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PubMed1979

An experimental analysis of the effects of d-amphetamine and cocaine on the acquisition and performance of response chains in monkeys.

In one component of a multiple schedule of food presentation, monkeys acquired a different four-response chain each session by responding sequentially on three keys in the presence of four geometric forms (learning). In the other component, the four-response chain was the same each session (performance). Both d-amphetamine and cocaine, at the higher doses, disrupted the behavior in the learning component; the overall response rate decreased, the overall accuracy was impaired (i.e., percent errors increased), and there was less within-session error reduction. The performance component was generally less sensitive than the learning component to the disruptive effects of both drugs on rate and accuracy. After pre-feeding or during an extended session, the response rate decreased in both components, but accuracy was generally unaffected. When the four discriminative stimuli in both components were removed, the behavior was disrupted to a greater extent in the performance component. The disruptive effects of both drugs on behavior in the learning component were attenuated when the drugs were administered during the session after the response chain had been acquired. It was concluded that the greater sensitivity of the learning component to disruptive drug effects is related to the relatively weak stimulus control and/or the lower rate of reinforcement associated with that component.

Animals↗
PubMed1984

Dose-response analysis of the behavioral effects of diazepam: I. Learning and memory.

A total of 120 healthy volunteers were randomly assigned to four treatments (placebo, 0.1, 0.2, and 0.3 mg/kg) and three testing times (7 AM, 1 PM and 7 PM). Immediate and delayed free recall of word lists revealed consistent decreases in performance as oral diazepam dose increased from 0.1, 0.2, to 0.3 mg/kg. Paradoxically, as the dose increased, the number of predrug list words recalled also increased. A serial number-learning task displayed a pattern of delayed improvement of acquisition as the dose increased. Response times in a semantic-categories task were prolonged as the dose increased. Parallel recovery functions were observed for all doses and tasks. Full recovery after a single administration of 0.1, 0.2, and 0.3 mg/kg doses was estimated to occur after 3.5, 4.5, and 5.5 h, respectively. Several analyses were consistent with the view that acquisition and not retrieval was impaired by diazepam. There were no circadian interactions with the effects of the drug.

Adolescent↗
PubMed1992

Skill learning in the elderly: diminished implicit and explicit memory for a motor sequence.

Explicit and implicit memory for a cognitive-motor sequence was studied in elderly and young adults. Implicit memory was examined in a serial reaction-time paradigm in which sequences of hand postures repeated cyclically, then shifted to random sequences. Two control groups received random sequences throughout. Movement times (MTs) across the first 4 blocks did not improve more in the elderly-repeated than in the elderly-random group. In contrast, the young-repeated group showed greater improvement in MT across these blocks than the young-random group. MT was less affected in the elderly than in the young by shifts between repeated and random sequences, indicating impaired implicit memory. Explicit memory, which was assessed by free recall and cued recall, also was impaired in the elderly. Diminished implicit memory in the elderly could not be explained solely by the possible intrusion of conscious recollection strategies.

Adult↗
PubMed1990

Interference with visual short-term memory.

Working memory (Baddeley and Hitch 1974) incorporates the notion of a visuo-spatial sketch pad; a mechanism thought to be specialized for short-term storage of visuo-spatial material. However, the nature and characteristics of this hypothesized mechanism are as yet unclear. Two experiments are reported which examined selective interference in short-term visual memory. Experiment 1 contrasted recognition memory span for visual matrix patterns with that for visually presented letter sequences. These two span tasks were combined with concurrent arithmetic or a concurrent task which involved manipulation of visuo-spatial material. Results suggested that although there was a small, significant disruption by concurrent arithmetic of span for the matrix patterns, there was a substantially larger disruption of the letter span task. The converse was true for the secondary visuo-spatial task. Experiment 2 combined the span tasks with two established tasks developed by Brooks (1967). Span for matrix patterns was disrupted by a visuo-spatial task but not by a secondary verbal task. The converse was true for letter span. These results suggest that the impairment in short-term visual memory resulting from secondary arithmetic reflects a small general processing load, but that the selective interference due to mode of processing is by far the stronger effect. Results are interpreted as being entirely consistent with the notion of a specialized visuo-spatial mechanism in working memory.

Adult↗
PubMed1990

Problems brought about by "reading" a sequence of pictures.

The "reading" of a sequence of narrative pictures has been studied as a specific cognitive area. Sequences of pictures were presented to children between 3 and 7 1/2 years old in either the right or wrong order. We studied four problems: the child's difficulty in seeing the same character throughout different representations, the liking-up process of several pictures into one story, the correlation between the temporal order and the spatial disposition of pictures, and the child's tendency to consider the setting of pictures as a puzzle to solve. The characteristic difficulties observed seem to be related to the double status of the picture, which is both a physical and a symbolic object. We set out to reconstruct the path taken from the initial dilemma in which a child finds herself/himself, caught between the signifier and the signified, up until the point where, all contradictions resolved, she/he definitively acquires the principles of the way in which a sequence of pictures functions. Although more or less distinct stages concerning the acquisition of different rules inherent in a sequence of pictures can be observed, the existence of transitional periods favors a continuous progression.

Attention↗
PubMed1995

Implicit learning and concept learning.

In Experiments 1 and 2, subjects were exposed to letter strings that followed a pattern--the second letter was always the same. This exposure was disguised as a test of immediate memory. Following this training, subjects could discriminate new letter strings following the pattern from letter strings not following the pattern more often than would be expected by chance, which is the traditional evidence for concept learning. Discrimination was also better than would be predicted from subjects' explicit report of the pattern, demonstrating the co-occurrence of concept learning and implicit learning. In Experiment 3, rules were learned explicitly. Discrimination was worse than would be predicted from subjects' explicit report, validating the implicit learning paradigm. In Experiment 4, deviations from a prototypical pattern were presented during training. In the test of discrimination, prototypes were as familiar as old deviations and more familiar than new deviations, even when considering only implicit knowledge. Experiment 5 found implicit knowledge of a familiar concept. These results are consistent with the hypothesis that the distinguishing features of a concept can be learned implicitly, and that one type of implicit learning is concept learning.

Adult↗
PubMed1982

Encoding strategies used by young and elderly adults in a keeping track task.

College students and older adults (mean ages 20.4 and 71.5 years) performed in a "keeping track" task that required them to recall, in response to probe questions, the most recently presented of each of a fixed set of categories. Questions alternated with presentations of new sets of items. Response accuracy, reaction times, and verbal reports provided information on the participants' strategies. The findings were consistent with the view (e.g., Hasher & Zacks, 1979) that older adults' poorer memory results from reduced use of effortful strategies. The older persons used fewer active encoding strategies than the college students and were less accurate and slower to respond. A subgroup of the elderly adults reported some active encoding activities; they performed more like the college students than the remaining elderly participants. A follow-up study in which college students were allowed reduced opportunity for active encoding produced performance intermediate between the other two groups.

Adolescent↗
PubMed1979

Assessment of cognitive asymmetries in brain-damaged and normal subjects: validation of a test battery.

A test battery designed to assess cognitive functions normally related to the left and right cerebral hemispheres was validated on 30 patients with unilateral (16 right, 14 left) lesions. The tests were preselected to reflect typical functioning of the hemispheres according to general agreement in the literature. A Cognitive Laterality Quotient (CLQ) was calculated from the difference in performance between the "right" and "left" test batteries and, therefore, reflected the relative functioning attributed to the right and left hemispheres. Using the CLQ measurement and a control group of 30 non-neurological patients matched for age and education, 28 out of 30 brain-damaged patients (93%) were categorised correctly according to side of lesion; the other two were considered to have either abnormal lateralisation (one was left handed) or asymmetrical premorbid cognitive profiles. Using only one (paired) test whose two subparts were designed to vary only slightly in task requirements to measure either right or left functioning, 29 out of 30 patients were correctly categorised. It is suggested that the concept of relative assessment of basic cognitive functions is more fruitful than general assessment of intellectual functions for use in diagnosis and rehabilitation of neurological patients or normal subjects with developmental or acquired behavioural cognitive abnormalities.

Adult↗
PubMed1994

Effect of multimodal stimulus presentation on recall.

This study was conducted to investigate how the mode of stimulus presentation affects recall in the classroom environment. 289 undergraduates were randomly assigned to one of 7 experimental groups. All subjects were presented the same stimuli in one of 7 possible modes: (1) Printed Word, (2) Spoken Word, (3) Picture, (4) Printed Word + Spoken Word, (5) Picture + Spoken Word, (6) Picture + Printed Word, and (7) Printed Word, Picture + Spoken Word. 30 words, 6 from each of 5 categories, were presented to each group. A new stimulus was presented every 5 sec. Subjects were to recall (in writing) as many stimuli as possible in 5 min. regardless of order. One-way between groups analyses of variance were conducted on recall and cluster index scores. A significant main effect of mode of presentation showed that recall was best for the Picture or multimodal group (Printed Word, Picture + Spoken Word). Groups receiving only the spoken or printed word showed significantly poorer recall than the multimodal groups. No statistically significant differences between groups were found on the cluster index score. It appears that the simultaneous presentation of redundant stimuli in multiple modalities does support the multiple-resource hypothesis by displaying enhanced recall when information is available from multiple attentional resources.

Adolescent↗
PubMed1991

Memory for temporal order in schizophrenia.

Memory for temporal order information was examined in patients with chronic schizophrenia using the recency discrimination task. In this task, subjects were shown a pair of previously studied words and were asked to choose which one of the two words they had seen more recently. In addition, subjects performed the Wisconsin Card Sorting Test (WCST). The results showed that schizophrenic patients differed from normal control subjects in their performance on the recency discrimination task. In addition, for schizophrenic patients, performance on the recency discrimination task was inversely related to the number of perseverative errors on the WCST. These results provide further evidence of prefrontal-type cognitive deficits in schizophrenia.

Adult↗
PubMed1994

Aetiological variation in the amnesic syndrome: comparisons using the list discrimination task.

In this study, the performance of amnesic patients with presumed temporal lobe damage was compared with that of patients with presumed diencephalic damage using the temporal list discrimination task. The two patient groups performed similarly on a measure of recognition, but the diencephalic group was impaired relative to the temporal lobe group on a measure of temporal discrimination. Discrimination performance in the temporal lobe group was significantly correlated with recognition memory. The data are interpreted as showing a qualitative difference in the form of amnesia arising from damage centred on the medial temporal lobes compared with that centred on the midline diencephalon.

Adult↗
PubMed1994

The effects of lesions to the fornix and dorsomedial thalamus on concurrent discrimination learning by rats.

Rats with lesions in either the fornix or the thalamic nucleus medialis dorsalis were unimpaired on the acquisition of two object discrimination tasks. The same animals were then tested on a concurrent learning task in which various object discriminations were presented at different rates during the same session. This arrangement was primarily designed to minimise any response bias effects. Animals were able to acquire the various concurrent tasks, even when only one trial per day was given for a particular discrimination. It was found that fornix lesions had little or no effect and only produced a mild impairment when the rate of stimulus presentation resembled that used in typical concurrent tasks. Lesions of medialis dorsalis produced a more general, but again mild, deficit. In a final task, the animals were trained to discriminate between two stimuli composed of common elements arranged in different spatial combinations. Fornix lesions impaired acquisition of this spatial configural discrimination, while lesions of medialis dorsalis had a variable effect. The results indicate that fornix lesions can spare concurrent discrimination learning, and that any deficits may be related to interference effects associated with common elements in the stimuli. Lesions in medialis dorsalis appear to affect the initial learning of reward-based performance rules.

Animals↗