Biomedical subjects

Stefanie Lis

Publications and source records attributed to Stefanie Lis.

4 recordsLinked to original sources

PubMed2006

Brain activation during mental maze solving.

BACKGROUND: So-called Porteus mazes are used to investigate prefrontal cortex (PFC) functioning in normal subjects and patients with different neuropsychiatric disorders. Here we present data confirming the involvement of the PFC for the first time by means of functional magnetic resonance imaging (fMRI). To minimize motor-related activation, mental mazes were used. METHODS: Mazes as well as pseudo-mazes without any bifurcations were presented to 49 healthy participants during fMRI scans. RESULTS: Both, mazes as well as pseudo-mazes, activated a large network from visual to parietal regions, reflecting the dorsal stream of visual information processing. Mazes but not pseudo-mazes also activated bilateral areas of the PFC indicating their special role in decision processes. In addition, although no motor response was required during maze performance, both tasks activated subcortical and cortical motor areas. CONCLUSIONS: These tasks are suitable for investigating and specifying PFC functioning and its impairment in psychiatric disorders such as schizophrenia. In addition, mental mazes might be a suitable task for the investigation of patients with motor disturbances.

Adolescent↗

PubMed2005

Oxytocin modulates neural circuitry for social cognition and fear in humans.

In non-human mammals, the neuropeptide oxytocin is a key mediator of complex emotional and social behaviors, including attachment, social recognition, and aggression. Oxytocin reduces anxiety and impacts on fear conditioning and extinction. Recently, oxytocin administration in humans was shown to increase trust, suggesting involvement of the amygdala, a central component of the neurocircuitry of fear and social cognition that has been linked to trust and highly expresses oxytocin receptors in many mammals. However, no human data on the effects of this peptide on brain function were available. Here, we show that human amygdala function is strongly modulated by oxytocin. We used functional magnetic resonance imaging to image amygdala activation by fear-inducing visual stimuli in 15 healthy males after double-blind crossover intranasal application of placebo or oxytocin. Compared with placebo, oxytocin potently reduced activation of the amygdala and reduced coupling of the amygdala to brainstem regions implicated in autonomic and behavioral manifestations of fear. Our results indicate a neural mechanism for the effects of oxytocin in social cognition in the human brain and provide a methodology and rationale for exploring therapeutic strategies in disorders in which abnormal amygdala function has been implicated, such as social phobia or autism.

Adolescent↗

PubMed2005

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.

Adult↗

PubMed2005

Executive function and cognitive subprocesses in first-episode, drug-naive schizophrenia: an analysis of N-back performance.

OBJECTIVE: This study investigated changes in the cognitive architecture of N-back performance in schizophrenia. METHOD: N-back performance of 12 patients with first-episode, drug-naive schizophrenia and matched healthy comparison subjects was studied in a reaction-time decomposition paradigm. RESULTS: Imposition of a working memory load led to a significant drop in response accuracy in patients. Reaction-time decomposition suggested slowing of visuomotor and choice reaction processing as well as an inability of parallel processing directed by working memory. DISCUSSION: Although N-back tasks validly access working memory function as a neurocognitive trait in the illness, several additional subprocesses and the ability for cognitive parallel processing are altered and require further study in schizophrenia.

Adult↗