COMBINATION-SENSITIVE NEURONS IN THE MEDIAL GENICULATE-BODY OF THE MOUSTACHED BAT - ENCODING OF RELATIVE VELOCITY INFORMATION
COMBINATION-SENSITIVE NEURONS IN THE MEDIAL GENICULATE-BODY OF THE MOUSTACHED BAT - ENCODING OF RELATIVE VELOCITY INFORMATION
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DOI：
10.1152/jn.1991.65.6.1254
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发表时间：
1991-06-01
影响因子：
2.5
通讯作者：
SUGA, N
中科院分区：
文献类型：
--
作者：
OLSEN, JF;SUGA, N
1. 胡须蝙蝠 (Pteronotus parnellii) 发出的定向声音（脉冲）最多包含四个谐波 (H-1-4)；每个谐波包含恒定频率（CF）分量和终端频率调制（FM）分量，因此总共有八个分量（CF1-4和FM1-4）。 通过将来自目标的回波与发射的脉冲进行比较，小胡子蝙蝠从多普勒频移中得出速度信息，并从回波延迟中得出距离信息。 在这项研究中，研究了内侧膝状体（MGB）中单个神经元对合成生物声纳信号的反应。 刺激由 CF、FM 和 CF-FM 声音组成。 成对的 CF-FM 声音用于模拟脉冲回波对的任意两个谐波。 发现 MGB 的背侧和内侧部分含有组合敏感神经元。 无论频率和幅度如何，这些神经元对单个声音的反应都很差，并且通过以特定频率、幅度和成分间间隔（模拟回声延迟）呈现的配对声音来促进。 对组合敏感的神经元被调谐到表征自然生物声纳信号的特定成分的频率，并根据与神经元的光谱选择性最匹配的脉冲回波对的成分进行分类。 发现了两类组合敏感神经元：CF/CF 和 FM-FM。 本文重点关注CF/CF组合敏感神经元，它从成对的CF分量中提取速度信息，以及CF2和CF3神经元，它们虽然不是组合敏感的，但被调谐到生物声纳信号的CF2和CF3分量的频率。2． CF2 和 CF3 神经元的频率急剧调整。 调谐最灵敏的 CF2 神经元的最佳频率均约等于 61.17 kHz (SD = 370 Hz)，这与帕氏松在补偿多普勒频移时稳定回波的 CF2 分量的频率非常匹配。 因此CF2神经元专门用于多普勒补偿回波的精细分析。3． 无论刺激水平如何，CF2 和 CF3 神经元的调谐曲线仍然很窄。 当在高刺激水平（高于最小阈值 30 和 50 dB）下进行比较时，CF2 和 CF3 神经元的调谐曲线带宽比调谐到 CF2 或 CF3 频率的外周听觉神经元的带宽小得多，但与调谐到 CF2 或 CF3 频率的皮质神经元的带宽大致相同。 因此，蝙蝠中枢听觉系统对神经调谐曲线的锐化发生在 MGB 之内或之前。4。 CF2 和 CF3 神经元的调谐曲线具有包围兴奋区并部分重叠的抑制区。 因此CF2和CF3神经元的频率和幅度被调节。 频率调节最剧烈的神经元的幅度调节也最剧烈。 这些结果表明CF2和CF3神经元的频率和幅度选择性通过侧抑制而增加。5． 促进 CF/CF 神经元所必需的信号元素是脉冲的 CF1 分量与回波的 CF2 或 CF3 分量的组合。6。 CF/CF 神经元被调整为配对刺激的每个分量的频率和幅度。 调谐到 CF2 或 CF3 频率非常尖锐且电平容差。 在那些 CF1 最佳促进频率在蝙蝠 CF1 静息频率 700 Hz 以内的神经元中，对 CF1 频率的调节非常敏锐，但对于其他神经元来说，调节范围相对较广。 大多数CF/CF神经元的抑制区与促进区相邻。7． 大多数 CF/CF 神经元调谐到的频率组合代表与精确谐波关系的微小偏差，例如在补偿过程中蝙蝠发出的脉冲的 CF1 分量与多普勒补偿回波的 CF2 或 CF3 分量之间发现的谐波关系。 当转换为相对速度时，大多数 CF/CF 神经元编码的频率偏差对应于回声定位蝙蝠的典型飞行速度。8。 MGB 中记录的 CF/CF 神经元的反应特性在质量上与皮质中对应的神经元的反应特性相同。 MGB 是上行听觉通路中最低的核，已知包含组合敏感神经元；已在下丘中寻找组合敏感神经元，但尚未发现。 因此，MGB 很可能是组合敏感性的起源地。 这些结果的意义在于，MGB 在从复杂声音中提取生物学重要信息方面发挥着积极作用。
1. Orientation sounds (pulses) emitted by the mustached bat (Pteronotus parnellii) consist of up to four harmonics (H-1-4); each harmonic contains a constant frequency (CF) component and a terminal frequency modulated (FM) component, so that there are eight components in total (CF1-4 and FM1-4). By referring the echo from a target to the emitted pulse, the mustached bat derives velocity information from Doppler shift and distance information from echo delay. In this study, the responses of single neurons in the medial geniculate body (MGB) to synthetic biosonar signals were investigated. Stimuli consisted of CF, FM, and CF-FM sounds. Paired CF-FM sounds were used to mimic any two harmonics of pulse-echo pairs. The dorsal and medial divisions of the MGB were found to contain combination-sensitive neurons. These neurons responded poorly to individual sounds regardless of frequency and amplitude and were facilitated by paired sounds presented at particular frequencies, amplitudes, and inter-component intervals (simulated echo delay). Combination-sensitive neurons were tuned to the frequencies that characterize particular components of natural biosonar signals and were classified according to the components of pulse-echo pairs that best matched the spectral selectivity of the neuron. Two classes of combination-sensitive neurons were found, CF/CF and FM-FM. This paper focuses on CF/CF combination-sensitive neurons, which extract velocity information from paired CF components, and on CF2 and CF3 neurons, which, although not combination-sensitive, are tuned to the frequencies of the CF2 and CF3 components of biosonar signals.2. CF2 and CF3 neurons were sharply tuned in frequency. The best frequencies of the most sharply tuned CF2 neurons were all approximately equal to 61.17 kHz (SD = 370 Hz), which closely matches the frequency at which P. parnellii stabilizes the CF2 component of an echo when compensating for Doppler shift. Thus CF2 neurons are specialized for a fine analysis of Doppler-compensated echoes.3. Tuning curves of CF2 and CF3 neurons remained narrow regardless of stimulus level. When compared at high stimulus levels (30 and 50 dB above minimum threshold), bandwidths of tuning curves of CF2 and CF3 neurons were much smaller than those of peripheral auditory neurons tuned to CF2 or CF3 frequencies but were about the same as those of cortical neurons tuned to CF2 or CF3 frequencies. Thus the sharpening of neural tuning curves by the bat's central auditory system occurs within or before the MGB.4. Tuning curves of CF2 and CF3 neurons had inhibitory areas that surrounded and partially overlapped the excitatory areas. Thus CF2 and CF3 neurons were tuned in frequency and amplitude. The neurons that were the most sharply tuned in frequency were also the most sharply tuned in amplitude. These results suggest that the frequency and amplitude selectivity of CF2 and CF3 neurons is increased through lateral inhibition.5. The signal elements essential to facilitate CF/CF neurons were the CF1 component of the pulse in combination with the CF2 or CF3 component of an echo.6. CF/CF neurons were tuned to the frequency and amplitude of each component of a paired stimulus. Tuning to CF2 or to CF3 frequencies were very sharp and level tolerant. Tuning to CF1 frequency was sharp in those neurons for which the best facilitative frequency of CF1 was within 700 Hz of the bat's CF1 resting frequency, but relatively broad for the others. Most CF/CF neurons had inhibitory areas adjacent to facilitative areas.7. The frequency combinations to which most CF/CF neurons were tuned represent small deviations from the exact harmonic relationship such as that found between the CF1 component of pulses emitted by the bat during compensation and the CF2 or CF3 component of Doppler-compensated echoes. When converted to relative velocities, the frequency deviations encoded by most CF/CF neurons corresponded to flight velocities typical of echolocating bats.8. The response properties of CF/CF neurons recorded in the MGB are qualitatively the same as those of their counterparts in the cortex. The MGB is the lowest nucleus in the ascending auditory pathway known to contain combination-sensitive neurons; combination-sensitive neurons have been sought in the inferior colliculus, but none has been found. Therefore the MGB is likely to be where combination-sensitivity originates. The significance of these results is that the MGB takes an active role in the extraction of biologically important information from complex sound.