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Effects of visual cortex activation on the nociceptive blink reflex in healthy subjects.

Sava SL, de Pasqua V, Magis D, Magis D, Schoenen J, Schoenen J - PLoS ONE (2014)

Bottom Line: 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.The results argue in favour of a top-down inhibitory pathway from the visual areas to trigemino-cervical nociceptors.

View Article: PubMed Central - PubMed

Affiliation: Headache Research Unit, University Department of Neurology, Liège University, Liège, Belgium.

ABSTRACT
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.

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First block of 5 ispilateral and contralateral nBR responses (area under the curve in µVxms ± sem) before (light bars) and after (dark bars) 1 Hz rTMS, 10 Hz rTMS over the visual cortex, or flash light stimulation.** p<0.01; * p<0.05. The inhibitory effect on the nBR is significantly stronger after flash light stimulation than after10 Hz rTMS over the visual cortex.
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pone-0100198-g001: First block of 5 ispilateral and contralateral nBR responses (area under the curve in µVxms ± sem) before (light bars) and after (dark bars) 1 Hz rTMS, 10 Hz rTMS over the visual cortex, or flash light stimulation.** p<0.01; * p<0.05. The inhibitory effect on the nBR is significantly stronger after flash light stimulation than after10 Hz rTMS over the visual cortex.

Mentions: Moreover, 1 Hz rTMS significantly increased amplitude of the 1st nBR block expressed as AUC/i2 both ipsi- and contralaterally to the supraorbital stimulation (p = 0.024 and p = 0.036 respectively) (Table 1, Fig. 1). By contrast, habituation was significantly potentiated contralaterally to the stimulated side (p = 0.0002) (Fig. 2).


Effects of visual cortex activation on the nociceptive blink reflex in healthy subjects.

Sava SL, de Pasqua V, Magis D, Magis D, Schoenen J, Schoenen J - PLoS ONE (2014)

First block of 5 ispilateral and contralateral nBR responses (area under the curve in µVxms ± sem) before (light bars) and after (dark bars) 1 Hz rTMS, 10 Hz rTMS over the visual cortex, or flash light stimulation.** p<0.01; * p<0.05. The inhibitory effect on the nBR is significantly stronger after flash light stimulation than after10 Hz rTMS over the visual cortex.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061134&req=5

pone-0100198-g001: First block of 5 ispilateral and contralateral nBR responses (area under the curve in µVxms ± sem) before (light bars) and after (dark bars) 1 Hz rTMS, 10 Hz rTMS over the visual cortex, or flash light stimulation.** p<0.01; * p<0.05. The inhibitory effect on the nBR is significantly stronger after flash light stimulation than after10 Hz rTMS over the visual cortex.
Mentions: Moreover, 1 Hz rTMS significantly increased amplitude of the 1st nBR block expressed as AUC/i2 both ipsi- and contralaterally to the supraorbital stimulation (p = 0.024 and p = 0.036 respectively) (Table 1, Fig. 1). By contrast, habituation was significantly potentiated contralaterally to the stimulated side (p = 0.0002) (Fig. 2).

Bottom Line: 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.The results argue in favour of a top-down inhibitory pathway from the visual areas to trigemino-cervical nociceptors.

View Article: PubMed Central - PubMed

Affiliation: Headache Research Unit, University Department of Neurology, Liège University, Liège, Belgium.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus