THE EFFICIENCY OF SENSORY INFORMATION CODING BY MECHANORECEPTOR NEURONS

Most sensory systems encode external signals into action potentials fo r transmission to the central nervous system, but little is known abou t the cost or efficiency of this encoding. We measured the information capacity at three stages of encoding in the neurons of a spider slit- sense mechanoreceptor organ. For the receptor current under voltage cl amp, the capacity was similar to 1400 bits/s, but when the neuron was allowed to generate a receptor potential, nonlinear membrane processes improved the capacity to >2000 bits/s. Finally, when action potential s were produced, the capacity dropped to similar to 200 bits/s, or sim ilar to 14% of the receptor current capacity. These measurements provi de a quantitative estimation of the cost of encoding analog signals in to action potentials.