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PubMed1991

Behavioural rigidity and rule-learning deficits following isolation-rearing in the rat: neurochemical correlates.

Isolation-reared rats were compared to those reared in social groups on the acquisition of a conditional visual discrimination (Expt. I), a simultaneous (simple) light/dark discrimination and serial reversal learning (Expt. II). In Expt. I, rats reared in social isolation made more errors during the acquisition of the conditional discrimination but did reach a level of accurate performance which was comparable with that of socially-reared rats. Discrimination performance in isolates was less disruptable by manipulations of the task requirements. Reducing the number of stimulus lights or the introduction of a distracting stimulus increased the number of errors committed by socially-reared rats but did not significantly affect accuracy in isolates. Performance in isolated rats was also remarkably resistant to changes in motivational variables. Isolates responded more frequently during conditions of extinction and were virtually unaffected by pre-feeding prior to testing. In Expt. II, isolation-reared rats were not impaired in the acquisition of a simultaneous discrimination but unlike socially-reared rats isolates failed to show improvement with successive reversals of this discrimination. Isolates exhibited stronger position habits than socially-reared rats following reversal of the contingencies. These results of these two experiments combined have demonstrated a specific impairment in rule learning in isolates. Isolated rats were not impaired on a simultaneous discrimination in which accurate performance can be achieved simply by approaching the stimulus associated with reinforcement, but performed worse than controls on both the conditional discrimination and on serial reversal learning, another form of conditional task. In both of these latter tasks each stimulus becomes equally associated with reward and therefore performance can be improved by learning a rule. Post-mortem neurochemical measurements made at the completion of Expt. II revealed selective alterations in dopaminergic, serotoninergic and cholinergic markers in isolated rats. Correlational analyses indicated specific relationships between neurochemical and behavioural measurements.

Animals↗
PubMed1995

Encoding specificity and intrusion in Alzheimer's disease and amnesia.

This study was designed to examine how the pattern of memory deficits and the interaction between episodic and semantic encoding/retrieval conditions influenced intrusions in a population of Alzheimer and amnesic patients. We used as a model for an encoding/retrieval experiment a 2 x 2 experimental design in which two encoding conditions are crossed with two retrieval conditions. It was found that encoding specificity affected intrusions only if patients, regardless of their clinical diagnosis, were grouped according to the type of memory impairment.

Aged↗
PubMed1995

High-priority event instructions affect implicit and explicit memory tests.

Previous work has shown that instructing subjects to give special priority to one target event in a list enhances recall for that event, but impairs recall for the events immediately preceding it (Tulving, 1969). We examined the benefit of high-priority instructions, and the retrograde amnesia for previous items, in three experiments that included two explicit tests of memory (free recall and cued recall with word-stem cues) and an implicit test (word-stem completion). Experiments 1 and 2 revealed a beneficial effect of high-priority instructions on memory for the target events in both free recall and primed word-stem completion. Retrograde amnesia for previous events was either absent (Experiment 1) or modest (Experiment 2) in free recall; however, no evidence for amnesia occurred on the implicit test. In Experiment 3, we asked if the benefit of high-priority instructions on the implicit test was due to contamination from intentional recollection, by employing the logic of the retrieval-intentionality criterion via a levels-of-processing manipulation. The results showed a beneficial effect of high-priority instructions on free recall, word-stem cued recall, and word-stem completion. Level of processing affected the two explicit tests, but not the implicit test, indicating that it induced incidental retrieval. We conclude that the benefit of high-priority instructions occurred on all three tests used in these experiments. In contrast, the phenomenon of retrograde amnesia occurred in free recall, but not in primed word-stem completion.

Adult↗
PubMed1994

Anomia for people's names.

The case of an anomia for people's names is reported. The study of this dissociation helps to clarify the difference in processing between proper and common names. Associated deficits in this and previously described cases provide support for the idea that an inability to retrieve arbitrary relations is the basis of the naming difficulty. This would confirm the role of proper names as purely referring expressions.

Adult↗
PubMed2003

Lesioning of spatial memory in mice treated with agroclavin.

This report presents results obtained from studies of the mnemotropic activity of the ergot alkaloid agroclavin. The effects of this substance were studied at concentrations of 1, 10, 25, 50, and 200 microg/kg on the learning and retention of a spatial habit in a Morris water maze. These doses of agroclavin had no effect on the process of formation of the spatial habit, but sharply disturbed retention of the habit. A long-lasting effect of memory trace disturbance was seen over a period of 48 h after dosage. On retraining, animals showed no delayed effects with agroclavin on learning a new spatial habit. The possible mechanisms for the effect of agroclavin on memory are discussed.

Animals↗
PubMed1985

Memorability as a measure of processing: a unit analysis of prose and list learning.

The percentage of subjects recalling each unit in a list or prose passage is considered as a dependent measure. When the same units are recalled in different tasks, processing is assumed to be the same; when different units are recalled, processing is assumed to be different. Two collections of memory tasks are presented, one for lists and one for prose. The relations found in these two collections are supported by an extensive reanalysis of the existing prose memory literature. The same set of words were learned by 13 different groups of subjects under 13 different conditions. Included were intentional free-recall tasks, incidental free recall following lexical decision, and incidental free recall following ratings of orthographic distinctiveness and emotionality. Although the nine free-recall tasks varied widely with regard to the amount of recall, the relative probability of recall for the words was very similar among the tasks. Imagery encoding and recognition produced relative probabilities of recall that were different from each other and from the free-recall tasks. Similar results were obtained with a prose passage. A story was learned by 13 different groups of subjects under 13 different conditions. Eight free-recall tasks, which varied with respect to incidental or intentional learning, retention interval, and the age of the subjects, produced similar relative probabilities of recall, whereas recognition and prompted recall produced relative probabilities of recall that were different from each other and from the free-recall tasks. A review of the prose literature was undertaken to test the generality of these results. Analysis of variance is the most common statistical procedure in this literature. If the relative probability of recall of units varied across conditions, a units by condition interaction would be expected. For the 12 studies that manipulated retention interval, an average of 21% of the variance was accounted for by the main effect of retention interval, 17% by the main effect of units, and only 2% by the retention interval by units interaction. Similarly, for the 12 studies that varied the age of the subjects, 6% of the variance was accounted for by the main effect of age, 32% by the main effect of units, and only 1% by the interaction of age by units.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed2004

Intentional control and implicit sequence learning.

Sequence knowledge acquired by repeated exposure to targets in a speeded localization task was studied in 3 experiments that sought to test A. Destrebecqz and A. Cleeremans's (2001, 2003) claim that, under certain circumstances, the expression of such sequence knowledge cannot be brought under intentional control. In Experiment 1 participants were trained on either a deterministic or a probabilistic sequence and then performed a free-generation test under either inclusion or exclusion instructions. Participants were found to be capable of both expressing (inclusion) and avoiding expressing (exclusion) sequence knowledge. These results were confirmed in Experiment 2 with a more exact replication of Destrebecqz and Cleeremans's methodology. In Experiment 3 participants performed a trial-by-trial generation test under both inclusion and exclusion conditions after a much longer period of training. All the findings are consistent with the proposal that information acquired during sequence learning is explicit in nature.

Adult↗
PubMed1991

Elicited responding in chain schedules.

An omission procedure was employed to study elicited pecking in the first component of a two-component chain schedule. Both components were fixed-interval schedules correlated with colored keylights. The first response following the initial-link schedule produced a second fixed-interval schedule. We studied several fixed-interval lengths in two conditions: a standard response-dependent condition and an omission-contingent condition. The omission-contingent condition differed from the response-dependent condition in that responses during the initial fixed interval terminated the trial (omitting the terminal component and grain). If the terminal component was not omitted, a response following the terminal link's requirement produced 4-s access to grain. Pigeons responded during more than 70% of the initial links in the omission-contingent condition and responded during more than 90% of the initial links in the response-dependent condition. In general, rates of responding were consistent with the percentage data. The responding in the omission condition suggests that there may be elicited pecking, in chain schedules using pigeons, that is not the result of contingent conditioned reinforcement.

Animals↗