Analog Axonal Signaling

Science's STKE  07 Mar 2006:
Vol. 2006, Issue 325, pp. tw87
DOI: 10.1126/stke.3252006tw87

Traditional accounts of intraneuronal electric signal transmission have distinguished between digital signals (action potentials) and analog (graded) signals. In mammals, analog signals are thought to occur only in primary sensory systems, like photoreceptors or bipolar cells. The brain has been thought to use digital action potentials to mediate dendritic input to the axon terminal. Alle and Geiger suggest that this may be wrong: Analog signaling is used by axons even in the middle of the brain. These recordings demonstrate passive transmission of dendritic potentials all the way up to the axonal terminal in a brain neuron and show the modulation of excitatory postsynaptic signals by analog presynaptic signals.

H. Alle, J. R. P. Geiger, Combined analog and action potential coding in hippocampal mossy fibers. Science 311, 1290-1293 (2006). [Abstract] [Full Text]