meanings to the stimuli than did Ss in the other 2 conditions. Exp II ruled out the possibility that the shift in meaning was due to Ss' adhering to the interpretation they assumed to be held by the majority. In Exp III, Ss were exposed to scores representing the meanings that were produced by the unanimous group and control conditions in Exp I. Results show that after observing the consensually produced meanings for these items, the Ss shifted their own opinions toward the position held by the UG in Exp I. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Paleostriatal lesions in the pigeon (Columba livia) potentiate classical conditioning: Evidence from fixed-interval responding, free operant go–no-go discrimination, and alternation.

Explored the existence of behavioral deficits in the paleostriatum augmentatum in 4 experiments in which pigeons were given bilateral electrolytic lesions. Exp I, conducted with 16 Ss, investigated the effects of lesions on keypecking for reinforcement on a 1-min FI schedule. The lesions increased total response rates, but response timing was not disrupted in paleostriatal Ss. In Exp II, 17 naive Ss were given VI baseline training and, in contrast to the results of Exp I, paleostriatal lesions did not increase responding. Go–no-go discrimination, which followed baseline training, revealed enhanced positive behavioral contrast in paleostriatal Ss, which was explained in terms of additivity theory. The results of Exps I and II suggest that potentiated classical conditioning occurred in paleostriatal Ss. In Exp III, 16 naive Ss were given spatial alternation training, and performance was temporarily impaired following paleostriatal lesions. The same paleostriatal Ss showed superior differentiation performance in Exp IV with a classical go–no-go alternation procedure (which also suggested potentiated classical conditioning). It is argued that disruption of (irrelevant) response-produced information may account for paleostriatal superiority. (55 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Discrimination skill as a predictor of prevocational performance of institutionalized mentally retarded clients.

Two experiments investigated whether an assessment of the discrimination skills of institutionalized mentally retarded clients would provide information regarding subsequent prevocational performance. During Exp I, the 2-choice discrimination skills of 20 Ss were assessed with 6 diagnostic tasks: imitation, position, visual, matching-to-sample, auditory, and combined auditory-visual. Following assessment, 12 (aged 19–55 yrs; IQs 17–58) of the 20 Ss were administered several criterion tasks to determine the accuracy of prediction of the assessment tasks on prevocational analog tasks. During Exp II, 9 of the 12 Ss were administered a prevocational sorting task, and the accuracy of prediction of the discrimination assessment was again evaluated. Findings indicate that the assessment was useful in predicting performance across most of the analog tasks and the prevocational sorting task. Implications for the assessment and prevocational training of moderately and severely handicapped persons are discussed. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hyperstriatal function in the pigeon: Response inhibition or response shift?

Conducted 2 experiments with a total of 32 pigeons to further investigate the behavioral role played by the avian hyperstriatal complex. Results of Exp I show that Ss with lesions of the anterior or posterior hyperstriatum were impaired relative to unoperated controls and to control operates having neostriatal lesions on both acquisition and reversal of a simultaneous position discrimination. The observation that hyperstriatal Ss showed more tendency than controls to halt responding altogether in this situation casts doubt on the notion that the reversal deficit was due to a loss of response inhibition. Results of Exp II support an alternative hypothesis, i.e., that hyperstriatal birds have a deficit in the ability to shift responding to an alternative stimulus as a consequence of nonreinforcement. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Premature cognitive commitment.

Examined the effect of conditions of initial exposure to information on the "mindless" processing of information and its subsequent use. In Exp I, 64 college students received information about perceptual deficits while the perceived relevance of that information was manipulated. On assessment tests, Ss "found" they had this deficit. On follow-up perceptual tasks, the group initially informed that the deficit was seemingly irrelevant showed severe performance decrements relative to other groups. Exp II (52 Ss) used a similar procedure for perceptual skill. Ss initially exposed to "irrelevant" information performed more productively than Ss initially exposed to "relevant" information. Results indicate that conditions surrounding initial exposure to information limit its subsequent use. Implications for social, psychological, and physical symptoms are discussed. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquired equivalence and distinctiveness in matching to sample by pigeons: Mediation by reinforcer-specific expectancies.

Assessed the ability of a reinforcer to mediate an association between 2 stimuli that independently predict the occurrence of that reinforcer (acquired equivalence of cues). In Exp I, 12 male White Carneaux pigeons were trained on shape (plus and circle) and color (red and green) matching-to-sample tasks. Correct responses were systematically reinforced with corn on some trials and wheat on others to establish associations between 1 stimulus from each task and a "common" outcome. Following training, Ss were transferred to a symbolic matching-to-sample task wherein a stimulus from one training task was presented as the sample, and the stimuli from the other training task were presented as comparisons. In the 1st session, experimental Ss made significantly more correct responses than controls (i.e., Ss "matched" stimuli previously associated with a common outcome). Exp II with 18 Ss replicated this acquired equivalence effect and controlled for food preference. Delayed matching-to-sample training demonstrated enhanced memory performance for Ss exposed to different reinforcement contingencies, but this effect was confined to the shape task. Results indicate that a reinforcer can serve as the basis for organizing otherwise unpaired predictive cues in memory and that animals will selectively use differential expectancies as cues for solving complex discrimination tasks, depending on the difficulty of the discrimination. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food searching strategies of rats: Variables affecting the relative strength of stay and shift strategies.

Examined the extent to which the food searching strategies of rats are influenced by training, information about food in an initially visited site, and type of memory required for correct choices. Exp I used a discrete-trial, delayed conditional-discrimination procedure on a T-maze with 32 male Sprague-Dawley rats. Ss entered 1 arm of the maze and were given a choice between that arm (stay strategy) or the other arm (shift strategy). During the initial visit, S either consumed all the food (depletion condition) or only some of it (nondepletion condition). Ss given the shift-depletion task learned most rapidly; those given the stay-depletion task learned most slowly. Depletion increased the rate at which the shift discrimination was learned but decreased the rate at which the stay discrimination was learned. Exp II used a similar procedure with the Maier 3-table maze and 16 male albino rats; the same pattern of results was found. Exp III, conducted with 15 male Sprague-Dawley rats, required each S to learn both a win-stay and a lose-shift contingency and to use associative memory. Early in training, Ss used only a shift strategy but eventually learned the discrimination. Results indicate that the shift-stay balance is influenced by the rat's species-specific predisposition, reinforcement contingencies, amount of food in the initially visited place, and the extent to which recognition memory by itself is sufficient to solve the discrimination. (48 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Habituation of the acoustic startle response in rats after lesions in the mesencephalic reticular formation or in the inferior colliculus.

Extensive damage to the mesencephalic reticular formation (MRF) in 24 male albino rats altered long-term habituation of the acoustic startle response without disrupting short-term habituation. The MRF lesions did not alter initial startle amplitudes, but the Ss with lesions were unable to attain as low a long-term asymptote of habituation as could 21 control Ss. Subsequent manipulation of stimulus intensity and interstimulus interval revealed no differences in short-term habituation between the 2 groups. Large lesions to the inferior colliculus (IC) of 22 Ss did not disrupt long-term habituation of the acoustic startle response, but these Ss were unable to suppress responding as much as controls to intense stimuli presented rapidly. The deficits in long-term habituation following MRF lesions suggest a disruption of an extrinsic, inhibitory mechanism of habituation. The deficits following IC lesions could have been due either to a disruption of a short-term habituation mechanism or to an increase in response sensitization produced by the lesions. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tests of a translational model of Stroop interference: Translation or attention?

Examined the hypothesis that Stroop interference would increase in both the position and word tasks when the 2 task were mixed. In Exp 1, 34 Ss reported the position of a word by a manual response or read the word aloud. Results show that substantial interference occurs when Ss must be prepared to respond to either dimension, suggesting that translation is an obligatory process when attention is divided between the 2 dimensions. Exp 2 (40 Ss) showed that this interference is reduced if a cue that indicates the relevant dimension is presented 300 or 1,000 ms prior to the stimulus. Results are discussed in terms of a strength of processing model in which the degree of Stroop interference is attributed to the degree of attention to the irrelevant dimension of the Stroop stimulus. This model assumes that the degree of attention to a stimulus dimension is subject to both top-down and bottom-up influences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Posterodorsal septal lesions impair performance on both shift and stay working memory tasks.

Two groups of male Long-Evans rats (N?=?42) were trained preoperatively on either a shift or a stay problem in a T-maze. Training trials consisted of 2 runs, an "information run" in which S was forced to go down 1 of the 2 arms of the T-maze, followed immediately by a "choice run" in which S could choose either arm. In the shift condition, Ss were rewarded with wet mash only for choosing the arm opposite the one they entered on the information run. In the stay condition, Ss were rewarded for entering the arm that was entered on the information run. The shift group reached 100% performance accuracy after fewer trials than the stay group. Choice accuracy in both groups declined as the delay increased and returned to 100% at the 0-sec delay. Half of the Ss in each condition then received either lesions of the posterodorsal septum—aimed at disconnecting the septum and hippocampus—or control surgery. Results indicate that deficits in maze performance by Ss with septo-hippocampal damage were not restricted to tasks that require alternation of spatial locations. This finding falsifies the notion that maze deficits reflect a spontaneous alternation deficit or changed "spatial strategy," but it supports the hypothesis of a working memory deficit in these Ss. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fimbria-Fornix lesions impair spatial working memory but not cognitive mapping.

Evaluated the relative merits of 2 theories of hippocampal function, the cognitive mapping theory, and the working memory theory. 49 albino male rats were tested in a series of maze tasks that varied in memory requirements. In Exps I and III, which required cognitive mapping but not working memory, Ss with fimbria–fornix lesions reached stable levels of performance that were as accurate as those of controls, and they also performed accurately during transfer tests, demonstrating that they used a cognitive mapping strategy to solve the discrimination. In Exp II, which required working memory, Ss with fimbria–fornix lesions performed at chance levels during all of postoperative testing, and they distributed their choices randomly between the correct and the incorrect goals. Results are consistent with the predictions of the working memory but not the cognitive mapping theory. Additional analyses examined the nature of a transitory impairment exhibited by Ss with fimbria–fornix lesions in 2 tasks that did not require working memory. Postoperatively, the performance of the Ss with lesions was initially impaired but recovered to normal levels with a time course similar to that seen during preoperative acquisition. Results require an extension of the working memory theory of hippocampal function, and discussion is focused on the possibility of a temporary retrograde amnesia following fimbria–fornix lesions and the distinctions between different types of memory abilities. (51 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mood, self-efficacy, and performance standards: Lower moods induce higher standards for performance.

Examined the effects of induced mood on personal standards for performance and judgments of one's performance capabilities, or self-efficacy judgments. Three experiments involving 208 undergraduates were conducted. In Exp 1, standards and self-efficacy judgments were assessed on common social and academic tasks. In Exp 2, these variables were assessed on 2 novel tasks. In both experiments, negative mood induced higher standards for performance. Induced mood had no effect on perceived self-efficacy. Negative mood Ss thus held minimal standards for performance that significantly exceeded the levels of performance they judged they actually could attain. Exp 3 provided support for the hypothesis that negative mood raises standards by lowering evaluations of prospective outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of neonatal dopamine depletion on spatial ability during ontogeny.

Investigated the effects of neonatal dopamine (DA) depletion on spatial discrimination tasks. Ss were lesioned at 3 and 6 days of age with intraventricular 6-hydroxydopamine preceded by Desipramine. In Exp 1, Ss were tested before weaning for the ability to spontaneously alternate in a T maze both in the presence of their home cage shavings and with a screen covering the shavings. Lesioned Ss were significantly impaired in their ability to spontaneously alternate. Control and lesioned Ss both showed a decrease in performance when the screen prevented full access to the shavings and the magnitude of the impairment was significantly greater for the lesioned animals. In Exp 2, Ss were tested after weaning in an appetitively motivated task in T maze. The task required both a functional working and reference memory. Lesioned Ss were impaired on both the working and the reference components of the task; however, the magnitude of the impairment was greater in the working memory task. Results suggest that early lesions of general DA systems produce deficits in tasks requiring spatial alternation behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Strychnine increases acoustic startle amplitude but does not alter short-term or long-term habituation.

Used the glycine antagonist strychnine (1.0 mg/kg, ip, 10 min before treatment) to investigate the involvement of glycinergic neurons in the development and/or expression of short-term (within-session) habituation (Exp I) and long-term (between-sessions) habituation (Exps II and III) of the acoustic startle response in 120 male albino Sprague-Dawley rats. Over a range of eliciting-stimulus intensities (95, 105, and 115 db) and interstimulus intervals (3, 7, 13, and 27 sec), strychnine markedly increased startle amplitude, relative to water injection, whereas it failed to attenuate the rate of within-session habituation (Exp I). In Exp II, Ss that were exposed to daily sessions of startle-eliciting stimuli for 4 days and then tested on Day 5 showed lower levels of startle amplitude than Ss with no prior habituation training. Strychnine injected prior to the test session again increased startle amplitude but did not block the expression of between-sessions habituation. In Exp III, Ss injected with either strychnine or water prior to each of 3 daily habituation training sessions and subsequently tested on Day 4 showed similar between-sessions habituation. In general, results show that strychnine increased startle amplitude without affecting either within-session or between-sessions habituation of acoustic startle. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory discrimination in rats with anterior amygdala lesions.

In Exp I, 12 male rats with posterior lateral olfactory tract/anterior amygdala lesions or with control neocortical lesions were tested for retention of a preoperatively learned odor detection task and for learning on new odor discrimination problems. All Ss had perfect or near-perfect retention of the detection task, and there were no discernible differences between groups in learning on the new odor discrimination problems. In Exp II, an intensity-difference threshold for olfaction was determined in 4 male Long-Evans rats before and after similar lesions. There were no apparent differences between pre- and postoperative performances on this psychophysical test. Results indicate that lateral olfactory tract projections to the amygdala and posterior olfactory cortex are not essential for normal performance on simple olfactory discrimination tasks, although the more caudal projections of the olfactory bulb play an important role in the arousal and maintenance of certain species-typical behaviors. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of overtraining on reversal and extradimensional shifts in schizophrenics.

In Exp. I, 50 schizophrenic Ss were trained under 1 of 3 discrimination learning conditions: reversal (R) shift, extradimensional (ED) shift, or control. 1/2 of the Ss in each shift condition received overtraining on the preshift discrimination. Performances of nonovertrained Ss on the R and ED shifts were very similar to performances of schizophrenic Ss tested by J. D. Nolan (see 42:11). Newman-Keuls analyses indicate that overtraining facilitated the R shift relative to the ED shift. The result was a significant overall effect due to shift type. In Exp. II, a replication of Exp. I, 60 undergraduates learned R shifts faster than ED shifts, but overtraining had no discernible effect. Results were compared with those reported by Nolan and were discussed in terms of a 2-stage attention model of discrimination learning. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Impulsivity and perception: Individual differences in the processing of the local and global dimensions of stimuli.

In Exp I, 48 undergraduates differing in impulsivity (as measured by a self-report inventory) performed 2 versions of filtering, interference, and invariant control tasks. In one version, Ss sorted according to the value of the local dimension; in the other, the global dimension was the relevant one. In addition, Ss performed a task in which the 2 dimensions were perfectly correlated. Results show that Ss sorted more quickly when the global dimension was relevant than when the local dimension was relevant. In Exp II, 43 of the Ss from Exp I were used to determine whether failure to find a relationship between impulsivity and filtering performance was due to correlations of local and global dimensions; results were negative. In Exp III, the same 43 Ss used in Exp II were used to test the information-integration hypothesis. Results support the hypothesis—high impulsives were more impaired than other Ss when the task required that they integrate information from the global dimension with information from the local dimension. Findings can be explained in terms of individual differences in the value placed on speed, relative to accuracy, in information processing. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)