Juergen Konczak

Learn More
We recorded reaching movements from nine infants longitudinally from the onset of reaching (5th postnatal month) up to the age of 3 years. Here we analyze hand and proximal joint trajectories and examine the emerging temporal coordination between arm segments. The present investigation seeks (a) to determine when infants acquire consistent, adult-like(More)
This experiment studied the effect of imposed optic flow on human locomotion. Six young and 6 older adults were exposed to various patterns of optic flow while walking in a moving hallway. Results showed few cases of impaired postural control (staggers, parachute reactions). No falls were recorded. Kinematic patterns of gait were altered when vision was(More)
We investigated how humans with hereditary cerebellar degeneration [spinocerebellar ataxia (SCA) type 6 and 8, n = 9] and age- and sex-matched healthy controls (n = 9) adapted goal-directed arm movements to an unknown external force field. We tested whether learning could be generalized to untrained regions in the workspace, an aspect central to the idea of(More)
Precise knowledge about limb position and orientation is essential for the ability of the nervous system to plan and control voluntary movement. While it is well established that proprioceptive signals from peripheral receptors are necessary for sensing limb position and motion, it is less clear which supraspinal structures mediate the signals that(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 interaction forces. At this point the exact mechanisms that lead to an abnormal control of interaction torques are not known. In principle, the(More)
Nine young infants were followed longitudinally from 4 to 15 months of age. We recorded early spontaneous movements and reaching movements to a stationary target. Time-position data of the hand (endpoint), shoulder, and elbow were collected using an optoelectronic measurement system (ELITE). We analyzed the endpoint kinematics and the intersegmental(More)
Parkinson's disease (PD) is a neurodegenerative disorder that leads to a progressive decline in motor function. Growing evidence indicates that PD patients also experience an array of sensory problems that negatively impact motor function. This is especially true for proprioceptive deficits, which profoundly degrade motor performance. This review(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(More)
Up to 50% of children and adolescents with attention deficit/hyperactivity disorder (ADHD) exhibit motor abnormalities including altered balance. Results from brain imaging studies indicate that these balance deficits could be of cerebellar origin as ADHD children may show atrophy in those regions of the cerebellum associated with gait and balance control.(More)
While high-resolution structural magnetic resonance imaging (MRI) combined with newer analysis methods has become a powerful tool in human cerebral lesion studies, comparatively few studies have used these advanced imaging techniques to study lesions of the human cerebellum and their associated symptoms. This review will summarize the methodology of(More)