|
The nervous system receives sensory input and generates- subject to the state of internal variables - behavioral output. The objective of a sensory pathway is not merely to transmit as much information about the stimulus as possible but to act as a filter that enables an organism to make appropriate perceptual decisions. This is reflected in a transformation of the stimulus representation as one ascends a neural pathway. We were interested in the transformations of the code for song in a small sensory system with limited coding capacity: the early auditory system of grasshoppers. These insects communicate acoustically in order to recognize, evaluate and localize mates. First processing steps take place in a small three layer network in the metathoracic ganglion of the animals. This network resembles a prototypical three-layer feed-forward architecture with an input layer (receptors), an intermediate layer (local neurons), and an output layer (ascending neurons). Natural calling songs were presented while recording intracellularly from neurons in the network. We analyzed sparseness and information at the single-cell level as well as the decorrelation and feature selectivity at the population level. Furthermore, we quantified the implications of the observed transformations for the population code. |
|