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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↗

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↗

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↗

Time-sharing in the continuous distractor paradigm: a reexamination of the long-term recency effect.

Long-term recency effects observed in the continuous distractor paradigm are often taken as evidence against the short-term store account of recency effects. In the present study, three experiments examined the function of time-sharing process in the continuous distractor paradigm. In the first two experiments, the effect of distractor difficulty on long-term recency was investigated with easy and hard distractor tasks. Distractor difficulty was manipulated in the recency portion and in the retention interval of a nine-word list and a hard distractor task eliminated long-term recency effects. In Exp. 3, distractor difficulty was manipulated across the first and the second halves of the retention interval. Long-term recency effects were larger if the first half of the retention interval contained an easy distractor task and the second half a hard task than if the order was hard-easy. These results indicate that subjects maintain recent items in short-term store and then transfer them to a long-term store by the time-sharing process during a distraction period. Long-term recency effects to a large extent depend on this time-sharing process.

Adult↗

List length and overlap effects in forced-choice associative recognition.

Two experiments examined forced-choice associative recognition for OLAP and NOLAP test conditions. OLAP test trials consist of pairs with overlapping items (e.g., AB vs. AD), whereas NOLAP test trials contain no overlapping items (e.g., AB vs. CF). Previous results show better performance for NOLAP than for OLAP tests, contrary to the predictions of global memory models. The present experiments varied list length to examine the hypothesis that the NOLAP advantage is produced by recall-like retrieval processes. The use of longer lists either eliminated (Experiment 1) or greatly reduced (Experiment 2) the NOLAP advantage. However, a reliable OLAP advantage was not obtained. Implications for models are discussed.

Adult↗

Encapsulation of implicit and explicit memory in sequence learning.

Contrasts between implicit and explicit knowledge in the serial reaction time (SJRT) paradigm have been challenged because they have depended on a single dissociation; intact implicit knowledge in the absence of corresponding explicit knowledge. In the SRT task, subjects respond with a corresponding keypress to a cue that appears in one of four locations. The cue follows a repeating sequence of locations, and subjects can exhibit knowledge of the repeating sequence through increasingly rapid performance (an implicit test) or by being able to recognize the sequence (an explicit test). In our study, amnesic patients were given extensive SRT training. Their implicit and explicit test performance was compared to the performance of control subjects who memorized the training sequence. Compared with control subjects, amnesic patients exhibited superior performance on the implicit task and impaired performance on the explicit task. This crossover interaction suggests that implicit and explicit knowledge of the embedded sequence are separate and encapsulated and that they presumably depend on different brain systems.

Aged↗

Negative priming in associative learning: evidence from a serial-conditioning procedure.

Three experiments investigated the suggestion that a predicted or primed stimulus commands less processing and consequently elicits a weaker conditioned response (CR) than a stimulus that is not primed. In each experiment rats received initial training in which the presentation of each of 2 serial compounds, A-X and B-Y, was followed by the delivery of food. Subsequently, X's capacity to elicit the CR, approaching the site of food delivery, was assessed when X was preceded by Stimulus A (i.e., primed) or was presented after Stimulus B. Stimulus X elicited a more vigorous response when it was presented after B than when it followed A. These results show that the ability of one event to elicit its CR is reduced if its presentation has been predicted by some other event. This negative priming effect supports one aspect of Wagner's (1981) model of Pavlovian conditioning.

Animals↗

The recall of digits by normal, deaf and autistic children.

Normal, autistic and deaf children were tested for their immediate memory of visually presented digits. The digits were exposed either with or without a left to right spatial display arrangement, and had to be recalled forewards as well as backwards. Normal and deaf children tended to be sensitive to both display conditions and recall requirements whereas autistic children were mainly affected by direction of recall. Serial position effects in the normal and deaf groups were more dependent on order of retrieval than on input order.

Autistic Disorder↗

Construct validity of various verbal and visual memory tests.

Factor analysis was conducted on attention, information processing, verbal and visual memory scores of 112 patients. Factor structure did not vary as a function of age. The Expanded Paired Associates Test, Verbal Selective Reminding Test, Continuous Recognition Memory Test, and Continuous Visual Memory Test defined a general memory factor. The PASAT, WMS Mental Control, and WAIS-R Digit Span defined an attention/information processing factor. Immediate Visual Reproduction (VR) loaded primarily on visual/nonverbal intelligence, whereas delayed VR loaded primarily with the memory factor. The Trail Making Test, Part B was more closely associated with visual/nonverbal intelligence than with attention/information processing. Serial Digit Learning was more closely associated with attention/information processing than with general memory.

Adolescent↗

Stimulus novelty and significance as determinants of electrodermal responsivity: the serial position effect.

Three experiments examined the effects of stimulus novelty and significance on the skin conductance component of the orienting response. The test stimuli used in the different experiments involved either a neutral change in stimulation (i.e., adding or deleting components to the standard stimuli), or an introduction of a significant element to the standard stimulus. The serial position of the test stimulus was manipulated in all three experiments. In Experiment 1, nonsignificant test stimuli were introduced at the second, fourth, sixth, or eighth trial of the complex sequence of eight stimuli (i.e., a sequence comprised of varying standard stimuli). None of the test stimuli produced enhanced skin conductance responses under these conditions. Experiment 2 utilized the same design with only one difference: the test stimuli were presented following a simple stimulus sequence (i.e., repetition of a fixed standard stimulus). In this design enhanced skin conductance responses to the test stimuli were observed in almost all experimental conditions, with an advantage of a late over an early presentation of the test stimulus. Experiment 3 was designed to compare serial position effects of significant and neutral test stimuli. A serial position effect was obtained only for the neutral test stimuli, showing once again an advantage for late presentations. It was suggested that different mechanisms might underlie skin conductance responses to significant stimuli and to novel neutral stimuli.

Adult↗