Department of Neurology, Zealand University Hospital, Roskilde, Denmark.
Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
J Alzheimers Dis. 2022;88(1):335-344. doi: 10.3233/JAD-220081.
Exposure to 40 Hz stroboscopic light, for one hour a day, has previously been published as a potential treatment option for Alzheimer's disease in animal models. However, exposure for an hour a day to 40 Hz stroboscopic light can be strenuous and examining other types of 40 Hz inducing stimuli is paramount if chronic treatment is wanted.
A core assumption behind ensuring a therapeutic outcome is that the visual stimuli can induce 40 Hz gamma entrainment. Here, we examine whether a specific visual stimulus, 40 Hz invisible spectral flicker (ISF), can induce gamma entrainment and how it differs from both continuous light (CON) and 40 Hz stroboscopic light (STROBE).
The study included non-simultaneous EEG-fMRI neuroimaging of 13 young healthy volunteers during light exposure. Each light condition (i.e., CON, ISF, or STROBE) was active for 30 seconds followed immediately by the next.
Entrainment of 40 Hz neural activity were significantly higher signal-to-noise ratio during exposure to ISF (mean: 3.03, 95% CI 2.07 to 3.99) and STROBE (mean: 12.04, 95% CI 10.18 to 13.87) compared to CON. Additionally STROBE had a higher entrainment than ISF (mean: 9.01, 95% CI 7.16 to 12.14).
This study presents a novel method of 40 Hz entrainment using ISF. This enables the possibility of future randomized placebo-controlled clinical trials with acceptable double blinding due to the essentially imperceivable flicker, which is expected to substantially reduce discomfort compared to interventions with stroboscopic flicker.
以前的动物模型研究表明，每天暴露在 40Hz 频闪光下 1 小时是治疗阿尔茨海默病的一种潜在选择。然而，如果需要慢性治疗，每天暴露在 40Hz 频闪光下 1 小时可能会很吃力，因此检查其他类型的 40Hz 诱导刺激至关重要。
确保治疗效果的一个核心假设是视觉刺激可以诱导 40Hz 伽马同步。在这里，我们研究了一种特定的视觉刺激，即 40Hz 不可见光谱闪烁（ISF），是否可以诱导伽马同步，以及它与连续光（CON）和 40Hz 频闪光（STROBE）有何不同。
这项研究包括对 13 名年轻健康志愿者进行非同步 EEG-fMRI 神经影像学检查，以记录他们在光照下的大脑活动。在光照暴露期间，每种光照条件（即 CON、ISF 或 STROBE）持续 30 秒，然后立即切换到下一种光照条件。
ISF（平均：3.03，95%置信区间 2.07 至 3.99）和 STROBE（平均：12.04，95%置信区间 10.18 至 13.87）暴露时，40Hz 神经活动的同步率明显高于 CON。此外，STROBE 的同步率高于 ISF（平均：9.01，95%置信区间 7.16 至 12.14）。
本研究提出了一种使用 ISF 进行 40Hz 同步的新方法。这种方法为未来的随机安慰剂对照临床试验提供了可能，由于闪烁几乎不可察觉，有望显著减少与频闪闪烁干预相关的不适，因此可以实现更好的双盲效果。
