Long latency postural reflexes are under supraspinal dopaminergic control

B. R. Bloem, D. J. Beckley, J. P P Van Vugt, J. G. Van Dijk, M. P. Remler, J. W. Langston, R. A C Roos

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Scaling of posturally stabilizing long latency (LL) reflexes in tibialis anterior muscles induced by 'toe-up' rotational perturbations is abnormal in standing patients with Parkinson's disease. To investigate the contribution of dopaminergic pathways to abnormal scaling, we studied LL reflexes in 22 patients with selective hypodopaminergic syndromes: 10 psychiatric patients taking chronic neuroleptic medication (7 with mild parkinsonism), 8 patients with young-onset Parkinson's disease, and 4 patients with MPTP-induced parkinsonism. Results were compared with those of 10 healthy controls. Stimuli consisted of (a) 10 serial (predictable) perturbations of 4° amplitude, (b) 10 serial (predictable) perturbations of 10° amplitude, and (c) 20 randomly mixed (unpredictable) perturbations of either 4 or 10° amplitude. In normal subjects, LL reflex amplitudes were adapted to match predictable variations in stimulus size, whereas under unpredictable conditions a 'default' response emerged that anticipated the 10° perturbation. LL reflex scaling under predictable conditions was intact in patients with neuroleptic-induced parkinsonism and young-onset Parkinson's disease, but the large default LL response under unpredictable conditions was absent. In patients with MPTP-induced parkinsonism, LL reflex scaling was absent during both predictable and unpredictable conditions. We conclude that abnormal scaling of posturally stabilizing LL reflexes is related to decreased supraspinal dopaminergic influence.

Original languageEnglish (US)
Pages (from-to)580-588
Number of pages9
JournalMovement Disorders
Volume10
Issue number5
DOIs
StatePublished - 1995
Externally publishedYes

Keywords

  • Dopamine
  • Long latency reflexes
  • Parkinson's disease
  • Posture

ASJC Scopus subject areas

  • Clinical Neurology
  • Neuroscience(all)

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