Performance In Short-term Memory Tasks Research Articles

Reduced benefit from long-term item frequency contributes to short-term memory deficits in dyslexia.

Dyslexia, a specific difficulty in acquiring proficient reading, is also characterized by reduced short-term memory (STM) capacity. Extensive research indicates that individuals with developmental dyslexia (IDDs) benefit less from exposure, and this hampers their long-term knowledge accumulation. It is well established that long-term knowledge has a great effect on performance in STM tasks, and thus IDDs' reduced benefit of exposure could potentially reduce their relative performance in such tasks, especially when frequent items, such as digit-words, are used. In this study we used a standard, widely used, STM assessment: the Digit Span subtest from the Wechsler Adult Intelligence Scale. The task was conducted twice: in native language and in second language. As exposure to native language is greater than exposure to second language, we predicted that IDDs' performance in the task administered in native language will reveal a larger group difference as compared to second language, due to IDDs' reduced benefit of item frequency. The prediction was confirmed, in line with the hypothesis that reduced STM in dyslexia to a large extent reflects reduced benefits from long-term item frequency and not a reduced STM per se.

Pain resilience, pain catastrophizing, and executive functioning: performance on a short-term memory task during simultaneous ischemic pain.

Among pain researchers there is a growing interest in the relationship between psychological resilience and pain experience. Whereas much of this work has focused on individual differences in pain perception or sensitivity, an equally important dimension of resilience is the capacity to persist with goal-directed activity despite experiencing pain. Consistent with this latter focus, the current study examined how pain resilience and pain catastrophizing combine to moderate the effects of ischemic pain on short-term memory task performance. Using a within-subjects design, 121 healthy participants completed four trials of a Corsi block-tapping task with pain exposure during the second and fourth trials. Results indicated that a combination of high pain resilience and low pain catastrophizing was associated with better task performance during the second pain exposure. These findings confirm existing evidence that resilience can moderate performance during pain, and offer new evidence that resilience and catastrophizing interact to shape this effect.

Does short-term memory develop?

Such is the consistency by which performance on measures of short-term memory (STM) increase with age that developmental increases in STM capacity are largely accepted as fact. However, our analysis of a robust but almost ignored finding – that span for digit sequences (the traditional measure of STM) increases at a far greater rate than span for other verbal material – fundamentally undermines the assumption that increased performance in STM tasks is underpinned by developmental increases in capacity. We show that this digit superiority with age effect is explained by the relatively greater linguistic exposure to random sequences of digits versus other stimuli such as words. A simple associative learning process that learns incrementally from exposure to language accounts for the effect, without any need to invoke an STM mechanism, much less one that increases in capacity with age. By extension, using corpus data directed at 2–3 year old children, 4–6 year old children, and adults, we show that age-related performance increases with other types of verbal material are equally driven by the same basic associative learning process operating on the expanding exposure to language experienced by the child. Our results question the idea that tests such as digit span are measuring a dedicated system for the temporary maintenance and manipulation of verbal material, and as such have implications for our understanding of those aspects of typical and atypical development that are usually accounted for with respect to the operation of such a system.

Long-term associative learning predicts verbal short-term memory performance

Studies using tests such as digit span and nonword repetition have implicated short-term memory across a range of developmental domains. Such tests ostensibly assess specialized processes for the short-term manipulation and maintenance of information that are often argued to enable long-term learning. However, there is considerable evidence for an influence of long-term linguistic learning on performance in short-term memory tasks that brings into question the role of a specialized short-term memory system separate from long-term knowledge. Using natural language corpora, we show experimentally and computationally that performance on three widely used measures of short-term memory (digit span, nonword repetition, and sentence recall) can be predicted from simple associative learning operating on the linguistic environment to which a typical child may have been exposed. The findings support the broad view that short-term verbal memory performance reflects the application of long-term language knowledge to the experimental setting.

A Postnatal Diet Containing Phospholipids, Processed to Yield Large, Phospholipid-Coated Lipid Droplets, Affects Specific Cognitive Behaviors in Healthy Male Mice

Background: Infant cognitive development can be positively influenced by breastfeeding rather than formula feeding. The composition of breast milk, especially lipid quality, and the duration of breastfeeding have been linked to this effect.Objective: We investigated whether the physical properties and composition of lipid droplets in milk may contribute to cognitive development.Methods: From postnatal day (P) 16 to P44, healthy male C57BL/6JOlaHsd mice were fed either a control or a concept rodent diet, in which the dietary lipid droplets were large and coated with milk phospholipids, resembling more closely the physical properties and composition of breast milk lipids. Thereafter, all mice were fed an AIN-93M semisynthetic rodent diet. The mice were subjected to various cognitive tests during adolescence (P35–P44) and adulthood (P70–P101). On P102, mice were killed and brain phospholipids were analyzed.Results: The concept diet improved performance in short-term memory tasks that rely on novelty exploration during adolescence (T-maze; spontaneous alternation 87% in concept-fed mice compared with 74% in mice fed control diet; P < 0.05) and adulthood (novel object recognition; preference index 0.48 in concept-fed mice compared with 0.05 in control-fed mice; P < 0.05). Cognitive performance in long-term memory tasks, however, was unaffected by diet. Brain phospholipid composition at P102 was not different between diet groups.Conclusions: Exposure to a diet with lipids mimicking more closely the structure and composition of lipids in breast milk improved specific cognitive behaviors in mice. These data suggest that lipid structure should be considered as a relevant target to improve dietary lipid quality in infant milk formulas.

Near-infrared spectroscopic study on the effects of chewing on short-term memory

Using near-infrared spectroscopy, we examined whether chewing gum improves performance in a short-term memory task – immediate recall of random eight-digit numbers – by assessing cerebral hemodynamic response in the prefrontal cortex. We found that the oxyhemoglobin concentration during and after chewing gum was higher than that before chewing; further, the concentration increased during the task, and this increase was reduced with chewing, although non-significantly. Chewing did not improve task performance. Therefore, chewing-induced hemodynamic responses were unrelated to the performance in short-term memory tasks.

Redintegration and lexicality effects in children: do they depend upon the demands of the memory task?

The effect of long-term knowledge upon performance in short-term memory tasks was examined for children from 5 to 10 years of age. The emergence of a lexicality effect, in which familiar words were recalled more accurately than unfamiliar words, was found to depend upon the nature of the memory task. Lexicality effects were interpreted as reflecting the use of redintegration, or reconstruction processes, in short-term memory. Redintegration increased with age for tasks requiring spoken item recall and decreased with age when position information but not naming was required. In a second experiment, redintegration was found in a recognition task when some of the foils rhymed with the target. Older children were able to profit from a rhyming foil, whereas younger children were confused by it, suggesting that the older children make use of sublexical phonological information in reconstructing the target. It was proposed that redintegrative processes in their mature form support the reconstruction of detailed phonological knowledge of words.

Perception and short-term memory for verbal information in children with specific language impairment: Further evidence for impaired short-term memory capacities

Most children with specific language impairment (SLI) present impaired performance in verbal short-term memory (STM) tasks. Weismer et al. (2000), for example, showed that repetition of non-words of increasing length, a frequently used STM measure, was a very reliable marker for distinguishing children with and without SLI. This has led a number of authors to consider that a verbal STM impairment might represent one of the core deficits of SLI (e.g., Gathercole & Baddeley, 1990). However, there is still important controversy regarding this view as the verbal STM impairment could also be the consequence of underlying language impairments. For example, James, Van Steenbrugge, and Chiveralls (1994) observed deficits in speech perception that explained impaired performance observed in verbal STM tasks in their SLI group. Furthermore, another possibility which has not yet been extensively explored is that the poor development of SLI children's phonological and lexico-semantic representations stored in long-term memory (LTM) could also account for reduced performance in STM tasks. Indeed, a number of studies in normally developing children have recently shown that performance in STM tasks is very strongly influenced by the integrity of underlying LTM language representations, as evidenced by better recall for words compared to nonwords and better recall for non-words containing familiar versus less familiar phoneme associations (e.g., Gathercole, Frankish, Pickering, & Peaker, 1999). In this context, we re-examined the specificity of verbal STM deficits in SLI by exploring the influence of phonological and lexico-semantic LTM representations on STM performance as well as the integrity of speech perception abilities.

Modality differences in short-term memory for rhythms.

Prior research has established that performance in short-term memory tasks using auditory rhythmic stimuli is frequently superior to that in tasks using visual stimuli. In five experiments, the reasons for this were explored further. In a same-different task, pairs of brief rhythms were presented in which each rhythm was visual or auditory, resulting in two same-modality conditions and two cross-modality conditions. Three different rates of presentation were used. The results supported the temporal advantage of the auditory modality in short-term memory, which was quite robust at the quickest presentation rates. This advantage tended to decay as the presentation rate was slowed down, consistent with the view that, with time, the temporal patterns were being recoded into a more generic form.

Human memory: psychology, pathology and pharmacology

Summary Cognitive psychologists discuss human memory in terms of the encoding processes that give rise to the internal representation of the information to be learned and in terms of the functional architecture of the system in which that information is represented. Performance in short-term memory tasks is thought to depend upon a form of working memory that consists of a central executive processor of limited capacity, together with a number of dedicated subsystems. One subsystem is a phonological store that is used to retain sequences of verbal items by means of articulatory rehearsal. Another subsystem is a visuospatial sketch-pad which retains information in the form of a spatial array. Long-term memory involves the retention of both declarative knowledge about the objects and events in the world and the procedural knowledge that underlies skilled behavior. Within the domain of declarative memory, a useful descriptive distinction is between episodic memory for particular autobiographical events and experiences, and semantic memory for general knowledge about language and the world. Disorders of memory are a frequent outcome of neurological damage and disease. A few rare cases have been described with selective disorders of verbal short-term memory, sometimes despite intact articulatory skills. Conversely, patients have been described with normal digit spans despite gross disorders of overt articulation. Selective disorders of long-term memory in the form of the amnesic syndrome are more common. In such cases episodic memory is conspicuously more impaired than either semantic memory or procedural memory. In particular, amnesic patients with frontal damage are able to acquire new knowledge but have no explicit recollection of the occasion when it was learned. The normal ageing process also involves a selective impairment of long-term memory, and especially of more effortful or abstract encoding operations, but progressive degenerative dementias tend to affect a much broader range of memory functions. Many psychoactive agents also influence learning and remembering. In particular, anticholinergic drugs disrupt the encoding of new information into long-term memory in young volunteers and mimic Alzheimer's disease in normal elderly people. The benzodiazepines also have a selective effect upon long-term storage, and this resembles the pattern of impairment found in certain amnesic disorders. The catecholamines have been implicated in Parkinson's disease and in Korsakoff's syndrome, but their role in human memory seems to be a purely extrinsic or modulatory one. The same appears to be true of neuropeptides such as vasopressin and adrenocorticotrophic hormone. A considerable amount of research has been devoted to developing pharmacological agents that might enhance memory function in neurological patients. In general, however, the effects of the drugs considered to date have been too slight and too transient to be of much therapeutic value.

Selective attention and rehearsal in the auditory short-term memory task performance of poor and normal readers.

The performance of poor and normal sixth-grade readers was compared on an auditory short-term memory task in two studies. In the first study, the effects of distraction, list length, and speed of stimulus presentation were investigated to test the hypothesis that the performance of the poor readers is affected by deficits in selective attention. Group differences in performance, however, were obtained for both distraction and no-distraction conditions. The second experiment examined the hypothesis that group differences may reflect differences in the use of rehearsal. In the second experiment, half the reading-disabled children and half the controls were provided with rehearsal training prior to completing the same short-term memory task a second time. Rehearsal training resulted in improved performance relative to children who were not trained; however, there was no rehearsal training X reading group interaction. The poor readers continued to show deficits in performance relative to the performance of control children. The results of these two studies suggest that deficits observed for poor readers on short-term memory tasks may reflect processing difficulties in some area that precedes rehearsal and affects performance under both distraction and no-distraction conditions.