S. Krieger

Executive functions and cognitive subprocesses in patients with obstructive sleep apnoea.

In recent years, special interest has been focused on impairments of executive functions in patients with obstructive sleep apnoea syndrome (OSAS). However, the majority of studies have not clearly separated deficits in executive functions from impairments in other cognitive processes involved in task solving. In the present study, working memory (WM) functions of 20 patients with OSAS were compared with those of 10 age‐, sex‐ and education‐matched healthy subjects. Cognitive functions were measured four times a day; each of these measurements was accompanied by an assessment of subjective and objective daytime sleepiness. To separate dysfunctions of WM from those of additionally involved processes, n‐back tasks were applied embedded in a reaction‐time‐decomposition approach. Deficits in n‐back tasks could be observed in OSAS patients in accuracy and reaction times. However, the slowing could already be observed in simple reaction time tasks. The drop in 1‐back accuracy in the morning was related to daytime sleepiness. During the afternoon, accuracy of OSAS patients dropped in 2‐back tasks, an effect which correlated neither with sleepiness nor with the extent of sleep apnoea or oxygen desaturation. In conclusion, our data reflect a complex perspective upon cognitive deficits in OSAS. Cross‐group differences in processing time on the higher level WM task appeared to be attributable to slowing at a more elementary cognitive processing level. In contrast, reduced accuracy during the WM task in the OSAS group could not be explained by deficits in more elementary cognitive processes.

Cognitive dysfunction in schizophrenia: a new set of tools for the assessment of cognition and drug effects.

Cognitive impairment in schizophrenia must be seen as a disturbance of cortico‐sub‐cortical connectivity with a neurotransmitter imbalance in a circuitry system, which connects thalamic input with prefrontal processing and supplementary motor cortex and basal ganglia output. The concept of maze‐solving behaviour as a continuous cognitive task evoking a conflict between prefrontal cortex and basal ganglia activity is explained and introduced to distinguish between the effects of D2 blocking agents and substances with a predominant 5HT2A receptor affinity, such as clozapine and risperidone. Complex mazes show a cognitive deficit in untreated schizophrenic patients that are impaired by conventional and improved by atypical antipsychotic substances. Processing speed improves most on clozapine, while parallel processing is best supported by the non‐sedative atypical substance risperidone. Maze paradigms are presented.

Cognitive subprocesses and schizophrenia. A. Reaction-time decomposition.

Objective: The aim of the study is to demonstrate that deficits of information processing in schizophrenic patients can be isolated with reaction‐time (RT) decomposition paradigms.

Cognitive subprocesses and schizophrenia. B. Maze tasks

Objective: In a companion paper we demonstrated that in reaction‐time tasks the response selection stage is selectively disturbed in schizophrenia. The aim of the present study is the investigation of subprocesses, which are incorporated into repeatedly activated loops of cognitive processes and need additional information from working memory.

Feedback about previous action improves executive functioning in schizophrenia: An analysis of maze solving behaviour

Disturbances of executive functions (EF) in schizophrenia have received special attention during the past years, but there is still an ongoing debate whether impairment in EF tasks can be linked to deficits of EF themselves or if they rather reflect impairment of other cognitive functions such as working memory processes that are additionally required for task solving. In the present study, we analyzed whether impairments in the maintenance of previous processing assumed to be related to working memory contribute to the impairments in EF tasks seen in schizophrenia. Twenty-five schizophrenic patients treated with atypical antipsychotic agents and 25 healthy controls matched according to age, sex, and education were instructed to solve novel two-dimensional maze tasks by steering a pen through a system of paths. Low demands on maintaining previous actions by giving feedback on preceding movements (visualising the trace of the pen) were contrasted with high demands, i.e. without such a trace of past processing. Without feedback of previous action, task solution was less successful and the control of motor action was deficient in schizophrenic patients. With feedback, both domains of behaviour improved to the level of healthy controls at the costs of higher time demands. The behaviour of healthy controls was not influenced by the experimental manipulation. Lower demands on the maintenance of previous action seem to enable schizophrenic patients to perform executive functions successfully. But data suggest that task solving of schizophrenic patients is characterized by alterations in the coordination of executive functions with other cognitive processes.

Neuropsychologische Aspekte der Therapie mit Psychopharmaka

Die letzten Jahrzehnte sind durch einen rasanten Erkenntnisfortschritt in der neurobiologischen und neuropharmakologischen Forschung gekennzeichnet (Davis et al. 2002). So konnte einerseits ein umfassendes Verstandnis von Signalubertragungsprozessen an der Nervenzellmembran erreicht werden, andererseits wurde die Moglichkeit geschaffen, Substanzen mit vorab definierten Transmitteraffinitaten gezielt pharmazeutisch herzustellen. Diese Entwicklungen haben die Psychiatrie in theoretischer wie in praktisch-therapeutischer Hinsicht massiv beeinflusst. Jedoch ist die auch gegenwartige Psychiatrie nach wie vor durch den Gegensatz zwischen neurobiologischer Grundlagenwissenschaft und eher phanomenologischer Psychopathologie gepragt. Auch wenn die Einfuhrung operationalisierter Diagnosesysteme Objektivitat und Reliabilitat psychiatrischer Diagnosen erheblich verbessern konnte, erscheint eine Verbindung zwischen basalen zerebralen Prozessen und deren pharmakologischen Beeinflussung einerseits und gestortem Verhalten, Denken und Fuhlen andererseits nur moglich uber eine Disziplin, die Kraepelin 1896 als »Physiologie der Seele« und Andreasen 1997 als »Scientific psychopathology« forderten. Gemeint ist hier eine naturwissenschaftliche Kriterien (Hypothesenprufung) genugende Aufklarung psychologisch definierter Sachverhalte vor dem Hintergrund nachweisbar alterierter Hirnprozesse. Genau dieses ist aber, was die Neuropsychologie seit ihren Anfangen im spaten 19. Jahrhundert leistet (Shallice 1988).

Differentiation of Antipsychotic Treatment Strategies by Reaction Time Decomposition in Chronically Ill Schizophrenic Patients

Abstract: In drug-naive, first-episode schizophrenic patients response-choice processes are selectively disturbed in a reaction-time decomposition paradigm (Krieger et al., in press). The present s...

Reaction‐times and bioelectrical brain signals of drug‐naive schizophrenic first‐onset patients in identification and classification tasks

Objective: The question of the present study is whether disturbances of response‐selection in schizophrenic patients are discernible only if overt motor‐actions are required, or also if covert cognitive actions are necessary.