Microelectronics In Nerve Cells: Dendritic Morphology and Information Processing
The electrical properties of the different anatomical types of retinal ganglion cells in the cat were calculated on the basis of passive cable theory from measurements made on histological material provided by Boycott and Wassle (1974). The interactions between excitation and inhibition when the inhibitory battery is near the resting potential can be strongly nonlinear in these cells. We analyse some of the integrative properties of an arbitrary passive dendritic tree and we then derive the functional properties which are characteristic for the various types of ganglion cells. In particular, we derive several general results concerning the spatial specificity of shunting inhibition in "vetoing" an excitatory input (the "on path" property) and its dependence on the geometrical and electric properties of the dendritic tree. Our main conclusion is that specific branching patterns coupled with a suitable distribution of synapses are able to support complex information processing operations on the incoming signals. Thus, a neuron seems likely to resemble an (analog) ISI circuit with thousands of elementary processing units ??he synapses ??ther than a single logical gate. A dendritic tree would be near to the ultimate in microelectronics with little patches of postsynaptic membrane representing the fundamental units for several elementary computations.