γ节律振荡机制在视觉研究中的新进展

The Progress in Visual Mechanism of Gamma Rhythm

γ节律振荡是大脑皮质中常见的,频率在30~80 Hz之间的神经振荡模式,在初级视觉通道中能观察到多种起源的γ节律振荡.在小鼠、猫与猴V1的视觉诱发的γ节律振荡主要起源于L2/3和L4B,并对刺激参数敏感.猫与小鼠初级视觉通道(视网膜、LGN与V1)中观察到起源于视网膜由亮度诱发的高频γ节律振荡;在猴LGN却没有观察到γ节律振荡,而在V1上记录到亮度诱发的γ活动.γ节律振荡的产生与抑制性中间神经元网络有重要的关系,其中抑制性中间神经元中PV细胞被认为与自发γ节律振荡的产生相关. SOM细胞的参与对低频γ节律振荡(20~40 Hz)的产生起到关键作用;而光栅诱发的高频γ节律振荡(65~80 Hz)主要与PV细胞有关.动物在不同生理状态、发育阶段与脑疾病状态下光栅诱发的γ节律振荡存在较大差异,反映大脑对视觉信息加工的变化.

Gamma rhythm ranges from 30 to 80 Hz, widely existing in neocortex. The key condition for the generation of gamma rhythm is the participation of inhibitory interneuron network. Spontaneous gamma rhythm is mainly related to parvalbumin inhibitory interneurons. In mouse, cat and monkey V1, the induced gamma rhythm is mainly derived from laminar 2/3 and 4 B, and are well tuned by grating parameters. In primary visual pathway of cat and mouse, the high frequency gamma rhythm induced by brightness is derived from retina.However, brightness evoked gamma oscillation in monkey was observed in V1, but was not recorded in LGN.Dendrite-targeting somatostatin interneurons are critical for a visually induced, context-dependent low gamma rhythm(20-40 Hz) in primary visual cortex. The visually induced high frequency gamma rhythm(65-80 Hz) was mainly associated with PV cells. Increases in background light intensity trigger proportional increases in narrowband gamma oscillations(55-65 Hz) of mouse early visual pathway, which originated from ipRGCs cells in the retina. The gamma rhythm is variable in different physiological state, development stage and brain disease,implying the change in the visual information processing.