Kammer Thomas, Beck Sandra
Department of Neurobiology, Max Planck Institute for Biological Cybernetics, Spemannstrasse 38, 72076 Tübingen, Germany.
Exp Brain Res. 2002 Aug;145(3):407-10. doi: 10.1007/s00221-002-1160-3. Epub 2002 Jun 13.
Transcranial magnetic stimulation applied over the occipital pole is able to induce the perception of light flashes called phosphenes. For phosphene detection and threshold measurement subjects are usually blindfolded or investigated in the dark. The question that we posed here is whether phosphene thresholds change with variations in ambient light. In six subjects we measured thresholds under four different conditions: closed eyes (5 min adaptation) and 0.5, 100, and 3,200 cd/m(2) background illumination. No systematic change in phosphene thresholds was observed with different lighting conditions. In three subjects we repeated the measurements after one week and again found similar values with no systematic modulation. Our data show that cortical excitability does not change with different light adaptation levels. This confirms that the main adaptation to light takes place at subcortical levels, namely at the retina. The practical conclusion is that it is unnecessary to blindfold subjects when determining phosphene thresholds.
经颅磁刺激作用于枕极能够诱发称为光幻视的闪光感知。对于光幻视检测和阈值测量，受试者通常要蒙上眼睛或在黑暗中进行检查。我们在此提出的问题是，光幻视阈值是否会随环境光的变化而改变。我们对6名受试者在四种不同条件下测量了阈值：闭眼（5分钟适应）以及背景光照为0.5、100和3200 cd/m²。在不同光照条件下未观察到光幻视阈值的系统性变化。我们对3名受试者在一周后重复了测量，再次发现相似的值且无系统性调节。我们的数据表明，皮质兴奋性不会随不同的光适应水平而改变。这证实了对光的主要适应发生在皮质下水平，即视网膜。实际结论是，在确定光幻视阈值时无需蒙住受试者的眼睛。
