An increase in stimulus strength leads to increase in sensory neuron firing rate, which leads in turn to increase in the intensity of the motor neuron response. The spatial and temporal summation of post-synaptic potentials in the motor neurons could explain the relationship between stimulus intensity and response. Sensory neurons also make synapses with interneurons, which in turn synapse with motor neurons. This forms a parallel arrangement of direct and indirect pathways for information to flow from sensory system to motor system - similar to the flight motor pattern generator in locusts. Optical monitoring of neuronal activity Ganglia are injected with a dye that changes spectral properties depending on the voltage of the cell membrane.
Light is shone through the ganglion, and the amount of light that passes through is recorded.
Changing neuronal activity shows up as changing patterns of light transmission. Although this technique is very useful, it does not allow recording from individual identified neurons. It turned out that hundreds of neurons in the abdominal ganglion are active during gill movements. 62 - 72 neurons were usually active during each movement, and almost all of these were active during all three kinds of movement. When you touch a locust on the leg it moves the leg away from the point of contact.