Local interneurons and projection neurons in the antennal lobe from a spiking point of view

J Neurophysiol. 2013 Nov;110(10):2465-74. doi: 10.1152/jn.00260.2013. Epub 2013 Sep 4.

Abstract

Local computation in microcircuits is an essential feature of distributed information processing in vertebrate and invertebrate brains. The insect antennal lobe represents a spatially confined local network that processes high-dimensional and redundant peripheral input to compute an efficient odor code. Social insects can rely on a particularly rich olfactory receptor repertoire, and they exhibit complex odor-guided behaviors. This corresponds with a high anatomical complexity of their antennal lobe network. In the honeybee, a large number of glomeruli that receive sensory input are interconnected by a dense network of local interneurons (LNs). Uniglomerular projection neurons (PNs) integrate sensory and recurrent local network input into an efficient spatio-temporal odor code. To investigate the specific computational roles of LNs and PNs, we measured several features of sub- and suprathreshold single-cell responses to in vivo odor stimulation. Using a semisupervised cluster analysis, we identified a combination of five characteristic features as sufficient to separate LNs and PNs from each other, independent of the applied odor-stimuli. The two clusters differed significantly in all these five features. PNs showed a higher spontaneous subthreshold activation, assumed higher peak response rates and a more regular spiking pattern. LNs reacted considerably faster to the onset of a stimulus, and their responses were more reliable across stimulus repetitions. We discuss possible mechanisms that can explain our results, and we interpret cell-type-specific characteristics with respect to their functional relevance.

Keywords: Fano factor; cluster analysis; coefficient of variation; electrophysiology; honeybee; olfaction; response latency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Arthropod Antennae / innervation
  • Arthropod Antennae / physiology
  • Bees
  • Interneurons / classification
  • Interneurons / physiology*
  • Nerve Net / physiology
  • Neurons / classification
  • Neurons / physiology*
  • Odorants
  • Smell / physiology*