Coding of sensory signals by neuronal populations: The role of correlated activity

How is sensory information encoded by the patterns of action potentials emitted by ensembles of neurons? Computational methods have recently been applied to this fundamental question and have found, both in the somatosensory and visual system, that the basic unit of information transmission is the timing of individual spikes. In systems studied to date, the neuronal population codes appear to be simple ones that do not rely on complex patterns of correlated spikes.