However, in humans and other primates, OKNd is typically dominated by another form of OKN with fast dynamics, referred to as the direct or early optokinetic response. This form shares similarities with the ocular following response and is thought to be driven by local retinal motion involving similar (if not the same) cortical and cerebellar pathways as smooth-pursuit eye movements (Abadi, Howard, Ohmi, & Lee,
2005; Büttner & Büttner-Ennever,
2006; Cohen, Henn, Raphan, & Dennett,
1981; Cohen, Matsuo, & Raphan,
1977; Gellman, Carl, & Miles,
1990; Miles,
1995,
1998; Miles, Kawano, & Optican,
1986; Simons & Büttner,
1985). This has been highlighted in clinical cases where the smooth-pursuit pathway was damaged and the early optokinetic response was lost, while the slow buildup of eye velocity generated from OKNd was preserved (Harris, Walker, Shawkat, Wilson, & Russell-Eggitt,
1993; Yee, Baloh, Honrubia, Lau, & Jenkins,
1979).