Temporal coding

Temporal coding is a type of neural coding which relies on precise timing of action potentials or inter-spike intervals. Combined with traditional rate coding models, temporal coding can provide additional information with the same rate. There is no precise definition of temporal code. Actually almost any coding scheme that is not rate coding can be referred to as a temporal code.

Unlike rate coding, the temporal coding model tries to account for short-term stimuli producing a small number of spikes and for fast decisions, in which upstream cells don't have adequate time to integrate rate. For example, if a neuron is capable of firing at a maximum rate of 100 spikes per second, then a stimulus <10ms would likely elicit only a single spike. This model is especially important for sound localization, which occurs within the brain on the order of milliseconds. Additionally, if low firing rates on the order of 10 spikes per second must be distinguished from arbitrarily close rates coding for different stimuli, then a neuron trying to discriminate these two stimuli may need to wait for a second or more to accumulate enough information.

The discovery of spike timing dependent plasticity, where synaptic efficacy is modulated by the precise timing of spikes, provides strong evidence that temporal codes are used for cortical information transmission.

It should not be confused with the coding of temporal information.

See also

• Sparse coding
• Independent-spike coding
• Correlation coding
• Population coding
• Neural synchronization

References

• Vanrullen, R., Guyonneau, R., and Thorpe, S. (2005). Spike times make sense. Trends in Neurosciences, 28(1):1--4.
• Rullen, R. V. and Thorpe, S. J. (2001). Rate Coding Versus Temporal Order Coding: What the Retinal Ganglion Cells Tell the Visual Cortex. Neural Computation, 13(6):1255--1283.
• Dayan P, Abbott LF. Theoretical Neuroscience: Computational and Mathematical Modeling of Neural Systems. Cambridge, Massachusetts: The MIT Press; 2001. ISBN 0-262-04199-5
• Rieke F, Warland D, de Ruyter van Steveninck R, Bialek W. Spikes: Exploring the Neural Code. Cambridge, Massachusetts: The MIT Press; 1999. ISBN 0-262-68108-0
• Theunissen F, Miller JP. Temporal Encoding in Nervous Systems: A Rigorous Definition. Journal of Computational Neuroscience, 2, 149—162; 1995.