Boroojerdi B, Bushara K O, Corwell B, Immisch I, Battaglia F, Muellbacher W, Cohen L G
Human Cortical Physiology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, USA.
Cereb Cortex. 2000 May;10(5):529-34. doi: 10.1093/cercor/10.5.529.
Long-term deprivation of visual input for several days or weeks leads to marked changes in the excitability and function of the occipital cortex. The time course of these changes is poorly understood. In this study, we addressed the question whether a short period of light deprivation (minutes to a few hours) can elicit such changes in humans. Noninvasive transcranial magnetic stimulation (TMS) of the human occipital cortex can evoke the perception of flashes or spots of light (phosphenes). To assess changes in visual cortex excitability following light deprivation, we measured the minimum intensity of stimulation required to elicit phosphenes (phosphene threshold) and the number of phosphenes elicited by different TMS stimulus intensities (stimulus-response curves). A reduced phosphene threshold was detected 45 min after the onset of light deprivation and persisted for the entire deprivation period (180 min). Following re-exposure to light, phosphene thresholds returned to predeprivation values over 120 min. Stimulus-response curves were significantly enhanced in association with this intervention. In a second experiment, we studied the effects of light deprivation on functional magnetic resonance imaging (fMRI) signals elicited by photic stimulation. fMRI results showed increased visual cortex activation after 60 min of light deprivation that persisted following 30 min of re-exposure to light. Our results demonstrated a substantial increase in visual cortex excitability. These changes may underlie behavioral gains reported in humans and animals associated with light deprivation.
数天或数周的长期视觉输入剥夺会导致枕叶皮质的兴奋性和功能发生显著变化。这些变化的时间进程尚不清楚。在本研究中，我们探讨了短时间的光剥夺（数分钟至数小时）是否能在人类中引发此类变化的问题。对人类枕叶皮质进行无创经颅磁刺激（TMS）可诱发闪光或光斑（光幻视）的感知。为了评估光剥夺后视觉皮质兴奋性的变化，我们测量了诱发光幻视所需的最小刺激强度（光幻视阈值）以及不同TMS刺激强度诱发的光幻视数量（刺激-反应曲线）。在光剥夺开始后45分钟检测到光幻视阈值降低，并在整个剥夺期（180分钟）持续存在。重新暴露于光线下后，光幻视阈值在120分钟内恢复到剥夺前的值。与此干预相关，刺激-反应曲线显著增强。在第二个实验中，我们研究了光剥夺对光刺激诱发的功能磁共振成像（fMRI）信号的影响。fMRI结果显示，光剥夺60分钟后视觉皮质激活增加，在重新暴露于光线下30分钟后仍持续存在。我们的结果表明视觉皮质兴奋性大幅增加。这些变化可能是人类和动物中与光剥夺相关的行为改善的基础。
