A measure of the somatosensory blink reflex to parametric variation of mechanical stimulation

Abstract

The trigeminal blink response is a familiar and easily evoked brainstem reflex. Despite a long history of clinical and research investigation, there has been limited study of how parametric manipulation of the intensity of somatosensory stimulation modulates the evoked response. The goal of this study was to measure the psychometric trigeminal sensitivity function and to test the resulting model parameters for differences between the eyelids contralateral and ipsilateral to the side of stimulation, and to test for individual differences in sensitivity. We measured the ipsilateral and contralateral blink in 17 healthy, adult participants in response to airpuffs delivered to the cornea over a range of five, log-spaced intensities (3.5 - 60 PSI). The temporal lid position vector was decomposed into amplitude, velocity, and shape components. We found that variation in blink amplitude was well fit with a two-parameter Weibull cumulative density function of log stimulus intensity. There was a reliable decrease in threshold sensitivity of the contralateral as compared to ipsilateral eyelid. This decrease was consistent across participants despite substantial individual differences in the threshold and slope of the overall sensitivity function, suggesting that the laterality effect arises subsequent to individual differences in the neural circuit. We conclude that a parametric measure of trigeminal sensitivity is a promising tool for examining neural mechanisms that modulate this response, including in various disease states.