Meditations on some influential papers in brain research and their authors.
The Cerebellum as a Neuronal Machine
John C. Eccles
Springer, New York, 1967
Can we reverse engineer the cerebellum?
Imagine we know the complete wiring diagram of a brain structure. Let's also say we know the sign, strength and time course of synaptic signals at each connection between the cells, the signals entering the circuit from the outside, and the way each cell's spiking changes in respone to each synaptic input. Shouldn't we be able to predict exactly what the circuit would do in response to any pattern of input? If we could do that, would we know the function of that brain structure?
A logical calculus of the ideas immanent in nervous activity
Warren S. McCulloch
Walter Pitts (1943)
Bulletin of Mathematical Biophysics, 5:115-133.
A logical neuron
It was 1943. A lot of what we know about neurons had not yet been discovered. What was known about the action potential came from studies of isolated peripheral nerve, not central neurons. Renshaw, Forbes, and Morrison published their first description of central nervous system single unit extracellular recordings using micro-electrodes only 3 years previously, and the method had not yet seen much use. Of course, there were no intracellular recordings from central neurons and synaptic potentials had not yet been discovered. What was known about synapses was inferred from studies of the timing of monosynaptic reflexes. Given the state of knowledge at the time, McCulloch and Pitts had to make some assumptions about how neurons worked.
The discharge of impulses in motor nerve fibres
Edgar D Adrian
Detlev W. Bronk
Part 1. Impulses in single fibres of the phrenic nerve. J Physiol. Sep 18; 66(1):81-101, 1928 and
Part II. The frequency of discharge in reflex and voluntary contractions. J. Physiol. Mar 20; 67(2): 119-151, 1929.
The Analog Language of the Motoneuron
The action potential is binary, in the sense that it either occurs at full size or not at all, but that does not make the brain a binary logic circuit. The action potential might even be incidental - just an implementation detail, or even a design liability that must be overcome. This view was championed by Edgar Adrian, co-discoverer of the all-or-nothing nature of the action potential. He and Detlev Bronk published two landmark papers in 1928 and 1929 arguing that rhythmic motoneuron spike trains command muscle contraction in a continuous analog way, on the basis of firing rate.