Optical imaging of neural activity in transient ischemia and plasticity in cortex

用电压敏感染料（RH 795）光学记录研究了哺乳动物听觉皮层声诱发神经活动的时空格局。该方法用于观察脑皮层活动的短暂性缺血变化。用12 × 12的光电二极管阵列记录了不同频率和压力水平下620nm诱导声的光强变化。响应的振幅显示为连续的二维图像。听觉皮层多区域存在张力局部组织。然而，通过功能组织的频率表示是短暂的。从主场开始的震源活动沿等频带向背侧传播。大鼠听觉皮层在缺血诱导1 min后，声音引起的光信号消失。在缺血30min期间，没有观察到任何成分的反应。再循环之后，144个站点的回复再次出现。然而，短暂缺血后的反应模式与对照组有显著差异。特别是后组分没有恢复到缺血前的水平。虽然出现了功能组织，但在组织内发现了易受伤害的区域，这些区域的视觉反应没有恢复到对照组。我们的结果表明，听觉皮层的功能变化先于这些大脑区域的缺血性神经元死亡。在豚鼠中，有一些病例显示短暂缺血导致皮层的光学反应强度增加。光学记录方法具有二维皮层活动实时成像的优点，具有广泛的应用前景。

The spatio-temporal pattern of sound-evoked neural activity in the mammalian auditory cortex was studied by optical recording with aid of voltage-sensitive dye (RH 795). This method was applied to observation of transient ischemic changes in the cortical activity. Changes in light intensity at 620 nm induced sounds at various frequency and pressure levels were recorded with a 12 x 12 array of photodiodes. The amplitude of the responses were displayed as sequential two-dimensional images. Tonotopical organization was found in the multi-fields of the auditory cortex. However, frequency representation through the functional organization was transient. The focal activity that began in the primary field propagated dorsally along the iso-frequency bands. In the rats auditory cortex, the optical signals induced by sounds were disappeared by 1 min after induction of ischemia. During the 30 min of ischemia, no components of the responses were observed. After recirculation the responses from 144 sites appeared again. However the pattern of the responses after the transient ischemia was significantly different from the control. Especially the later component did not recover to the preischemic level. Although functional organization appeared, but vulnerable regions were found within the organization where the optical responses ded not return to the control Our results suggest that the functional changes in the auditory cortex precede the post-ischemic neuronal death in those cerebral regions. In guinea pigs, there were some cases which showed an increase in the magnitude of optical responses from the cortex by transient ischemia. The optical recording method has the advantage of real-time imaging of two-dimensional cortical activity and will be used widely in the future.