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PubMed1981

Syndrome produced by lesions of the amygdala in monkeys (Macaca mulatta).

Behavioral effects of subtotal amygdaloid lesions were investigated in an attempt to dissociate some of the abnormalities seen after total amygdalectomy. Twelve monkeys received bilateral stereotaxic lesions centered in the basolateral amygdala, lateral amygdala, dorsal amygdala, or the temporal white matter lying adjacent to the lateral amygdala. These monkeys were compared with others with control operations. The control monkeys then received total amygdaloid lesions (AMX). The AMX monkeys exhibited the typical amygdaloid syndrome of hypoemotionality, meat eating, coprophagia, and excessive exploration. In contrast, the monkeys with subtotal amygdaloid lesions would not eat meat or feces, though they were more willing than control monkeys to investigate inanimate objects. Although minor changes in affect were observed, the extreme emotional changes seen after total amygdalectomy were found only in the monkey with the largest subtotal lesion. Only those animals that were hypoemotional showed a deficit in learning successive reversals of an object discrimination. This close association suggests that both the hypoemotionality and the successive reversal deficit arise from the same underlying dysfunction.

Amygdala↗
PubMed2002

Functional equivalence of WAIS-III/WMS-III digit and spatial span under forward and backward recall conditions.

The purpose of the current study was to examine the performance characteristics of the Wechsler Spatial Span subtest in a mixed clinical sample. Contrary to expectation, differential patterns of performance were obtained on the Digit and Spatial Span tasks. Forward Digit Span scores were significantly higher than backward recall scores, but this was not the case for Spatial Span. There were no differences between forward and backward raw Spatial Span scores at the mean level. Further, about one third of the sample showed better performance on backward compared to forward Spatial Span. In addition, performance on the Spatial Span backward task correlated unexpectedly with that of the WMS-III Immediate and Delayed Auditory Index scores. Overall, the findings suggest that clinicians should be hesitant when interpreting the Spatial Span task, and the backward condition in particular, as a measure of working memory. Finally, methodological concerns with the Spatial Span task are noted, raising additional concerns regarding the meaning of this task.

Humans↗
PubMed1987

The effects of visual conspicuousness and the concept of randomness on the recognition of randomness in sequences.

In a number of studies, tendencies toward nonrepetition in judgments of randomness of visually presented sequences of events have been attributed to a biased concept of randomness. The present study proposed that such bias is due to "bottom-up" visual processes rather than a concept of randomness. Experiment 1 showed that judgments of randomness were less biased when repetitions were made less conspicuous by increasing the distance between adjacent items. Experiment 2 produced comparable results for increasing dissimilarity of categorically identical items. A third experiment showed that the bias in the judgment task was not related to a more direct measure of knowledge of random processes, the assignment of probabilities of repetition to imagined random sequences. The results supported the view that judgments of randomness are determined to a high degree by the conspicuousness of repetitions and are independent of the concept of randomness.

Attention↗
PubMed2003

The influence of response--effect compatibility in a serial reaction time task.

Participants performed a serial reaction time task, responding to either asterisks presented at varying screen locations or centrally presented letters. Stimulus presentation followed a fixed second-order conditional sequence. Each keypress in the experimental groups produced a contingent, key-specific tone effect. The critical variation concerned the mapping of tones to keys. In Experiment 1, keypresses in one control condition produced noncontingent tone effects, while in another control condition there were no tone effects. In Experiment 2, three different keytone mappings were compared to a control condition without tone effects. The results show that tone effects improve serial learning when they are mapped to the response keys contingently and in a highly compatible manner. The results are discussed with reference to an ideomotor mechanism of motor sequence acquisition.

Adult↗
PubMed1995

Mathematical and connectionist models of human memory: a comparison.

Recent convolution-based models of human memory (e.g. Lewandowsky & Murdock, 1989), have accounted for a wide range of data. However such models require the relevant mathematical operations to be provided to the network. Connectionist models, in contrast, have generally addressed different data, and not all architectures are appropriate for modelling single-trial learning. Furthermore, they tend to exhibit catastrophic interference in multiple list learning. In this paper we compare the ability of convolution-based models and DARNET (Developmental Associative Recall NETwork), to account for human memory data. DARNET is a connectionist approach to human memory in which the system gradually learns to associate vectors, in one trial, into a memory trace vector. Either of the vectors can than be retrieved. It is shown that the new associative mechanism can be used to account for a wide range of relevant experimental data as successfully as can convolution-based models with the same higher-level architectures. Limitations of the models are also addressed.

Computer Simulation↗
PubMed2004

Memory span on the Wechsler Scales.

This study had two goals. One was to assess whether the WMS-III Spatial Span subtest operates as a visual analogue of Digit Span while the second was to determine whether backward span is a more sensitive measure of working memory than the forward span condition. Analyses based on the WAIS-III-WMS-III standardization and clinical group data revealed some important distinctions between Digit and Spatial Span. The two tasks exhibited differences in patterns of performance on the forward versus backward conditions, in their relationships with age, and in their methodology. Moreover, the backward conditions of both Digit and Spatial Span did not appear more affected by risk factors such as aging or pathology than the forward scores. This runs contrary to the widespread notion that backward span provides differential sensitivity regarding working memory processing.

Adolescent↗
PubMed1995

Short-term memory in persons with intellectual disabilities and Down's syndrome.

The present study was designed to investigate verbal and spatial short-term memory abilities in persons with Down's syndrome (DS) and intellectual disability (ID) of different aetiology. For this purpose, we compared performances of DS (n = 15; mean mental age = 5.2 years; SD = 1.2 years; mean chronological age = 16.6 years; SD = 2.9 years) and ID subjects (n = 14; mean mental age = 5.8 years; SD = 2.1 years; mean chronological age = 16.4 years; SD = 2.5 years) with those of normally developed subjects matched for mental age (n = 24) on tasks of forward and backward immediate recall of verbal and spatial sequences. Our results are discussed in the light of the Working Memory model developed by Baddeley (1986, 1990). Altogether, our data documents a deficit of verbal and spatial backward spans in persons with DS. The deficit seems to be specific for this particular aetiology group, confirming the hypothesis that ID is not a uniform condition, characterized by an undifferentiated delay of the cognitive development, but rather that it is characterized by a deficit in a complex cognitive system in which some cognitive abilities can be disrupted more than others (Detterman 1987; Vicari et al. 1992).

Adolescent↗
PubMed1980

Modality differences in relation to grouping in immediate recall.

An earlier study of auditory grouped presentation of digit strings had shown recall to be impaired by recalling the last group first. From this, it has been concluded that the item codes formed at Stage 1 of processing, and before conversion to a group code at Stage 2, were not yet in an output buffer. The present paper employs visual presentation for two similar studies, with results opposite to the earlier one; in a third experiment, ungrouped auditory stimulation gave results which were a compromise between those for vision and those for grouped auditory stimulation. These results suggest a use of echoic storage, over long intervals; in the visual case this is not so and an output buffer is employed.

Adult↗
PubMed1983

Effect of lecithin on memory in normal adults.

In a double-blind, placebo-controlled, crossover study of the effect of lecithin on memory test performance, nine normal paid volunteers (age range = 22-55 years) took single oral doses of placebo and lecithin (20 g) 5 hours before cognitive testing. Lecithin raised plasma choline levels during the test session to nearly double the placebo levels, but a categorized serial learning task, a word recognition task, a paired associates learning task, and a test of retrieval by category demonstrated no significant change in memory performance. Lecithin did not selectively enhance memory for low-imagery words. Lecithin also had no effect on psychomotor speed.

Adult↗
PubMed1985

Symmetry and transitivity of conditional relations in monkeys (Cebus apella) and pigeons (Columba livia).

In Experiment 1 six monkeys were tested with discriminative relations that were backward relative to their training in a 0-second conditional ("symbolic") matching procedure. Although there was some indication of backward associations, the evidence was generally weak, and statistical evaluations did not reach conventional significance levels. Unlike children, who show backward associations to the point of symmetry, monkeys and pigeons display at best only weak and transient backward associations. In Experiment 2 associative transitivity was assessed across two sets of conditional matching tasks. All four monkeys tested demonstrated strong transitivity. In contrast, in Experiment 3 there was no evidence of transitivity in three pigeons tested under conditions closely comparable to those of Experiment 2. These results may identify some key features of interspecies differences and contribute to analyses of serial learning in animals.

Journal Article↗
PubMed1991

Substitutability between conditioned and primary reinforcers in discrimination acquisition.

Rats and pigeons were trained on a series of reversals of a conditional simultaneous discrimination. The percentage of reinforcement for correct trials was varied across reversals. When nonreinforced correct trials produced the same feedback as incorrect trials, the number of errors to reach an acquisition criterion was greater for smaller percentages of reinforcement, but the number of reinforcers required was either approximately constant or smaller for the smaller percentages. When a stimulus paired with food (the conditioned reinforcer) was added on nonreinforced correct trials, both measures were substantially decreased. When the same stimulus was presented, but without a history of food pairing, learning rate was similar to when no stimulus was presented on nonreinforced trials. The results provide direct evidence that conditioned reinforcers may substitute, although imperfectly, for a primary reinforcer, and that pairing with the primary reinforcer is a necessary condition for such substitutability to occur.

Animals↗
PubMed1996

Auditory and visual recall of forward and backward digit spans.

Increasingly, clinicians obtain data from tests across modalities. Little actual information, however, exists as to normal patterns. An example is auditory and visual recall of digit span. The effects of modality on recall of digit span, sequence, and order were examined with 80 subjects (M age 24.3 yr.). Subjects were given the Wechsler Adult Intelligence Scale-Revised, and a research version of MicroCog: Assessment of Cognitive Functioning. Both contain forward and backward digit spans. Recall for visual presentation was significantly stronger than for auditory presentation of backward digit span. Recall for visual backward digit span was also superior to auditory backward digit span when the sequence of presentation was controlled. The mean number of digits recalled was higher when visual digit span was preceded by auditory digit span.

Adult↗
PubMed1990

Differential importance of hierarchical learning, abstractness, and imagery.

This research examined the relative contribution of hierarchical sequencing, abstractness, and imagery to learning. In the past, hierarchical, logical sequencing was not shown to be superior to other modes of instruction, and the interaction of imagery, abstractness, and sequencing had not been examined, especially regarding the possible superiority of any of these as a contributor to learning. The data were produced by 108 high school students who studied sequences of hierarchically related information arranged in a 2 x 2 x 2 factorial design the dimensions of which varied according to the degree of imagery (high and low), abstractness (abstract and concrete), and type of sequencing (logical and scrambled). Analyses of the amount of learning under these conditions showed that hierarchical sequencing is not only relevant to learning but more related than either imagery or the abstractness of material to be learned. Additional suggestions are made regarding instruction and research especially in relation to matrix rather than hierarchial arrangements of information.

Attention↗