Valentine Pamela A, Eggermont Jos J
Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada.
Hear Res. 2004 Oct;196(1-2):119-33. doi: 10.1016/j.heares.2004.05.011.
The frequency-tuning curve is a static representation of the neuron's sensitivity to stimulus frequency. The temporal aspects of the frequency sensitivity can be captured in the spectro-temporal receptive field (STRF), often presented as the average spectrogram of the stimulus preceding a spike but also as the average frequency-dependent post-stimulus time histogram (PSTH). The temporal envelope of the stimulus produces considerable smoothing, and as a consequence the PSTH representation is finer-grained than the spectrogram representation. Here we compare STRFs for 1/s and 20/s single-frequency stimuli with 120/s steady-state multi-frequency stimuli for 87 recording sites in primary auditory cortex of cats. For the 672 estimated STRFs, which for multi-frequency stimuli were mostly obtained at 55 dB SPL, we found lateral inhibition in 17% of the cases, in 32% post-activation suppression, and in 51% only excitation. In 35% of the recordings the excitatory frequency-tuning curves were very similar for single and multi-frequency stimuli, in the remaining 65% the common finding was the emergence of an intensity independent bandwidth for the multi-frequency stimuli. Comparison of the 20/s and 120/s stimuli showed that the resulting increase in inhibition was strongest in the center of the STRF.
频率调谐曲线是神经元对刺激频率敏感性的一种静态表示。频率敏感性的时间特性可以在频谱-时间感受野（STRF）中体现，STRF通常呈现为尖峰之前刺激的平均频谱图，也可呈现为平均频率依赖的刺激后时间直方图（PSTH）。刺激的时间包络会产生相当程度的平滑，因此PSTH表示比频谱图表示的粒度更细。在这里，我们比较了猫初级听觉皮层中87个记录位点对于1/s和20/s单频刺激与120/s稳态多频刺激的STRF。对于672个估计的STRF（多频刺激的STRF大多在55 dB SPL下获得），我们发现17%的情况存在侧向抑制，32%存在激活后抑制，51%仅存在兴奋。在35%的记录中，单频和多频刺激的兴奋性频率调谐曲线非常相似，在其余65%的记录中，常见的情况是多频刺激出现了与强度无关的带宽。对20/s和120/s刺激的比较表明，由此产生的抑制增加在STRF的中心最为强烈。
