BITS AND BRAINS - INFORMATION-FLOW IN THE NERVOUS-SYSTEM

Until recently there have been no convincing quantitative measurements on the rates of information transmission in real neurons. Here we rev iew the theoretical basis for making such measurements, together with the data which demonstrate remarkably high information rates in a vari ety of systems. In fact these rates are within a factor of two of the absolute physical limits set by the entropy of neural spike trains. Th ese observations lead to sharp theoretical questions about the structu re of the code and the strategy for adapting the code to different ens embles of input signals.