ABSTRACT
Anesthetized Mice ............................................................................ 178 6.5 Voltage-Sensitive Dye Imaging .................................................................... 181
6.5.1 Experimental Strategies .................................................................... 181 6.5.2 State-Dependent Sensory Processing ............................................... 183 6.5.3 Imaging the Cortical Response during Active Touch ....................... 185
6.6 Discussion ..................................................................................................... 185 6.7 Future Perspectives ....................................................................................... 186
6.7.1 New Dyes and Nonlinear Optics ...................................................... 186 6.7.2 Voltage-Sensitive Fluorescent Proteins ............................................ 187 6.7.3 Fiber Optic VSD Imaging ................................................................. 187
Acknowledgments .................................................................................................. 188 References .............................................................................................................. 188
Electrophysiological measurements have demonstrated that information can be processed on the time scale of milliseconds in the mammalian brain. Neuronal electrical changes are probably the fastest events occurring in the nervous system, and they are likely to orchestrate many of the subsequent slower events, such as changes in second-messenger concentration, structural alterations, and regulation of gene expression. Whereas electrophysiological recordings from individual electrodes have revealed many important aspects of brain function, it is also clear that complex neuronal processing of information does not derive from the activity of individual neurons, but rather results from the concerted actions of many neurons distributed across different brain areas. Indeed, considerable progress has been made toward increasing the number of electrodes in electrophysiological recordings in order to begin to understand the coordinated function of neuronal networks.1-2 Despite these very important technical developments, it remains clear that the spatial organization of neuronal electrical activity will be difcult to study with electrophysiological approaches, even using arrays of more than 100 electrodes.
