Working memory and focal attention.

Measures of retrieval speed indicated that only a small subset of representations in working memory falls within the focus of attention. An n-back task, which required tracking an item 1, 2, or 3 back in a sequentially presented list, was used to examine the representation and retrieval of recent events and how control processes can be used to maintain an item in focal attention while concurrently processing new information. A speed–accuracy trade-off procedure was used to derive measures of the availability and the speed with which recent events can be accessed. Results converge with other time course studies in demonstrating that attention can be concurrently allocated only to a small number of memory representations, perhaps just 1 item. Measures of retrieval speed further demonstrate that order information is retrieved by a slow search process when an item is not maintained within focal attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working and strategic memory deficits in schizophrenia.

Working memory and its contribution to performance on strategic memory tests in schizophrenia were studied. Patients (n?=?18) and control participants (n?=?15), all men, received tests of immediate memory (forward digit span), working memory (listening, computation, and backward digit span), and long-term strategic (free recall, temporal order, and self-ordered pointing) and nonstrategic (recognition) memory. Schizophrenia patients performed worse on all tests. Education, verbal intelligence, and immediate memory capacity did not account for deficits in working memory in schizophrenia patients. Reduced working memory capacity accounted for group differences in strategic memory but not in recognition memory. Working memory impairment may be central to the profile of impaired cognitive performance in schizophrenia and is consistent with hypothesized frontal lobe dysfunction associated with this disease. Additional medial-temporal dysfunction may account for the recognition memory deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory for visual features and conjunctions in schizophrenia.

The visual working memory (WM) storage capacity of patients with schizophrenia was investigated using a change detection paradigm. Participants were presented with 2, 3, 4, or 6 colored bars with testing of both single feature (color, orientation) and feature conjunction conditions. Patients performed significantly worse than controls at all set sizes but demonstrated normal feature binding. Unlike controls, patient WM capacity declined at set size 6 relative to set size 4. Impairments with subcapacity arrays suggest a deficit in task set maintenance: Greater impairment for supercapacity set sizes suggests a deficit in the ability to selectively encode information for WM storage. Thus, the WM impairment in schizophrenia appears to be a consequence of attentional deficits rather than a reduction in storage capacity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability of formal thought disorder and referential communication disturbances in schizophrenia.

This study examined the degree to which different types of communication disturbances in the speech of 48 schizophrenia patients and 28 controls were variable and state related versus stable and traitlike. Clinically rated formal thought disorder and 5 types of referential disturbance showed substantial stability within participants over time. The sixth type of referential disturbance, the vague reference, was not stable over time. Formal thought disorder was associated with the severity of core psychotic symptoms in patients, whereas referential disturbances showed little or no association with positive or negative symptom severity. Furthermore, changes in psychotic symptoms over time were accompanied by corresponding changes in formal thought disorder but not referential disturbances. These results support the idea that some types of referential disturbances are traitlike and may be reflective of vulnerability as well as manifest illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative affective reactivity of different types of communication disturbances in schizophrenia.

Twenty-nine schizophrenic outpatients provided speech samples on affectively positive and negative topics. These samples were assessed for several different types of communication failures by using the Communication Disturbances Index. Frequencies of overinclusive references, ambiguous word meanings, and ambiguous referents increased in the affectively negative condition; frequencies of missing referents and instances of syntactic unclarity did not change across affective conditions. Degree of overall affective reactivity of speech was associated with severity of the core positive schizophrenic syndrome. These findings support the idea that different types of schizophrenic communication disturbances are associated with different underlying pathophysiological processes, that some are more reactive to affect than others, and that affective reactivity of these symptoms is associated with the positive schizophrenic process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Boundary disturbances in schizophrenia.

Studied 4 types of index associated with the concept of "boundary" with 171 psychiatric inpatients who were tested with the Rorschach and independently assessed on other aspects of psychopathology (e.g., measures of depersonalization, stimulus overinclusion, and derealization). Contaminations and fabulized combinations were correlated with indices of pathology from Rorschach and with other psychopathology measures. Penetration scores were related to some indices of psychopathology, while barrier scores were unrelated to pathology. Contaminations were more frequent in schizophrenics than in any other diagnostic group. Fabulized combinations were more frequent among schizophrenics and latent schizophrenics than in depressives. Penetration responses were less frequent in depressives than in any other group. Support was found for the hypothesis that schizophrenics give certain types of responses considered indicative of boundary disturbance such as contamination responses. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attention in schizophrenia.

Administered 8 dichotic shadowing tasks to 4 groups of patients, (delusional and nondelusional schizophrenics, nonschizophrenic psychiatric patients, and nonpsychiatric patients). The distraction used in the tasks was varied to determine which, if any, of the mechanisms involved in selective attention may be dysfunctional in schizophrenics. It was found that the topic of the distraction affected the performance of delusional schizophrenics differently than it affected the performance of the other groups. The loudness of the distraction affected all groups identically. Results suggest that attentional dysfunction in schizophrenia may be the product not of a breakdown of any of the mechanisms of selective attention but rather of an unusual manner of allocation attention. Delusional schizophrenics evidently differ from nonschizophrenics in the nature of the stimuli to which they attend and not in the actual ability to attend. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and control of attention in persons with Alzheimer's disease and mild cognitive impairment.

The goal of the present study was to assess 3 attentional control processes--divided attention, manipulation capacities, and inhibition--in persons with mild cognitive impairment (MCI) and with mild Alzheimer's disease (AD). Manipulation capacities were tested by comparing immediate serial recall with alphabetical-order recall of words. Divided attention was tested with the Brown-Peterson procedure, in which participants divide their attention between simple addition tasks and consonant trigrams over delays. Inhibition was tested with the Hayling procedure, in which participants complete sentences with words irrelevant to their context. Persons with AD showed severe impairment on the 3 attentional control components. Persons with MCI exhibited impaired performance on the Brown-Peterson procedure but normal performance on the other 2 tasks. With AD and MCI participants, there was a negative correlation between general cognitive deficits and impairment on attentional control tasks, indicating that attentional control deficits increase in the MCI/AD continuum. When separating MCI with and without significant subsequent decline, those with subsequent decline showed impaired performance on both the Brown-Peterson procedure and manipulation task. These data suggest that control of attention tasks can track AD at a preclinical stage and that impairment increases gradually during the preclinical phase of AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory, attention control, and the n-back task: A question of construct validity.

The n-back task requires participants to decide whether each stimulus in a sequence matches the one that appeared n items ago. Although n-back has become a standard "executive" working memory (WM) measure in cognitive neuroscience, it has been subjected to few behavioral tests of construct validity. A combined experimental- correlational study tested the attention-control demands of verbal 2- and 3-back tasks by presenting n = 1 "lure" foils. Lures elicited more false alarms than control foils in both 2- and 3-back tasks, and lures caused more misses to targets that immediately followed them compared with control targets, but only in 3-back tasks. N-back thus challenges control over familiarity-based responding. Participants also completed a verbal WM span task (operation span task) and a marker test of general fluid intelligence (Gf; Ravens Advanced Progressive Matrices Test; J. C. Raven, J. E. Raven, & J. H. Court, 1998). N-back and WM span correlated weakly, suggesting they do not reflect primarily a single construct; moreover, both accounted for independent variance in Gf. N-back has face validity as a WM task, but it does not demonstrate convergent validity with at least 1 established WM measure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory disturbances in schizophrenia

The recent literature on memory disorders in schizophrenic persons is reanalysed. The present interest in memory disorders as a core symptom of cognitive changes in schizophrenia derives from the fact that brain imaging methods have revealed a reduction of substance in the regions surrounding the lateral ventricles. Given this localisation, schizophrenics should suffer from pronounced memory deficits. The paper addresses (1) the role of memory disorders in an overall view of cognitive losses, (2) the pattern of memory losses (verbal vs non-verbal, short-term memory vs long-term memory, implicit vs explicit memory etc.) and (3) recent investigations based on simultaneous use of imaging procedures (fNMR, PET) and cortical activation during memory tasks. A survey of the literature renders it likely that frontal functions play an essential role in the type of memory deficits found among schizophrenics. Thus, a purely temporal localisation is unlikely. The reduced learning efficiency which accounts for most of the schizophrenics' cognitive problems points to a working memory disturbance. On the basis of these results, a model for the memory disorders of schizophrenics is developed. The model covers recent literature on working memory as well as neural network models of schizophrenic disorders. However, a differential psychopathological symptom and syndrome analysis remains a prerequisite for reducing the great variance of the schizophrenics' performance in memory tasks. The importance of cognitive rehabilitation for sociopsychiatric efforts aimed at re-integrating mentally ill persons should not be underestimated.     

Depression, self-focused attention, and the negative memory bias.

On the basis of self-regulatory perseveration theory, we hypothesized that the negative memory bias commonly found among depressed people is mediated by excess levels of self-focused attention and thus can be reduced by preventing depressed people from focusing on themselves. In Experiment 1, nondepressed and subclinically depressed college students were induced to either focus on themselves or externally and then to recall 10 events that had happened to themselves during the previous 2 weeks. Consistent with our hypotheses, events recalled by depressed Ss were more negative than events recalled by nondepressed Ss under conditions of self-focus but not under conditions of external focus. We conducted Experiment 2 to determine whether this effect was specific to self-referent events or generalizable to events that happened to other people. Experiment 2's findings replicated the previous findings for self-referent events but showed a different pattern for recall of events that happened to others, suggesting that self-focus reduces the negative memory bias among depressed individuals by deactivating their self-schemas. Theoretical and practical implications of these findings are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in Alzheimer-type dementia.

Reviews experimental studies of working memory in dementia of the Alzheimer type (DAT), mainly focusing on investigations using A. D. Baddeley and G. J. Hitch's (1974) working memory model as a framework (e.g., Baddeley, see record 1992-26150-001). These studies show that the articulatory or phonological loop system is intact in early dementia, with a substantial impairment in the central executive system. The neural basis for this impairment is discussed, as are the practical implications of the working memory deficits for the diagnosis and management of Alzheimer's disease (AD). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and changing-state hypothesis.

Effects of secondary tasks on serial short-term memory were investigated to test conflicting predictions derived from the working-memory model (A. D. Baddeley, 1986, 1997) and the changing-state hypothesis (D. M. Jones, P. Farrand, G. Stuart, & N. Morris, 1995). In Experiments 1 and 2, disruptions due to the changing-state characteristic of secondary tasks occurred in the encoding phase of spatial and verbal serial memory tasks but not in a retention interval. Experiments 3 and 4 revealed changing-state effects on tasks relying on central-executive resources. In Experiments 5 and 6, interference between central-executive demanding secondary tasks and serial short-term memory was larger during the encoding phase than the retention interval. Crossover dissociations emerged between spatial and verbal serial short-term memory. The results extend the findings of D. M. Jones et al. (1995) and support the working-memory account for interference in short-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory capacity and aphasia.

The talk presents a capacity theory of syntactic comprehension disorders in aphasia. The work described was done in collaboration with Patricia Carpenter and Akira Miyake. The theory assumes that aphasic patients still possess the structural (syntactic) and procedural knowledge necessary to perform syntactic analysis, but that they suffer from reductions in working memory capacity for language. The theory explains how reductions in working memory capacity can lead to the pattern of comprehension breakdown observed in aphasic patients. According to a resource-reduction view of comprehension impairments in aphasia, patients are assumed to have intact structural and procedural knowledge to parse various sentences, but suffer from consequences of severely reduced working memory resources. Two types of experiments provide relevant supporting data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in aged rats.

The performances of young and aged rats were compared on a spatial (spatial delayed nonmatching-to-sample) and a nonspatial (object delayed nonmatching-to-sample) test of working memory. Although evidence was found that aging slowed acquisition of both of these tasks, performance over different retention intervals of up to 60 sec was normal once the task was mastered. An impairment was found, however, in the performance of the spatial test when the number of locations to be remembered on each trial was increased from one to two. The conclusions of this study are that under some conditions, the retention capabilities of aged rats may not change and that some acquisition impairments do not reflect alterations in learning or memory per se, but, in common with other studies, deficits in the remembrance of spatial locations may be found. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory, short-term memory, and general fluid intelligence: A latent-variable approach.

A study was conducted in which 133 participants performed 11 memory tasks (some thought to reflect working memory and some thought to reflect short-term memory), 2 tests of general fluid intelligence, and the Verbal and Quantitative Scholastic Aptitude Tests. Structural equation modeling suggested that short-term and working memories reflect separate but highly related constructs and that many of the tasks used in the literature as working memory tasks reflect a common construct. Working memory shows a strong connection to fluid intelligence, but short-term memory does not. A theory of working memory capacity and general fluid intelligence is proposed: The authors argue that working memory capacity and fluid intelligence reflect the ability to keep a representation active, particularly in the face of interference and distraction. The authors also discuss the relationship of this capability to controlled attention, and the functions of the prefrontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory across nostrils.

Whether olfactory working memory involves verbal representations or neural images of odor per se remains unclear. This study investigated whether verbal representation influences performance in an olfactory delayed-match-to-sample task and used monorhinal presentation to generate hypotheses as to the underlying anatomy of this mechanism. The main findings were that (a) nameable odorants were easier to remember than hard-to-name odorants and (b) the nameability effect was more pronounced when the evaluation was done across nostrils. Considering these results within a proposed model implies dual representation in olfactory working memory: All odors, nameable and hard to name, are represented both perceptually and verbally. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuroendocrine influence on attention and memory.

Examined the effects of melanocyte-stimulating hormone (MSH) on attention and memory under conditions of constant darkness and constant illumination in a study with 60 male Holtzman albino rats. After acquiring a brightness discrimination problem, Ss were given either a reversal or memory task. Ss treated with MSH and those tested in the dark performed the reversal task significantly faster than Ss tested under constant illumination. Although differences in memory were detected between groups, these were not statistically significant. Results are interpreted to suggest that increased MSH levels lead to increased awareness of the environment in the rat and that functionally equivalent behavior among other species may derive from similar neuroendocrine substrates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)