Working memory plasticity in old age: Practice gain, transfer, and maintenance.

Adult age differences in cognitive plasticity have been studied less often in working memory than in episodic memory. The authors investigated the effects of extensive working memory practice on performance improvement, transfer, and short-term maintenance of practice gains and transfer effects. Adults age 20-30 years and 70-80 years practiced a spatial working memory task with 2 levels of processing demands across 45 days for about 15 min per day. In both age groups and relative to age-matched, no-contact control groups, we found (a) substantial performance gains on the practiced task, (b) near transfer to a more demanding spatial n-back task and to numerical n-back tasks, and (c) 3-month maintenance of practice gains and near transfer effects, with decrements relative to postpractice performance among older but not younger adults. No evidence was found for far transfer to complex span tasks. The authors discuss neuronal mechanisms underlying adult age differences and similarities in patterns of plasticity and conclude that the potential of deliberate working memory practice as a tool for improving cognition in old age merits further exploration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Induction of COX-2 expression by mechanical tension force in human periodontal ligament cells

Spectral EEG powers were compared in 4 frequency ranges (8-13, 15-25, 25-35, and 35-45 Hz) in a group of 20 subjects during the performance of tasks requiring mental rotation of two- and three-dimensional objects. Only those EEG segments corresponding to tasks with identical solution times were analyzed. The spectral powers of oscillations in the alpha range were higher in control conditions than during task performance. Power in the frequency range 15-45 Hz was greater during task performance than in control conditions; this supports the concept that alpha rhythm desynchronization accompanies the synchronization of higher-frequency EEG rhythms. Frequency power during task performance with two-dimensional objects was greater than that during tasks with three-dimensional objects. Since the angle of rotation between two-dimensional objects was greater than that between three-dimensional objects, this factor, rather than the depth of the perceived space, increased the level of cortical activation. In all experimental situations, power at frequencies of 15-45 Hz was significantly greater in the occipital regions than any other regions, reflecting the visual modality of the stimulus. Particular changes were noted in the gamma range (35-45 Hz), where power in the first second of task performance was significantly higher than in the second second; this may provide evidence that this range is more closely associated with perception and recognition processes than with mental transformation of the image.     

Mitigating disruptive effects of interruptions through training: What needs to be practiced?

It is generally accepted that, with practice, people improve on most tasks. However, when tasks have multiple parts, it is not always clear what aspects of the tasks practice or training should focus on. This research explores the features that allow training to improve the ability to resume a task after an interruption, specifically focusing on task-specific versus general interruption/resumption-process mechanisms that could account for improved performance. Three experiments using multiple combinations of primary tasks and interruptions were conducted with undergraduate psychology students. The first experiment showed that for one primary and interruption task-pair, people were able to resume the primary task faster when they had previous practice with the interruption. The second experiment replicated this finding for two other sets of primary and interruption task-pairs. Finally, the third experiment showed that people were able to resume a primary task faster only when they had previous practice with that specific primary and interruption task-pair. Experience with other primary and interruption task-pairs, or practice on the primary task alone, did not facilitate resumption. This suggests that a critical component in resuming after an interruption is the relationship between two tasks. These findings are in line with a task-specific mechanism of resumption and incompatible with a general-process mechanism. These findings have practical implications for developing training programs and mitigation strategies to lessen the disruptive effects of interruptions which plague both our personal and professional environments. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Adults' knowledge about memory: Awareness and use of memory strategies across tasks.

Two studies investigated college students' knowledge about the effectiveness of alternative memory strategies for different tasks and the relationship of this knowledge to strategy use and performance. In Experiment 1 students made paired-comparison judgments of the relative effectiveness of six strategies for increasing performance on one of three memory tasks. For each task some strategies were judged to be significantly more effective than others, whereas across tasks certain strategies were more likely to be judged effective for one task than for another. Experiment 2 examined the relationship of judgments of strategy effectiveness to actual strategy use and memory performance. Results indicated that different strategies were adopted across tasks and students were more likely to adopt strategies subsequently judged effective for that task. Students in Experiment 2 showed clearer discrimination among the strategies and an increased awareness of the efficacy of task-specific strategies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of repeated practice and contextual-writing experiences on college students' writing skills.

The authors examined the effects of both general and task-specific writing experiences on college students' writing-skill development. On the basis of theories of expertise development and a cognitive process theory of writing-skill development, the authors predicted that repeated practice would be associated with superior writing skills and that after controlling for repeated practice, writing within a specific task domain would be associated with superior writing skills. Undergraduate students participated in a field experiment in which 279 students practiced their writing skills in a professionally relevant task domain, whereas another group of 385 students practiced their writing skills in a more general domain. The results were consistent with the predictions. The authors discuss implications for teaching writing skills and for general theories of expertise development in writing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Individual differences in skill learning: An integration of psychometric and information processing perspectives.

Reexamines the nature of individual differences in novel and practiced performance on skill learning tasks from an information processing framework. Two major sources of data and discussion are reanalyzed and critically evaluated. One source concerns the changes in interindividual between-subjects variability with task practice; the other pertains to associations between intellectual abilities and task performance during skill acquisition. Early studies yielded mixed results regarding the convergence or divergence of individual differences with practice. Other studies indicated small or trivial correlations between individual differences in intelligence and "gain" scores. More recent studies indicated small correlations between performance measures on skill learning tasks and standard intellectual and cognitive ability measures, as well as increasing amounts of task-specific variance over learning trials. Data confirm the proposition that individuals converge on performance as tasks become less dependent on attentional resources with practice. When appropriate methodological techniques are used and crucial task characteristics are taken into account, intellectual abilities play a substantial part in determining individual differences in skill learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dissociation of mnemonic and perceptual processes during spatial and nonspatial working memory using fMRI

Neuroimaging studies in humans have consistently found robust activation of frontal, parietal, and temporal regions during working memory tasks. Whether these activations represent functional networks segregated by perceptual domain is still at issue. Two functional magnetic resonance imaging experiments were conducted, both of which used multiple-cycle, alternating task designs. Experiment 1 compared spatial and object working memory tasks to identify cortical regions differentially activated by these perceptual domains. Experiment 2 compared working memory and perceptual control tasks within each of the spatial and object domains to determine whether the regions identified in experiment 1 were driven primarily by the perceptual or mnemonic demands of the tasks, and to identify common brain regions activated by working memory in both perceptual domains. Domain-specific activation occurred in the inferior parietal cortex for spatial tasks, and in the inferior occipitotemporal cortex for object tasks, particularly in the left hemisphere. However, neither area was strongly influenced by task demands, being nearly equally activated by the working memory and perceptual control tasks. In contrast, activation of the dorsolateral prefrontal cortex and the intraparietal sulcus (IPS) was strongly task-related. Spatial working memory primarily activated the right middle frontal gyrus (MFG) and the IPS. Object working memory activated the MFG bilaterally, the left inferior frontal gyrus, and the IPS, particularly in the left hemisphere. Finally, activation of midline posterior regions, including the cingulate gyrus, occurred at the offset of the working memory tasks, particularly the shape task. These results support a prominent role of the prefrontal and parietal cortices in working memory, and indicate that spatial and object working memory tasks recruit differential hemispheric networks. The results also affirm the distinction between spatial and object perceptual processing in dorsal and ventral visual pathways.     

Simultaneous Cognitive Operations in Working Memory After Dual-Task Practice.

The authors tested the hypothesis that with adequate practice, people can execute 2 cognitive operations in working memory simultaneously. In Experiment 1, 6 students practiced updating 2 items in working memory through 2 sequences of operations (1 numerical, 1 spatial). In different blocks, imperative stimuli for the 2 sequences of operations were presented either simultaneously or sequentially. Initially, most participants experienced substantial dual-task costs. After 24 sessions of practice, operation latencies for simultaneous presentation were equal to the maximum of times for the 2 operations in the sequential condition, suggesting perfect timesharing. Experiment 2 showed that a reduction of dual-task costs requires practice on the combination of the 2 updating tasks, not just practice on each individual task. Hence, the reduction of dual-task costs cannot be explained by shortening or automatization of individual operations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Foot and hand area mu rhythms

Spontaneous EEG can display spatio-temporal patterns of desynchronized or synchronized alpha band activity. Event-related desynchronization (ERD) of rhythms within alpha and lower beta bands is characteristic of activated cortical areas ready to process information or to prepare a movement, while event-related synchronization (ERS) in the same frequency bands can be seen as an electrophysiological correlate of resting or idling cortical areas. EEG was investigated over primary sensorimotor and premotor areas during discrete hand and foot movements. ERD was found over the primary hand area during finger movement and over the primary foot area during toe movement. The former was observed in every subject, the latter was more difficult to find. From these results it can be speculated that each primary sensorimotor area has its own intrinsic rhythm, which becomes desynchronized when the corresponding area is activated. ERS, in the form of an enhanced mu rhythm on electrodes overlying the primary hand area, was observed not only during visual processing but also during foot movement. In both cases, the hand area is not needed to perform a task and, therefore, can be considered to be in an idling state. The supplementary motor area (SMA) also plays an important role in preparation and planning of movement. It is demonstrated that this area also displays rhythmic activity within the alpha band, that is both linearly and non-linearly phase coupled to the intrinsic (mu) rhythm of the primary hand area. With planning and preparation of movement, this SMA rhythm is desynchronized and also the degree of coupling between the two areas decreases.     

Depression in multiple sclerosis: Relationship to working memory capacity.

Recent research has shown that depression in multiple sclerosis (MS) is associated with deficits on cognitively demanding tasks. One explanation for this relationship is that depressed NIS patients may have reduced working memory capacity. The present study was designed to test this hypothesis. Depressed NIS patients were compared with nondepressed MS patients and nondepressed healthy controls on a task of working memory capacity (reading span) and a short-term memory task not taxing working memory capacity (word span). In support of the capacity-reduction model, compared with the nondepressed groups, depressed MS patients performed significantly worse on reading span but not on word span. Additionally, reading span was significantly correlated with capacity-demanding tasks shown to be impaired in depressed NIS patients in previous reports. Results suggest that depressed MS patients are characterized by limited working memory capacity and that the central executive component of the working memory system may be most affected. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral blood flow in hypertensive patients: an initial report of reduced and compensatory blood flow responses during performance of two cognitive tasks

We asked whether the altered cerebral vasculature associated with essential hypertension might dampen or redirect the regional cerebral blood flow (rCBF) response to cognitive work. Relative rCBF was assessed with [(15)O]water positron emission tomography during a working memory task, a memory span task, and two perceptual control tasks. Unmedicated hypertensive patients and control subjects differed in rCBF response during both memory tasks. Hypertensives showed relatively diminished rCBF responses in right hemisphere areas combined with compensatory activation of homologous areas in the left cerebral cortex. Essential hypertension appears to selectively influence the circulatory reserve of portions of cerebral cortex and secondarily induce recruitment of other cortical areas to process certain tasks.     

Dynamic cortical networks of verbal and spatial working memory: effects of memory load and task practice

Working memory (WM), the ability to briefly retain and manipulate information in mind, is central to intelligent behavior. Here we take advantage of the high temporal resolution of electrophysiological measures to obtain a millisecond timescale view of the activity induced in distributed cortical networks by tasks that impose significant WM demands. We examined how these networks are affected by the type and amount of information to be remembered, and by the amount of task practice. Evoked potentials (EPs) were obtained from eight subjects performing spatial and verbal versions of a visual n-back WM task (n = 1, 2, 3) on each of three testing days. In well-trained subjects, WM tasks elicited transient responses reflecting different subcomponents of task processing, including transient (lasting 0.02-0.3 s) task-sensitive and load-sensitive EPs, as well as sustained responses (lasting 1-1.5 s), including the prestimulus Contingent Negative Variation (CNV), and post-stimulus frontal and parietal Slow Waves. The transient responses, with the exception of the P300, differed between the verbal and spatial task versions, and between trials with different response requirements. The P300 and the Slow Waves were not affected by task version but were affected by increased WM load. These results suggest that WM emerges from the formation of a dynamic cortical network linking task-specific processes with non-specific, capacity-limited, higher-order attentional processes. Practice effects on the EPs suggested that practice led to the development of a more effective cognitive strategy for dealing with lower-order aspects of task processing, but did not diminish demands made on higher order processes. Thus a simple WM task is shown to be composed of numerous elementary subsecond neural processes whose characteristics vary with type and amount of information being remembered, and amount of practice.     

Pretraining enhances recovery from visuospatial deficit following cerebellar dentate nucleus lesion.

Following bilateral lesions targeting lateral deep cerebellar nuclei, rats were subjected to a bridge test as a measure of visuomotor coordination and were trained on the Morris water maze (MWM) as a measure of visuospatial processing. Lesioned rats were significantly impaired in visuospatial processing, but not visuomotor coordination, relative to sham rats. In a 2nd experiment, rats were pretrained on a delayed spatial alternation task (T maze) before MWM training. Pretraining reversed the visuospatial deficit caused by the lesions as compared with nonpretrained rats. Results suggest that lateral deep cerebellar nuclei contribute to visuospatial processing with a negligible contribution to visuomotor skills and that visuospatial deficits resulting from lateral nuclei damage can be reversed with pretraining on a spatial working memory task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospective memory impairment in individuals with Parkinson's disease.

This study investigated prospective memory and its relationship to executive and memory functions in persons with Parkinson's disease (PD). Twenty-three individuals with PD and 25 healthy comparison participants participated in the study. In the prospective memory tasks, participants were asked to execute 3 actions after 20 min (time-based condition) or after a timer ring (event-based condition). A score was computed for the correct recall of the intention to perform the actions (prospective component) and for the correct execution of the actions (retrospective component). Participants with PD also received an extensive neuropsychological test battery. PD participants were less accurate than comparison participants in the prospective component of the time-based but not the event-based task. Individuals with PD were also impaired on the retrospective component of both tasks. In the PD group, a general trend toward significant correlations was found between performance level on the prospective memory component of the time-based task and scores on executive and working memory measures. These results document that prospective memory is impaired in PD possibly in relation to a dysregulation of cognitive functions associated with frontal systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Practice and working memory effects in building procedural skill.

Several theories assume that practice (a) results in restructuring of component processes and (b) reduces demand on working memory. Eight subjects practiced judgments about digital logic gates for over 8,000 trials. At two practice levels, subjects made judgments while retaining short-term memory loads irrelevant to the judgments, relevant but not accessed, or accessed to make the judgments. Four phenomena together provide constraints for theory: First, performance declined in moving from blocked practice to randomized practice. Second, gate and judgment type strongly affected latency. Third, these effects declined but did not disapppear with practice. Fourth, the cost of accessing information in working memory remained substantial. These results are interpreted as reflecting a serial process with constant structure, while component processes become faster. The results challenge theories assuming that all learning results from restructuring or that restructuring is an automatic consequence of practice, and they support a distributed view of working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The development of prospective memory in typically developing children.

Objective: This study aimed to use specifically designed tasks to capture time-based, activity-based, and event-based prospective memory (PM) performance in typically developing school-age children. Method: Two PM tasks (Fishing Game & Happy Week) were used to examine the developmental patterns of PM in these children. Retrospective memory (RM) was also examined in these tasks. A total of 120 children aged between 7 and 12 years (10 girls and 10 boys in each age band) were recruited. Tests of working memory, inhibition, and IQ were also administered. Results: The age effect on PM accuracy was significant, with improvements identified between ages 7 to 8 and 10 to 11 years. For both tasks, performance on the time-based PM task was significantly poorer than that on the event-based PM task, which in turn was significantly poorer than that on the activity-based PM task. In terms of errors, results indicated that while errors associated with the PM component of the tasks decreased with age, errors associated with the RM component showed an inverted-U shape. The different patterns of errors suggest qualitative as well as quantitative differences in PM development in children. Finally, IQ, working memory, and inhibition were found to relate to PM when age was partialed out. Conclusions: Results of the study highlight the importance of contextual cues, such as activities and events, for prospective remembering in children. In addition, they have provided a general picture of PM development in school-age children and have implications for educators and parents. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Spatial working memory deficits in the relatives of schizophrenic patients

BACKGROUND: Studies in nonhuman primates provide evidence that intact spatial working memory depends on the integrity of specific areas in the prefrontal cortex. Patients with schizophrenia have been shown to be impaired on spatial working memory tasks. Relatives of schizophrenic patients show a range of cognitive deficits in the absence of clinical symptoms (eg, thought disorder, eye tracking dysfunctions). We predicted that a significant proportion of relatives of schizophrenic patients would show deficits in working memory as measured by a delayed response task. METHODS: In experiment 1, we tested 18 schizophrenic patients, 15 first-degree relatives of schizophrenic patients, and 18 normal control subjects on an oculomotor delayed response task. In experiment 2, we assessed the performance of another group of 12 first-degree relatives of schizophrenic patients and 16 different normal control subjects on a visual-manual delayed response task. RESULTS: Relatives of schizophrenic patients showed significant deficits in working memory on both the oculomotor and visual-manual delayed response tasks. CONCLUSIONS: Some relatives of schizophrenic patients are impaired on tasks that tap spatial working memory and that implicate the prefrontal system. The delayed response paradigm may be useful in elucidating the multidimensionality of the schizophrenic phenotype.     

Working memory, response selection, and effortful processing in rats with medial prefrontal lesions.

Examined the effects of lesions of the prelimbic area of the prefrontal cortex on acquisition and retention of nonmatching (NMTS) and matching-to-sample (MTS) tasks. 64 male rats participated. Both tasks involved a reference and a working memory component, but only working memory was impaired by the lesions. A comparison of the 2 tasks revealed quantitatively similar deficits in postoperatively trained rats. In preoperatively trained rats, however, the deficits were more important in the MTS task than in the NMTS task. In addition, an effect of interference between successive trials was observed in the NMTS task but not in the MTS task. Perseverative tendencies were observed in the MTS task only. Results suggest that prefrontal lesions induce working memory deficits as a result of poor temporal encoding and increased susceptibility to interference, and impair effortful processing, such as that engaged in response selection mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory constraints on linear reasoning with spatial and temporal contents

The present article reports two experiments testing the use of working memory components during reasoning with temporal and spatial relations in four-term series problems. In the first experiment four groups of subjects performed reasoning tasks with temporal and with spatial contents either without (control) or with a secondary task (articulatory suppression, visuo-spatial suppression or central executive suppression). The second experiment tested the secondary task effects in a within-subjects design either on problems with a spatial content or on problems with a temporal content, and within each content domain either under conditions of self-paced or of fixed presentation of the premises. Both experiments found effects of all three secondary tasks on reasoning accuracy. This supports the hypothesis that the subjects construct spatial representations of the premise information with the support of visuo-spatial resources of working memory. The second experiment also showed that during premise intake, only visuo-spatial and central executive secondary tasks had an effect. The implications of the data for the working memory requirements of reasoning and for theories of linear reasoning are discussed.     

The biology of menopause

Rats with bilateral electrolytic lesions of perirhinal cortex (PRC) or sham control (SHAM) lesions were tested in spatial reference and working memory tasks in the radial arm maze. In experiment 1, one arm of the maze was baited and always located in a fixed position relative to the extra-maze environment. PRC lesioned animals made a significantly greater number of errors than did SHAM animals during initial training in this reference memory task and exhibited a delay-dependent impairment on trial 5 in a series when a delay period of 5, 60, 120, or 240 s was inserted between trials 4 and 5. In experiment 2, when a second group of the animals was tested on the standard radial arm maze working memory task, the performance of the PRC group was markedly impaired relative to controls. These data demonstrate that electrolytic PRC lesions result in a deficit in both spatial reference and spatial working memory tasks. These effects are interpreted as being consistent with the idea that PRC plays an important role in episodic memory processes. These processes may include the storage of information, which is required for the performance of spatial tasks.