Hans-Theo Weiler’s research while affiliated with Otto-von-Guericke University Magdeburg and other places

We investigated event-related brain potentials (ERPs) to passive ramp movements of the knee joint. The knee movements were either attended or unattended and were either very easy or very hard to detect. We used special methods to ensure that movement only activated muscle spindle and joint receptors. The first movement-related ERP started 20 ms after movement onset, and had a contralateral maximum. This initial ERP did not differ as a function of attention and movement discriminability. Signal detection analysis of the behavioral data suggested that hard-to-detect movements could be discriminated above chance level, but were not reported because of a decision bias. At 60-100 ms, an ERP was observed that discriminated detected from undetected hard-to-detect movements. Starting at 80 ms, we found an ERP that was unique to movements that were attended and easy to detect. We discuss that (1) the initial ERP reflects activation of preconscious sensory processors, (2) the second ERP may reflect detection that fails to attract attention, and (3) the third ERP reflects active focusing of attention on the movement.

Ängste sind eine natürliche menschliche Eigenschaft und zeigen eine Abhängigkeit von der kindlichen Entwicklung. Für die Ätiopathogenese pathologischer Ängste in Form von Angststörungen spielen biologische, psychische und soziale Risikofaktoren eine Rolle. Die einzelnen klinischen Angststörungen, wie sie nach der internationalen Klassifikation (ICD-10) definiert sind, werden beschrieben. Der Verlauf dieser Angststörungen hat relativ hohe, aber individuell unterschiedliche Remissionsraten. Für die Therapie stehen verschiedene Formen wie Psychoedukation und mehrere psychotherapeutische Verfahren sowie pharmakologische Interventionen zur Verfügung. Zum Schluss werden die Kriterien dargestellt, die erfüllt sein müssen, damit Ängste einen Krankheitswert erlangen und damit behandelt werden müssen, um ein Persistieren ins Erwachsenenalter hinein zu verhindern. The significance of anxiety and fear as natural symptoms, as well as their pathological forms, during the developmental course of childhood is discussed. Risk factors like biological, psychological and social factors have an important impact for the occurrence of clinically significant anxiety disorders. Specific disorders, as defined according to the international classification of diseases (ICD10), their course and outcome are described. Regarding therapy, psychoeducation, various behavioural psychotherapeutical techniques and pharmacological interventions are presented. Criteria to distinguish between normal and pathological forms of fear and anxiety are given. An appropriate and prompt treatment to help to return to normal functioning and to prevent persistence to adulthood is important.

Human proprioceptive performance of movement detection in joints is currently believed to be based on information from muscle spindles. In previous studies investigating proprioception, we found remarkable differences in threshold values using a conventional movement-detection paradigm and a threshold-hunting paradigm. One reason could be that central processing, the evaluation of the peripheral sensation, was responsible. Therefore, the study was designed to determine, besides the proprioceptive performance, the central processing of movement detection in the knee joint by means of a signal-detection technique (SDT). Only this technique provides parameters such as detectability (d') and the decision criterion (beta), which distinguish between these performances. From the resulting psychometric functions, the threshold (a parameter of classical psychophysics) also was evaluated. This threshold parameter (PCmax), derived from the SDT parameter d', indicates that detection is above threshold when subjects detect only 20-30% of the applied stimuli, as sham stimuli were detected also. The detectability increased with increasing velocity and up to a certain value with increasing amplitude. The threshold for movement detection was lower than 0.25 degree for the three faster angular velocities (0.1 degree s-1, 0.5 degree s-1, 0.6 degree s-1) and lower than 0.75 degree for the slowest velocity (0.05 degree s-1). The decision criterion beta, a measure for central processing which determines acuity, might reflect the central processing output on fusimotor neurones and thus be an indirect measure of the gamma-drive evoked by fusimotor neurones.

During muscle lengthening in a movement cycle the firing rate of muscle spindles is higher than during shortening. This phenomenon, known as hysteresis, has implications for movement control. Therefore, it should have an impact on joint position sense (JPS), the subject's awareness of the static position of a joint. JPS has been tested on the human knee joint by means of an angle reproduction test. This task included the following sequences. The leg was moved passively, by means of a motor drive, from two different start positions (15°and 75°) to a certain target angle and, after a time of 8 s, it was returned to the start position; subjects had to reproduce the former target angle. Several target angles, mild flexion (30°), intermediate flexion (45°), and strong flexion (60°), were used. Depending on the start position, the movements matching these targets were flexions or extensions. At least for the intermediate position different threshold values should be expected for flexions and extensions, if hysteresis has an impact. Moreover, the JPS measure should show a dependence on movement velocity and independence on distance. Of the variables tested, only movement direction but not movement velocity or distance had a statistically significant impact on the dependent constant angle error (difference between reproduction and target angle). The target angle of 30°was exactly reproduced (-0.14°), independently of the start position. The 45°target angle was significantly underestimated (-4.39°) when matching that position by flexions (starting at 15°) compared to an overestimation (2.27°) when matching that position by extensions (starting at 75°). The target angle of 60°has been constantly underestimated (-3.80°), independently of the start position. Therefore, hysteresis, the dependency of the movement's direction, neglected in the past, should be considered in future tests of JPS or studies considering the role of movement parameters for motor control.

To test the role of joint receptors for proprioception in patients with bilateral knee osteoarthritis (OA) and patients who had undergone unilateral total knee arthroplasty (TKA). Nine patients were tested bilaterally with a conventional movement detection paradigm that evaluated conscious detection perception and a newly developed hunting paradigm that measured maximal sensory performance (hunting perception). For detection perception, patients exhibited a slightly lower threshold on the arthritic side than on their TKA side. For hunting perception, the patients showed threshold values that were an order of magnitude smaller than for the conventional paradigm in both knees. Performance was much better on prosthetic knees than on OA knees. The joint receptors of OA knees might have an adverse effect on the maximal proprioceptive performance, being important for the normal reflexive knee joint functions. These deficits may be overcome by joint receptor removal during knee replacement.

Perception has commonly been seen as a conscious performance. Thus, regarding proprioception in some publications, it has been proposed that the term is properly used only when subjects are able to report on the direction as well as presence of imposed movements. Consequently, detections of movements without movement-direction perception have not been accepted as perceived, since these detections were regarded as unspecific. Unspecific sensation has been suggested to precede perception. From this "two-state model", it follows that threshold values should be lower for unconscious unspecific perception than for conscious specific perception. The aim of the present study was to test this suggested dichotomy. Proprioception was compared in unspecific detection trials (only the occurrence of a movement had to be detected, not its direction) and direction-specific detection trials (the occurrence of a movement of a specific direction had to be detected). Two types of specific detection trials and two types of unspecific detection trials were studied. Pairs of threshold values were determined, regarding amplitude detection using different angular velocities and regarding velocity detection using different angular displacements, for flexion and extension. Our results showed that, independent of each other, both threshold paradigms (amplitude detection and velocity detection) revealed the same perception characteristics. In specific detection paradigms, the proprioceptive thresholds were two times lower than in unspecific detection paradigms. Thus, movements of a particular type could be detected more easily than movement per se. The suggested "two-state model" might, therefore, not be appropriate in describing proprioceptive perception.

Perception has commonly been seen as a conscious performance. Thus, regarding proprioception in some publications, it has been proposed that the term is properly used only when subjects are able to report on the direction as well as presence of imposed movements. Consequently, detections of movements without movement-direction perception have not been accepted as perceived, since these detections were regarded as unspecific. Unspecific sensation has been suggested to precede perception. From this "two-state model", it follows that threshold values should be lower for unconscious unspecific perception than for conscious specific perception. The aim of the present study was to test this suggested dichotomy. Proprioception was compared in unspecific detection trials (only the occurrence of a movement had to be detected, not its direction) and direction-specific detection trials (the occurrence of a movement of a specific direction had to be detected). Two types of specific detection trials and two types of unspecific detection trials were studied. Pairs of threshold values were determined, regarding amplitude detection using different angular velocities and regarding velocity detection using different angular displacements, for flexion and extension. Our results showed that, independent of each other, both threshold paradigms (amplitude detection and velocity detection) revealed the same perception characteristics. In specific detection paradigms, the proprioceptive thresholds were two times lower than in unspecific detection paradigms. Thus, movements of a particular type could be detected more easily than movement per se. The suggested "two-state model" might, therefore, not be appropriate in describing proprioceptive perception.

A debate exists in the literature as to what extent perception is conscious. In some publications regarding proprioception, the term proprioception has explicitly only been seen as properly used when subjects were able to report the imposed movement's direction. Detections of movements without movement-direction perception, have been seen as nonspecific. Since a lot of studies discussed this point but never tested it explicitly, we tested it by using nonspecific hunting paradigms (only the occurrence of a movement has to be detected, not its direction) with the following rationale. If the perception performance is really nonspecific, no difference regarding the movement's direction should be found. Thus, if we found a different detection performance regarding flexion and extension by means of a nonspecific paradigm, it would demonstrate that this "nonspecific" perception is already specific. Therefore, we measured the perception characteristics separately for flexion and extension. The perception characteristics have been determined from the amplitude-velocity-relation curve. Two different, nonspecific hunting paradigms, modifications of our previously published specific hunting paradigm, have been used. Thus, we determined pairs of threshold values, regarding amplitude hunting using three different angular velocities (0.1 degrees s(-1), 0.25 degrees s(-1), and 0.5 degrees s(-1)) and regarding velocity hunting using three different angular displacements (0.25 degrees, 0.5 degrees, and 1 degrees) as well, for flexion and extension, respectively. We found that both threshold paradigms (velocity hunting and amplitude hunting) revealed the same perception characteristics for a given movement direction. With an increasing angular velocity, angular displacement threshold values converged toward a common value for flexion and extension (about 0.2 degrees); with an increasing angular displacement, angular velocity threshold values converged toward separate values for flexion (about 0.06 degrees s(-1)) and extension (about 0.1 degrees s(-1)). Thus, our findings demonstrate that detection performance is specific and not bound to conscious perception, since specific thresholds for flexion and extension were revealed with nonspecific hunting paradigms.

We determined proprioception in replaced and unreplaced arthrotic knees by measuring threshold levels for the perception of passive knee motion. In addition, results of these proprioception measurements were compared with the clinical outcomes in patients with a total knee arthroplasty. Threshold detection levels were significantly higher in the replaced than in the unreplaced knees. Moreover, detection-failure rates were significantly higher in the replaced knees as well. In contrast to this diminished movement sense in the replaced knees, clinical examination of these knees showed good or excellent outcome in all cases. A correlation between the clinical outcome and the ability to perceive passive motion in either patient group could not be found. We hypothesize that our findings may be due to the operative removal of intraarticular receptor-rich tissue that is affected by arthrosis. This would not only contribute to marked clinical improvements but also to a significant decrease in proprioception.

The inability to fully activate the quadriceps femoris muscle voluntarily is known to accompany several different knee-joint pathologies. The extent of a voluntary-activation deficit in patients after isolated rupture of the anterior cruciate ligament (ACL), however, has been reported to be small or nonexistent, making it questionable if a voluntary-activation deficit is a relevant factor for these patients at all. In this study the ability to voluntarily activate the quadriceps femoris muscles was quantified in 22 male patients with arthroscopically-proven isolated ACL ruptures using an established highly sensitive twitch-interpolation technique. Furthermore, the maximal voluntary contraction force of the quadriceps muscle was obtained by isometric knee-joint torque measurements. The results were compared with an age-, gender-, and activity-matched control group. There was a moderate but significant mean reduction in maximal voluntary activation (VA) in both the injured (VA: 83.9 +/- 2.3%, mean +/- SEM) and uninjured side (VA: 84.7 +/- 2.2%) in comparison with controls (VA: 91.1 +/- 0.8%). However, of the patients the 23% who presented a considerably reduced voluntary-activation of less than 80% were mainly responsible for the significant mean deficit. The deficit of isometric muscle strength on the injured side compared with that of controls was explained by the voluntary-activation deficit and a true muscle weakness. On the other hand, the diminished muscle strength of the uninjured side was explained sufficiently by the voluntary-activation deficit alone. Considering the bilateral voluntary-activation deficit, functional muscle tests might not be valid when the uninjured extremity serves as reference.