Aging of the trigeminal blink system

Area of Science:

• Neuroscience
• Ophthalmology
• Gerontology

Background:

• The trigeminal reflex blink is crucial for eye protection.
• Age-related changes in neuronal function can impact motor control, including blinking.
• Parkinson's disease is characterized by dopamine neuron degeneration, affecting motor functions.

Purpose of the Study:

• To investigate age-related alterations in human and guinea pig trigeminal blinks.
• To compare trigeminal blink characteristics in normal aging versus Parkinson's disease.
• To explore the role of dopamine in age-related trigeminal blink changes and blink oscillations.

Main Methods:

• Characterization of trigeminal blinks in human subjects across age groups (20-80 years).
• Assessment of trigeminal blinks in young and aged guinea pigs.
• Evaluation of trigeminal blinks in Parkinson's disease patients and age-matched controls.
• Analysis of blink duration, latency, amplitude, and excitability.

Main Results:

• Trigeminal blink duration and latency increase significantly with age in humans and guinea pigs.
• Reflex blink amplitude changes inconsistently with age, but blink duration is similar for both eyelids.
• Aged humans and guinea pigs exhibit 'blink oscillations'—additional blinks following an initial stimulus—not seen in younger subjects.
• Parkinson's disease increases blink duration and excitability, supporting the role of dopamine loss.

Conclusions:

• Age-related dopamine neuron loss likely contributes to increased trigeminal blink excitability and duration.
• Blink oscillations, a newly characterized trigeminal blink type, emerge after age 40 in humans and in aged guinea pigs.
• Altered blink oscillation mechanisms may be implicated in dry eye and benign essential blepharospasm.