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Long-term depression of the human blink reflex
1Department of Experimental and Clinical Pharmacology and Toxicology, Emil-Fischer Center, Friedrich-Alexander University of Erlangen-Nuremberg, Fahrstrasse 17, 91054 Erlangen, Germany.
Experimental Brain Research
|November 22, 2002
Summary
Low-frequency stimulation (LFS) can induce long-term depression (LTD) in trigeminal sensory neurons in humans. This study demonstrates LTD of the blink reflex in healthy volunteers, bridging in vitro and in vivo findings.
Area of Science:
- Neuroscience
- Human Physiology
Background:
- Long-term depression (LTD) of synaptic transmission is typically induced by low-frequency stimulation (LFS) in vitro.
- LTD of basal transmission is challenging to induce in vivo in awake or anesthetized animals.
Purpose of the Study:
- To investigate the effect of LFS on trigeminal somatosensory processing in healthy human volunteers.
- To bridge the gap between in vitro LTD studies and in vivo observations.
Main Methods:
- Investigated trigeminal sensory neuron excitability using the blink reflex (BR).
- Applied LFS to supraorbital nerve afferents in healthy volunteers.
- Measured BR integral, onset latency, and stimulus intensity ratings.
Main Results:
- LFS induced a significant reduction in the BR integral.
- A significant increase in BR onset latency was observed post-LFS.
- Stimulus intensity ratings significantly decreased after LFS.
- The depressive effect on the BR persisted for at least 1 hour.
Conclusions:
- This study provides the first documentation of long-term depression in trigeminal somatosensory processing in healthy human volunteers.
- LFS can effectively induce a measurable and lasting depression of trigeminal sensory processing in humans.