Representative ERG traces from one wild-type and two R6/2 mice for each recorded stimulus parameter at 8 weeks of age.

<p>Column A: Normal ERGs derived from a wild-type mouse. Column B: The least affected R6/2 mouse showing decreased amplitudes but preserved waveforms. Column C: A severely affected R6/2 mouse having only a hint of a minor positive going intrusion after a-wave for log 0.5 cd*s/m<sup>2</sup> flashes, and a minor b-wave for the –log 1.5 cd*s/m<sup>-2</sup> flash. Note: animals having no b-waves were cut out from further statistical analysis.</p>