幼年大鼠视皮层神经元对闪光刺激的反应特性

哺乳动物视觉系统的发育延续到出生后，大鼠出生后 3~5 周是视觉系统发育的关键期 . 在关键期中，视皮层的兴奋性和抑制性突触连接逐渐成熟，形成有效的皮层内回路 . 为了观察发育关键期大鼠视皮层神经元的反应特性与成年大鼠的异同，使用胞外单细胞记录的方法对比研究了幼年和成年大鼠对闪光刺激的视觉反应特性 . 结果显示：与成年大鼠相比较，幼年大鼠视皮层神经元对持续闪光刺激显示出更强的适应性，对光刺激的诱发放电频率更低，而在没有光刺激时的自发放电频率更高，从而导致信噪比更低 . 这一结果表明，幼年大鼠视皮层对连续刺激的反应能力下降，对信号的分辨能力也更弱，其原因可能是兴奋性突触和抑制性突触发育的不同步所致 .

Neural Response Characteristic of Neuron to Flashing Stimulus in Visual Cortex of Young Rats

Mammalian visual system develops after birth. In rats, postnatal 3 to 5 weeks are critical for their development (namely, critical period), during which the excitatory and inhibitory synapses mature to form functional circuits in visual cortex. Extracelluar single-unit recording techniques were used in vivo to investigate the difference of response characteristics of between neurons in young and adult rats' primary visual cortexes. It was found that: (1) The adaptation to sustaining flashing stimuli is significantly higher in neurons of young rats; (2) The evoked response rate of young visual cortex neurons is significantly lower than that of adult rats; (3) The spontaneous rate (without flashing stimuli) is significantly higher in young instead of adult rats; (4) Signal to noise ratio (SNR) is significantly lower in young visual cortex. These results indicate that the response capability to continued stimuli and the detectability is lower in developing visual cortex. It might result from the sequential development of excitatory and inhibitory synapses in postnatal rat neocortex.