Neural coding

Separate neurons encode information by the virtue of two properties. At first, the firing frequency signals stimulus intensity and how it changes with the time. In the similar way motor neuron firing rate encodes the timing and force of contraction of a discrete population of muscle fibers. This is known as rate coding. Secondly, the address of an afferent neuron, that is, how it is connected through its inputs and outputs, encodes the spatial position of a stimulus, and the nature of the stimulus (that is, touch, vision), a property known as modality. The address of a motor neuron donated to the kind of movement executed and its direction.

In both sensory and motor systems the precise encoding of a given feature can sometimes be identified by few neurons (example, skin itch, whisker movements in rats). This is known as sparse coding and has the benefit of being energy efficient. More frequently features are identified by activity in an ensemble of cells (example, skin temperature or the direction of a limb movement). This is termed to as population coding. It is thought to compensate for the fact that normally neurons are very noisy, however as the noise in one neuron in a population is not independent of the noise in others (the noise is supposed to be correlated) it is verifying hard to understand how the population coding works.

The temporal coding refers to a range of situations in which the neurons fire at very accurate time (example, only at a specific phase of a sound wave or whenever two inputs are coincident), that permits the neural systems to time events much more accurately than is possible by rate coding. A temporal code in which the neurons are broadly distributed in the brain are driven to fire synchronously is a key region of current neuroscience research as it could be significant in perception, attention, and in the memory.