刺激呈现率影响小鼠下丘神经元声反应特性

自由声场条件下，以强度为特征频率阈上5dBSPL、时程为40ms的短纯音为声刺激，记录了小鼠下丘神经元对不同呈现率（0．5～20Hz）的声刺激反应．结果显示，随呈现率的增高，绝大多数神经元（87．3％，103／118）的冲动发放数单调下降，少数（12．7％，15／118）神经元的冲动发放数呈非单调变化，冲动发放数与刺激呈现率之间有显著相关性．即使在低范围内改变呈现率也能显著影响多数神经元的声反应特性，其临界呈现率及最大呈现率低于3．3Hz的神经元分别超过70％（75．4％，89／118）和40％（44．9％，53／118）．此外，提高刺激呈现率，部分神经元（17．8％，21／118）的发放模式发生改变，主要是由紧张型或相位爆发型向相位型转变．可见，下丘神经元声反应特性与声刺激呈现率密切相关．

Presentation rate of stimulation affected the sound response properties of the mouse inferior colliculus neurons

To study the effect of stimulus presentation rate on the sound response properties of mouse inferior colliculus(IC) neurons,the tones with duration of 40 ms at characteristic frequency(CF) of recorded neurons were presented to Nembutal anesthetic mice(Mus musculus,Km) at different rates(PR,ranged from 0.5~20 Hz) under free field stimulation conditions.The stimulus intensities were relative to 5 dB above minimum threshold(MT).The post-stimuli-time histograms(PSTHs) of 118 neurons were recorded.The results showed that firing rate of the majority of neurons((87.3%,) 103/118) monotonically decreased with the PR increasing,whereas in a smaller fraction of neurons(12.7%,15/118) it non-monotonically varied.There was significant correlation between the firing rate and the PR(P<0.01).The sound response properties of most recorded neurons could be dramatically influenced by changing the PR even in the low PR range(<3.3 Hz).The total number of neurons with the critical presentation rate(CPR,(<3.3) Hz) and the maximal presentation rate(MPR,< 3.3 Hz) were more than 70%(75.4%,89/118) and 40%(44.9%,53/148),respectively.Moreover,the discharge patterns in part of neurons(17.8%,21/118) were transformed with the PR alteration.Many neurons with tonic responder(T) and phasic-burst responder(PB) were changed into the phasic responder(P).The present data demonstrate that the sound response properties of IC neurons were closely correlated to the PR of acoustic stimulation.