Stefan Kaiser

University of Zurich, Zürich, Zurich, Switzerland

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Publications (45)123.8 Total impact

  • Schizophrenia Research; 04/2014
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    ABSTRACT: Cognitive remediation is a promising pathway for ameliorating cognitive impairment of patients with schizophrenia. Here, we investigate predictors of improvement in problem-solving ability for two different types of cognitive remediation - specific problem-solving training and training of basic cognition. For this purpose we conducted a re-analysis of a randomized controlled trial comparing these two training approaches. The main outcome measure was improvement in problem-solving performance. Correlational analyses were used to assess the contribution of clinical, cognitive and training-related predictors. In the problem-solving training group, impaired pre-training planning ability was associated with stronger improvement. In contrast, in the basic cognition training group antipsychotic medication dose emerged as a negative predictor. These results demonstrate that predictors for successful cognitive remediation depend on the specific intervention. Furthermore, our results suggest that at least in the planning domain patients with impaired performance benefit particularly from a specific intervention. (JINS, 2014, 20, 1-6).
    Journal of the International Neuropsychological Society 03/2014; · 2.70 Impact Factor
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    ABSTRACT: Schizophrenia is a chronic disorder, which severely limits the social and occupational functioning. Employment, education, relationships, housing and health are among the most frequently stated life and treatment goals among persons suffering from schizophrenia. Rehabilitation for persons with schizophrenia aims at preservation and improvement of psychosocial functions in areas such as work, social relationship and independent living skills, promotes recovery-oriented interventions and, therefore, serves the central goals of affected persons. Cognitive functioning, education, negative symptoms, social support and skills, age, work history, and rehabilitation service to restore community functioning have proven to be strong predictors for successful psychiatric rehabilitation. It makes sense to concentrate on these predictors when improvement of psychiatric rehabilitation is targeted. Cognitive remediation produces moderate improvements in cognitive performance and, when combined with functional training and embedded in comprehensive psychiatric rehabilitation, also enhances functional outcome. Germany provides a highly differentiated system of psychosocial support for schizophrenic patients. However, the "German disease" with different care providers being in charge in subsequent stages of recovery hampers efficient organisation of psychiatric rehabilitation. Improvement of overall organisation, i. e., configuration of interfaces, understanding of the complex interactions of measures, design of disease specific programmes, research and economic evaluation constitute major challenges in the field of psychiatric rehabilitation.
    Fortschritte der Neurologie · Psychiatrie 03/2014; 82(3):128-34. · 0.85 Impact Factor
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    ABSTRACT: Although the effects of caffeine on basic cognitive functions are well-known, its effects on more complex decision making, particularly on option generation, is yet to be explored. We examined the effects of caffeine on option generation in decision making using everyday life decisional situations. In a double-blind placebo-controlled experiment, participants (N = 47) either received 300 mg of caffeine or a placebo. Participants had to generate choice options (things they could do) for a series of high and low familiar real-world scenarios and, subsequently, to decide among these options. Analyses revealed that participants in the caffeine condition generated significantly fewer options than participants in the placebo condition. Moreover, caffeine significantly reduced the option generation onset time, that is, participants in the caffeine condition generated their first option significantly faster than participants in the placebo condition. Regarding subsequent choice, we found evidence supporting the "take-the-first" heuristic, that is, the tendency to select the first generated option. This tendency was neither affected by caffeine nor by the familiarity of the scenarios. Caffeine results in fewer options generated in unconstrained real-life decision-making situations and decreases generation onset times.
    Psychopharmacology 02/2014; · 4.06 Impact Factor
  • Schizophrenia Research 01/2014; 153:S247-S248. · 4.59 Impact Factor
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    ABSTRACT: When humans and other animals make decisions in their natural environments prospective rewards have to be weighed against costs. It is well established that increasing costs lead to devaluation or discounting of reward. While our knowledge about discount functions for time and probability costs is quite advanced, little is known about how physical effort discounts reward. In the present study we compared three different models in a binary choice task in which human participants had to squeeze a handgrip to earn monetary rewards: a linear, a hyperbolic, and a parabolic model. On the group as well as the individual level, the concave parabolic model explained most variance of the choice data, thus contrasting with the typical hyperbolic discounting of reward value by delay. Research on effort discounting is not only important to basic science but also holds the potential to quantify aberrant motivational states in neuropsychiatric disorders.
    Behavioural processes 10/2013; · 1.53 Impact Factor
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    ABSTRACT: The present study investigated the specificity of planning impairments in schizophrenia compared to unipolar major depression. Multiple measures of planning ability were employed to assess the task independence of a planning deficit. Furthermore, the predictive power of planning ability with regard to functional outcome was analyzed. A total of 80 participants completed a comprehensive neuropsychological assessment with an emphasis on executive functions and planning ability. The sample consisted of 28 patients with schizophrenia, 28 patients with depression and 24 healthy controls. Both patient groups were impaired on measures of attention, working memory and planning, but only planning ability differentiated between patient groups. The deficit was evident across different measures of planning ability and was the best overall predictor of functional outcome. These results provide evidence for the relative specificity of a planning deficit in schizophrenia and show that the deficit is not task-specific but likely affects central cognitive control processes critical for planned behavior. The observed relation to functional outcome supports the clinical relevance of planning ability.
    Schizophrenia Research 07/2013; · 4.59 Impact Factor
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    ABSTRACT: Decision-making research has thoroughly investigated how people choose from a set of externally provided options. However, in ill-structured real-world environments, possible options for action are not defined by the situation but have to be generated by the agent. Here, we apply behavioral analysis (Study 1) and functional magnetic resonance imaging (Study 2) to investigate option generation and subsequent choice. For this purpose, we employ a new experimental task that requires participants to generate options for simple real-world scenarios and to subsequently decide among the generated options. Correlational analysis with a cognitive test battery suggests that retrieval of options from long-term memory is a relevant process during option generation. The results of the fMRI study demonstrate that option generation in simple real-world scenarios recruits the anterior prefrontal cortex. Furthermore, we show that choice behavior and its neural correlates differ between self-generated and externally provided options. Specifically, choice between self-generated options is associated with stronger recruitment of the dorsal anterior cingulate cortex. This impact of option generation on subsequent choice underlines the need for an expanded model of decision making to accommodate choice between self-generated options.
    Cognitive Affective & Behavioral Neuroscience 05/2013; · 3.87 Impact Factor
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    ABSTRACT: Most empirical studies on decision-making start from a set of given options for action. However, in everyday life there is usually no one asking you to choose between A, B, and C. Recently, the question how people come up with options has been receiving growing attention. However, so far there has been neither a systematic attempt to define the construct of "option" nor an attempt to show why decision-making research really needs this construct. This paper aims to fill that void by developing definitions of "option" and "option generation" that can be used as a basis for decision-making research in a wide variety of decision-making settings, while clarifying how these notions relate to familiar psychological constructs. We conclude our analysis by arguing that there are indeed reasons to believe that option generation is an important and distinct aspect of human decision-making.
    Frontiers in Psychology 01/2013; 4:555. · 2.80 Impact Factor
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    ABSTRACT: Over the past years a growing research effort has investigated the relation between cannabis use and schizophrenia at a neurobiological, epidemiological and clinical level. A number of systematic reviews and meta analyses have summarized the available evidence in the field. Conversely the patient's perception of the link between cannabis use and psychosis has been under investigation. Since patient's beliefs and attitudes strongly correlate with adherence to all forms of treatment, we conducted a systematic PUBMED database search for any English and German-language articles published until January 2012 that addressed patient's perception of a cannabis psychosis link. Six studies including psychotic subjects met inclusion criteria yielding a total sample of 97. The vast majority of patients with either schizophrenia or a recent psychosis disagreed with a causal link between cannabis use and their mental illness. We qualitatively reviewed the explanatory models underlying their views, which were multi-factorial, psychological, social, biological, esoteric and irrational factors. Most patient's believed that the temporal sequence of events did not clearly indicate a causal relationship for them. They thus discarded the hypothesis of a causal link between cannabis use and psychosis. Despite the heterogeneity of the included studies, findings are comparable and support the robustness of this review. Limitations and implications for clinicians and psychosis research are discussed.
    Current pharmaceutical design 06/2012; 18(32):5105-12. · 4.41 Impact Factor
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    ABSTRACT: Recent theories of schizophrenia have proposed a fundamental instability of information processing on a neurophysiological level, which can be measured as an increase in latency variability of event-related potentials (ERPs). If this reflects a fundamental deficit of the schizophrenic illness, it should also occur in high-functioning patients. These patients have also been observed to show a more diffuse activation pattern in neuroimaging studies, which is thought to reflect compensatory processes to maintain task performance. In the present study we investigated temporal variability and spatial diffusion of the visual N2 component in a group of high-functioning patients with preserved cognitive performance. 28 patients with schizophrenia and 28 control participants matched for gender, age and education participated in the study. Subjects performed a visual Go/Nogo task, while event-related potentials were obtained. Trial-to-trial latency variability was calculated with a Wavelet-based method. Patients with schizophrenia showed a robust increase in N2 latency variability at electrodes Fz and Cz in all task conditions. Regarding spatial distribution healthy participants showed a focused fronto-central N2 peak. In contrast, patients with schizophrenia showed a more diffuse pattern and additional negative peaks over lateral electrodes in the Nogo condition. These results clearly show that even in high-functioning patients with schizophrenia a higher temporal variability of ERPs can be observed. This provides support for temporal instability of information processing as a fundamental deficit associated with schizophrenia. The more diffuse scalp distribution might reflect processes that compensate for this instability when cognitive control is required.
    Schizophrenia Research 09/2011; 131(1-3):206-13. · 4.59 Impact Factor
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    ABSTRACT: This study addresses the question of whether frontal activation in response-inhibition tasks is specifically associated with the suppression of a motor response. An alternative model suggests a role in the detection of behaviorally relevant or salient events. For this purpose, we used functional MRI with an auditory go/no-go paradigm. This paradigm allowed the disentangling of inhibition-related from salience-related effects, which were associated with different frontal regions. Importantly, the right ventrolateral prefrontal cortex consistently showed sensitivity for salience but not for inhibition requirements. This reflects a more general salience-detection mechanism, which is not specific for response-inhibition tasks.
    Neuroreport 08/2011; 22(15):778-82. · 1.40 Impact Factor
  • Stefan Kaiser, Karsten Heekeren, Joe J Simon
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    ABSTRACT: Negative symptoms have been considered to be specific to schizophrenia or a subtype of schizophrenia: the deficit syndrome. In other words, these symptoms have been considered to be categorically different from other forms of human behavior and experience, whether they occur in healthy persons or patients with other psychiatric disorders. In this paper, we advocate a dimensional approach to negative symptoms, which is supported by two main arguments. First, enduring negative symptoms can even be observed in a variety of psychiatric disorders and they are not specific to schizophrenia. Second, we review evidence that negative symptoms show a continuous distribution from apparently healthy subjects to those with a fully developed clinical syndrome. Although the evidence does not allow for a definite decision concerning the dimensional distribution of negative symptoms, it certainly justifies exploring a dimensional approach with respect to its clinical and scientific utility. Understanding negative symptoms as a variation of normal mental processes will strengthen the development of neurocognitive models and treatment approaches.
    Psychopathology 08/2011; 44(6):345-53. · 1.62 Impact Factor
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    ABSTRACT: Most previous studies finding positive results in the emotional Stroop test did not control for concurrent anxiety symptoms. This study investigated depressive patients without comorbid anxiety disorders in order to clarify existing inconsistent findings. Furthermore, we examined the relationship between anxiety level and the emotional Stroop effect in patients and healthy subjects. Twenty-three depressive patients without comorbid anxiety disorder and 27 healthy subjects performed a mixed computerized version of the emotional Stroop test (attentional bias test). We assessed the state and trait anxiety and examined its correlation with the emotional Stroop effect. We failed to find evidence for attentional bias in the patients as measured by longer reaction times to the emotional stimuli. However, there was a positive correlation between state anxiety and attentional bias in depressed patients. On the other hand, in healthy subjects the trait anxiety correlated negatively with attentional bias. Attentional bias is not found in depressed patients if only patients without comorbid anxiety disorders are included. Furthermore, healthy subjects with high trait anxiety levels may be vulnerable to affective disorders because they use avoidance strategies when encountering negative information.
    Psychopathology 03/2011; 44(3):193-200. · 1.62 Impact Factor
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    ABSTRACT: Fronto-posterior networks have been implicated in various cognitive processes that are impaired in schizophrenia. This is the first study on time and frequency resolved fronto-posterior coherence during cognitive control in schizophrenia. We examined 16 schizophrenic/schizoaffective patients and 20 age-matched controls performing a choice-reaction task. Fronto-posterior coherence was analyzed for event-related increases with respect to the inter-trial interval. Furthermore, we compared the two groups for event-related coherence during the task-related time intervals which showed a significant coherence increase with respect to the inter-trial interval, as well as for absolute coherence during the inter-trial interval. Event-related coherence was significantly reduced in patients during time intervals (0-250 ms poststimulus) when controls showed significant event-related coherence increases. However, patients showed significantly higher absolute coherence during the inter-trial interval. These results pointed to differential deficits in fronto-posterior connectivity during the inter-trial interval and task-related conditions in schizophrenia. Cognitive deficits in schizophrenia might be driven by abnormal fronto-posterior communication. Task-related hypo-connectivity and inter-trial interval hyper-connectivity point to resource allocation deficits. The timing of cortico-cortical interactions during crucial task-related intervals may be impaired, while frontal and posterior areas may exhibit increased interactions between the trials.
    Acta Psychiatrica Scandinavica 02/2011; 123(2):125-35. · 4.86 Impact Factor
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    ABSTRACT: Deficits in executive functioning are closely related to the level of everyday functioning in patients with schizophrenia. However, many existing neuropsychological measures are limited in their ability to predict functional outcome. To contribute towards closing this gap, we developed a computer-based test of planning ability ("Plan-a-Day") that requires participants to create daily activity schedules in a simulated work setting. Eighty patients diagnosed with schizophrenia were tested with Plan-a-Day and a battery of cognitive ability tests. Plan-a-Day showed satisfactory psychometric properties in terms of consistency, reliability, and construct validity. Compared to other neuropsychological tests used in this study, it also demonstrated incremental validity with regard to the Global Assessment of Functioning. The Plan-a-Day approach, therefore, seems to represent a valid alternative for measuring planning ability in patients with executive function deficits, occupying a middle ground between traditional neuropsychological tests and real-life assessments.
    Journal of the International Neuropsychological Society 02/2011; 17(2):327-35. · 2.70 Impact Factor
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    ABSTRACT: 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. 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. 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. 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. ClinicalTrials.gov NCT00507988.
    BMC Psychiatry 01/2011; 11:73. · 2.23 Impact Factor
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    ABSTRACT: Functional magnetic resonance imaging in a Go/Nogo task was employed to investigate the relationship between trait impulsivity and brain activation during motor response inhibition. We found a positive correlation between motor impulsivity and activation of bilateral ventrolateral prefrontal cortex during successful inhibitions, which suggests stronger recruitment to maintain task performance.
    Psychiatry Research 07/2010; 183(1):89-91. · 2.68 Impact Factor
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    ABSTRACT: Intra-individual variability of reaction times (IIV) can be employed as a measure of the stability of information processing, which has been proposed to be fundamentally disturbed in schizophrenia. However, the theoretical and clinical significance of IIV is not clear, in part because it has previously been investigated in subject groups with generalized cognitive impairment. Therefore, the purpose of the study was to assess IIV in high-functioning patients with schizophrenia and relatively preserved cognitive performance. 28 high-functioning patients with schizophrenia and 28 controls performed a Go/Nogo task and a Continuous Performance Test. In contrast to average measures of task performance, IIV differentiated consistently and with large effect size between groups. Modelling with an Ex-Gaussian distribution revealed that patients have a higher proportion of slow responses reflected by an increased tau parameter. The tau parameter was correlated with work capability in the sample with schizophrenia. In conclusion, IIV is an easily obtained measure, which is highly sensitive to fundamental cognitive deficits not directly visible in a high-functioning patient group. The response pattern with more exceedingly slow reactions could reflect a core deficit in the stability of information processing. The relationship with work capability suggests investigation of IIV as a clinical measure.
    Psychiatry Research 05/2010; 178(1):27-32. · 2.68 Impact Factor
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    ABSTRACT: Delusional experience is a fundamental symptom of psychotic illness. Over recent years, a multidimensional perspective has become increasingly important regarding this phenomenon. Several instruments to measure different dimensions of delusions have been constructed. The aims of this study were to examine the reliability and validity of a German version of the Dimensions of Delusional Experience Scale (DDE). Two hundred inpatients with a schizophrenic spectrum disorder or an affective disorder with delusions were examined with the DDE, the Positive and Negative Syndrome Scale (PANSS) and other rating scales for delusional experiences. The scale was found to have good reliability and excellent inter-rater reliability. The 2 factors, delusional involvement and delusional construct, found by Kendler et al. [Am J Psychiatry 1983;140:466-469] could be replicated. The convergent and differential validity of the scale was supported. Besides the content-related aspect 'bizarreness', the DDE mainly assesses cognitive aspects, emotional and behavioral aspects are not incorporated. The results support the value of a multidimensional perspective of delusional experiences. The German version of the DDE is a reliable and valid assessment tool for different dimensions of delusions, and an economical instrument for research and clinical practice. Further research is needed to reveal the dimensional structure underlying delusional experience.
    Psychopathology 04/2010; 43(3):189-96. · 1.62 Impact Factor

Publication Stats

570 Citations
123.80 Total Impact Points

Institutions

  • 2011–2013
    • University of Zurich
      • Laboratory for Social and Neural Systems Research - SNS Lab
      Zürich, Zurich, Switzerland
  • 2009–2013
    • Universiteit Utrecht
      • Department of Philosophy
      Utrecht, Provincie Utrecht, Netherlands
  • 2003–2013
    • Universität Heidelberg
      • • Department of Geriatric Psychiatry
      • • Center of Psychosocial Medicine
      Heidelburg, Baden-Württemberg, Germany
  • 2005
    • Psychiatrische Universitätsklinik Zürich
      Zürich, Zurich, Switzerland