The mass response from the retina (the electroretinogram, or ERG) that is evoked by pattern stimulation is called the pattern electroretinogram (PERG). Riggs and coworkers⁴⁷ were the first to record a PERG after they had successfully devised a local stimulus without stray light artifacts. Interestingly, they did not yet know that the generators for PERG and luminance ERG differ and did not call it PERG. While the luminance ERG is evoked by changes in stimulus luminance, the PERG is evoked by changes of stimulus contrast (in sign or magnitude). The PERG is therefore a retinal response (figure 13.1) that is evoked in the absence of a net change of stimulus luminance. This property has profound implications for the generators of the responses, which are mainly the retinal ganglion cells, as we will see in this chapter. Consequently, the PERG is a valuable diagnostic tool to examine diseases that are associated with a loss of ganglion cell activity as described in chapters 12 and 77. The ISCEV has developed a standard⁶ with the aim to make PERG recordings comparable worldwide across laboratories while still allowing extension into any new fruitful direction. For an earlier comprehensive review of the physiological basis of the PERG, see Zrenner.⁵⁹

Figure 13.1.  

Top, The transient PERG with three major deflections (n35, p55, and N95). Bottom, The sinusoidally shaped steady-state PERG with corresponding Fourier spectrum.