The effects of dark isolation on the performance of a white-black discrimination task in the rat.

Four experiments were performed on rats using a white-black discrimination task. In Exp. 1 the animals that were isolated in darkness for four hours after each learning trial performed with fewer errors than the animals that spent the same posttrial periods in enriched environments in groups. In Exp. 2 training was carried further and retention after 10 days was investigated. The isolated animals again performed with fewer errors. In Exp. 3 a control was added to the Isolated and Enriched conditions. Animals in the control group were returned to their home cages after each training trial. No difference was found between Enriched and Control animals. In Exp 4 Dark-Isolated, Light-Isolated, Dark-Crowded and Light-Crowded groups were used. The performance of the two Dark-treated groups was superior to that of the Light-treated groups. The findings are discussed with reference to interference and consolidation theory.     

Acute and repeated effects of three organophosphorus pesticides on the acquisition and retention of an instrumental learning task in rats

The effects of organophosphorus pesticides on higher functions of the central nervous system are not well understood yet. As a first approach, the acute and repeated effects of three organophosphorus pesticides on learning and memory capabilities of behaving adult rats were studied here. Prior to training, animals received acute or repeated (5-day, 15-day, and 30-day) doses of diazinon, malathion, or fenitrothion. Animals were trained with an operant conditioning test, using a fixed-interval (FI 2 min) paradigm. Fifteen days later, animals were tested for retention of the learned task. Specific modifications in some selected behavioral displays were also quantified across the training process. Although their motor behaviors were not affected, treated animals required longer times for the acquisition of the fixed-interval test than did controls. As opposed to controls, not all (45.8% for diazinon, 66.6% for malathion, and 62.5% for fenitrothion) treated animals reached criterion during the retention test. Specific behaviors, such as grooming, rearing, exploratory whisking, and freezing, were modified at different levels by some (or all) of the three organophosphorus pesticides. According to these results, the three organophosphorus pesticides used here affected the acquisition and, mainly, the retention of instrumental conditioning, using a fixed-interval paradigm. The presentation of some specific behavioral displays was also modified in treated animals.     

An operant serial implicit learning task (SILT) in rats: task acquisition, performance and the effects of striatal lesions

We describe the serial implicit learning task (SILT), a novel test for assessing implicit and procedural learning in rodents, and have used the task to test whether striatal lesions disrupt the speed and accuracy of responding to stimulus-response (S-R) sequences that may be either predictable or unpredictable. In this task, the rats must learn to respond to two consecutive stimulus lights, S1 and S2, which may occur on each trial in any of five alternative response locations, for food reward. For two of the S1 locations, the location of the subsequent S2 is predictable, whereas for the other three S1 locations, the location of S2 is unpredictable and can appear with equal probability in any of the other four locations (i.e. any open hole other than S1 itself). All rats learned to make the serial responses rapidly and accurately. Effective implicit learning was demonstrated by there being a significant advantage in both speed and accuracy in responding to predictable than to unpredictable S2 stimuli. Following quinolinic acid lesions of the medial or lateral striatum, the lesioned rats showed significantly reduced accuracy and increased latencies in responding to both S1 and S2, although (contrary to initial hypothesis) the benefits of predictability of S2 were retained. These data establish a novel and efficient operant test for implicit learning in the rat.     

Multiple learning modes in the development of performance on a rule-based category-learning task

Behavioral and neuropsychological data suggest that multiple systems are involved in category-learning. In this paper, the existence and the development of multiple modes of learning of a rule-based category structure was examined, and features of different learning processes were identified. Data were obtained in a cross-sectional study by Raijmakers et al. [Raijmakers, M. E. J., Dolan, C. V., & Molenaar, P. C. M. (2001). Finite mixture distribution models of simple discrimination learning. Memory and Cognition, 29, 659-677], in which subjects aged 4-20 years carried out a rule-based category-learning task. Learning models were employed to investigate the development of the learning processes in the sample. The results support the hypothesis of two distinct learning modes, rather than a single general mode of learning with a continuum of appearances. One mode represents sudden rational learning by means of hypothesis testing. In the second, slow learning mode, learning also occurs suddenly as opposed to incrementally. The probability of rational learning increases with age, and seems to be related to dimension preference in the younger age groups. However, the finding of distinct learning modes does not necessarily imply that distinct learning systems are involved. Implications for the interpretation and clinical use of tasks with a category-learning component, such as the Wisconsin Card Sorting Test (WCST [Heaton, R. K., Chelune, G. J., Talley, J. L., Kay, G. G., & Curtis, G. (Eds.). (1993). Wisconsin card sorting test manual: Revised and expanded. Odessa, FL: Psychological Assessment Resources]), are discussed.     

The role of dopamine in learning, memory, and performance of a water escape task

Dopamine-deficient (DD) mice have selective inactivation of the tyrosine hydroxylase gene in dopaminergic neurons, and they die of starvation and dehydration at 3-4 weeks of age. Daily injections of L-DOPA (50 mg/kg, i.p.) starting approximately 2 weeks after birth allow these animals to eat and drink enough for survival and growth. They are hyperactive for 6-9 h after receiving L-DOPA and become hypoactive thereafter. Because these animals can be tested in the presence or absence of DA, they were used to determine whether DA is necessary for learning to occur. DD mice were tested for learning to swim to an escape platform in a straight alley in the presence (30 min after an L-DOPA injection) or absence (22-24 h after an L-DOPA injection) of dopamine. The groups were split 24 h later and retested 30 min or 22-24 h after their last L-DOPA injection. In the initial test, DD mice without dopamine showed no evidence of learning, whereas those with dopamine had a learning curve similar in slope to controls but significantly slower. A retest after 24 h showed that DD mice can learn and remember in the absence of dopamine, leading to the inference that the lack of dopamine results in a performance/motivational decrement that masks their learning competence for this relatively simple task.     

The effects of pregnenolone sulfate and ethylestrenol on retention of a passive avoidance task

Two experiments using male rats evaluated the effects of a range of doses of the neurosteroid, pregnenolone sulfate (PS), or of the synthetic neurosteroid, ethylestrenol (E), on the retention of a passive avoidance task. The steroids either were given immediately after the training trial or 1 h before the first retention test. Retention tests were given both 24 h and 48 h after acquisition. In both experiments, separate groups of animals were trained under low or moderate footshock conditions. At all doses tested both PS and E improved retention under the low footshock conditions. In groups trained with the higher footshock, the steroid-treated groups performed no better than the vehicle controls. Indeed, there were suggestions that some doses impaired retention. These results seem best understood as an induction of bimodality or ‘turbulence’ in behavior as used in Chaos theory rather than a shift in an inverted U-shaped retention function. In the second experiment in which the steroids were given before retention testing, they were generally without effect.     

Motor learning in children with spina bifida: intact learning and performance on a ballistic task.

Learning and performance on a ballistic task were investigated in children with spina bifida meningomyelocele (SBM), with either upper level spinal lesions (n = 21) or lower level spinal lesions (n = 81), and in typically developing controls (n = 35). Participants completed three phases (20 trials each) of an elbow goniometer task that required a ballistic arm movement to move a cursor to one of two target positions on a screen, including (1) an initial learning phase, (2) an adaptation phase with a gain change such that recalibration of the ballistic arm movement was required, and (3) a learning reactivation phase under the original gain condition. Initial error rate, asymptotic error rate, and learning rate did not differ significantly between the SBM and control groups. Relative to controls, the SBM group had reduced volumes in the cerebellar hemispheres and pericallosal gray matter (the region including the basal ganglia), although only the pericallosal gray matter was significantly correlated with motor adaptation. Congenital cerebellar dysmorphology is associated with preserved motor skill learning on voluntary, nonreflexive tasks in children with SBM, in whom the relative roles of the cerebellum and basal ganglia may differ from those in the adult brain.     

The effects of aging on the neural basis of implicit associative learning in a probabilistic triplets learning task

Few studies have investigated how aging influences the neural basis of implicit associative learning, and available evidence is inconclusive. One emerging behavioral pattern is that age differences increase with practice, perhaps reflecting the involvement of different brain regions with training. Many studies report hippocampal involvement early on with learning becoming increasingly dependent on the caudate with practice. We tested the hypothesis that the contribution of these regions to learning changes with age because of differential age-related declines in the striatum and hippocampi. We assessed age-related differences in brain activation during implicit associative learning using the Triplets Learning Task. Over three event-related fMRI runs, 11 younger and 12 healthy older adults responded to only the third (target) stimulus in sequences of three stimuli ("triplets") by corresponding key press. Unbeknown to participants, the first stimulus' location predicted one target location for 80% of trials and another target location for 20% of trials. Both age groups learned associative regularities but differences in favor of the younger adults emerged with practice. The neural basis of learning (response to predictability) was examined by identifying regions that showed a greater response to triplets that occurred more frequently. Both age groups recruited the hippocampus early, but with training, the younger adults recruited their caudate whereas the older adults continued to rely on their hippocampus. This pattern enables older adults to maintain near-young levels of performance early in training, but not later, and adds to evidence that implicit associative learning is supported by different brain networks in younger and older adults.     

The effects of handedness,family history and sex on the performance of a dichotic listening task

The effects of handedness, family history of handedness, sex, and ear differences on the performance of a dichotic listening task by 120 college students were studied. The sample, as a whole, showed a significant right ear superiority. Females made fewer errors than males. There were no significant main effects of family history or handedness nor were any of the interactions significant. It was suggested that right ear dominance is more prevalent than is generally supposed. A possible relationship between ear asymmetries and intellectual level was discussed.     

The significance of circadian phase for performance on a reward-based learning task in hamsters

In humans and animal models, circadian modulation of learning has been demonstrated on numerous tests. However, it is unclear which aspects of the cognitive process are rhythmically regulated. In these experiments, we used a conditioned place preference task in hamsters to ask whether memory acquisition (hypothesis 1) or memory recall and performance (hypothesis 2) were subject to circadian modulation. In golden hamsters, access to a running wheel has been used as a reward to condition a place preference, but when given unrestricted access to a wheel, animals perform most of their spontaneous running within a few hours each day or circadian cycle. This suggested that either the perceived reward value of the wheel changes through the day or that the response to this reward is temporally restricted. Contrary to the hypotheses, we found that learning was not tied to the time of training nor to the time of testing, but rather animals showed a preference for a reward-paired context only at the circadian time that training had taken place. Timing is not an explicit discriminative cue in these experiments. Hence, the learning mechanism must be predisposed to register circadian time as an attribute during context learning.     

The effects of number of trials per day, retention interval, gender and time of day on acquisition of a two-choice, win-stay water-escape working memory task in the rat.

A 2 x 2 x 2 factorial study was conducted to examine the effects of gender, trials/day (TPD), and retention interval (RI) on acquisition of a two-choice win-stay water-escape task in 4-month-old Sprague-Dawley rats. Variations of this task have previously been shown to be sensitive to changes in working memory that occur with age (Means and Kennard, 1991) or to follow treatment with an anxiolytic (Bass et al., 1989) or with cognitive enhancers (Comer and Moore, in press) in males or to estrogen in ovariectomized females (O'Neal et al., 1990). Both training with 1 TPD and with a 5-min RI, time between an information "run" and a test "run", reduced errors during acquisition as compared to giving 3 TPD and a 1-min RI (P less than 0.05 in all cases). Males made fewer errors than did females (P less than 0.05). The three effects were additive: males trained with 1 TPD and a 5-min RI performed best and females trained with 3 TPD and a 1-min RI performed worst. Also, rats given 1 TPD made fewer acquisition errors when trained 2 h before the lights were turned off than when trained during the middle of the light portion of the light/dark cycle (P less than 0.05). Finally, when given 3 TPD, the rats, especially the females, performed significantly worse on their third trial (P less than 0.05). It was concluded that two-choice win-stay water-escape is a very sensitive assay of working memory with much potential for neurobehavioral research.     

Circadian modulation of performance on an aversion-based place learning task in hamsters

In golden hamsters, the expression of a reward-conditioned place preference (CPP) is regulated in a circadian pattern such that the preference is exhibited strongly at the circadian time of prior training but not at other circadian times. We now report that the same “time-stamp” phenomenon is expressed following context conditioning with an aversive stimulus (conditioned place avoidance, CPA). Animals that were trained at a specific circadian time to discriminate between a “safe” context and one paired with foot shock, showed strong avoidance of the paired context at 24 and 48 h following the last training session, and showed no avoidance at 32 and 40 h following training. Circadian time is a feature that is learned during conditioning even though timing itself is not an explicit discriminative cue in these experiments. The results suggest that in hamsters, the emotional valence associated with the place where arousing stimulation (rewarding and aversive) is encountered is highest at the circadian time of occurrence. The golden hamster may be predisposed to anticipate the recurrence of arousing events at circa-24 h intervals.     

GF 109203X, a selective inhibitor of protein kinase C, impairs retention performance in an operant task.

The effects of post-training administration of GF 109203X (5 and 50 ng i.c.v.), a selective inhibitor of protein kinase C, on retention performance were investigated in a positively reinforced lever press task, in male Swiss mice. Both doses of GF 109203X suppressed the spontaneous improvement of performance observed in control animals between the last 5 min of the acquisition session and the first 5 min of the retention session 24 h later. GF 109203X had no effect on food intake and locomotor activity. These data suggest that GF 109203X selectively interferes with mechanisms underlying post-training organization of information and that protein kinase C is involved in this memory process.     

Coping styles, cortisol reactivity, and performance in a vigilance task of patients with persistent postconcussive symptoms after a mild head injury.

Some patients experience persistent postconcussive symptoms (PCS) after a mild head injury (MHI). According to the coping hypothesis, PCS result from the increased stress that head-injured patients experience when they are not able to cope with environmental demands. This study examined the coping ability and cortisol reactivity of MHI patients with and without PCS and in uninjured controls. Patients with PCS 12-34 months after injury were individually matched with MHI patients without PCS (N = 11) and healthy controls (N = 11) for the time elapsed since the injury, age, sex, education, and IQ. First, we found that patients with PCS reported being less able to cope with problems. These patients appeared to be inferior in active problem solving and had a more depressive attitude toward problems than subjects of the two control groups. Second, we found no differences between the three groups in the mean cortisol response during a vigilance task. These results only partly support the coping hypothesis. With respect to cognitive performance, we found that decrements in a vigilance task were related to an increased cortisol response during this task, especially in apparently "recovered" (asymptomatic) MHI patients. The latter finding may point to an increased cognitive vulnerability of apparently recovered MHI patients when exposed to a CNS stressor.     

Evaluating the effects of organizational variables on task performance of administrators

The performance of managerial task activities by mental health/human services administrators is reviewed. Variations in performance of these managerial activities are analyzed to determine the effects of institutional variables. Significant associations of task performance and the four institutional variables of size of administrative staff, size of professional staff, industry/organization type, and professional background of the administrator were found.Alton C. Johnson, Ph.D is with the Graduate School of Business, University of Wisconsin-Madison. Christopher R. Forrest, Ph.D. is with the Department of Continuing Education in Administration, Health and Human Services Area, University of Wisconsin-Extension, Madison, WI53706. Portions of the research here were supported by the Center for State Mental Health Manpower Department, Division of Manpower and Training Programs of the National Institute of Mental Health, Grant #ST23MH15017-02. This article is based in part on a paper presented at the National Academy of Management Meeting, August, 1980.     

Hippocampal lesions impair performance on a conditional delayed matching and non-matching to position task in the rat

The hippocampus is thought to be involved in a range of cognitive processes, from the ability to acquire new memories, to the ability to learn about spatial relationships. Humans and monkeys with damage to the hippocampus are typically impaired on delayed matching to sample tasks, of which the operant delayed matching to position task (DMTP) is a rat analogue. The reported effects of hippocampal damage on DMTP vary, ranging from delay-dependent deficits to no deficit whatsoever. The present study investigates a novel memory task; the conditional delayed matching/non-matching to position task (CDM/NMTP) in the Skinner box. CDM/NMTP uses the presence of specific stimulus cues to signify whether a particular trial is matching or non-matching in nature. Thus, it incorporates both the task contingencies within one session, and supplements the requirement for remembering the side of the lever in the sample phase with attending to the stimulus and remembering the conditional discrimination for the rule. Rats were trained preoperatively and the effects of bilateral excitotoxic lesions of the hippocampus were examined on postoperative retention of the task. Rats with lesions of the hippocampus incurred a significant impairment on the task that was manifest at all delays intervals. Despite a bias towards matching during training, trials of either type were performed with equivalent accuracy and neither rule was affected differentially by the lesion. This task may prove useful in determining the cognitive roles of a range of brain areas.     

ERP development in the rat in the course of learning two-tone discrimination task

To clarify some neurophysiological aspects of learning, we investigated the relationship between the course of learning and development of ERP and investigated developmental processes of ERPs. Nine male Sprague-Dawley rats were trained for a two-tone discrimination task and rat P3 and N1 component were longitudinally recorded. Both rat P3 and N1 gradually increased with learning only for target tones. An improvement in the proportion of correct responses preceded the increase in ERPs, and the increase in P3 and N1 proceeded almost simultaneously. These findings suggest that multiple kinds of information processing were acquired with learning the two-tone discrimination task. ERP development could be utilized as an index of establishment of learning.