Peripheral modulation of taste responses
The extensive environmental damage caused by swarming locusts has generated longstanding scientifi c interest in their biology and in particular their feeding physiology. Many studies have focused on nutritional regulation and on the way in which they regulate food intake as it is thought to apply across the animal kingdom. The work of Stephen Simpson and his group led to the formulation of the ‘geometric framework’ model which defi nes functional rules utilised by feeding animals (Simpson and Raubenheimer, 1993a). However, studies of nutritional regulation have also raised a strong interest in the sensory physiology of locusts, and led to a detailed knowledge of the function of taste receptors in these and other insects. In addition the robustness and accessibility of the locust central nervous system (CNS) for electrophysiological studies has made them ideal animals in which to understand how tastes are encoded in the CNS. Recordings from individual, identifi able neurones can be readily performed and that has generated a thorough understanding of how neural networks are activated by sensory inputs, and how motor patterns are generated that underlie well-defi ned behavioural activities (Burrows, 1996). Data derived from electrophysiological studies on locusts now provide a fi rm basis for modelling approaches and for attempts to utilise the rules of information processing that are found in the insect nervous system, in other fi elds, including robotics. Of particular interest in the context of nutritional regulation is the adaptability of information processing to changing internal and environmental conditions, and the plasticity within the insect nervous system. Alongside conventional electrophysiological methods functional imaging with fl uorescent probes and markers is now increasingly deployed to study neural processing and the modulation of feeding-related neural activity.