Limits...
When the sun prickles your nose: an EEG study identifying neural bases of photic sneezing.

Langer N, Beeli G, Jäncke L - PLoS ONE (2010)

Bottom Line: Remarkably, we found a generally enhanced excitability of the visual cortex (mainly in the cuneus) to visual stimuli in 'photic sneezers' compared with control subjects.In addition, a stronger prickling sensation in the nose of photic sneezers was found to be associated with activation in the insula and stronger activation in the secondary somatosensory cortex.The 'photic sneeze reflex' is therefore not a classical reflex that occurs only at a brainstem or spinal cord level but, in stark contrast to many theories, involves also specific cortical areas.

View Article: PubMed Central - PubMed

Affiliation: Psychological Institute, Division of Neuropsychology, University of Zurich, Zurich, Switzerland. n.langer@psychologie.uzh.ch

ABSTRACT

Background: Exposure to bright light such as sunlight elicits a sneeze or prickling sensation in about one of every four individuals. This study presents the first scientific examination of this phenomenon, called 'the photic sneeze reflex'.

Methodology and principal findings: In the present experiment, 'photic sneezers' and controls were exposed to a standard checkerboard stimulus (block 1) and bright flashing lights (block 2) while their EEG (electro-encephalogram) was recorded. Remarkably, we found a generally enhanced excitability of the visual cortex (mainly in the cuneus) to visual stimuli in 'photic sneezers' compared with control subjects. In addition, a stronger prickling sensation in the nose of photic sneezers was found to be associated with activation in the insula and stronger activation in the secondary somatosensory cortex.

Conclusion: We propose that the photic sneeze phenomenon might be the consequence of higher sensitivity to visual stimuli in the visual cortex and of co-activation of somatosensory areas. The 'photic sneeze reflex' is therefore not a classical reflex that occurs only at a brainstem or spinal cord level but, in stark contrast to many theories, involves also specific cortical areas.

Show MeSH

Related in: MedlinePlus

Comparing photic sneezers with control subjects.(A) Visual event-related potential (global field power) 0–400 ms after stimulus onset of block1 (checkerboard-paradigm) for both groups (photic sneezers vs. controls). Two time segments at 56–68 ms and 200–212 ms after stimulus presentation survived the FDR-correction (p<0.05). These time segments are marked by transparent rectangles. (B) sLORETA-analysis of the FDR-corrected time segments revealed significantly increased activity of the photic sneezers compared with control subjects. Neural generators for the time segment 56–68 ms are located in the primary visual cortex. The increased activation for the time segment 200–212 ms was found in the secondary visual cortex. Cortical activation differences estimated with sLORETA are displayed in red. X, Y, Z MNI-coordinates of the local maximum of the activation difference.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2821404&req=5

pone-0009208-g001: Comparing photic sneezers with control subjects.(A) Visual event-related potential (global field power) 0–400 ms after stimulus onset of block1 (checkerboard-paradigm) for both groups (photic sneezers vs. controls). Two time segments at 56–68 ms and 200–212 ms after stimulus presentation survived the FDR-correction (p<0.05). These time segments are marked by transparent rectangles. (B) sLORETA-analysis of the FDR-corrected time segments revealed significantly increased activity of the photic sneezers compared with control subjects. Neural generators for the time segment 56–68 ms are located in the primary visual cortex. The increased activation for the time segment 200–212 ms was found in the secondary visual cortex. Cortical activation differences estimated with sLORETA are displayed in red. X, Y, Z MNI-coordinates of the local maximum of the activation difference.

Mentions: For the analysis of block 2, the rating of the subjective intensity of the sneezing sensation was used and related to the cortical activation measures. This analysis therefore includes only the group of photic sneezers (PS). We identified the trials eliciting the subjectively strongest tickling sensations and compared them with those trials evoking the subjectively weakest tickling sensations (PSstrong vs. PSweak). For these trials the GFPs were compared using a t test for dependent samples separately for each time point. As for block 1, we only report the FDR-corrected results. In order to visualize the significantly different GFP time points surviving our conservative statistical threshold these are marked by transparent rectangles overlaid onto the corresponding GFPs in Figs. 1 and 2.


When the sun prickles your nose: an EEG study identifying neural bases of photic sneezing.

Langer N, Beeli G, Jäncke L - PLoS ONE (2010)

Comparing photic sneezers with control subjects.(A) Visual event-related potential (global field power) 0–400 ms after stimulus onset of block1 (checkerboard-paradigm) for both groups (photic sneezers vs. controls). Two time segments at 56–68 ms and 200–212 ms after stimulus presentation survived the FDR-correction (p<0.05). These time segments are marked by transparent rectangles. (B) sLORETA-analysis of the FDR-corrected time segments revealed significantly increased activity of the photic sneezers compared with control subjects. Neural generators for the time segment 56–68 ms are located in the primary visual cortex. The increased activation for the time segment 200–212 ms was found in the secondary visual cortex. Cortical activation differences estimated with sLORETA are displayed in red. X, Y, Z MNI-coordinates of the local maximum of the activation difference.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2821404&req=5

pone-0009208-g001: Comparing photic sneezers with control subjects.(A) Visual event-related potential (global field power) 0–400 ms after stimulus onset of block1 (checkerboard-paradigm) for both groups (photic sneezers vs. controls). Two time segments at 56–68 ms and 200–212 ms after stimulus presentation survived the FDR-correction (p<0.05). These time segments are marked by transparent rectangles. (B) sLORETA-analysis of the FDR-corrected time segments revealed significantly increased activity of the photic sneezers compared with control subjects. Neural generators for the time segment 56–68 ms are located in the primary visual cortex. The increased activation for the time segment 200–212 ms was found in the secondary visual cortex. Cortical activation differences estimated with sLORETA are displayed in red. X, Y, Z MNI-coordinates of the local maximum of the activation difference.
Mentions: For the analysis of block 2, the rating of the subjective intensity of the sneezing sensation was used and related to the cortical activation measures. This analysis therefore includes only the group of photic sneezers (PS). We identified the trials eliciting the subjectively strongest tickling sensations and compared them with those trials evoking the subjectively weakest tickling sensations (PSstrong vs. PSweak). For these trials the GFPs were compared using a t test for dependent samples separately for each time point. As for block 1, we only report the FDR-corrected results. In order to visualize the significantly different GFP time points surviving our conservative statistical threshold these are marked by transparent rectangles overlaid onto the corresponding GFPs in Figs. 1 and 2.

Bottom Line: Remarkably, we found a generally enhanced excitability of the visual cortex (mainly in the cuneus) to visual stimuli in 'photic sneezers' compared with control subjects.In addition, a stronger prickling sensation in the nose of photic sneezers was found to be associated with activation in the insula and stronger activation in the secondary somatosensory cortex.The 'photic sneeze reflex' is therefore not a classical reflex that occurs only at a brainstem or spinal cord level but, in stark contrast to many theories, involves also specific cortical areas.

View Article: PubMed Central - PubMed

Affiliation: Psychological Institute, Division of Neuropsychology, University of Zurich, Zurich, Switzerland. n.langer@psychologie.uzh.ch

ABSTRACT

Background: Exposure to bright light such as sunlight elicits a sneeze or prickling sensation in about one of every four individuals. This study presents the first scientific examination of this phenomenon, called 'the photic sneeze reflex'.

Methodology and principal findings: In the present experiment, 'photic sneezers' and controls were exposed to a standard checkerboard stimulus (block 1) and bright flashing lights (block 2) while their EEG (electro-encephalogram) was recorded. Remarkably, we found a generally enhanced excitability of the visual cortex (mainly in the cuneus) to visual stimuli in 'photic sneezers' compared with control subjects. In addition, a stronger prickling sensation in the nose of photic sneezers was found to be associated with activation in the insula and stronger activation in the secondary somatosensory cortex.

Conclusion: We propose that the photic sneeze phenomenon might be the consequence of higher sensitivity to visual stimuli in the visual cortex and of co-activation of somatosensory areas. The 'photic sneeze reflex' is therefore not a classical reflex that occurs only at a brainstem or spinal cord level but, in stark contrast to many theories, involves also specific cortical areas.

Show MeSH
Related in: MedlinePlus