Doucette Wilder, Restrepo Diego
Department of Cell and Developmental Biology, Neuroscience Program, Rocky Mountain Taste and Smell Center, University of Colorado Denver Anschutz Medical Campus, Aurora, Colorado, United States of America.
PLoS Biol. 2008 Oct 28;6(10):e258. doi: 10.1371/journal.pbio.0060258.
On the basis of its primary circuit it has been postulated that the olfactory bulb (OB) is analogous to the retina in mammals. In retina, repeated exposure to the same visual stimulus results in a neural representation that remains relatively stable over time, even as the meaning of that stimulus to the animal changes. Stability of stimulus representation at early stages of processing allows for unbiased interpretation of incoming stimuli by higher order cortical centers. The alternative is that early stimulus representation is shaped by previously derived meaning, which could allow more efficient sampling of odor space providing a simplified yet biased interpretation of incoming stimuli. This study helps place the olfactory system on this continuum of subjective versus objective early sensory representation. Here we show that odor responses of the output cells of the OB, mitral cells, change transiently during a go-no-go odor discrimination task. The response changes occur in a manner that increases the ability of the circuit to convey information necessary to discriminate among closely related odors. Remarkably, a switch between which of the two odors is rewarded causes mitral cells to switch the polarity of their divergent responses. Taken together these results redefine the function of the OB as a transiently modifiable (active) filter, shaping early odor representations in behaviorally meaningful ways.
基于其初级回路，有人推测嗅球（OB）类似于哺乳动物的视网膜。在视网膜中，反复暴露于相同的视觉刺激会导致一种神经表征，随着时间的推移，这种表征会保持相对稳定，即使该刺激对动物的意义发生了变化。在处理的早期阶段，刺激表征的稳定性使得高阶皮质中枢能够对传入的刺激进行无偏差的解释。另一种情况是，早期刺激表征受先前获得的意义影响，这可能允许对气味空间进行更有效的采样，从而对传入刺激提供一种简化但有偏差的解释。这项研究有助于将嗅觉系统置于这种主观与客观早期感觉表征的连续统一体中。在这里，我们表明，在一个“去 - 不去”气味辨别任务中，嗅球的输出细胞——二尖瓣细胞的气味反应会短暂变化。反应变化的方式增强了该回路传递区分密切相关气味所需信息的能力。值得注意的是，两种气味中哪种被奖励的切换会导致二尖瓣细胞改变其发散反应的极性。综合这些结果，重新定义了嗅球的功能，即作为一个可短暂修改（活跃）的过滤器，以行为上有意义的方式塑造早期气味表征。
