Observation of neuronal activity using real-time voltage-sensitive dye imaging

Sensory systems are confronted with the problem of taking “information” in the outside world and encoding and manipulating it in forms that can be used in the neuronal world. A major challenge is to document how the transition between these worlds takes place (transduction) and, once it has taken place, how the data are manipulated by neural circuits (integration). Since the brain is an intrinsically parallel device, carrying out many functions simultaneously, it would appear as important to record brain activity in a similarly parallel manner as to record events in single cells and membranes. Optical recording of neuronal events offers a first step toward thing to observe events that are distributed among the cells and processes of a neuronal network.In the sense of smell odors appear to be encoded by activity distributed across many neurons at each level of the system studied so far, from the sensory cells in the nose to the pyramidal cells in prepyriform cortex (for review see). Thus, to elucidate how the molecular properties of odorants are represented by neurons it is probably necessary to observe the patterns of distributed activation. The distribution of activity across many neuronal elements, in contrast to representing odor molecules by dedicated “labelled lines”, confers redundancy and fault tolerance on a system that is crucial for complex behaviors that underly survival for many animals species, as well as providing flexibility for being sensitive to large numbers of compounds.