TEMPORAL RESPONSE FEATURES OF CAT AUDITORY-CORTEX NEURONS CONTRIBUTING TO SENSITIVITY TO TONES DELIVERED IN THE PRESENCE OF CONTINUOUS NOISE
TEMPORAL RESPONSE FEATURES OF CAT AUDITORY-CORTEX NEURONS CONTRIBUTING TO SENSITIVITY TO TONES DELIVERED IN THE PRESENCE OF CONTINUOUS NOISE
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DOI：
10.1016/0378-5955(85)90145-5
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发表时间：
1985-01-01
期刊：
影响因子：
2.8
通讯作者：
PHILLIPS, DP
中科院分区：
文献类型：
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作者：
PHILLIPS, DP
单个猫听皮层神经元的特征频率（CF）音的强度动态范围有限。在存在连续宽谱噪声的情况下，这些小区的音调响应经历朝向更高SPL的动态范围移位。在本研究中，这种动态范围转移的机制进行了研究，通过探测的敏感性的CF音的细胞在各种延迟后的发病和/或偏移的一个长时间的噪声掩模。在7只麻醉猫的皮质中，通过校准的密封刺激系统，使用声学混合音调和噪声刺激单耳呈现给对侧耳，研究了50个细胞。对于大多数神经元，由连续噪声引起的动态范围移位在噪声掩蔽开始后100-250 ms对CF音调的响应中得到充分发展。对于非单调细胞，噪声和音调发作之间的较短延迟导致音调反应的深刻抑制，这与噪声刺激引起这些神经元的短潜伏期，但短暂的抑制反应的观点是一致的。对具有短音调延迟的单调细胞的研究表明，通常对噪声开始的兴奋反应有时会伴随着一段时间的抑制。在大多数细胞中，只要掩模发病后，CF音调能够引起尖峰放电，这些反应的潜伏期相当于那些在连续噪声中提供的相同SPL的音调的反应。在800 ms噪声掩蔽的偏移对CF音调产生15-25 dB的动态范围偏移之后，音调灵敏度恢复到控制水平的5 dB以内通常需要50-200 ms。基于这些观察，有人认为，为了使CF音调在噪声掩蔽开始之后激发皮层神经元，音调幅度必须足以克服噪声开始的瞬时中枢神经后果和可能起源于外周的短期适应。这些数据的影响皮层细胞的敏感性随时间变化的刺激进行了讨论。
Single cat auditory cortex neurons have limited intensity dynamic ranges for characteristic frequency (CF) tones. In the presence of continuous wide-spectrum noise, these cells'' tone responses undergo a dynamic range shift towards higher SPLs. In the present study, the mechanisms underlying this dynamic range shift were examined by probing the sensitivity of the cells of CF tones delivered at various delays after the onset and/or offset of a long duration noise mask. Fifty cells were studied in the cortex of 7 anesthesized cats using acoustically mixed tonal and noise stimuli presented monaurally to the contralateral ear through a calibrated, sealed stimulating system. For most neurons, the dynamic range shift induced by continuous noise was fully developed in the responses to CF tones delivered 100-250 ms after the onset of a noise mask. For nonmonotonic cells, shorter delays between noise and tone onsets resulted in a profound suppression of tone responses that was consistent with the view that noise stimuli evoke a short latency, but transient, inhibitory response in these neurons. Studies of monotonic cells with short tone delays revealed that the usual excitatory response to noise onset was sometimes followed by a period of inhibition. In most cells, as soon after mask onset that CF tones were able to evoke spike discharges, those responses had latent periods comparable to those of responses to tones of the same SPL delivered in continuous noise. After the offset of an 800 ms noise mask effecting a 15-25 dB dynamic range shift for CF tones, recovery of tone sensitivity to within 5 dB of control levels typically took 50-200 ms. On the basis of these observations, it is argued that in order for a CF tone to excite a cortical neuron after the onset of a noise mask, the tone amplitude must be sufficient to overcome both the transient central neural consequences of noise onset, and a short-term adaptation that is probably peripheral in origin. The implications of these data for the sensitivity of cortical cells to temporally varying stimuli are discussed.