Finneran James J, Mulsow Jason, Houser Dorian S, Schlundt Carolyn E
U.S. Navy Marine Mammal Program, Space and Naval Warfare Systems Center Pacific Code 71510, 53560 Hull Street, San Diego, California 92152, USA.
National Marine Mammal Foundation; 2240 Shelter Island Drive #200, San Diego, California 92106, USA.
J Acoust Soc Am. 2017 May;141(5):3379. doi: 10.1121/1.4983191.
The neural representation of the dolphin broadband biosonar click was investigated by measuring auditory brainstem responses (ABRs) to "self-heard" clicks masked with noise bursts having various high-pass cutoff frequencies. Narrowband ABRs were obtained by sequentially subtracting responses obtained with noise having lower high-pass cutoff frequencies from those obtained with noise having higher cutoff frequencies. For comparison to the biosonar data, ABRs were also measured in a passive listening experiment, where external clicks and masking noise were presented to the dolphins and narrowband ABRs were again derived using the subtractive high-pass noise technique. The results showed little change in the peak latencies of the ABR to the self-heard click from 28 to 113 kHz; i.e., the high-frequency neural responses to the self-heard click were delayed relative to those of an external, spectrally "pink" click. The neural representation of the self-heard click is thus highly synchronous across the echolocation frequencies and does not strongly resemble that of a frequency modulated downsweep (i.e., decreasing-frequency chirp). Longer ABR latencies at higher frequencies are hypothesized to arise from spectral differences between self-heard clicks and external clicks, forward masking from previously emitted biosonar clicks, or neural inhibition accompanying the emission of clicks.
通过测量对被具有不同高通截止频率的噪声脉冲掩蔽的“自听”滴答声的听觉脑干反应（ABR），研究了海豚宽带生物声呐滴答声的神经表征。通过依次从具有较高截止频率的噪声获得的反应中减去具有较低高通截止频率的噪声获得的反应，得到窄带ABR。为了与生物声呐数据进行比较，还在被动聆听实验中测量了ABR，在该实验中向海豚呈现外部滴答声和掩蔽噪声，并再次使用减法高通噪声技术得出窄带ABR。结果表明，从28至113kHz，ABR对自听滴答声的峰值潜伏期变化很小；即，对自听滴答声的高频神经反应相对于外部的、频谱呈“粉红”色的滴答声的反应有所延迟。因此，自听滴答声的神经表征在整个回声定位频率上高度同步，并且与调频下扫频（即频率递减的啁啾声）的表征不太相似。较高频率下较长的ABR潜伏期被推测是由于自听滴答声与外部滴答声之间的频谱差异、先前发出的生物声呐滴答声的前向掩蔽或滴答声发射伴随的神经抑制引起的。
