Jürgen Konczak | University of Minnesota (original) (raw)

Publications by Jürgen Konczak

Allgemeine Psychologie, 2017

Dieses Buchkapitel gibt einen Überblick, wie Menschen Handlungen planen, wie geplante Handlungen ... more Dieses Buchkapitel gibt einen Überblick, wie Menschen Handlungen
planen, wie geplante Handlungen vom Nervensystem in koordiniertes und zielgerichtetes Verhalten umgesetzt werden. Zunächst wird dargestellt, welche grundlegenden Formen der Bewegungskontrolle dem menschlichen Nervensystem zur Verfügung stehen. Im Anschluss werden Modellvorstellungen zur neuronalen Repräsentation von Bewegung diskutiert: Das in der Psychologie etablierte Konzept der motorischen Programmierung wird kontrastiert mit der Theorie der internen motorischen Modelle. Anschließend wird erläutert, welche Teile des Gehirns an sensomotorischen Prozessen beteiligt und wie neue Bewegungen und Handlungssequenzen im zentralen Nervensystem abgelegt sind. In diesem Zusammenhang wird auch darauf eingegangen, welche neurologischen Defizite bei der Schädigung motorischer Hirnareale auftreten. Diese klinische Betrachtung wird die Notwendigkeit einer integrativen Betrachtung von Hirnfunktionen verdeutlichen, da Läsionen
in klassischen „motorischen“ Arealen auch zu Defiziten in der
Wahrnehmung und Kognition führen können.

Allgemeine Psychologie, 2002

Dieses Buchkapitel gibt eine Abriss über die Grundlagen der motorischen Kontrolle menschlicher Be... more Dieses Buchkapitel gibt eine Abriss über die Grundlagen der motorischen Kontrolle menschlicher Bewegung.

Handbuch Bewegungswissenschaft, 2003

Dieses Kapitel gibt eine Einführung in die neuronale Basis der menschlichen Motorik. Eingangs wer... more Dieses Kapitel gibt eine Einführung in die neuronale Basis der menschlichen Motorik. Eingangs werden die neuronalen Korrelate der verschiedenen Formen der motorischen Kontrolle (Regelung und Steuerung) vorgestellt. Es wird unterschieden zwischen willkürlicher und unwillkürlicher Motorik und ausgeführt, wie das Zusammenspiel spinaler und supraspinaler Strukturen eine intakte Motorik bedingen. Der weitere Teil des Kapitels ist drei Hirnstrukturen gewidmet, die maßgeblich sind für die Willkürmotorik: der motorische Kortex, die Basalganglien und das Kleinhirn. Die spezifische Funktion jeder dieser Strukturen für die Motorik wird auf der Basis neurowissenschaftlicher Befunde erläutert und diskutiert. Abschließend werden die motorischen Defizite dargestellt, die sich aus der Schädigung dieser Hirnareale ergeben.

It has been suggested that the movement impairments experienced by patients with neglect are not ... more It has been suggested that the movement impairments
experienced by patients with neglect are not
restricted to spatial disorders, but also affect higher-order
kinematics (velocity and acceleration) to the extent that
movements towards the neglected side are slower than
movements away from it. In a recent study, we could not
confirm this hypothesis, but found that patients with unilateral
neglect exhibited no distinct direction-specific
deficits in hand velocity when performing goal-directed
reaching movements. Here we investigated whether neglect
patients might reveal direction-specific deficits
during exploratory hand movements. Six patients with
left-sided neglect and six age-matched healthy control
subjects scanned with their right hands the surface of a
large table searching for a (non-existent) tactile target.
Movements were performed in darkness. Time-position
data of the hand were recorded with an optoelectronic
camera system. Median activity of the patients’ exploratory
hand movements was shifted to the right (Karnath
and Perenin 1998). Hand trajectories were partitioned into
sections of leftward/rightward or, along the sagittal
plane, into sections of near/far movements. For each
movement section average and peak velocities were
computed. The patients’ hand movements were bradykinetic
when compared with the control group. However,
we found no evidence that average or peak velocities of
leftward intervals were systematically lower than during
rightward motion. Direction-specific deficits in velocity
were also not observed for movements to and away from
the body (sagittal plane). In conclusion, we found evidence
for general bradykinesia in neglect patients but not
for a direction-specific deficit in the control of hand velocity
during exploratory hand movements.

In cerebellar ataxia, kinematic aberrations of multijoint movements are thought to originate from... more In cerebellar ataxia, kinematic aberrations of multijoint movements are thought to originate from deficiencies in generating muscular torques that are adequate to control the mechanical consequences of dynamic inter- action forces. At this point the exact mechanisms that lead to an abnormal control of interaction torques are not known. In principle, the generation of inadequate muscular torques may result from an impairment in generating sufficient levels of torques or from an inaccurate assessment and prediction of the mechanical consequences of movements of one limb segment on adjacent joints. We sought to differentiate the relative contribution of these two mechanisms and, therefore, analyzed intersegmental dynamics of multijoint pointing movements in healthy subjects and in patients with cerebellar degeneration. Un- restrained vertical arm movements were performed at three different target movement velocities and recorded using an optoelectronic tracking system. An inverse dynamics approach was employed to compute net joint torques, muscular torques, dynamic interaction torques and gravitational torques acting at the elbow and shoulder joint. In both groups, peak dynamic interaction forces and peak muscular forces were largest during fast movements. In contrast to normal subjects, patients produced hypermetric movements when executing fast movements. Hypermetric movements were associated with smaller peak muscular torques and smaller rates of torque change at elbow and shoulder joints. The patients􏰅 deficit in generating appropriate levels of muscular force were prominent during two different phases of the pointing movement. Peak muscular forces at the elbow were reduced during the initial phase of the movement when simultaneous shoulder joint flexion generated an extensor influence upon the elbow joint. When attempting to terminate the movement, gravitational and dynamic interaction forces caused overshooting extension at the elbow joint. In normal subjects, muscular torque patterns at shoulder and elbow joint were synchronized in that peak flexor and extensor muscular torques occurred simultaneously at both joints. This temporal pattern of muscular torque generation at shoulder and elbow joint was preserved in patients. Our data suggest that an impairment in generating sufficient levels of phasic muscular torques significantly contributes to the patients􏰅 difficulties in controlling the mechanical consequences of dynamic interaction forces during multijoint movements.

Kinematic abnormalities of fast multijoint movements in cerebellar ataxia include abnormally incr... more Kinematic abnormalities of fast multijoint movements in cerebellar ataxia include abnormally increased curvature of hand trajectories and an increased hand path and are thought to originate from an impairment in generating appropriate levels of muscle torques to support normal coordination between shoulder and elbow joints. Such a mechanism predicts that kinematic abnormalities are pronounced when fast movements are performed and large muscular torques are required. Experimental evidence that systematically explores the effects of increasing movement velocities on movement kinematics in cerebellar multijoint movements is limited and to some extent contradictory. We, therefore, investigated angular and hand kinematics of natural multijoint pointing movements in patients with cerebellar degenerative disorders and healthy controls. Subjects performed self-paced vertical pointing movements with their right arms at three different target velocities. Limb movements were recorded in three-dimensional space using a two-camera infra-
red tracking system. Differences between patients and healthy subjects were most prominent when the subjects performed fast movements. Peak hand acceleration and deceleration were similar to normals during slow and moderate velocity movements but were smaller for fast
movements. While altering movement velocities had little or no effect on the length of the hand path and angular motion of elbow and shoulder joints in normal subjects, the patients exhibited overshooting motions (hypermetria) of the hand and at both joints as movement velocity increased. Hypermetria at one joint always accompanied hypermetria at the neighboring joint. Peak elbow angular deceleration was markedly delayed in patients compared with normals. Other temporal movement variables such as the relative timing of shoulder and elbow joint motion onsets were normal in patients. Kinematic abnormalities of multijoint arm movements in cerebellar ataxia include hypermetria at both the elbow and the shoulder joint and, as a consequence, irregular and enlarged paths of the hand, and they are marked with fast but not with slow movements. Our findings suggest that kinematic movement abnormalities that characterize cerebellar limb ataxia are related to an impairment in scaling movement variables such as joint acceleration and deceleration normally with movement speed. Most likely, increased hand paths and decomposition of movement during slow movements, as described earlier, result from compensatory mechanisms the patients may employ if maximum movement accuracy is required.

Do patients with unilateral neglect exhibit direction-specific deficits in the control of movemen... more Do patients with unilateral neglect exhibit direction-specific deficits in the control of movement velocity when performing goal-directed arm movements? Five patients with left-sided neglect performed unrestrained three-dimensional pointing movements to visual targets presented at body midline, the left and right hemispace. A group of healthy adults and a group of patients with right-hemispheric brain damage but no neglect served as controls. Pointing was performed under normal room light or in darkness. Time-position data of the hand were recorded with an opto-electronic camera system. We found that compared to healthy controls, movement times were longer in both patient groups due to prolonged acceleration and deceleration phases. Tangential peak hand velocity was lower in both patient groups, but not significantly different from controls. Single peak, bell-shaped velocity profiles of the hand were preserved in all right hemispheric patients and in three out of five neglect patients. Most important, the velocity profiles of neglect patients to leftward targets did not differ significantly from those to targets in the right hemispace. In summary, we found evidence for general bradykinesia in neglect patients, but not for a direction-specific deficit in the control of hand velocity. We conclude that visual neglect induces characteristic changes in exploratory behavior, but not in the kinematics of goal-directed movements to objects in peripersonal space.

Neuromagnetic responses to separate tactile stimulation of digits I, II and V and simultaneous st... more Neuromagnetic responses to separate tactile stimulation of digits I, II and V and simultaneous stimulation of digit pairs II and I, and II and V, were recorded in six healhty adult subjects using a 122-channel whole-head neuromagnetometer in order to investigate functional overlap of finger representations in primary somatosensory cortex (SI). Evoked responses to single digit stimulation were explained by time-varying equivalent current dipoles (ECDs) located in SI. These ECDs were then used to explain responses to stimulation of digit pairs. A cortical interaction ratio (IR( was defined as the vector sum of peak source amplitudes to separate stimulation of two fingers divided by the vector sum of source amplitudes to simultaneous stimulation of the two digits. Mean IR was significantly higher (P<0.05; Wilcoxon test) for digital pair II + I (1.69 +/- 0.15) compared to digit pair II + V ((1.14 +/- 0.12). These results indicate that there is an overlap of finger representations in human SI which differs between anatomically adjacent and non-adjacent digit pairs.

The aim of the present paper is to propose that the adoption of a framework of biological develop... more The aim of the present paper is to propose that the adoption of a framework of biological development is suitable for the construction of artificial systems. We will argue that a developmental approach does provide unique insights on how to build highly complex and adaptable artificial systems. To illustrate our point, we will use as an example the acquisition of goal-directed reaching. In the initial part of the paper we will outline (a) how mechanisms of biological development can be adapted to the artificial world, and (b) how this artificial development differs from traditional engineering approaches to robotics. An experiment performed on an artificial system initially controlled by motor reflexes is presented, showing the acquisition of visuomotor maps for ballistic control of reaching without explicit knowledge of the system’s kinematic parameters.

Knowledge of how stiffness, damping and the equilibrium position of specific limbs change during ... more Knowledge of how stiffness, damping and the equilibrium position of specific limbs change during voluntary motion is important for understanding basic strategies of neuromotor control. Presented here is an algorithm for identifying time-dependent changes in joint stiffness, damping, and equilibrium position of the human forearm. The procedure requires data from only a single trial. The method relies neither on an analysis of the resonant frequency of the arm nor on the presence of an external bias force. Its validity was tested with a stimulated forward model of the human forearm. Using the parameter estimations as forward model input, the angular kinematics (model output) were reconstructed and compared to the empirically measure data. Identification of mechanical impedance is based on a least-squares solution of the model equation. As a regularization technique and to improve the temporal resolution of the identification process, a moving temporal window with a variable width was imposed. The method's performance was tested by (a) identifying a priori known hypothetical time-series of stiffness, damping and equilibrium position, and (b) determining impedance parameters from recorded single joint forearm movements during a hold and a goal-directed movement task. The method reliably reconstructed the original angular kinematics of the artificial and human data with an average positional error of less than .05 rad for movement amplitudes of up to 0.9 rad, and did not yield hypermetric trajectories like previous procedures not accounting for damping.

It has been suggested that the movement impairments experienced by patients with neglect are not ... more It has been suggested that the movement impairments experienced by patients with neglect are not restricted to spatial disorders, but also affect higher order kinematics (velocity and acceleration) to the extent that movements towards the neglected side are slower than movements away from it. In a recent study, we could not confirm this hypothesis, but found that patients with unilateral neglect exhibited no distinct direction-specific deficits in hand velocity when performing goal-directed reaching movements. Here we investigated whether neglect patients might reveal direction-specific deficits during exploratory hand movements. Six patients with left-sided neglect and six age-matched healthy control subjects scanned with their right hands the surface of a large table searching for a (non-existent) tactile target. Movements were performed in darkness. Time-position data of the hand were recorded with an optoelectronic camera system. Median activity of the patients’ exploratory hand movements was shifted to the right (Karnath and Perenin 1998). Hand trajectories were partitioned into sections of leftward/rightward or, along the sagittal plane, into sections of near/far movements. For each movement section average and peak velocities were computed. The patients’ hand movements were bradykinetic when compared with the control group. However, we found no evidence that average or peak velocities of leftward intervals were systematically lower than during rightward motion. Direction-specific deficits in velocity were also not observed for movements to and away from the body (sagittal plane). In conclusion, we found evidence for general bradykinesia in neglect patients but not for a direction-specific deficit in the control of hand velocity during exploratory hand movements.

Objectives—To examine changes in predictive control of early antagonist responses to limb perturb... more Objectives—To examine changes in predictive control of early antagonist responses to limb perturbations in patients with defined lesions of the cerebellum. Methods—Eight cerebellar patients and eight sex and age matched control subjects participated. Subjects held a handle that was rotated around the elbow joint. They were instructed to hold the forearm at 90° flexion against a mechanical perturbation. Extensor torque (5 Nm) was applied for 140 ms (pulse), or for 1400 ms (step) through an external motor. Motor responses were tested under two divergent conditions of anticipatory information. In the expected condition, subjects anticipated and received a pulse. Under the unexpected condition, subjects expected steps, but received unexpected pulses. Biceps and triceps EMG as well as angular kinematics were compared between expected and unexpected pulse perturbations to quantify possible effects of prediction. Results—In all healthy subjects, the degree of overshoot in the return flexion movement was significantly less in expected pulse perturbations compared with unexpected trials. The degree of amplitude reduction was significantly smaller in the patient group than in the control group (22.8% v 40.0%). During the expected trials, latency of peak triceps activity was on average 20% shorter in the control group, but 4% larger in the cerebellar patients. Conclusions—In the expected condition, controls achieved a significant reduction in angular amplitude by generating triceps activity earlier, whereas the ability to use prediction for adjusting early antagonist responses after limb perturbation was impaired in cerebellar patients.

Short term vibration of the dorsal neck muscles (10–35 s) is known to induce involuntary movement... more Short term vibration of the dorsal neck muscles (10–35 s) is known to induce involuntary movements of the head in patients with spasmodic torticollis. To investigate whether neck muscle vibration might serve as a therapeutic tool when applyed for a longer time interval, we compared a vibration interval of 5 seconds with a 15 minute interval in a patient with spasmodic torticollis with an extreme head tilt to the right shoulder. Head position was recorded with a two camera optoelectronic motion analyzer in six diVerent test conditions. Vibration regularly induced a rapid change of head position that was markedly closer to a normal, upright posture. After 5 seconds of vibration, head position very quickly returned to the initial position within seconds. During the 15 minute interval, head position remained elevated. After terminating vibration in this condition, the corrected head position remained stable at first and then decreased slowly within minutes to the initial tilted position. Conclusions—(1) In this patient, muscle vibration was the specific sensory input that induced lengthening of the dystonic neck muscles. Neither haptic stimulation nor transcutaneous electrical stimulation had more than a marginal eVect. (2) The marked diVerence in the change of head position after short and prolonged stimulation supports the hypothesis that spasmodic torticollis might result from a disturbance of the central processing of the aVerent input conveying head position information—at least in those patients who are sensitive to sensory stimulation in the neck region. (3) Long term neck muscle vibration may provide a convenient non-invasive method for treating spasmodic torticollis at the central level by influencing the neural control of head on trunk position.

This study examined the movement process-product relationship from a developmental perspective. T... more This study examined the movement process-product relationship from a developmental perspective. The authors used multiple regression to investigate the changing relationship between qualitative movement descriptions of the overarm throw and the throwing outcome, horizontal ball velocity. Seventeen girls and 22 bays were filmed longitudinally at ages 6, 7, 8, and 13 years. Their movements were assessed using Robertons (Roberton & Halverson, 1984) developmental sequences for action of the humerus, forearm, trunk, stepping, and stride length. The sequences accounted for 69-85 % (adjusted) of the total velocity variance each year. The components that best predicted ball velocity changed overtime, although humerus or forearm action always accounted for considerable variance. Gender was a good predictor of ball velocity, but if the developmental descriptions were entered first in a stepwise regression, gender then explained no more than 2 % additional variance.

Within the context of the Ebbinghaus illusion, adults regularly misjudge the physical size of a c... more Within the context of the Ebbinghaus illusion, adults regularly misjudge the physical size of a centre disc, yet scale their hand aperture according to its actual size. Separate visual pathways for perception and action are assumed to account for this finding. The dorsal visual stream is said to elaborate on egocentric (visuomotor), while the ventral stream is involved in allocentric transformations (object recognition). This study examines the ontogenetic development of this dissociation between perception and action in 35 children between the ages of 5 and 12 years. We report four major results. First, when children judged object size without grasping the disc, their judgements were deceived by the illusion to the same extent as adults. However, when asked to estimate size and then to grasp the disc, young children's (5–7 years) perceptual judgements became unreliable, while adults were still reliably deceived by the illusion in 80% of their trials. Second, the younger the children, the more their aperture was affected by the illusional surround. Discs of the same size were grasped with a smaller aperture when surrounded by a small annulus, although they were perceived as being larger. Third, young children used the largest safety margin during grasping. Fourth, the reliance on visual feedback decreased with increasing age, which was documented by shorter movement times and earlier maximum hand opening during grasping in the older children (feedforward control). Our results indicate that grasping behaviour in children is subject to an interaction between ventral and dorsal processes. Both pathways seem not to be functionally segregated in early and middle childhood. The data are inconclusive about whether young children predominantly use a specific visual stream for either a perceptual or motor task. However, our data demonstrate that children were relying on both visual processing streams during perceptual as well as visuomotor tasks. We found that children used egocentric cues to make perceptual judgements, while their grasping gestures were not exclusively shaped by viewer-centred but also by object-centred information .

Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the bas... more Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the basis for feed-forward motor control in humans. This study investigates the role of visual feedback for the acquisition of inverse motor models in children and adults. Eight 9-year-old and 5-year-old children and eight adults performed goal-directed horizontal forearm movements using a single-joint arm manipulandum. When visual feedback was not available before and after movement execution (partial feedback), spatial error increased in adults and children. however, the lack of visual information during the movement execution did not affect adult motor performance. In contrast, spatial error increased in both children groups when visual feedback was removed. Spatial accuracy was improved during the partial feedback condition, if children had prior practice under full visual feedback. The increased dependence on visual feedback, especially in the younger children, is a sign that children relied predominantly on central feedback mechanisms for motor control, because their feed--forward control was not yet functional. The reasons for the lack of feed-forward control are twofold: First, there are problems in motor planning, specifically with the inverse kinematics transformation (from hand position to join angles). Second, there are deficits in the neural controller, specifically due to imprecise neural estimations of the true limb dynamics.

When humans perform goal-directed arm movements under the influence of an external damping force,... more When humans perform goal-directed arm movements under the influence of an external damping force, they learn to adapt to these external dynamics. After removal of the external force field, they reveal kinematic aftereffects that are indicative of a neural controller that still compensates the no longer existing force. Such behavior suggests that the adult human nervous system uses a neural representation of inverse arm dynamics to control upper-extremity motion. Central to the notion of an inverse dynamic model (IDM) is that learning generalizes. Consequently, aftereffects should be observable even in untrained workspace regions. Adults have shown such behavior, but the ontogenetic development of this process remains unclear. This study examines the adap-tive behavior of children and investigates whether learning a force field in one hemifield of the right arm work-space has an effect on force adaptation in the other hemi-field. Thirty children (aged 6–10 years) and ten adults performed 30° elbow flexion movements under two conditions of external damping (negative and null). We found that learning to compensate an external damping force transferred to the opposite hemifield, which indicates that a model of the limb dynamics rather than an association of visited space and experienced force was acquired. Aftereffects were more pronounced in the younger children and readaptation to a null-force condition was prolonged. This finding is consistent with the view that IDMs in children are imprecise neural representations of the actual arm dynamics. It indicates that the acquisition of IDMs is a developmental achievement and that the human motor system is inherently flexible enough to adapt to any novel force within the limits of the organism's biomechanics.

Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the bas... more Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the basis for feed-forward motor control in humans. This study investigates the role of visual feedback for the acquisition of inverse motor models in children and adults. Eight 9-year-old and eight 5-year-old children and eight adults performed goal-directed horizontal forearm movements using a single-joint arm manipulandum. When visual feedback was not available before and after movement execution did not affect adult motor performance. In contrast, spatial error increased in both children groups when visual feedback was removed. Spatial accuracy was improved during the partial feedback condition, if children had prior practice under full visual feedback. The increased dependence on visual feedback, especially in the younger children, is a sign that children relied predominantly on central feedback mechanisms for motor control, because their feed-forward control was not yet functional. The reasons for the lack of feed-forward control are twofold: first, there are problems in motor planning, specifically with the inverse kinematic transformation (from hand position to joint angles). Second, there are deficits in the neural controller, specifically due to imprecise neural estimations of the true limb dynamics.

Allgemeine Psychologie, 2017

Allgemeine Psychologie, 2002

Handbuch Bewegungswissenschaft, 2003

It has been suggested that the movement impairments experienced by patients with neglect are not ... more It has been suggested that the movement impairments experienced by patients with neglect are not restricted to spatial disorders, but also affect higher order kinematics (velocity and acceleration) to the extent that movements towards the neglected side are slower than movements away from it. In a recent study, we could not confirm this hypothesis, but found that patients with unilateral neglect exhibited no distinct direction-specific deficits in hand velocity when performing goal-directed reaching movements. Here we investigated whether neglect patients might reveal direction-specific deficits during exploratory hand movements. Six patients with left-sided neglect and six age-matched healthy control subjects scanned with their right hands the surface of a large table searching for a (non-existent) tactile target. Movements were performed in darkness. Time-position data of the hand were recorded with an optoelectronic camera system. Median activity of the patients’ exploratory hand movements was shifted to the right (Karnath and Perenin 1998). Hand trajectories were partitioned into sections of leftward/rightward or, along the sagittal plane, into sections of near/far movements. For each movement section average and peak velocities were computed. The patients’ hand movements were bradykinetic when compared with the control group. However, we found no evidence that average or peak velocities of leftward intervals were systematically lower than during rightward motion. Direction-specific deficits in velocity were also not observed for movements to and away from the body (sagittal plane). In conclusion, we found evidence for general bradykinesia in neglect patients but not for a direction-specific deficit in the control of hand velocity during exploratory hand movements.

Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the bas... more Neurobiological evidence reveals that neurally coded inverse models of limb dynamics form the basis for feed-forward motor control in humans. This study investigates the role of visual feedback for the acquisition of inverse motor models in children and adults. Eight 9-year-old and eight 5-year-old children and eight adults performed goal-directed horizontal forearm movements using a single-joint arm manipulandum. When visual feedback was not available before and after movement execution did not affect adult motor performance. In contrast, spatial error increased in both children groups when visual feedback was removed. Spatial accuracy was improved during the partial feedback condition, if children had prior practice under full visual feedback. The increased dependence on visual feedback, especially in the younger children, is a sign that children relied predominantly on central feedback mechanisms for motor control, because their feed-forward control was not yet functional. The reasons for the lack of feed-forward control are twofold: first, there are problems in motor planning, specifically with the inverse kinematic transformation (from hand position to joint angles). Second, there are deficits in the neural controller, specifically due to imprecise neural estimations of the true limb dynamics.

Neuroscience & Biobehavioral Reviews, 2007

Discussion on the clinical relevance of activity-dependent plasticity after an insult to the deve... more Discussion on the clinical relevance of activity-dependent plasticity after an insult to the developing brain is presented.

Archives of physical medicine and rehabilitation, Apr 1, 2024