Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA; Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, 80045, USA.
Department of Physiology & Biophysics, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA; Neuroscience Training Program, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
Hear Res. 2018 Aug;365:62-76. doi: 10.1016/j.heares.2018.04.011. Epub 2018 Apr 27.
Despite the common use of guinea pigs in investigations of the neural mechanisms of binaural and spatial hearing, their behavioral capabilities in spatial hearing tasks have surprisingly not been thoroughly investigated. To begin to fill this void, we tested the spatial hearing of adult male guinea pigs in several experiments using a paradigm based on the prepulse inhibition (PPI) of the acoustic startle response. In the first experiment, we presented continuous broadband noise from one speaker location and switched to a second speaker location (the "prepulse") along the azimuth prior to presenting a brief, ∼110 dB SPL startle-eliciting stimulus. We found that the startle response amplitude was systematically reduced for larger changes in speaker swap angle (i.e., greater PPI), indicating that using the speaker "swap" paradigm is sufficient to assess stimulus detection of spatially separated sounds. In a second set of experiments, we swapped low- and high-pass noise across the midline to estimate their ability to utilize interaural time- and level-difference cues, respectively. The results reveal that guinea pigs can utilize both binaural cues to discriminate azimuthal sound sources. A third set of experiments examined spatial release from masking using a continuous broadband noise masker and a broadband chirp signal, both presented concurrently at various speaker locations. In general, animals displayed an increase in startle amplitude (i.e., lower PPI) when the masker was presented at speaker locations near that of the chirp signal, and reduced startle amplitudes (increased PPI) indicating lower detection thresholds when the noise was presented from more distant speaker locations. In summary, these results indicate that guinea pigs can: 1) discriminate changes in source location within a hemifield as well as across the midline, 2) discriminate sources of low- and high-pass sounds, demonstrating that they can effectively utilize both low-frequency interaural time and high-frequency level difference sound localization cues, and 3) utilize spatial release from masking to discriminate sound sources. This report confirms the guinea pig as a suitable spatial hearing model and reinforces prior estimates of guinea pig hearing ability from acoustical and physiological measurements.
尽管豚鼠在研究双耳和空间听觉的神经机制中被广泛应用，但它们在空间听觉任务中的行为能力却出人意料地没有被彻底研究过。为了填补这一空白，我们使用基于声惊反射前脉冲抑制（PPI）的范式，在几项实验中测试了成年雄性豚鼠的空间听觉。在第一个实验中，我们从一个扬声器位置呈现连续宽带噪声，并在呈现短暂的、约 110dB SPL 的惊反射诱发刺激之前，沿方位切换到第二个扬声器位置（“ prepulse”）。我们发现，对于扬声器交换角度的较大变化（即较大的 PPI），惊反射响应幅度系统减小，表明使用扬声器“交换”范式足以评估对空间分离声音的刺激检测。在第二组实验中，我们在中线上交换低通和高通噪声，分别估计它们分别利用耳间时间和水平差异线索的能力。结果表明，豚鼠可以利用双耳线索来区分水平方位的声源。第三组实验使用连续宽带噪声掩蔽和宽带啁啾信号检查空间掩蔽释放，两者同时在不同的扬声器位置呈现。一般来说，当掩蔽器在与啁啾信号相近的扬声器位置呈现时，动物的惊反射幅度（即较低的 PPI）增加，而当噪声从更远的扬声器位置呈现时，惊反射幅度（增加的 PPI）降低，表明检测阈值降低。总之，这些结果表明豚鼠可以：1）在半视野内以及中线两侧区分声源位置的变化，2）区分低通和高通声音的声源，表明它们可以有效地利用低频耳间时间和高频水平差异声音定位线索，3）利用空间掩蔽释放来区分声源。本报告证实豚鼠是一种合适的空间听觉模型，并强化了先前基于声学和生理学测量的豚鼠听觉能力的估计。
