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1. We have examined rapid postural adjustments associated with a class of voluntary movements that disturb postural equilibrium. In the text that follows, these motor activities are termed associated postural adjustments and voluntary focal movements, respectively. Standing human subjects performed a variety of movement tasks on a hand-held manipulandum,(More)
1. Recent studies have shown that the CNS uses proprioceptive information to coordinate multijoint movement sequences; proprioceptive input related to the kinematics of one joint rotation in a movement sequence can be used to trigger a subsequent joint rotation. In this paper we adopt a broad definition of "proprioception," which includes all somatosensory(More)
The representation of joint position at rest and during movement was investigated in 44 muscle spindle primary afferents originating from the extensor carpi radialis brevis (ECRb) and extensor digitorum (ED) of normal human subjects. Position sensitivity was estimated for each afferent, and 43 of 44 were position sensitive. In each trial, six sequential(More)
A cardinal feature of Parkinson's disease (PD) is muscle hypertonicity, i.e. rigidity. Little is known about the axial tone in PD or the relation of hypertonia to functional impairment. We quantified axial rigidity to assess its relation to motor symptoms as measured by UPDRS and determine whether rigidity is affected by levodopa treatment. Axial rigidity(More)
1. Previous studies have used tendon vibration to investigate kinesthetic illusions in the isometric limb and end point control in the moving limb. These previous studies have shown that vibration distorts the perceptions of static joint angle and movement and causes systematic errors in the end point of movement. In this paper we describe the effects of(More)
Across the entire human body, postural tone might play its most critical role in the body's axis because the axis joins the four limbs and head into a single functioning unit during complex motor tasks as well as in static postures. Although postural tone is commonly viewed as low-level, tonic motor activity, we hypothesized that postural tone is both(More)
The present study addressed whether dynamic position sense at the ankle--or sense of position and velocity during movement--shows a similar decline as a result of aging as previously described for static position sense and movement detection threshold. Additionally, the involvement of muscle spindle afferents in the possible age-related decline was studied.(More)
Integration of sensory and motor inputs has been shown to be impaired in appendicular muscles and joints of Parkinson's disease (PD) patients. As PD advances, axial symptoms such as gait and balance impairments appear, which often progresses to complete inability stand or walk unaided. The current study evaluates kinesthesia in the axial musculature of PD(More)
Kinesthetic information about a perturbation can quickly modify motor activity by producing reflexive compensation. The purpose of the present study was to determine how quickly kinesthetic information about target movement can modify motor activity. Visual information about target movement is known to guide motor activity both quickly and accurately.(More)
Motor coordination has been too poorly defined to be a useful construct in studying the control of movement. In general, motor coordination involves controlling both the timing and the kinematics of movement. Yet the motor behaviors typically used for the study of coordination have required controlling only the timing or the spatial aspects of a movement.(More)