研究: 外膝状体神经元的亮度反应与感受野ON-OFF反应的关系

外膝体是视觉信息进入新皮层的主要通路,其编码亮度信息的神经机制还不清楚.我们采用随机呈现的连续快速变化(50 Hz)的均匀亮度刺激,显著地提高了猫外膝体神经元对均匀亮度的反应强度,通过反相关算法抽提出神经元的亮度反应函数.约81%的神经元的亮度反应函数为单调性上升或下降,有19%的神经元亮度反应函数为V型.通过分析这些神经元对亮度上升和下降的反应强度与感受野ON和OFF反应强度的关系,表明83%的神经元对亮度的反应模式是由其感受野ON-OFF反应的相对强度决定的,其余17%则与其感受野ON-OFF区的兴奋和抑制的变化相关.这些结果揭示了外膝体神经元编码亮度变化的机制.

Review: Relationships Between Responses to Luminance Changes and Receptive Field ON-OFF Responses of Neurons in Lateral Geniculate Neucleus

In the early visual pathway, the lateral geniculate nucleus (LGN) is the major relay station from where visual information is transmitted to the cerebral cortex. How LGN neurons code luminance remains unclear. We addressed the issue by presenting the luminance stimuli that were continuously changing at 50 Hz to neurons of cat LGN. The rapid changes in luminance enhanced responses of LGN neurons to uniform stimuli. Responses of a neuron to the luminance stimuli were sorted using the reverse correlation algorithm and luminance response function (LRF) was extracted from the responses. Most neurons (81%) had either increase or decrease LRFs, and the remaining neurons (19%) had V-shape LRFs. The relationships between the response magnitudes to luminance increments and decrements of uniform stimuli and those to ON and OFF stimuli presented inside receptive field (RF) revealed that the increase, decrease, and V-shape LRFs of most neurons (83%) were determined by the relative strength of ON-OFF responses of their RFs, and the LRFs of the other neurons (17%) were related to the excitation-inhibition interactions between RF ON-center (or surround) and OFF-surround (or center) of RF structure. The results unveiled the neural mechanisms underlying the responses of LGN neurons to uniform luminance.