The Bactra Review   Spikes
See S. P. Strong, Roland Koberle, Rob R. de Ruyter van Steveninck, and William Bialek, ``Entropy and Information in Neural Spike Trains,'' Physical Review Letters 80 (1998) 197--200 for the thrilling details on the motion-sensitive neuron H1 of the fly visual system, and, in note 19, motion sensitive cells of the ``monkey'' (which?) visual cortex. Both clocked in at about 2 bits/spike, and about 50% efficiency.