Neural basis of wind-receptive fields of cockroach giant interneurons

The pattern of connectivity between the nine most prominent columns of sensory hairs of one cercus and ipsilateral giant interneurons (GIs) 1 and 2 of the cockroach Periplaneta americana was studied using intracellular methods. GI 1, a somewhat directionally selective interneuron receives excitatory synaptic input from all hair columns of the ipsilateral cercus. GI 2, an omni-directional cell, also receives synaptic input from all ipsilateral hair columns. However, for 2 of the 9 columns of hairs the response in GI 2 is greater than in GI 1. This difference in response magnitude represents a real difference in the functional strength of connection and not the number of synapsing afferents since the response in both GI 1 and 2 declines stepwise as the number of hairs tested was reduced one-by-one. Thus, the difference in the shapes of the wind-receptive fields of GI 1 and 2 can be explained by differences in the functional strength of connection of certain identified afferents.