[Dissociative seizures: a diagnostic and therapeutic challenge on the borderline between psychiatry and neurology]. / Dissoziative Anfälle : Eine diagnostische und therapeutische Herausforderung im Grenzbereich von Psychiatrie und Neurologie.

Dissociative seizures, albeit a psychiatric symptom, are encountered only rarely in psychiatric settings and more often in a neurologic context. Due to the clinical similarity of these dissociative states with neurological symptoms, optimal treatment is often hampered and lies on the border between psychiatric and neurologic approaches. Diagnostic work-up as well as the therapy may prove to be complex and tedious, partly due to the underlying psychopathology of these patients. Management by neurologists, psychiatrists, and primary care physicians should take into account specific therapeutic and diagnostic guidelines aimed at improving outcome and minimizing the negative social and occupational effect which often burden these patients.

Cognitive, but not mood dysfunction develops in multiple sclerosis during 7 years of follow-up.

Long-term development of psychological deficits in disability-free early multiple sclerosis (MS) was evaluated in 27 female patients over a period of 7 years and compared with healthy controls. Physical and cognitive parameters deteriorated significantly but not depression scores. In particular, the self-assessed somatic complaints remained non-similar between patients and controls. This indicates that although depression is clinically relevant and frequent in MS, in contrast to cognition it is not related to physical disease progression.

Linear and non-linear dynamics of heart rate variability in brain dead organ donors.

Recent studies outlined linear and non-linear dynamics in heart rate variability; however, their physiological origin is still unknown. The present study investigated the impact of cerebral function on linear and non-linear dynamics in heart rate variability. Electrocardiograms from seven brain dead organ donors and seven healthy volunteers were analyzed. Atropine was used in healthy volunteers to adjust their heart rate to that of the donors. As compared to healthy volunteers without atropine, the linear dynamics of heart rate variability, determined by time and frequency domain analyses, were significantly reduced in healthy volunteers with atropine and, to an even greater extent, in donors. Atropine tended to increase the complexity and non-linearity of heart rate variability in healthy volunteers, as determined by the correlation dimension D and the largest Lyapunov exponent L, respectively (D = 9.43 +/- 2.93 vs. 7.65 +/- 0.97 and L = 0.525 +/- 0.099 vs. 0.504 +/- 0.047 bits.beat-1; both NS), while these indices were significantly reduced in donors by 19.5 +/- 12.8% and 15.0 +/- 11.7%, respectively (D = 6.16 +/- 0.98 and L = 0.428 +/- 0.059 bits.beat-1; both p < 0.05 vs. volunteers). Thus, loss of cerebral function reduces both linear and non-linear components of heart rate variability.

Dynamic complexity of visuo-motor coordination: an extension of Bernstein's conception of the degrees-of-freedom problem.

Extending Bernstein's spatial conception of the degrees-of-freedom problem in the human motor system, we introduce a method developed from the theory of non-linear dynamics that allows one to quantify the spatio-temporal, i.e. dynamic, complexity of visuo-motor coordination. The correlation dimension D is used to measure the effective number of dynamic degrees of freedom in the coordination that a subject uses when performing a visuo-motor tracking task. The validity of the estimator employed is demonstrated. Visuo-motor coordination had a low-dimensional (mean D-SD=6.07 -0.82) dynamic structure, which was consistent with deterministic chaos rather than with pure stochastic noise. D correlated with tracking performance, P. Both D and P were closely related to the degree of visuo-motor compatibility that the task presented to the subject. However, for short periods of training P increased, but D did not. As these seemingly contradictory results suggest, our dynamic conception of the degrees-of-freedom problem may reveal far more intricate visuo-motor interactions than Bernstein could identify on the basis of his spatial analyses of bodily movement patterns and by the methods of evaluation that were available to him at the time.

Functional coupling between the central-autonomic and the cognitive systems is enhanced in states after optic neuritis and early multiple sclerosis.

We studied the relation between central-autonomic adaptability (largest Lyapunov exponent of heart rate dynamics) and visual learning capability (total net score in Kimura's Recurring-Figures-Test) in 15 healthy subjects and 35 patients with cerebral white matter diseases (12 with optic neuritis and 23 with multiple sclerosis), aged between 18 and 39 years. In optic neuritis patients and in those with very early, clinically asymptomatic multiple sclerosis, we found high correlations between these central-autonomic and cognitive functions (r = .66 and r = .86, respectively, p < .02). In contrast, in healthy subjects and in patients suffering from an already clinically symptomatic multiple sclerosis, there were no such significant correlations. These results are interpreted in terms of stochastic resonance within a postulated meta-system which integrates autonomic and cognitive functions.

A program for the user-independent computation of the correlation dimension and the largest Lyapunov exponent of heart rate dynamics from small data sets.

We propose a specially optimized computer program for the user-independent calculation of the correlation dimension D and the largest Lyapunov exponent L of heart rate dynamics on the basis of only 1024 electrocardiographically recorded RR intervals (heartbeat intervals). The validity of our program was established by analyzing a set of artificial standard signals. Our norm values of the correlation dimension (D = 5.37 +/- 0.62) and the largest Lyapunov exponent (L = 0.561 +/- 0.037 bits/beat) of RR dynamics, obtained from 79 healthy adults aged 26.3 +/- 4.8 years, were independent of gender and age; D and L correlated slightly with each other (Pearson correlation coefficient r = 0.26). Short-term reliability, tested for 25 of our subjects by two successive recordings, was fair: the intraclass correlation coefficients (ICCs) were 0.45 and 0.41 for D and L of RR dynamics, respectively. However, long-term reliability, tested for eight of our subjects by ten weekly recordings, was acceptable for L (ICC = 0.40) but not for D (ICC = 0.01). These results permit group comparisons on the basis of single measurements of L of RR dynamics. A reliable differentiation between young healthy individuals requires four measurements of L.

Central cardio-autonomic disorganization in interictal states of epilepsy detected by phase space analysis.

In a study of central autonomic organization in interictal states of idiopathic generalized epilepsy, we measured the spontaneous oscillations of the heart rate in 8 young epileptics with normal interictal electroencaphalograms (EEGs), 6 young epileptics with epileptiform discharges in the interictal EEGs and 8 healthy controls. The temporal structure of the heart rate (HR) dynamics was operationalized through the estimation of the largest Lyapunov exponent (LLE). For all patients and controls, the LLEs of the HR dynamics were positive, indicating chaotic oscillations. The patients with interictal epileptiform discharges showed significantly lower LLEs of the HR dynamics than the epileptics with normal EEGs and the healthy controls. By comparison, the values of the epileptics with normal EEGs und those of the healthy controls did not differ significantly. This finding suggests a more rigid and thus less adaptable central cardio-autonomic organization in epileptics with epileptiform discharges in the interictal EEG.

Central autonomic dysorganization in the early stages of experimental meningitis in rabbits induced by complement-C5A-fragment: a pathophysiological validation of the largest lyapunov exponent of heart rate dynamics.

In a study of central autonomic organization in early stages of experimental meningitis in rabbits, the temporal oscillations of the momentary heart rate (heart rate dynamics) were measured. In 10 anesthetized rabbits an experimental meningitis was induced by intracisternal injection of complement-C5a-fragment in a carrier solution of sodium chloride and bovine serum albumin. 10 rabbits were injected with the above carrier solution only and served as controls. The temporal structure of the heart rate dynamics was operationalized phase-space analytically through the estimation of the largest Lyapunov exponent. Without exception, positive Lyapunov exponents of the heart rate dynamics were found, which revealed chaotic oscillations. In contrast to the controls, the intracisternal injection of C5a caused a significant decrease of the analytical index and reduced its reproducibility significantly. This result suggests a subtle central-autonomic dysfunction and a loss of the autonomic steady-state induced by the acute inflammatory process.

The Lyapunov exponent of heart rate dynamics as a sensitive marker of central autonomic organization: an exemplary study of early multiple sclerosis.

In a study of central autonomic dynamics in early multiple sclerosis, we measured the temporal oscillations of the momentary heart rate (heart rate dynamics). 11 young patients suffering from relapsing remitting definite multiple sclerosis in relapse-free and early stages of illness and 11 healthy controls were examined under vagotonic and sympathicotonic conditions. The temporal structure of the heart rate dynamics was operationalized phase-space analytically through the estimation of the largest Lyapunov exponent. Positive Lyapunov exponents were found in all participants under all conditions indicating deterministically chaotic heart rate oscillations. The variance analysis of these exponents detected no significant effect of sympathetic or vagal activity (experimental condition) but a significant group difference (p < .02). The multiple sclerosis patients were characterized by significantly lower Lyapunov exponents than the healthy controls. This finding suggests a more stable and thus less adaptive central-autonomic organization in early multiple sclerosis.

[Stimulus and response characteristics as determinants of the electrodermal orienting reaction in the Rorschach trial]. / Reiz- und Antwortcharakteristiken als Determinanten der elektrodermalen Orientierungsreaktion im Rorschach-Versuch.

The Rorschach test was used as an experiment of perception to analyze (external and internal) stimulus-response and individual response specificity of electrodermal orienting response OR (skin conductance response SCR) to presentations of unstructured material. On a sample of 84 subjects (medical students and colleagues of the medical department) the partial effects of "card" (external stimulus), "affective content of the signification" (internal stimulus), and "subject" on the (range-corrected) electrodermal OR were analyzed. The variance-analytic model was highly significant. The highly significant card effect with a physiological variance component of about 9% was interpreted as a "novelty" component of the electrodermal OR. The examined response characteristic also had a significant effect on the electrodermal OR with a physiological variance component of about 1%. Yet the determining variable was not the affective content of the signification, but rather the complexity of the (affective) signification. This result was discussed in terms of information processing and conflict theory. The important interindividual OR variance of nearly 40% supported the concept of the individual specificity of physiological response.