Institute of Biotechnology, National Tsing Hua University, Hsinchu 30013, Taiwan.
Science. 2013 Jun 14;340(6138):1338-41. doi: 10.1126/science.1236693.
Different stimulus intensities elicit distinct perceptions, implying that input signals are either conveyed through an overlapping but distinct subpopulation of sensory neurons or channeled into divergent brain circuits according to intensity. In Drosophila, carbon dioxide (CO2) is detected by a single type of olfactory sensory neuron, but information is conveyed to higher brain centers through second-order projection neurons (PNs). Two distinct pathways, PN(v)-1 and PN(v)-2, are necessary and sufficient for avoidance responses to low and high CO2 concentrations, respectively. Whereas low concentrations activate PN(v)-1, high concentrations activate both PN(v)s and GABAergic PN(v)-3, which may inhibit PN(v)-1 pathway-mediated avoidance behavior. Channeling a sensory input into distinct neural pathways allows the perception of an odor to be further modulated by both stimulus intensity and context.
不同的刺激强度会产生不同的感觉，这表明输入信号要么通过重叠但不同的感觉神经元亚群传递，要么根据强度进入不同的大脑回路。在果蝇中，二氧化碳（CO2）由单一类型的嗅觉感觉神经元检测到，但信息通过二级投射神经元（PN）传送到高级大脑中枢。两条不同的通路，PN（v）-1 和 PN（v）-2，分别是对低和高 CO2 浓度的回避反应所必需和充分的。虽然低浓度激活 PN（v）-1，但高浓度同时激活 PN（v）和 GABA 能 PN（v）-3，后者可能抑制 PN（v）-1 通路介导的回避行为。将感觉输入引导到不同的神经通路中，可以进一步调节对气味的感知，这既取决于刺激强度，也取决于环境。
