Foust Amanda J, Schei Jennifer L, Rojas Manuel J, Rector David M
Washington State University, Department of Veterinary and Comparative Anatomy, Pharmacology and Physiology, College of Veterinary Medicine, 205 Wegner Hall, Pullman, Washington 99164-6520, USA.
J Biomed Opt. 2008 Jul-Aug;13(4):044038. doi: 10.1117/1.2952295.
Laser diodes (LD) are commonly used for optical neural recordings in chronically recorded animals and humans, primarily due to their brightness and small size. However, noise introduced by LDs may counteract the benefits of brightness when compared to low-noise light-emitting diodes (LEDs). To understand noise sources in optical recordings, we systematically compared instrument and physiological noise profiles in two recording paradigms. A better understanding of noise sources can help improve optical recordings and make them more practical with fewer averages. We stimulated lobster nerves and a rat cortex, then compared the root mean square (RMS) noise and signal-to-noise ratios (SNRs) of data obtained with LED, superluminescent diode (SLD), and LD illumination for different numbers of averages. The LED data exhibited significantly higher SNRs in fewer averages than LD data in all recordings. In the absence of tissue, LED noise increased linearly with intensity, while LD noise increased sharply in the transition to lasing and settled to noise levels significantly higher than the LED's, suggesting that speckle noise contributed to the LD's higher noise and lower SNRs. Our data recommend low coherence and portable light sources for in vivo chronic neural recording applications.
激光二极管（LD）常用于对长期记录的动物和人类进行光学神经记录，主要是因为其亮度高且尺寸小。然而，与低噪声发光二极管（LED）相比，LD引入的噪声可能会抵消其亮度优势。为了了解光学记录中的噪声源，我们在两种记录范式中系统地比较了仪器噪声和生理噪声特征。更好地理解噪声源有助于改进光学记录，并使其在较少平均次数的情况下更具实用性。我们刺激了龙虾神经和大鼠皮层，然后比较了在不同平均次数下，使用LED、超发光二极管（SLD）和LD照明获得的数据的均方根（RMS）噪声和信噪比（SNR）。在所有记录中，LED数据在较少平均次数下的SNR显著高于LD数据。在没有组织的情况下，LED噪声随强度呈线性增加，而LD噪声在进入激光状态时急剧增加，并稳定在明显高于LED的噪声水平，这表明散斑噪声导致了LD的高噪声和低SNR。我们的数据推荐使用低相干性和便携式光源用于体内慢性神经记录应用。
