Graduate Neuroscience Program, University of California , Riverside, CA 92521.
Department of Biological Sciences, Boise State University , Boise, ID 83725.
eNeuro. 2017 Mar 2;4(1). doi: 10.1523/ENEURO.0018-17.2017. eCollection 2017 Jan-Feb.
In active sensing, animals make motor adjustments to match sensory inputs to specialized neural circuitry. Here, we describe an active sensing system for sound level processing. The pallid bat uses downward frequency-modulated (FM) sweeps as echolocation calls for general orientation and obstacle avoidance. The bat's auditory cortex contains a region selective for these FM sweeps (FM sweep-selective region, FMSR). We show that the vast majority of FMSR neurons are sensitive and strongly selective for relatively low levels (30-60 dB SPL). Behavioral testing shows that when a flying bat approaches a target, it reduces output call levels to keep echo levels between ∼30 and 55 dB SPL. Thus, the pallid bat behaviorally matches echo levels to an optimized neural representation of sound levels. FMSR neurons are more selective for sound levels of FM sweeps than tones, suggesting that across-frequency integration enhances level tuning. Level-dependent timing of high-frequency sideband inhibition in the receptive field shapes increased level selectivity for FM sweeps. Together with previous studies, these data indicate that the same receptive field properties shape multiple filters (sweep direction, rate, and level) for FM sweeps, a sound common in multiple vocalizations, including human speech. The matched behavioral and neural adaptations for low-intensity echolocation in the pallid bat will facilitate foraging with reduced probability of acoustic detection by prey.
在主动感知中,动物会进行运动调整,以使感觉输入与专门的神经回路匹配。在这里,我们描述了一种用于声音电平处理的主动感测系统。白腹蝙蝠使用向下调频(FM)扫频作为用于一般定向和障碍物回避的回声定位叫声。蝙蝠的听觉皮层包含一个对这些 FM 扫频选择性的区域(FM 扫频选择性区域,FMSR)。我们表明,绝大多数 FMSR 神经元对相对较低的水平(30-60dB SPL)敏感且具有强烈的选择性。行为测试表明,当飞行的蝙蝠接近目标时,它会降低输出呼叫水平,以使回声水平保持在约 30 至 55dB SPL 之间。因此,白腹蝙蝠在行为上使回声水平与声音水平的优化神经表示相匹配。FMSR 神经元对 FM 扫频的声音水平比音调更具选择性,这表明跨频率整合增强了电平调谐。在感受野中高频侧抑制的与水平相关的定时为 FM 扫频的增强水平选择性形成了形状。结合以前的研究,这些数据表明,相同的感受野特性为包括人类语音在内的多种发声中常见的 FM 扫频形成了多个滤波器(扫频方向、速率和水平)。白腹蝙蝠的低强度回声定位的匹配行为和神经适应将有助于觅食,减少猎物被声学检测的可能性。