Division of Biology, Computation and Neural Systems Program, California Institute of Technology, Pasadena, CA 91125, USA.
Science. 2011 May 6;332(6030):721-5. doi: 10.1126/science.1201835.
Sparse coding presents practical advantages for sensory representations and memory storage. In the insect olfactory system, the representation of general odors is dense in the antennal lobes but sparse in the mushroom bodies, only one synapse downstream. In locusts, this transformation relies on the oscillatory structure of antennal lobe output, feed-forward inhibitory circuits, intrinsic properties of mushroom body neurons, and connectivity between antennal lobe and mushroom bodies. Here we show the existence of a normalizing negative-feedback loop within the mushroom body to maintain sparse output over a wide range of input conditions. This loop consists of an identifiable "giant" nonspiking inhibitory interneuron with ubiquitous connectivity and graded release properties.
稀疏编码为感觉表示和记忆存储提供了实际优势。在昆虫嗅觉系统中，一般气味的表示在触角叶中是密集的，但在蘑菇体中是稀疏的，仅在下游一个突触。在蝗虫中，这种转变依赖于触角叶输出的振荡结构、前馈抑制回路、蘑菇体神经元的内在特性以及触角叶和蘑菇体之间的连接。在这里，我们展示了蘑菇体中存在一个正常化的负反馈回路，以在广泛的输入条件下维持稀疏输出。这个回路由一个可识别的具有普遍连接和分级释放特性的“巨大”非放电抑制性中间神经元组成。
