Activation in neural networks controlling ingestive behaviors: what does it mean, and how do we map and measure it?

Over the past thirty years many of different methods have been developed that use markers to track or image the activity of the neurons within the central networks that control ingestive behaviors. The ultimate goal of these experiments is to identify the location of neurons that participate in the response to an identified stimulus, and more widely to define the structure and function of the networks that control specific aspects of ingestive behavior. Some of these markers depend upon the rapid accumulation of proteins, while others reflect altered energy metabolism as neurons change their firing rates. These methods are widely used in behavioral neuroscience, but the way results are interpreted within the context of defining neural networks is constrained by how we answer the following questions. How well can the structure of the behavior be documented? What do we know about the processes that lead to the accumulation of the marker? What is the function of the marker within the neuron? How closely in time does the marker accumulation track the stimulus? How long does the marker persist after the stimulus is removed? We will review how these questions can be addressed with regard to ingestive and related behaviors. We will also discuss the importance of plotting the location of labeled cells using standardized atlases to facilitate the presentation and comparison of data between experiments and laboratories. Finally, we emphasize the importance of comprehensive and accurate mapping for using newly emerging technologies in neuroinfomatics.