Neural code - Neural encoding

Neurons encode information using rate coding or temporal coding

Neurons encode information using two main schemes: rate coding (frequency of firing) and temporal coding (timing or pattern of firing). By the term "firing", we refer to the generation of an action potential, also called a "spike", which corresponds to a peak of electric voltage and to an associated electric currents. These are propagated along the neuron and from one neuron to the other.

As mentioned in Wikipedia, "binary symbols can be used to mark the spikes: 1 for a spike, 0 for no spike". Also, "temporal coding allows the sequence 000111000111 to mean something different from 001100110011". Citing the same Wikipedia article, candidates for temporal codes include [26]: 

1) time-to-first-spike after the stimulus onset, 

2) phase-of-firing with respect to background oscillations, 

3) characteristics based on the second and higher statistical moments of the ISI (Inter-Symbol Interference) probability distribution, 

4) spike randomness, 

5) precisely timed groups of spikes (temporal patterns)

A selected excerpt from the mentioned above Wikipedia article is provided:

"Information is carried either in terms of the relative timing of spikes in a population of neurons (temporal patterns) or with respect to an ongoing brain oscillation (phase of firing)[3][6]. Spikes occurring at specific phases of an oscillatory cycle are more effective in depolarizing the post-synaptic neuron [27]." Therefore, timing is a main factor affecting outcomes.

Neurons function as filters

Please refer to this reference.

More details:

Mathieu Beraneck, and Hans Straka. “Vestibular Signal Processing by Separate Sets of Neuronal Filters.” Journal of Vestibular Research, vol. 21, no. 1, 15 Mar. 2011, pp. 5–19, (PDF)