27 results on '"Kaiser ST"'
Search Results
2. Performance of Coded Uplink MC-CDMA with Combined Pre- and Post-Equalization in Fading Channels
- Author
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Cosovic, I., Kaiser, St., Schnell, M., and Springer, A.
- Subjects
MC-CDMA ,Performance ,Coded Uplink ,Fading Channel - Published
- 2004
3. The Doppler Spread—Gaining Diversity for Future Mobile Radio Systems
- Author
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Raulefs, R., Dammann, A., Kaiser, St., and Auer, G.
- Subjects
Mobile Radio Systems ,Spread-Gaining ,Doppler - Published
- 2003
4. Rotatet Spreading Sequences for Broadband Multicarrier-CDMA
- Author
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Raulefs, R., Dammann, A., Kaiser, St., and Auer, G.
- Subjects
MC-CDMA ,Spreading Sequences - Published
- 2003
5. Rotated Transforms for MC-CDMA
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Raulefs, R., Dammann, A., Sand, S., and Kaiser, St.
- Subjects
MC-CDMA ,Rotatet Transforms - Published
- 2003
6. Multi User Detetection and Channel Estimation with Rotatet Transforms for MC-CDMA
- Author
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Raulefs, R., Dammann, A., Kaiser, St., and Auer, G.
- Subjects
MC-CDMA ,Multi User Detetection ,Rotatet Transforms ,Channel Estimation - Published
- 2003
7. Combining a ML Detector with Rotated Transforms for MC-CDMA
- Author
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Raulefs, R., Dammann, A., Kaiser, St., and Auer, G.
- Subjects
MC-CDMA ,ML Detector ,Rotatet Transform - Published
- 2003
8. Transmitter Space-Time Diversity for Broadband MC-CDMA Systems
- Author
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Raulefs, R., Dammann, A., Kaiser, St., and Auer, G.
- Subjects
MC-CDMA ,Space-Time Diversity ,Transmitter - Published
- 2003
9. Literaturrecherchen zum Einsatz von Lichtwellenleitern in Composite Health Monitoring
- Author
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Kaiser, St.
- Published
- 1997
10. Who are „Young Carers'? Analysis of the Use of the Term in German Speaking Countries and Development of a Definition / Wer sind Young Carers? Analyse der Begriffsverwendung im deutschsprachigen Raum und Entwicklung einer Definition
- Author
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Frech Marianne, Nagl-Cupal Martin, Leu Agnes, Schulze Gisela C., Spittel Anna-Maria, and Kaiser Steffen
- Subjects
young carers ,young caregivers ,definition ,concept analysis ,pflegende kinder und jugendliche ,junge pflegende ,kinder und jugendliche als pflegende angehörige ,begriffsanalyse ,Public aspects of medicine ,RA1-1270 - Abstract
Children and adolescents with caring responsibility who are looking after a family member or a person close are often hiding from the view of the public. They are not well recognised from professionals from health care, education and social services. Several research as well as support programmes have been initiated within the last years. It became obvious that the term ‘young carers’ was translated in various ways into German and connected with different attributes. An integral understanding is yet of high relevance for the international dialogue as well as for the transfer from theory to practice.
- Published
- 2019
- Full Text
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11. Person–Environment Analysis: A Framework for Participatory Holistic Research
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Kaiser Steffen and Schulze Gisela C.
- Subjects
person–environment analysis ,kurt lewin ,field theory ,gestalt psychology ,participatory research ,Philosophy. Psychology. Religion ,Psychology ,BF1-990 - Abstract
This article presents the person–environment analysis as a framework for participatory and holistic research. By using common methods of qualitative research and analysis, it is possible to capture the present situation of a person. The person–environment analysis is built on Kurt Lewin’s field theory and a further development of its system of visual representation of the life space. It is argued that the person–environment analysis offers a frame to represent the perceived subjective situation of a person, which can be used in research, yet offers the possibility of counseling and intervention.
- Published
- 2018
- Full Text
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12. Editorial
- Author
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Petré Frederik, Kondoz Ahmet, Kaiser Stefan, and Pandharipande Ashish
- Subjects
Telecommunication ,TK5101-6720 ,Electronics ,TK7800-8360 - Published
- 2005
- Full Text
- View/download PDF
13. Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System
- Author
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Raulefs Ronald, Dammann Armin, Sand Stephan, Kaiser Stefan, and Auer Gunther
- Subjects
code division multiaccess ,Walsh-Hadamard spreading sequences ,multicarrier ,fading channels ,concatenated channel coding ,Telecommunication ,TK5101-6720 ,Electronics ,TK7800-8360 - Abstract
We investigate rotated Walsh-Hadamard spreading matrices for a broadband MC-CDMA system with robust channel estimation in the synchronous downlink. The similarities between rotated spreading and signal space diversity are outlined. In a multiuser MC-CDMA system, possible performance improvements are based on the chosen detector, the channel code, and its Hamming distance. By applying rotated spreading in comparison to a standard Walsh-Hadamard spreading code, a higher throughput can be achieved. As combining the channel code and the spreading code forms a concatenated code, the overall minimum Hamming distance of the concatenated code increases. This asymptotically results in an improvement of the bit error rate for high signal-to-noise ratio. Higher convolutional channel code rates are mostly generated by puncturing good low-rate channel codes. The overall Hamming distance decreases significantly for the punctured channel codes. Higher channel code rates are favorable for MC-CDMA, as MC-CDMA utilizes diversity more efficiently compared to pure OFDMA. The application of rotated spreading in an MC-CDMA system allows exploiting diversity even further. We demonstrate that the rotated spreading gain is still present for a robust pilot-aided channel estimator. In a well-designed system, rotated spreading extends the performance by using a maximum likelihood detector with robust channel estimation at the receiver by about 1 dB.
- Published
- 2004
- Full Text
- View/download PDF
14. Pulsatile dry cupping in patients with osteoarthritis of the knee – a randomized controlled exploratory trial
- Author
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Teut Michael, Kaiser Stefan, Ortiz Miriam, Roll Stephanie, Binting Sylvia, Willich Stefan N, and Brinkhaus Benno
- Subjects
Cupping ,Complementary and alternative medicine ,Randomized controlled trial ,Knee osteoarthritis ,Other systems of medicine ,RZ201-999 - Abstract
Abstract Introduction Cupping is used in various traditional medicine forms to relieve pain in musculoskeletal diseases. The aim of this study was to investigate the effectiveness of cupping in relieving the symptoms of knee osteoarthritis (OA). Methods In a two-group, randomized controlled exploratory pilot study patients with a clinically and radiological confirmed knee OA (Kellgren-Lawrence Grading Scale: 2-4) and a pain intensity > 40 mm on a 100 mm visual analogue scale (VAS) were included. 40 Patients were randomized to either 8 sessions of pulsatile dry cupping within 4 weeks or no intervention (control). Paracetamol was allowed on demand for both groups. Outcomes were the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) score, the pain intensity on a VAS (0 mm = no pain to 100 mm = maximum intensity) and Quality of Life (SF-36) 4 and 12 weeks after randomization. Use of Paracetamol was documented within the 4-week treatment period. Analyses were performed by analysis of covariance adjusting for the baseline value for each outcome. Results 21 patients were allocated to the cupping group (5 male; mean age 68 ± SD 7.2) and 19 to the control group (8 male; 69 ± 6.8). After 4 weeks the WOMAC global score improved significantly more in the cupping group with a mean of 27.7 (95% confidence interval 22.1; 33.3) compared to 42.2 (36.3; 48.1) in the control group (p = 0.001). After 12 weeks the WOMAC global score were still significantly different in favor for cupping (31.0 (24.9; 37.2) vs. 40.8 (34.4; 47.3) p = 0.032), however the WOMAC subscores for pain and stiffness were not significant anymore. Significantly better outcomes in the cupping group were also observed for pain intensity on VAS and for the SF-36 Physical Component Scale compared to the control group after 4 and 12 weeks. No significant difference was observed for the SF-36 Mental Component Scale and the total number of consumed Paracetamol tablets between both groups (mean 9.1, SD ± 20.0 vs. 11.5 ± 15.9). Conclusion In this exploratory study dry cupping with a pulsatile cupping device relieved symptoms of knee OA compared to no intervention. Further studies comparing cupping with active treatments are needed. Trial registration Clinicaltrials.gov Identifier: NCT01057043
- Published
- 2012
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15. Planning and problem-solving training for patients with schizophrenia: a randomized controlled trial
- Author
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Backenstraß Matthias, Roesch-Ely Daniela, Holt Daniel V, Rentrop Mirjam, Rodewald Katlehn, Funke Joachim, Weisbrod Matthias, and Kaiser Stefan
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Psychiatry ,RC435-571 - Abstract
Abstract Background The purpose of this study was to assess whether planning and problem-solving training is more effective in improving functional capacity in patients with schizophrenia than a training program addressing basic cognitive functions. Methods Eighty-nine patients with schizophrenia were randomly assigned either to a computer assisted training of planning and problem-solving or a training of basic cognition. Outcome variables included planning and problem-solving ability as well as functional capacity, which represents a proxy measure for functional outcome. Results Planning and problem-solving training improved one measure of planning and problem-solving more strongly than basic cognition training, while two other measures of planning did not show a differential effect. Participants in both groups improved over time in functional capacity. There was no differential effect of the interventions on functional capacity. Conclusion A differential effect of targeting specific cognitive functions on functional capacity could not be established. Small differences on cognitive outcome variables indicate a potential for differential effects. This will have to be addressed in further research including longer treatment programs and other settings. Trial registration ClinicalTrials.gov NCT00507988
- Published
- 2011
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16. Anemia is an independent risk for mortality after acute myocardial infarction in patients with and without diabetes
- Author
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Kaiser Stephanie M, Cox Jafna L, O'Connell Colleen M, Ransom Thomas PP, Shu David H, Gee Shirl A, Rowe Richard C, Ur Ehud, and Imran Syed
- Subjects
Diseases of the circulatory (Cardiovascular) system ,RC666-701 - Abstract
Abstract Introduction Anemia and diabetes are risk factors for short-term mortality following an acute myocardial infarction(AMI). Anemia is more prevalent in patients with diabetes. We performed a retrospective study to assess the impact of the combination of diabetes and anemia on post-myocardial infarction outcomes. Methods Data relating to all consecutive patients hospitalized with AMI was obtained from a population-based disease-specific registry. Patients were divided into 4 groups: diabetes and anemia (group A, n = 716), diabetes and no anemia (group B, n = 1894), no diabetes and anemia (group C, n = 869), and no diabetes and no anemia (group D, n = 3987). Mortality at 30 days and 31 days to 36 months were the main outcome measures. Results 30-day mortality was 32.3% in group A, 16.1% in group B, 21.5% in group C, 6.6% in group D (all p < 0.001). 31-day to 36-month mortality was 47.6% in group A, 20.8% in group B, 34.3% in group C, and 10.4% in group D (all p < 0.001). Diabetes and anemia remained independent risk factors for mortality with odds ratios of 1.61 (1.41–1.85, p < 0.001) and 1.59 (1.38–1.85, p < 0.001) respectively at 36 months. Cardiovascular death from 31-days to 36-months was 43.7% of deaths in group A, 54.1% in group B, 47.0% in group C, 50.8% group D (A vs B, p < 0.05). Interpretation Patients with both diabetes and anemia have a significantly higher mortality than those with either diabetes or anemia alone. Cardiovascular death remained the most likely cause of mortality in all groups.
- Published
- 2006
- Full Text
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17. Editorial
- Author
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Kondoz Ahmet, Pandharipande Ashish, Kaiser Stefan, and Petré Frederik
- Subjects
Telecommunication ,TK5101-6720 ,Electronics ,TK7800-8360 - Published
- 2005
18. Rotated Walsh-Hadamard Spreading with Robust Channel Estimation for a Coded MC-CDMA System
- Author
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Auer Gunther, Raulefs Ronald, Dammann Armin, Sand Stephan, and Kaiser Stefan
- Subjects
code division multiaccess ,Walsh-Hadamard spreading sequences ,multicarrier ,fading channels ,concatenated channel coding ,Telecommunication ,TK5101-6720 ,Electronics ,TK7800-8360 - Abstract
We investigate rotated Walsh-Hadamard spreading matrices for a broadband MC-CDMA system with robust channel estimation in the synchronous downlink. The similarities between rotated spreading and signal space diversity are outlined. In a multiuser MC-CDMA system, possible performance improvements are based on the chosen detector, the channel code, and its Hamming distance. By applying rotated spreading in comparison to a standard Walsh-Hadamard spreading code, a higher throughput can be achieved. As combining the channel code and the spreading code forms a concatenated code, the overall minimum Hamming distance of the concatenated code increases. This asymptotically results in an improvement of the bit error rate for high signal-to-noise ratio. Higher convolutional channel code rates are mostly generated by puncturing good low-rate channel codes. The overall Hamming distance decreases significantly for the punctured channel codes. Higher channel code rates are favorable for MC-CDMA, as MC-CDMA utilizes diversity more efficiently compared to pure OFDMA. The application of rotated spreading in an MC-CDMA system allows exploiting diversity even further. We demonstrate that the rotated spreading gain is still present for a robust pilot-aided channel estimator. In a well-designed system, rotated spreading extends the performance by using a maximum likelihood detector with robust channel estimation at the receiver by about 1 dB.
- Published
- 2004
19. Hyperfocusing of attention on goal-related information in schizophrenia: Evidence from electrophysiology.
- Author
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Sawaki R, Kreither J, Leonard CJ, Kaiser ST, Hahn B, Gold JM, and Luck SJ
- Subjects
- Adult, Female, Humans, Male, Middle Aged, Attention physiology, Evoked Potentials physiology, Executive Function physiology, Goals, Schizophrenia physiopathology
- Abstract
Schizophrenia clearly involves impairments of attention, but the precise nature of these impairments has been difficult to determine. One possibility is that the deficit in attention is a secondary consequence of a deficit in goal maintenance. However, recent research suggests that people with schizophrenia (PSZ) actually focus attention more strongly on objects containing goal-relevant features. To test these competing hypotheses, we recorded event-related potentials (ERPs) from PSZ (N = 20) and healthy control subjects (HCS; N = 20) while they looked for a particular target color at fixation and tried to ignore lateral distractors that sometimes matched the target color (target-color distractors). Goal maintenance was made trivially easy by the continual presentation of a goal reminder. We found that HCS were able to successfully suppress target-color distractors (leading to a distractor positivity ERP component), whereas PSZ focused attention on these items (leading to an N2-posterior-contralateral ERP component). This suggests that, when maintaining a task set, PSZ engage in aberrant focusing of attention, or hyperfocusing, on goal-relevant features. (PsycINFO Database Record, ((c) 2017 APA, all rights reserved).)
- Published
- 2017
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20. Testing sensory and cognitive explanations of the antisaccade deficit in schizophrenia.
- Author
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Leonard CJ, Robinson BM, Kaiser ST, Hahn B, McClenon C, Harvey AN, Luck SJ, and Gold JM
- Subjects
- Adult, Analysis of Variance, Case-Control Studies, Female, Humans, Male, Memory, Short-Term physiology, Photic Stimulation, Sensory Thresholds physiology, Visual Pathways physiology, Cognition physiology, Saccades physiology, Schizophrenia physiopathology
- Abstract
Recent research has suggested that people with schizophrenia (PSZ) have sensory deficits, especially in the magnocellular pathway, and this has led to the proposal that dysfunctional sensory processing may underlie higher-order cognitive deficits. Here we test the hypothesis that the antisaccade deficit in PSZ reflects dysfunctional magnocellular processing rather than impaired cognitive processing, as indexed by working memory capacity. This is a plausible hypothesis because oculomotor regions have direct magnocellular inputs, and the stimuli used in most antisaccade tasks strongly activate the magnocellular visual pathway. In the current study, we examined both prosaccade and antisaccade performance in PSZ (N = 22) and matched healthy control subjects (HCS; N = 22) with Gabor stimuli designed to preferentially activate the magnocellular pathway, the parvocellular pathway, or both pathways. We also measured working memory capacity. PSZ exhibited impaired antisaccade performance relative to HCS across stimulus types, with impairment even for stimuli that minimized magnocellular activation. Although both sensory thresholds and working memory capacity were impaired in PSZ, only working memory capacity was correlated with antisaccade accuracy, consistent with a cognitive rather than sensory origin for the antisaccade deficit., (PsycINFO Database Record (c) 2013 APA, all rights reserved.)
- Published
- 2013
- Full Text
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21. Toward the neural mechanisms of reduced working memory capacity in schizophrenia.
- Author
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Leonard CJ, Kaiser ST, Robinson BM, Kappenman ES, Hahn B, Gold JM, and Luck SJ
- Subjects
- Adult, Electroencephalography, Evoked Potentials physiology, Female, Humans, Male, Memory Disorders etiology, Memory Disorders physiopathology, Neuropsychological Tests, Schizophrenia complications, Signal Processing, Computer-Assisted, Brain physiopathology, Memory, Short-Term physiology, Schizophrenia physiopathology
- Abstract
People with schizophrenia (PSZ) demonstrate reliable reductions in working memory (WM) capacity (i.e., the number of objects that can be held in memory). The present study asked whether WM impairments in PSZ can be explained by the same neural mechanisms that underlie individual differences in WM capacity among healthy individuals. Specifically, we examined event-related potentials in PSZ and healthy matched controls during a change detection task that required the storage of multiple objects in WM. The amplitude of contralateral delay activity (CDA), which correlates with WM capacity in healthy individuals, was larger in controls than in PSZ for memory loads of 3 and 5 objects, but larger in PSZ than in controls for a memory load of 1. This same pattern was found in the subgroups of PSZ and controls with an equivalent WM capacity. Moreover, the increase in CDA amplitude was correlated with individual differences in capacity in controls, but not in PSZ. These results demonstrate that WM impairment in PSZ is not associated with the same patterns of neural activity that characterize low WM capacity in healthy individuals. We propose that WM impairment in PSZ instead reflects a specific impairment in the ability to distribute attention broadly.
- Published
- 2013
- Full Text
- View/download PDF
22. Kraepelin and Bleuler had it right: people with schizophrenia have deficits sustaining attention over time.
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Hahn B, Robinson BM, Kaiser ST, Matveeva TM, Harvey AN, Luck SJ, and Gold JM
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- Adolescent, Adult, Humans, Male, Middle Aged, Neuropsychological Tests, Photic Stimulation, Reaction Time physiology, Young Adult, Attention physiology, Schizophrenia physiopathology, Schizophrenic Psychology, Visual Perception physiology
- Abstract
An inability to sustain attention was noted in the original clinical descriptions of schizophrenia, but the vast majority of experimental studies have failed to report a performance decrement over time, calling this observation into question. To test for such deficits when task conditions conform to basic science taxonomy for the validity of sustained attention tasks, a dynamic stimulus array was presented in which targets, differing subtly from standard stimuli, were presented infrequently and unpredictably. Both people with schizophrenia (PSZ, n=40) and healthy control subjects (HCS, n=29) displayed a reduction in hit rate and an increase in reaction time (RT) from the first to the second 5-min period. Thereafter, the hit rate of HCS recovered and remained stable, while that of PSZ continued to decline. When performance at task onset was equated between groups, the decrement over time in PSZ remained of the same robust magnitude. Thus, when the nature of the task challenges sustaining attention over time, PSZ display a clear deficit in this ability., (PsycINFO Database Record (c) 2012 APA, all rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
23. Visuospatial attention in schizophrenia: deficits in broad monitoring.
- Author
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Hahn B, Robinson BM, Harvey AN, Kaiser ST, Leonard CJ, Luck SJ, and Gold JM
- Subjects
- Adult, Cues, Female, Humans, Male, Middle Aged, Reaction Time, Visual Fields physiology, Young Adult, Attention physiology, Schizophrenia physiopathology, Space Perception physiology
- Abstract
Although selective attention is thought to be impaired in people with schizophrenia (PSZ), prior research has found no deficit in the ability to select one location and withdraw attention from another. PSZ and healthy control subjects (HCS) performed a stimulus detection task in which one, two, or all four peripheral target locations were cued. When one or two locations were cued, both PSZ and HCS responded faster when the target appeared at a cued than uncued location. However, increases in the number of validly cued locations had much more deleterious effects on performance for PSZ than HCS, especially for targets of low contrast whose detection was more dependent on attention. PSZ also responded more slowly in trials with four cued locations relative to trials with one or two invalidly cued locations. Thus, visuospatial attention deficits in schizophrenia arise when broad monitoring is required rather than when attention must be focused narrowly., (PsycINFO Database Record (c) 2012 APA, all rights reserved.)
- Published
- 2012
- Full Text
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24. Response activation impairments in schizophrenia: evidence from the lateralized readiness potential.
- Author
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Kappenman ES, Kaiser ST, Robinson BM, Morris SE, Hahn B, Beck VM, Leonard CJ, Gold JM, and Luck SJ
- Subjects
- Adult, Electroencephalography, Female, Functional Laterality physiology, Humans, Male, Middle Aged, Motor Cortex physiology, Psychomotor Performance, Reaction Time, Contingent Negative Variation physiology, Schizophrenia physiopathology
- Abstract
Previous research has demonstrated deficits in preresponse motor activity in schizophrenia, as evidenced by a reduced lateralized readiness potential (LRP). The LRP deficit could be due to increased activation of the incorrect response (e.g., failure to suppress competition) or to reduced activation of the correct response (e.g., a low-level impairment in response preparation). To distinguish these possibilities, we asked whether the LRP impairment is increased under conditions of strong response competition. We manipulated the compatibility of stimulus-response mappings (Experiment 1) and the compatibility of the target with flankers (Experiment 2). In both experiments, the patient LRP was reduced as much under conditions of low response competition as under high competition. These results are incompatible with a failure of patients to suppress competition and are instead consistent with a deficit in activating the correct response., (Copyright © 2011 Society for Psychophysiological Research.)
- Published
- 2012
- Full Text
- View/download PDF
25. Control of working memory content in schizophrenia.
- Author
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Hahn B, Hollingworth A, Robinson BM, Kaiser ST, Leonard CJ, Beck VM, Kappenman ES, Luck SJ, and Gold JM
- Subjects
- Adolescent, Adult, Case-Control Studies, Cues, Female, Humans, Male, Memory Disorders complications, Middle Aged, Schizophrenia complications, Memory Disorders physiopathology, Memory, Short-Term, Schizophrenia physiopathology
- Abstract
People with schizophrenia (PSZ) exhibit signs of reduced working memory (WM) capacity. However, this may reflect an impairment in managing its content, e.g. preventing irrelevant information from taking up available storage space, rather than a true capacity reduction. We tested the ability to eliminate and update WM content in 38 PSZ and 30 healthy control subjects (HCS). Images of real-world objects were presented consecutively, and a tone cued the item most likely to be tested for memory. On half the trials, randomly intermixed, a second tone occurred. Participants were informed that the item cued by the second tone was now the most likely to be tested, and the item cued by the first tone now the least likely, providing incentive to eliminate the first cued item from WM. Both HCS and PSZ displayed a robust performance advantage for cued items. Unexpectedly, PSZ more efficiently removed the no-longer-essential item from WM than HCS. The magnitude of the WM clearance of this first cued item correlated with memory performance for the newly prioritized second cued item in PSZ, indicating that it was adaptive. However, WM clearance was not associated with WM capacity, ruling out the need to budget limited resources as an explanation for greater clearance in PSZ. A robust correlation between WM clearance and poverty of speech in PSZ instead suggests that the propensity to rapidly clear non-essential information and minimize the number of items in WM may be the reflection of a negative symptom trait. This finding may reflect a more general tendency of PSZ to focus processing more narrowly than HCS., (Copyright © 2011 Elsevier B.V. All rights reserved.)
- Published
- 2012
- Full Text
- View/download PDF
26. Failure of schizophrenia patients to overcome salient distractors during working memory encoding.
- Author
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Hahn B, Robinson BM, Kaiser ST, Harvey AN, Beck VM, Leonard CJ, Kappenman ES, Luck SJ, and Gold JM
- Subjects
- Adult, Analysis of Variance, Female, Flicker Fusion physiology, Humans, Male, Middle Aged, Neuropsychological Tests, Photic Stimulation methods, Reaction Time physiology, Space Perception, Statistics as Topic, Young Adult, Attention Deficit Disorder with Hyperactivity etiology, Memory, Short-Term physiology, Schizophrenia complications, Schizophrenic Psychology
- Abstract
Background: Prior demonstrations of impaired attentional control in schizophrenia focused on conditions in which top-down control is needed to overcome prepotent response tendencies. Attentional control over stimulus processing has received little investigation. Here, we test whether attentional control is impaired during working memory encoding when salient distractors compete with less salient task-relevant stimuli., Methods: Patients with schizophrenia (n = 28) and healthy control subjects (n = 25) performed a visuospatial working memory paradigm in which half of the to-be-encoded stimuli flickered to increase their salience. After a 2-second delay, stimuli reappeared and participants had to decide whether or not a probed item had shifted location., Results: In the unbiased condition where flickering and nonflickering stimuli were equally likely to be probed, both groups displayed a trend toward better memory for the flickering items. In the flicker-bias condition in which the flickering stimuli were likely to be probed, both groups displayed a robust selection advantage for the flickering items. However, in the nonflicker-bias condition in which the nonflickering stimuli were likely to be probed, only healthy control subjects showed selection of the nonflickering items. Patients displayed a trend toward preferential memory for the flickering items, as in the unbiased condition., Conclusions: Both groups were able to select salient over nonsalient stimuli, but patients with schizophrenia were unable to select nonsalient over salient stimuli, consistent with impairment in the effortful control of attention. These findings demonstrate the generality of top-down control failure in schizophrenia in the face of bottom-up competition from salient stimuli as with prepotent response tendencies., (Copyright © 2010 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)
- Published
- 2010
- Full Text
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27. Auditory sensory gating in the neonatal ventral hippocampal lesion model of schizophrenia.
- Author
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Vohs JL, Chambers RA, Krishnan GP, O'Donnell BF, Hetrick WP, Kaiser ST, Berg S, and Morzorati SL
- Subjects
- Analysis of Variance, Animals, Animals, Newborn, Beta Rhythm, Disease Models, Animal, Electrodes, Implanted, Electroencephalography, Evoked Potentials, Auditory, Rats, Rats, Sprague-Dawley, Theta Rhythm, Time Factors, Auditory Perception physiology, Hippocampus physiopathology, Schizophrenia physiopathology
- Abstract
Background/aims: The neonatal ventral hippocampal lesion (NVHL) rat model shows biological and behavioral abnormalities similar to schizophrenia. Disturbed sensory gating reflects a consistent neurobiological abnormality in schizophrenia. Although of critical interest, sensory gating has not been evaluated in the NVHL model., Methods: The N40 rat analog of the human P50 was measured to assess sensory response and gating in NVHL and sham rats. Epidural electrodes recorded evoked potentials (EPs), from which amplitudes, latencies, difference scores (S1-S2) and gating ratios (S2/S1) were assessed. Power and phase locking were computed for evoked EEG activity, to test for frequency-specific abnormalities., Results: Prolonged S1 N40 latency was detected in the NVHL group, but amplitude and power measures did not differ. NVHL rats demonstrated disturbed phase-locked sensory gating at theta and beta frequencies, as well as reduced phase-locked gamma activity across stimuli, most robustly at S1., Conclusions: While measures of sensory gating obtained from the EP were relatively insensitive to the NVHL model, phase locking across trials was affected. NVHL rats may have increased evoked response temporal variability, similar to patients with schizophrenia. This pattern of findings likely reflects core developmental NVHL disturbances in dorsal hippocampal circuits associated with temporal and frontal areas., (Copyright 2009 S. Karger AG, Basel.)
- Published
- 2009
- Full Text
- View/download PDF
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