Conductance-based models of reciprocally inhibiting burst neurons suggest that intrinsic membrane properties and postinhibitory rebound (PIR) determine the amplitude and frequency of saccadic oscillations. Reduction of the low-threshold calcium currents (I T) in the model decreased the amplitude but increased the frequency of the simulated oscillations. Combined reduction of hyperpolarization-activated cation current (I h) andI T in the model abolished the simulated oscillations. We measured the effects of a selective blocker ofI T (ethosuximide) in healthy subjects on the amplitude and frequency of saccadic oscillations evoked by eye closure and of a nonselective blocker ofI h andI T (propronolol) in a patient with microsaccadic oscillation and limb tremor syndrome (mSOLT). Ethosuximide significantly reduced the amplitude but increased the frequency of the saccadic oscillations during eye closure in healthy subjects. Propranolol abolished saccadic oscillations in the mSOLT patient. These results support the hypothetical role of postinhibitory rebound,I h, andI T, in generation of saccadic oscillations and determining their kinematic properties.
- Burst neurons
- Hyperpolarization-activated cation current
- Low-threshold calcium current
- Reciprocal innervations
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- History and Philosophy of Science