Effects of Visual Cortex Activation on the Nociceptive Blink Reflex in Healthy Subjects

• Published in: PloS one Vol. 9; no. 6; p. e100198
• Main Authors: Sava, Simona L., de Pasqua, Victor, Magis, Delphine, Schoenen, Jean
• Format: Journal Article Web Resource
• Language: English
• Published: United States Public Library of Science 17.06.2014; Public Library of Science (PLoS)
• Subjects: Adult; Age; Blink reflex; Blinking; Blinking - physiology; Case-Control Studies; Cortex (occipital); Discomfort; Electrodes; Female; Follow-Up Studies; Habituation; Habituation (learning); Headache; Headaches; Healthy Volunteers; Human health sciences; Humans; Hypotheses; Light; Magnetic fields; Male; Medicine and Health Sciences; Migraine; Neurologie; Neurology; Nociceptors; Nociceptors - physiology; Pain; Pain perception; Prognosis; Reflex - physiology; Sciences de la santé humaine; Sensory stimulation; Thresholds; Transcranial Magnetic Stimulation; Visual cortex; Visual Cortex - physiology; Visual effects
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0100198

Bright light can cause excessive visual discomfort, referred to as photophobia. The precise mechanisms linking luminance to the trigeminal nociceptive system supposed to mediate this discomfort are not known. To address this issue in healthy human subjects we modulated differentially visual cortex activity by repetitive transcranial magnetic stimulation (rTMS) or flash light stimulation, and studied the effect on supraorbital pain thresholds and the nociceptive-specific blink reflex (nBR). Low frequency rTMS that inhibits the underlying cortex, significantly decreased pain thresholds, increased the 1st nBR block ipsi- and contralaterally and potentiated habituation contralaterally. After high frequency or sham rTMS over the visual cortex, and rMS over the right greater occipital nerve we found no significant change. By contrast, excitatory flash light stimulation increased pain thresholds, decreased the 1st nBR block of ipsi- and contralaterally and increased habituation contralaterally. Our data demonstrate in healthy subjects a functional relation between the visual cortex and the trigeminal nociceptive system, as assessed by the nociceptive blink reflex. The results argue in favour of a top-down inhibitory pathway from the visual areas to trigemino-cervical nociceptors. We postulate that in normal conditions this visuo-trigeminal inhibitory pathway may avoid disturbance of vision by too frequent blinking and that hypoactivity of the visual cortex for pathological reasons may promote headache and photophobia.