The equilibrium detecting system of the cricket: Physiology and morphology of an identified interneuron

Summary

• 1. The clavate receptor-to-interneuron system of the cricket,Acheta domesticus, was investigated physiologically and morphologically.

• 2. Intracellular recordings made during controlled displacements of the cricket's cerci allowed the identification of a pair of position sensitive interneurons (PSIs). Changes in the position of the cerci resulted in modulation of the membrane potential and altered the action potential frequency recorded from the PSIs (Fig. 2).

• 3. Subsequent dye injection demonstrated that the PSIs were a bilaterally symmetric pair of interneurons that received their primary afferent input from club-shaped receptors, called clavate hairs (Fig. 1). The somata of the PSIs are located at the anterior edge of the terminal abdominal ganglion (Fig. 1 C), and the axons are located dorsolaterally in the connectives (Fig. 1 E).

• 4. Receptive fields for the interneurons were determined by recording the extracellular neural activity from the ventral nerve cord while simultaneously displacing the animal in various orientations. The PSI receptive fields were essentially mirror images, each predominantly occupying one quadrant when plotted in polar coordinates. The receptive fields for the left and right PSIs occupy the left posterior and right posterior quadrants respectively (Fig. 5).

• 5. Selective deletion of clavate hairs revealed that receptors located in the proximal, medial region of the clavate array provided the strongest input to the ipsilateral interneuron (Fig. 6).

• 6. Clavate sensory neuron terminal arborizations were stained in order to examine their relationship with the dendrites of the PSIs (Fig. 7).