strawberry notch encodes a conserved nuclear protein that functions downstream of Notch and regulates gene expression along the developing wing margin of Drosophila

Although many individuals with traumatic brain injury (TBI) perform well on standard neuropsychological tests, they often exhibit marked functional difficulties. The functions which are impaired seem to be analogous to the role of the central executive system (CES) in Baddeley's [Working Memory, 1986, Oxford University Press, New York] widely accepted model of working memory. The purpose of this study was to investigate CES function in individuals with TBI with a dual-task paradigm. We studied 25 non-demented persons who were at various stages in their recovery from severe TBI and compared their performance on a dual-task paradigm to a group of age-matched controls. Our dual-task paradigm measured performance on a simple visual reaction time task both alone (baseline) and during concurrent tasks of articulation or digit span. Subjects were also assessed with other neuropsychological tests of executive function. TBI patients had slower reaction times on the primary task when performed alone (P < 0.05) and greater decrements in performance during dual-task conditions (P < 0.01). They also exhibited significantly greater deficits than control subjects on other measures of executive function. Although correlations between dual-task performance and other executive measures were quite low, principle components analysis suggested that a common factor does exist between these measures. These findings support the conclusion that TBI patients have a working memory impairment that is due to dysfunction of the CES and which may be related to executive function deficits as measured by standard neuropsychological testing.     

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)     

Memory span procedures in Alzheimer's disease.

In a working memory framework, the forward memory span involves a subsidiary system that maintains information, and the backward span relies on a central executive system (CES) that allocates processing resources. The authors hypothesized that a measure of the CES derived from the backward span would distinguish Alzheimer's disease (AD) patients (n&≠&?9) from elderly controls without dementia (n&≠&?9), vary as a function of disease severity, and underlie other cognitive disturbances. Memory span procedures were Digit Span Forward and Backward and Visual Memory Span Forward and Backward. Derived CES measures discriminated between groups, predicted dementia severity, and predicted performance on some of the cognitive tasks examined. However, working memory subsidiary systems also appeared to be affected in AD, and some cognitive deficits in AD were independent of working memory disturbances. The visual memory span backward was the best predictor of group and of dementia severity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Depressed mood in multiple sclerosis: Relationship to capacity-demanding memory and attentional functioning.

Because it is theorized that depression results in reduced available attentional capacity that, in turn, can explain the impaired performance on capacity-demanding tasks in depressed individuals, the authors predicted that multiple sclerosis (MS) patients with depressed mood would have difficulty with these types of tasks. Twenty depressed mood MS participants were compared with 41 nondepressed mood MS participants and 8 nondepressed mood controls on 5 attentional capacity-demanding clinical memory and attentional tasks and 3 tasks with minimal capacity demands. Depressed mood MS patients performed significantly worse than both nondepressed mood groups on the 3 speeded capacity-demanding attentional measures but not on any of the tasks requiring few capacity demands, supporting the authors' predictions. The possibility that the impaired performance of depressed mood MS patients on speeded attentional tasks was mediated by reduced verbal working memory capacity, impaired deployment of executive strategies that access working memory capacity, or psychomotor slowing is explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory and the control of action: Evidence from task switching.

A series of 7 experiments used dual-task methodology to investigate the role of working memory in the operation of a simple action-control plan or program involving regular switching between addition and subtraction. Lists requiring switching were slower than blocked lists and showed 2 concurrent task effects. Demanding executive tasks impaired performance on both blocked and switched lists, whereas articulatory suppression impaired principally the switched condition. Implications for models of task switching and working memory and for the Vygotskian concept of verbal control of action are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interfering with the central executive by means of a random interval repetition task

Four dual-task experiments are reported in which a short-term memory task is performed concurrently with a random interval repetition task, which was designed to interfere with functions normally attributed to the central executive in the working memory model of Baddeley and Hitch (1974). The task was found to interfere with supra-span serial recall and with backward memory span, but did not disrupt performance on a forward-memory-span task. The effects were observed in dissociation with effects of articulatory suppression and matrix tapping, so that the locus of the effects of the new task is not due to the slave systems. In addition, single-task random-interval repetition performance was sampled and compared to performance in the dual-task conditions of all four experiments. Although quality of tapping performance differed between the single-task and the dual-task conditions, it was not related to recall performance. All the results are discussed with reference to the working memory model.     

Study of Verbal Working Memory in Patients With Parkinson's Disease.

The authors examined the nature of the working memory deficit in persons with Parkinson's disease (PD). Three hypotheses were tested: a limited storage capacity, an impaired executive component, and a reduction of psychomotor speed. Verbal working memory was assessed in 14 PD patients without dementia and 14 matched control participants. Participants were administered a classical verbal span test, working memory tasks that required either updating or manipulation capacities, and motor and psychomotor speed tasks. Patients' performance was comparable to that of control participants on the verbal span test. However, results on the working memory tasks indicated a deficit in manipulation with normal updating capacities. Motor and psychomotor slowing were found in the patient group, but slowing could not fully account for the impairment observed in the manipulation task. Results indicated that there is a genuine but selective working memory impairment in patients with PD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distribution of the Rhesus haplotype frequencies in the Düsseldorf administrative center (North Rhine-Westphalia)

Patients with medically intractable epilepsy and either hippocampal sclerosis or frontal lobe lesions were compared with healthy controls, to investigate a possible neuroanatomical correlate of a component of working memory: the central executive. Patients were tested on a short-term memory task which comprised visuo-spatial and verbal components, in single and concurrent trials. Differences were found between the patient groups for dual-task capacity, despite being equated on single-task trials. Patients with frontal lobe damage were the most affected by the demands of attention division. The results of this study do not support the thesis of a hippocampal role in the working memory component examined, but point to a frontal lobe focus for this janusian cognitive function. An unexpected finding of an increment in performance over the trials of visuo-spatial assessment, in patients with hippocampal sclerosis, is presented.     

Differential deficit in executive control in euthymic bipolar disorder.

Patients with remitted bipolar disorder (BD) have persistent cognitive deficits, but the nature and specificity of this deficit remain unclear. The authors evaluated the executive hypothesis of BD by determining whether (a) patients' executive deficits qualify as differential deficits, that is, that these significantly exceed deficits in other cognitive domains; (b) deficits in particular executive functions are evident, and (c) executive difficulties mediate declarative memory deficits in BD. The cognitive performance of 63 prospectively verified euthymic bipolar patients was compared with controls, using J. Baron and R. Trieman's (1980) method of testing for differences in nonindependent correlations. There were no differential deficits within the executive domain. Patients' generic executive performance was differentially impaired relative to primary verbal memory and retention in declarative memory, but not relative to their declarative recall, recognition, or their psychomotor performance. However, patients' executive deficit was not an artifact of their poor psychomotor performance. Executive performance accounted for all but a trivial portion of the between-group variance in declarative memory. Persistent cognitive difficulties in euthymic bipolar disorder (EBD) are thus usefully characterized as a generic dysexecutive syndrome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Objective Measurement of Cognitive Fatigue in Multiple Sclerosis.

Objective: Objective examination of cognitive fatigue in persons with multiple sclerosis (MS). Participants: Fifty-six individuals with MS and 39 age- and education-matched healthy control subjects. Main Outcome Measures: Cognitive fatigue, operationalized as the failure to sustain effort over the course of a continuous working memory task; performance on the Paced Auditory Serial Addition Test was examined, with number of correct responses generated and responses produced under conditions of sustained central executive load as the dependent variables. Results: Cognitively impaired MS subjects produced significantly fewer correct responses than either nonimpaired MS subjects or healthy control subjects, who performed at a comparable level. Both MS groups, however, showed susceptibility to cognitive fatigue significantly earlier in time than the healthy group. Conclusions: Fatigue can influence performance even in the absence of cognitive impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Executive Functioning, Memory, and Learning in Phenylketonuria.

The executive deficit hypothesis of treated phenylketonuria (PKU) suggests that dopaminergic depletion in the lateral prefrontal cortex leads to selective executive impairment. This was examined by comparing adults with PKU on a lifelong diet with a matched healthy control group. Those with PKU were impaired on selective and sustained attention, working memory (Self-Ordered Pointing), and letter fluency. However, they failed to show differential sensitivity to increased cognitive load on the attentional and working memory tasks, and they did not differ significantly on the remaining executive tasks (rule finding, inhibition, and multitasking). Nor did they differ significantly on recall or recognition memory. Overall, the findings provided little support for the executive deficit hypothesis. A possible explanation in terms of slowed information processing speed is explored. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Working memory in learning disability subgroups

The purpose of this study was to investigate (a) the degree to which working memory differences between learning-disabled and nondisabled children reflect a specific or generalized deficit, and (b) whether limitations in the enhancement of learning-disabled student's working memory performance are attributable to process or storage functions. To this end, performances of reading-disabled, math-disabled, chronological age (CA)-matched, and achievement-matched children were compared on verbal and visual-spatial working memory measures under initial, gain, and maintenance conditions. The results indicated that: (a) learning-disabled subtypes were not differentiated by their performance on verbal and visual-spatial working memory measures; and (b) learning-disabled children's working memory performance was inferior to CA-matched and superior to achievement-matched counterparts across initial, gain, and maintenance conditions. The results suggest that learning-disabled children suffer generalized working memory deficits, possibly due to storage constraints in the executive system.     

Modification of glassy carbon surfaces with synthetic laminin-derived peptides for nerve cell attachment and neurite growth

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.     

Categorization of novel animals by patients with Alzheimer's disease and corticobasal degeneration.

We taught a novel animal category by rule-based and similarity-based processes to participants with Alzheimer's disease (AD), corticobasal degeneration (CBD), and healthy age-matched participants. Healthy participants successfully categorized by either process. AD patients' rule-based categorization was impaired, while their similarity-based categorization resembled that of healthy participants. Correlations of AD patients' performance with measures of executive functioning suggested a deficit in the cognitive resources necessary for engaging rule-based categorization. The contribution of limited executive resources to categorization difficulty in AD was further demonstrated in a second experiment in which features determining category membership were of lower salience. CBD patients were relatively impaired at similarity-based processing, suggesting that qualitatively distinct categorization processes can be selectively compromised in patients with focal neurodegenerative diseases. Moreover, AD patients' impaired categorization correlated with performance on a measure of semantic memory, implicating this categorization deficit in AD patients' semantic memory difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Memory dysfunction in multiple sclerosis: Its relation to working memory, semantic encoding, and implicit learning.

Memory disturbance is common in patients with multiple sclerosis (MS), as previously demonstrated on clinical memory tests of explicit learning using effortful retrieval paradigms. To better understand the mechanisms underlying memory failure, the authors compared the performance of 46 MS patients and 47 demographically matched normal controls on experimental tests of working memory, semantic encoding, and implicit memory. On the working memory task, MS patients demonstrated an exaggerated word length effect, which indicates a deficit in the control process of articulatory rehearsal. In contrast, MS patients demonstrated a normal buildup and release from proactive inhibition, which suggests intact semantic encoding. Finally, on priming and procedural memory tasks, MS patients performed without difficulty. The MS patients' test performance was not correlated with illness duration or course, severity of physical disability, or psychoactive medication use. (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)     

Cognitive estimation impairment in Alzheimer disease and mild cognitive impairment.

Intact executive functioning is believed to be required for performance on tasks requiring cognitive estimations. This study used a revised version of a cognitive estimations test (CET) to investigate whether patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) were impaired on the CET compared with normal elderly controls (NECs). Neuropsychological tests were administered to determine the relationship between CET performance and other cognitive domains. AD patients displayed impaired CET performance when compared with NECs but MCI patients did not. Negative correlations between tests of working memory (WM) and semantic memory and the CET were found in NECs and AD patients, indicating that these cognitive domains were important for CET performance. Regression analysis suggests that AD patients were unable to maintain semantic information in WM to perform the task. The authors conclude that AD patients display deficits in working memory, semantic memory, and executive function, which are required for adequate CET performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age and working memory: The role of perceptual speed, the central executive, and the phonological loop.

In a study (N?=?61) comparing older (age range?=?60–80 years, M?=?67) and younger (age range?=?20-33 years, M?=?25) people, age deficits were observed in working memory, perceptual speed, and central executive functioning but not in phonological loop functioning. Controlling for age differences in central executive performance removed over 50% of the age-related variance in working memory span. However, controlling for perceptual speed removed all of the age-related variance in working memory span. In addition, age differences in central executive functioning were largely eliminated after controlling for age deficits in perceptual speed. These findings suggest that age differences in central executive functioning are primarily attributable to a general slowdown in the rate at which information is activated within the working memory system and that no specific deficits in the central executive occur as a consequence of aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anatomical specificity and time-dependence of chlordiazepoxide-induced spatial memory impairments.

Injection of the benzodiazepine (BDZ) chlordiazepoxide (CDP) into the medial septum (MS) produced a dose-dependent retrograde working memory deficit in a delayed non-match-to-sample radial-arm maze task. CDP (30 nmol; 10 μg) decreased the number of correct choices and increased the number of errors without altering latency to make arm choices. The effects of CDP were site specific; injection into regions proximate to the MS, including the lateral septum, the anterior cingulate, and the nucleus basalis magnocellularis, did not affect any index of performance. The second experiment demonstrated that CDP impaired working memory only when rats were injected either 0 or 60 min, but not 15, 30, or 45 min, following training. The MS appears (a) to contribute to both early (encoding/maintenance) and late (retrieval/utilization) phases of working memory and (b) to be a critical site of action for BDZ-induced deficits in spatial working memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Performance of everyday actions in mild Alzheimer's disease.

Early neuropsychological deficits associated with mild Alzheimer's disease (AD) have been characterized as memory deficits and impaired executive function or attention. The functional impact of early impairment was investigated by evaluating performance of everyday actions in older adults with mild AD (n = 15) as compared with healthy age-matched controls (n = 16). Everyday actions were familiar activities, for example, making a cup of tea, but were varied in complexity (simple, complex) and were performed under varied attention demand (single task, dual task). Although both participant groups responded to increasing task complexity by making more errors, the AD group made more errors under dual-task conditions regardless of the complexity of the task. Furthermore, a task requiring strategic retrieval of semantic information from long-term memory and manipulation of attention online (category fluency) was able to account for a large proportion of the group-related variance in everyday task performance. Results are discussed in relation to the role of components of working memory in performance of everyday actions in mild AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)