Direct mapping of bioelectric activity

Much can be learned about physiological function in heart, brain, and other tissues from measuring the electrical activity that mediates mechanical or neural phenomena. The study of electrophysiology has progressed from acqui sition of a single or a few channels to hundreds of signals acquired simult aneously. Data acquisition, signal processing, and visualization in electro physiology have benefitted from the parallel advances in electronics and co mputing hardware and software. The two primary technologies for mapping ele ctrical activity at many sites are electrical, using electrodes directly pl aced on tissue, and optical, using voltage sensitive dyes to estimate membr ane parameters. Each is valuable and provides information that is complemen tary to the other. This article is a description of the current state of el ectrical and optical mapping.