2007 Sensory Physiology

Stimulus Intensity

Coding mechanisms

1. FREQUENCY CODING :

  • increase the firing rate of individual primary afferent fibres by increasing the size of the receptor potential
  • most common way to do this is by increasing the size of the receptive field stimulated

Graded potential (reprise)

S&G Figure 10.7

Sensory unit (reprise)

S&G Figure 10.3

Population coding2. POPULATION CODING :

  • increase the number of primary afferent fibres responding
  • this process is called RECRUITMENT
  • recruited fibres will not respond equally
    • because of frequency coding, the primary afferent whose receptive field is in the centre of the point of stimulation (i.e. the green fibre) will respond with the largest number of action potentials
    • this concept is critical with respect to understanding lateral inhibition

S&G Figure 10.8

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