Smooth pursuit can suppress optokinetic reflex- could this lead to a reduced afternystagmus?

[RhianB88]

I am currently completing a peice of work looking at an extra-retinal motion after-effect, after prolonged pursuit of a target in the dark on a black background followed by fixation to a stationary test (measuring MAE). I know that both cortical mechanisms responsible for pursuit and subcortical mechanisms responsible for optokinetic nystagmus are responsible for the MAE. However, I want to know how smooth pursuit systems can affect the suppression of the OKR response. A few papers suggest extra-retinal mechanisms during smooth pursuit (info about eye-movements) can suppress this but I don't know whether that implies that the subsequent afternystagmus (which is thought to be a suppression response in itself when fixating to a stationary test) would be reduced if OKN is reduced? Would reduced OKN mean that these subcortical mechanisms are less adapted during pursuit resulting in less of an after-effect? Or could it be that greater suppression of OKN infact gives rise to a greater afternystagmus (ANS) because ANS is a nystagmus-suppression response that leaks into perception? I'm very confused! The papers I have looked at are Lindner & Ilg (2006) Suppression of optokinesis during smooth puruit eye movements revisted: The role of extra-retinal information, and Ventre-Dominay & Luyat (2009) asymmetry of visuo-vestibular mechanisms contributes to reversal of optokinetic afternystagmus. Also are OKR and OKN pretty much the same thing?

 

Any help or advice would be greatly appreciated

 

Regards

Rhian