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PubMed1999

Time course of gaze influences on postural responses to neck proprioceptive and galvanic vestibular stimulation in humans.

We have previously shown that postural responses to vibration of neck dorsal muscles (NS) and to galvanic stimulation of the vestibular system (GS) are influenced by the direction of gaze. Here, we describe the time course of this effect. We found that eye orienting movements during NS induce shifts of body inclination toward the direction of gaze with a latency of about 2 s: the time course is smooth and a steady state is attained after about 5 s from eye movements. If eye eccentricity is maintained and NS or GS are sequentially repeated for as long as 2 min, the direction of sway drifts in the direction opposite to eye deviation. The findings reveal that the frames of reference for the control of posture may have a dynamic nature.

Adult↗
PubMed1999

Vestibular and vestibulo-proprioceptive perception of motion in the horizontal plane in blindfolded man--II. Estimations of rotations about the earth-vertical axis.

Perception of angular displacement in the horizontal plane was studied in blindfolded human subjects. Subjects sitting on a rotating chair were turned and turned themselves about the earth-vertical axis. Magnitudes of left- and rightward directed rotations were in steps of 30 degrees and overlapped an entire circle. The averaged relative angular error in estimation of passive turns was 0.19 +/- 0.014 (M +/- m), that of active turns 0.16 +/- 0.011. Passively rotated subjects tended to overestimate turns with an increase in the rotation magnitude. Estimations of passive turns were linearly related to the turn magnitude (Y= -0.357+1.065X; R2=0.864). When turning themselves, subjects tended to overestimate rotations of lower magnitudes and underestimate those of higher magnitudes. Linearity was observed between estimations of active turns and their magnitude (Y=26.456+0.862X; R2=0.857). Turn estimation is regarded as a geometrical task, which associates subjectively defined angular and linear parameters of circular motion. It is proposed that during rotation blindfolded subjects perceive the horizontal plane as a heterometric space, the extent of which depends on the estimation of a turn.

Adult↗
PubMed1999

Vestibular and vestibulo-proprioceptive perception of motion in the horizontal plane in blindfolded man--I. Estimations of linear displacement.

Perception of linear displacement in the horizontal plane was studied in blindfolded human subjects. Subjects were transported and walked with guidance along 2-6 m straight lines and then had to retrace these paths walking backwards. Subjects solved a double orientational task: firstly, they defined the direction of the backward path and, secondly, estimated its length. Following passive transportation overestimation of shorter distances was observed, which tended towards underestimation with path lengthening. The absolute average error in estimating a 2-m path was 0.4 +/- 0.18 m (M +/- m), a 6-m path -0.2 +/- 0.19 m. Guided subjects constantly overestimated the path length with an averaged error of 0.51 +/- 0.064 m. In defining the direction of the backward path subjects made errors scattered over a range of 0-30 degrees. These errors did not vary in relation to path length. A reverse proportionality was revealed between errors in direction and estimation of path lengths following passive transportation. It is suggested that accuracy in perceiving a linear displacement is dependent upon subjective perception of the preceding change in the trajectory of movement.

Adult↗
PubMedDate not supplied

TrkB signalling inhibits p75-mediated apoptosis induced by nerve growth factor in embryonic proprioceptive neurons.

Neurotrophins mediate their effects by binding to members of the Trk family of receptor tyrosine kinases and the neurotrophin receptor p75 [1]. Whereas Trks are essential for the trophic effects of neurotrophins [1], p75 has distinct functions in different cells. For example, it enhances the survival response of certain neurons to nerve growth factor (NGF) [2], but mediates a cytotoxic response to NGF in certain other cell types and neurons [3] [4] [5] [6]. We investigated whether the p75-mediated responses to NGF can be modulated through the activation of different signalling pathways in the same neurons. Neurons of the embryonic trigeminal mesencephalic nucleus (TMN) are supported in culture by brain-derived neurotrophic factor (BDNF) and an unrelated neurotrophic factor, ciliary neurotrophic factor (CNTF), but not by NGF [7] [8] [9]. We found that NGF killed TMN neurons that were grown in the presence of CNTF; this effect of NGF was inhibited by anti-p75 antibodies and therefore occurred via a p75-dependent mechanism. NGF did not affect the survival of neurons grown in the presence of BDNF, and very low concentrations of BDNF inhibited NGF cytotoxicity. These results indicate that the activation of different signalling pathways in TMN neurons influences their susceptibility to p75-mediated NGF cytotoxicity.

Animals↗
PubMed2002

Vibratory proprioceptive stimulation affects Parkinsonian tremor.

Previous research on tremor pathophysiology showed that tremor can be affected, e.g. by electrical stimulation of the peripheral nerve, mechanical perturbation of the limb and by transcranial magnetic stimulation of the motor cortex. This report is focused on possible effects of muscle vibration (MV) on resting tremor in Parkinson's Disease (PD). Vibratory stimulation was applied to the tendons of M. extensor carpi radialis longus and M. flexor ulnaris in 27 subjects with moderate PD resting tremor. The following effects were observed: (1) tremor stopped or started time-locked to MV onset and offset, (2) tremor persisted during MV but its frequency pattern changed. These results are discussed with specific emphasis to effects of MV on spinal and supraspinal levels.

Aged↗
PubMed2000

Approach and avoidance: the influence of proprioceptive and exteroceptive cues on encoding of affective information.

In 3 experiments, the authors tested the assumption that perceived movements toward a person trigger the approach system and thereby facilitate the processing of positive affective concepts, whereas perceived movements away from a person trigger the avoidance system and thereby facilitate the processing of negative affective concepts. In the 1st study, participants categorized positive words more quickly than negative words while flexing the arm and negative words more quickly than positive words while extending the arm. The 2nd study revealed that positive words were categorized more rapidly than negative words if viewers had the impression that they were moving toward the computer screen, whereas negative words were categorized faster if viewers had the impression that they were moving away from the screen. These findings were replicated in Experiment 3 using a lexical decision task instead of an adjective evaluation task.

Adult↗
PubMed1978

On the plasticity of visual-proprioceptive bias effects.

Recent research has suggested that attentional factors play a role in determining the direction of intermodality adaptation. The present work explored the role of such factors in the visual/proprioceptive dominance, or bias, paradigm. In a preliminary experiment, an instructional approach was used and proved totally ineffective in shifting dominance. In Experiments 1 and 2, an active pointing approach was used, in which the subject was caused to concentrate on one modality or the other by having him localize a large number of unconflicted targets in that modality. This approach was successful in changing the normal dominance relation. Such an altered dominance relation may indeed be a necessary part of the shifting of normal adaptation patterns.

Attention↗
PubMed2005

Somatosensory processing and schizophrenia liability: proprioception, exteroceptive sensitivity, and graphesthesia performance in the biological relatives of schizophrenia patients.

In the present study, the authors examined somatosensory processing in 30 biological relatives of persons with schizophrenia (hereafter called "schizophrenia relatives"), 30 biological relatives of persons with bipolar affective disorder (psychiatric family control subjects), and 30 healthy control subjects with no family history of psychopathology. All 3 groups completed a weight discrimination task, a 2-point discrimination task, and a complex cognitive somatosensory task (i.e., graphesthesia). The schizophrenia relatives performed significantly worse on all 3 somatosensory tasks compared with both the healthy control subjects and the bipolar relatives. The healthy control subjects and psychiatric family control subjects showed no significant differences on any of the somatosensory tasks. Within the weight discrimination and 2-point discrimination tasks, schizophrenia relatives showed group differences on the d' index, the measure of sensitivity, whereas all 3 groups did not differ on lnbeta, the measure of response bias, suggesting a genuine difference in weight and touch sensitivity. The d' value of the weight discrimination task was significantly associated with both the cognitive-perceptual factor and negative symptom factor of the clinical questionnaire (e.g., Schizotypal Personality Questionnaire; SPQ), whereas the 2-point discrimination d' value and graphesthesia scores were significantly associated only with the cognitive-perceptual factor of the SPQ. Implications for the possible relation between somatosensory task performance and schizophrenia liability are discussed.

Adolescent↗