Martin B A, Sigal A, Kurtzberg D, Stapells D R
Department of Otolaryngology, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
J Acoust Soc Am. 1997 Mar;101(3):1585-99. doi: 10.1121/1.418146.
This study investigated the effects of decreased audibility produced by high-pass noise masking on cortical event-related potentials (ERPs) N1, N2, and P3 to the speech sounds /ba/and/da/presented at 65 and 80 dB SPL. Normal-hearing subjects pressed a button in response to the deviant sound in an oddball paradigm. Broadband masking noise was presented at an intensity sufficient to completely mask the response to the 65-dB SPL speech sounds, and subsequently high-pass filtered at 4000, 2000, 1000, 500, and 250 Hz. With high-pass masking noise, pure-tone behavioral thresholds increased by an average of 38 dB at the high-pass cutoff and by 50 dB one octave above the cutoff frequency. Results show that as the cutoff frequency of the high-pass masker was lowered, ERP latencies to speech sounds increased and amplitudes decreased. The cutoff frequency where these changes first occurred and the rate of the change differed for N1 compared to N2, P3, and the behavioral measures. N1 showed gradual changes as the masker cutoff frequency was lowered. N2, P3, and behavioral measures showed marked changes below a masker cutoff of 2000 Hz. These results indicate that the decreased audibility resulting from the noise masking affects the various ERP components in a differential manner. N1 is related to the presence of audible stimulus energy, being present whether audible stimuli are discriminable or not. In contrast, N2 and P3 were absent when the stimuli were audible but not discriminable (i.e., when the second formant transitions were masked), reflecting stimulus discrimination. These data have implications regarding the effects of decreased audibility on cortical processing of speech sounds and for the study of cortical ERPs in populations with hearing impairment.
本研究调查了高通噪声掩蔽所产生的可听度降低对皮质事件相关电位（ERP）N1、N2和P3的影响，这些电位是针对以65和80 dB SPL呈现的语音/ba/和/da/。听力正常的受试者在奇偶数范式中对偏差声音按下按钮。宽带掩蔽噪声以足以完全掩蔽对65 dB SPL语音响应的强度呈现，随后在4000、2000、1000、500和250 Hz进行高通滤波。使用高通掩蔽噪声时，纯音行为阈值在高通截止频率处平均增加38 dB，在截止频率以上一个八度处增加50 dB。结果表明，随着高通掩蔽器截止频率的降低，对语音的ERP潜伏期增加而幅度减小。与N2、P3和行为测量相比，N1首次出现这些变化的截止频率以及变化速率有所不同。随着掩蔽器截止频率的降低，N1显示出逐渐变化。N2、P3和行为测量在掩蔽器截止频率低于2000 Hz时显示出明显变化。这些结果表明，噪声掩蔽导致的可听度降低以不同方式影响各种ERP成分。N1与可听刺激能量的存在有关，无论可听刺激是否可辨别都存在。相比之下，当刺激可听但不可辨别时（即当第二共振峰过渡被掩蔽时），N2和P3消失，反映了刺激辨别。这些数据对于可听度降低对语音皮质处理的影响以及听力受损人群皮质ERP的研究具有启示意义。
