Determining the valence of an odor to guide rapid approach–avoidance behavior is thought to be one of the core tasks of the olfactory system, and yet little is known of the initial neural mechanisms supporting this process or of its subsequent behavioral manifestation in humans. In two experiments, we measured the functional processing of odor valence perception in the human olfactory bulb (OB)—the first processing stage of the olfactory system—using a noninvasive method as well as assessed the subsequent motor avoidance response. We demonstrate that odor valence perception is associated with both gamma and beta activity in the human OB. Moreover, we show that negative, but not positive, odors initiate an early beta response in the OB, a response that is linked to a preparatory neural motor response in the motor cortex. Finally, in a separate experiment, we show that negative odors trigger a full-body motor avoidance response, manifested as a rapid leaning away from the odor, within the time period predicted by the OB results. Taken together, these results demonstrate that the human OB processes odor valence in a sequential manner in both the gamma and beta frequency bands and suggest that rapid processing of unpleasant odors in the OB might underlie rapid approach–avoidance decisions.

确定气味的效价以指导快速接近-回避行为被认为是嗅觉系统的核心任务之一，但人们对支持这一过程的初始神经机制或其随后在人类中的行为表现知之甚少。在两个实验中，我们使用非侵入性方法测量了人类嗅球 (OB)（嗅觉系统的第一个处理阶段）中气味效价感知的功能处理，并评估了随后的运动回避反应。我们证明气味效价感知与人类 OB 中的 gamma 和 beta 活动相关。此外，我们表明，消极的，但不是积极的，气味在 OB 中启动了早期的 β 反应，这种反应与运动皮层中的预备性神经运动反应有关。最后，在另一项实验中，我们表明在 OB 结果预测的时间段内，负面气味会触发全身运动回避反应，表现为快速远离气味。综上所述，这些结果表明人类 OB 在 γ 和 β 频带中以顺序方式处理气味效价，并表明 OB 中令人不快的气味的快速处理可能是快速接近-避免决策的基础。