Wehr M, Laurent G
California Institute of Technology, Biology Division, Computation and Neural Systems Program, Pasadena, California 91125, USA.
J Neurosci. 1999 Jan 1;19(1):381-90. doi: 10.1523/JNEUROSCI.19-01-00381.1999.
Odors evoke synchronized oscillations and slow temporal patterns in antennal lobe neurons and fast oscillations in the mushroom body local field potential (LFP) of the locust. What is the contribution of primary afferents in the generation of these dynamics? We addressed this question in two ways. First, we recorded odor-evoked afferent activity in both isolated antennae and intact preparations. Odor-evoked population activity in the antenna and the antennal nerve consisted of a slow potential deflection, similar for many odors. This deflection contained neither oscillatory nor odor-specific slow temporal patterns, whereas simultaneously recorded mushroom body LFPs exhibited clear 20-30 Hz oscillations. This suggests that the temporal patterning of antennal lobe and mushroom body neurons is generated downstream of the olfactory receptor axons. Second, we electrically stimulated arrays of primary afferents in vivo. A brief shock to the antennal nerve produced compound PSPs in antennal lobe projection neurons, with two peaks at an approximately 50 msec interval. Prolonged afferent stimulation with step, ramp, or slow sine-shaped voltage waveforms evoked sustained 20-30 Hz oscillations in projection neuron membrane potential and in the mushroom body LFP. Projection neuron and mushroom body oscillations were phase-locked and reliable across trials. Synchronization of projection neurons was seen directly in paired intracellular recordings. Pressure injection of picrotoxin into the antennal lobe eliminated the oscillations evoked by electrical stimulation. Different projection neurons could express different temporal patterns in response to the same electrical stimulus, as seen for odor-evoked responses. Conversely, individual projection neurons could express different temporal patterns of activity in response to step stimulation of different spatial arrays of olfactory afferents. These patterns were reliable and remained distinct across different stimulus intensities. We conclude that oscillatory synchronization of olfactory neurons originates in the antennal lobe and that slow temporal patterns in projection neurons can arise in the absence of temporal patterning of the afferent input.
气味可诱发蝗虫触角叶神经元的同步振荡和缓慢时间模式，以及蘑菇体局部场电位（LFP）的快速振荡。初级传入神经在这些动力学产生过程中起到了什么作用？我们通过两种方式解决了这个问题。首先，我们在分离的触角和完整标本中记录了气味诱发的传入神经活动。触角和触角神经中气味诱发的群体活动由一个缓慢的电位偏转组成，许多气味的情况相似。这种偏转既不包含振荡也不包含气味特异性的缓慢时间模式，而同时记录的蘑菇体LFP则表现出清晰的20 - 30赫兹振荡。这表明触角叶和蘑菇体神经元的时间模式是在嗅觉受体轴突的下游产生的。其次，我们在体内电刺激初级传入神经阵列。对触角神经的短暂电击在触角叶投射神经元中产生复合兴奋性突触后电位（PSP），有两个峰值，间隔约50毫秒。用阶跃、斜坡或缓慢正弦形电压波形进行长时间的传入神经刺激，可在投射神经元膜电位和蘑菇体LFP中诱发持续的20 - 30赫兹振荡。投射神经元和蘑菇体振荡是锁相的，并且在不同试验中是可靠的。在成对的细胞内记录中直接观察到了投射神经元的同步。向触角叶压力注射荷包牡丹碱消除了电刺激诱发的振荡。与气味诱发的反应一样，不同的投射神经元对相同的电刺激可能表现出不同的时间模式。相反，单个投射神经元对不同空间排列的嗅觉传入神经的阶跃刺激可能表现出不同的活动时间模式。这些模式是可靠的，并且在不同的刺激强度下保持不同。我们得出结论，嗅觉神经元的振荡同步起源于触角叶，并且投射神经元中的缓慢时间模式可以在传入输入没有时间模式的情况下产生。
