Neural correlates and mechanisms of spatial release from masking: Single-unit and population responses in the inferior colliculus
Neural correlates and mechanisms of spatial release from masking: Single-unit and population responses in the inferior colliculus
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DOI：
10.1152/jn.01112.2004
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发表时间：
2005-08-01
影响因子：
2.5
通讯作者：
Delgutte, B
中科院分区：
文献类型：
--
作者：
Lane, CC;Delgutte, B
掩蔽的空间释放（SRM）是噪声环境中收听的一个因素，是当信号在空间中与掩蔽物分离时获得的听觉信号检测的改善。为了研究SRM的神经机制，我们记录了巴比妥酸盐麻醉猫下丘（IC）的单个单位，重点是对耳间时间差敏感的低频神经元。刺激是一个宽带线性调频列车与40 Hz的重复率在连续的宽带噪声，和单位的反应进行了测量，为几个信号和掩蔽（虚拟）的位置。掩蔽阈值（最低的信号噪声比，SNR，信号可以检测到75%的刺激介绍）系统地改变与信号和掩蔽位置。单个单位阈值不一定随着信号和掩蔽物的分离而提高;相反，它们倾向于反映单位的方位偏好。如何检测信号（通过速率增加或减少）以及噪声如何掩蔽信号响应（抑制性或兴奋性掩蔽）随信号和掩蔽器方位角而变化，与双耳处理的互相关器模型一致。然而，额外的处理，可能与信号的调幅率，似乎影响单位的反应。总体掩蔽阈值（在每个信号和掩蔽物位置处的最敏感单元的阈值）确实随着信号和掩蔽物分离而改善，这是由于我们的单元样本中的方位角偏好的变化。群体阈值在SNR值和形状上与人类行为阈值相似，表明这些单位可能为低频SRM提供神经基质。
Spatial release from masking (SRM), a factor in listening in noisy environments, is the improvement in auditory signal detection obtained when a signal is separated in space from a masker. To study the neural mechanisms of SRM, we recorded from single units in the inferior colliculus (IC) of barbiturate-anesthetized cats, focusing on low-frequency neurons sensitive to interaural time differences. The stimulus was a broadband chirp train with a 40-Hz repetition rate in continuous broadband noise, and the unit responses were measured for several signal and masker ( virtual) locations. Masked thresholds ( the lowest signal-to-noise ratio, SNR, for which the signal could be detected for 75% of the stimulus presentations) changed systematically with signal and masker location. Single-unit thresholds did not necessarily improve with signal and masker separation; instead, they tended to reflect the units' azimuth preference. Both how the signal was detected ( through a rate increase or decrease) and how the noise masked the signal response ( suppressive or excitatory masking) changed with signal and masker azimuth, consistent with a cross-correlator model of binaural processing. However, additional processing, perhaps related to the signal's amplitude modulation rate, appeared to influence the units' responses. The population masked thresholds ( the most sensitive unit's threshold at each signal and masker location) did improve with signal and masker separation as a result of the variety of azimuth preferences in our unit sample. The population thresholds were similar to human behavioral thresholds in both SNR value and shape, indicating that these units may provide a neural substrate for low-frequency SRM.