Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093, USA.
Department of Physics, University of California, San Diego, La Jolla, CA 92093, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
Curr Biol. 2017 Mar 6;27(5):688-696. doi: 10.1016/j.cub.2017.01.013. Epub 2017 Feb 16.
The delineation of sensorimotor circuits that guide exploration begins with an understanding of the pattern of motor outputs [1]. These motor patterns provide a clue to the form of the underlying circuits [2-4] (but see [5]). We focus on the behaviors that rodents use to explore their peripersonal space through goal-directed positioning of their nose, head, and vibrissae. Rodents sniff in response to novel odors, reward expectation, and as part of social interactions [6-12]. Sniffing serves olfaction [13, 14], while whisking synchronized to sniffing serves vibrissa-based touch [6, 15, 16]. We quantify the ethology of exploratory nose and head movements in relation to breathing. We find that sniffing is accompanied by prominent lateral and vertical deflections of the nose, i.e., twitches, which are driven by activation of the deflector nasi muscles [17]. On the timescale of individual breaths, nose motion is rhythmic and has a maximum deflection following the onset of inspiration. On a longer timescale, excursions of the nose persist for several breaths and are accompanied by an asymmetry in vibrissa positioning toward the same side of the face. Such directed deflections can be triggered by a lateralized source of odor. Lastly, bobbing of the head as the animal cranes and explores is phase-locked to sniffing and to movement of the nose. These data, along with prior results on the resetting of the whisk cycle at the onset of inspiration [15, 16, 18], reveal that the onset of each breath initiates a "snapshot" of the orofacial sensory environment. VIDEO ABSTRACT.
引导探索的感觉运动回路的描绘始于理解运动输出的模式[1]。这些运动模式为潜在回路的形式提供了线索[2-4]（但参见[5]）。我们专注于啮齿动物通过定向定位其鼻子、头部和触须来探索其近体空间的行为。啮齿动物会因新奇气味、奖励预期以及作为社交互动的一部分而嗅探[6-12]。嗅探服务于嗅觉[13,14]，而与嗅探同步的触须振动则服务于触须感知的触觉[6,15,16]。我们量化了与呼吸有关的探索性鼻子和头部运动的行为学。我们发现，嗅探伴随着鼻子明显的侧向和垂直偏转，即抽搐，这是由鼻中隔肌的激活驱动的[17]。在单个呼吸的时间尺度上，鼻子运动是有节奏的，并且在吸气开始时具有最大的偏转。在更长的时间尺度上，鼻子的运动持续几个呼吸，并且伴随着触须向面部同一侧的定位不对称。这种定向的偏转可以由嗅觉的侧化源触发。最后，当动物伸展脖子并探索时，头部的摆动与嗅探和鼻子的运动同步。这些数据，以及先前关于在吸气开始时重置触须周期的结果[15,16,18]，揭示了每次呼吸的开始都会引发“近体感觉环境的快照”。视频摘要。
