A new approach to optical imaging applied to rat barrel cortex

Several groups have described using intrinsic optical imaging to form images of activity patterns in the cortex. Because the signal is small, the general approach has been to use expensive camera equipment with a high dynamic range to make these measurements. However, by using signal averaging to compensate for lower dynamic range, images can be obtained using equipment already available in many laboratories. This modified technique has been used for imaging activity in ‘barrel’ cortex of the rat. A map of the representation of a single whisker as determined by the imaging technique corresponded well with a similar map made using standard electrophysiology. A map of several whiskers was made by overlaying images of single-whisker representations. The details of the images differ from those previously described. Possible mechanisms for the signal are discussed.