Analysis of synaptic integration using the laser photoinactivation technique

Summary Crickets (and many other insects) have two antenna-like appendages at the rear of their abdomen, each of which is covered with hundreds of filiform hairs resembling the bristles on a bottle brush. Deflection of these filiform hairs by wind currents activates mechanosensory neurons at the base of the hairs. The axons from these sensory neurons project into the terminal abdominal ganglion to form a topographic representation (or map) containing information about the direction, velocity and acceleration of wind currents around the animal. Information is extracted from this map by primary sensory interneurons that are also located within the terminal abdominal ganglion. In this paper, we review the progress that has been made toward understanding the mechanisms underlying directional sensitivity of an identified sensory interneuron in the cricket,Acheta domesticus. The response properties of the cell have been found to depend to a large extent upon the structure of its dendritic branches, which determines its synaptic connectivity with the sensory afferents in the map of wind space and the relative efficacy of its different synaptic inputs.     

Threshold and directional sensitivity of air-current-sensitive giant interneurons of a cricket

Summary Some of the directional characteristics of air-current-sensitive giant interneurons (GIs) of a cricket were investigated by using an exactly defined unidirectional air-current stimulus. In each GI, the velocity thresholds for the stimulating air-current in two different directions were measured, using various time-courses of the velocity change (frequency). Each GI showed identical velocity threshold curves, depending on the stimulus direction.