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Short-term memory scan in normal individuals and individuals with aphasia.

Ten matched pairs of normal adults and adults with aphasia participated in a short-term memory, visual recognition paradigm wherein each determined whether or not a probe digit appeared in a subset of digits previously presented. Reaction times, measured in milliseconds from onset of probe digits until completion of visual-motor responses, were analyzed as a function of increasing subset size (two, four, and six digits) and the positive versus the negative response condition. Reaction times were significantly slower for the subjects with aphasia. Both groups of subjects demonstrated linear increases in reaction time across levels of subset size. For both groups, increases in reaction time were similar in the positive vs the negative-response conditions. Resulting parallel slopes suggested that both groups of subjects used a serial exhaustive scan of short-time memory. Results from this study did not support results obtained by others in previous studies which may have been confounded by group differences in visual retention spans.

Adult↗

Characterization of serial order encoding in the monkey anterior cingulate sulcus.

In a previous report we showed that neurons in the anterior cingulate cortex might encode the serial order of the three components (first, second and third) of motor sequences, irrespective of which component is performed, and irrespective of the component that precedes or follows. Here we further explore these data by comparing the magnitude of cell activity at the different ranks. We also compare the activity recorded in the motor sequences and in tasks with only one motor component. We finally discuss functional hypotheses, which may account for the serial order encoding.

Animals↗

Working memory and everyday cognition in adults with Down's syndrome.

A number of previous studies have suggested that young people with Down's syndrome (DS) have a specific deficit of the phonological loop component of the working memory. However, there have also been studies which have proposed a specific deficit of the central executive component of working memory and suggested similarities of working memory functioning with patients with Alzheimer's disease. Fifteen middle-aged people with DS were matched for their individual scores of non-verbal intelligence to 15 individuals with mixed aetiology of intellectual disability. A versatile range of tasks was used in order to evaluate the functioning of working memory components. In addition, several everyday cognition skills were assessed. The subjects with DS performed significantly more poorly in all tasks assessing the phonological loop. Performance in other working memory tasks and compound variables representing different working memory components was equal in the groups. In addition, both groups had equal everyday cognition skills. The functioning of the phonological loop seems to be clearly deficient in people with DS. Interestingly, the deficit does not seem to affect the vocabulary or other everyday cognition skills in individuals with DS. No signs of specific deficit of the central executive component of working memory were found.

Activities of Daily Living↗

Word-length effect in verbal short-term memory in individuals with Down's syndrome.

BACKGROUND: Many studies have indicated that individuals with Down's syndrome (DS) show a specific deficit in short-term memory for verbal information. The aim of the present study was to investigate the influence of the length of words on verbal short-term memory in individuals with DS. METHODS: Twenty-eight children with DS and 10 control participants matched for memory span were tested on verbal serial recall and speech rate, which are thought to involve rehearsal and output speed. RESULTS: Although a significant word-length effect was observed in both groups for the recall of a larger number of items with a shorter spoken duration than for those with a longer spoken duration, the number of correct recalls in the group with DS was reduced compared to the control subjects. The results demonstrating poor short-term memory in children with DS were irrelevant to speech rate. In addition, the proportion of repetition-gained errors in serial recall was higher in children with DS than in control subjects. CONCLUSIONS: The present findings suggest that poor access to long-term lexical knowledge, rather than overt articulation speed, constrains verbal short-term memory functions in individuals with DS.

Adolescent↗

[Serial reactions in aphasic patients].

A symptom is reported that has hitherto not been described in neuropsychological literature: Not infrequently, severe aphasics mix automatized verbal series or parts of them not only into their spontaneous speech but also into other modalities of the expressive language. Sometimes this form of automatism replaces a demanded answer. In the speech data of 134 aphasics this symptom was observed in half of the cases. Its incidence was analysed in relation to aetiology, type of aphasia and the modalities in which it was observed. 6 cases are described in detail. The serial reaction is a neuropsychological sign of clinical value, because it indicates an organic brain lesion.

Aged↗

Serial adaptation to conflicting prismatic rearrangement effects in monkey and man.

Seven adult male squirrel monkeys adapted successfully to prisms displacing in equal and opposite directions. After protracted training under certain conditions, they succeeded in conserving adaptation to both prisms without benefit of readaptation trials. Results obtained with thirty-six undergraduates under similar conditions of test (although for a much shorter period) are also reported.

Adaptation, Ocular↗

Tactile memory in sighted and blind observers: the influence of orientation and rate of presentation.

Sighted, early blind, and late blind subjects attempted to identify numerals or number sequences printed on their palms. The numerals were either upright, or inverted, or rotated perpendicular to the arm axis. Stimulus rotation degraded recognition in the early blind subjects, suggesting the influence of experience with visual frames of reference. Slower rates of presentation with upright number sequences improved recall in both sighted and blind observers. An experiment on tactual-visual braille recognition in the sighted observers showed that tilt degraded pattern identification, but visual guidance of the fingertip and ballpoint minimized this loss. A further experiment was performed to distinguish between visual imagery and visual frame of reference explanations of the visual guidance effect on recognition of rotated braille. Subjects explored upright or tilted braille characters while viewing only a light emitting diode on the exploratory fingertip. Sight of scanning movements did not aid pattern recognition with tilt. The results indicate that the benefits of visual guidance on recognition of tilted patterns were probably due to frame of reference information. It is concluded that spatial reference information may aid tactile memory in the sighted and late blind, since the early blind performed at a lower level in the retention task. It is proposed that visual imagery may only explain the superiority of the sighted and late blind when familiar stimuli are studied.

Adult↗

Memory performances in young, elderly, and very old healthy individuals versus patients with Alzheimer's disease: evidence for discontinuity between normal and pathological aging.

In this study we compared memory performances of 29 probable patients with AD (17 mildly and 12 moderately demented) with those of 39 healthy young subjects, 36 elderly subjects (matched with the AD group for age and years of schooling), and 19 healthy very old subjects. In most of the memory tasks used in the present study, a progressive decline in performance was observed passing from the Young to the Elderly to the Very Old to the AD group. However, patients with AD were selectively impaired in the backward reproduction of verbal and spatial span sequences and in the semantic encoding of verbal material. These data are consistent with the hypothesis of not only quantitative but also a qualitative discontinuity between the process of normal aging and the dementia syndrome.

Adult↗

Obsessive-compulsive disorder (OCD) patients are impaired in remembering temporal order and in judging their own performance.

Obsessive-compulsive disorder (OCD) has been related to frontostriatal dysfunction, but some inconsistencies between studies and a relative paucity of neuropsychological research still characterizes the study of OCD. We compared 28 patients with OCD and matched healthy controls on two neuropsychological tests sensitive to frontal dysfunction: temporal ordering and a "feeling-of-doing" (FOD) judgment about ordering. The OCD group performed significantly worse than controls in the temporal ordering task despite showing normal recognition memory. Patients were also impaired in "feeling-of-doing" judgments suggesting they have a lack of self-awareness of their performance. Thus, the results of the current study reinforces previous research that indicates that OCD patients fail on tasks that require adequate functioning of the frontal-striatal pathways.

Adolescent↗

Semantic relations and repetition of items enhance the free recall of words by multiple sclerosis patients.

We compared 25 patients with multiple sclerosis (MS) and 24 normal controls on a test of free recall of words. Some lists contained words that were all unrelated, while in others the intermediary words were semantically related. In another set, the mid-list words were repeated across the lists, or, in addition to the repetition, were semantically associated. Immediate recall was assessed using these lists. Delayed recall was assessed using different lists (delay-unrelated and delay-related) after distractor tasks. Recency was not affected in MS patients, but the primacy effect was lower than in controls, this effect being interpreted as due to a deficiency in articulatory rehearsal. The delay interval after each list abolished recency in both groups and resulted in impaired recall in MS patients. However the patients, like the controls, benefited from semantic relations in the middle of the lists and from spaced repetition of words across the lists, in either immediate and delayed recall. The enhancing effects of word relatedness and of spaced repetition are seen as being due to automatic processes preserved in MS patients.

Adult↗

A new approach in clinical neuropsychology to the assessment of spatial working memory: the block suppression test.

The Block Suppression Paradigm developed by Beblo, Klaver, Grubich, Wachowius, and Herrmann (1999) is based on the Corsi Block tapping test and requires that a subject reproduces every 2nd block in a given sequence. Results from two studies of a standardized version, the Block Suppression Test (BST), are presented here. In Study 1 the BST was administered to 48 healthy subjects along with a battery of comprehensive neuropsychological tests. The reliability of the BST proved satisfactory under psychometric analysis, while Principal Component Analysis (PCA) confirmed its validity. In Study 2 the BST was administered to a clinical sample of 31 brain-damaged patients to demonstrate its clinical practicability.

Adult↗

Verbal encoding deficits in a patient with a left retrosplenial lesion.

Over the past decade, memory impairments associated with retrosplenial damage have received increased attention among neuroscientists, although the exact role of the retrosplenial region in memory has not been clearly defined. Evidence from lesion studies and functional neuroimaging has implicated the retrosplenial region in verbal episodic memory, temporal ordering of information, and topographical memory. In addition, recent positron emission tomography studies have shown increased activation of the retrosplenial cortex during tasks involving both the encoding and retrieval of episodic information. The objective of this study was to define more clearly the nature of memory impairments observed in retrosplenial amnesia. A 47-year-old amnesic male with a left retrosplenial arteriovenous malformation was examined on neurocognitive tasks of automatic and directed encoding, temporal ordering of information, and remote memory. Despite normal performance on frontal cognitive tasks, intact memory for remote information, and a superior IQ, this individual exhibited a profound deficit in the encoding of information, evidenced by poor release from proactive interference, poor category clustering on word list recall, poor semantic encoding on a levels of processing task, and mild impairments in temporal ordering. These results imply that the retrosplenial region plays a role in the verbal encoding of information, which contributes to the profound verbal memory impairment reported in previous case studies of patients with retrosplenial damage.

Adult↗

The effects of hyperbaric air in combination with ethyl alcohol and dextroamphetamine on serial choice-reaction time.

The effects of ethyl alcohol (1.5 ml/kg body weight) and dextroamphetamine (15 mg) on nitrogen narcosis were investigated in two experiments using a 2-, 3- and 4-choice serial reaction time (RT) task with accuracy held constant. Narcosis was induced with air at 6.4 atmospheres absolute (ATA) and a heliox mixture was used as a control. Heliox at 6.4 ATA did not affect RT. Alcohol alone and air at 6.4 ATA increased the intercept of the Hick-Hyman function whereas amphetamine alone decreased it. The increased intercept with air at 6.4 ATA was exacerbated additively by alcohol and ameliorated antagonistically by amphetamine. The slope of the Hick-Hyman function was unaffected. Frequency distributions were shifted as a whole and their shapes were unaltered. It is concluded that these data are consistent with the slowed processing model which proposes that the effects of narcosis on performance are due to a decrease in arousal in conjunction with secondary changes in task strategy.

Adult↗

Serial position effects in HIV-infected injecting drug users.

This study examined memory and serial position effects in HIV-positive injecting drug users (IDUs), HIV-negative IDUs, and nondrug using control participants. Exploratory analyses investigating a possible mediating role of executive functions with HIV infection, drug use, and memory were also performed. Control participants showed stronger primacy effects than did both HIV-positive and HIV-negative IDUs and also outperformed the drug using groups on all memory measures. Interestingly, analysis of the role of executive functions with HIV infection, drug use, and memory suggested that executive functioning may mediate the verbal memory deficits associated with HIV infection, but not those associated with IDU.

Adolescent↗