Table 1.

Classification of MST neurons

	Smooth pursuit (no background)	Optic flow
Type A: 35 (69%)	Responded	Responded
Type B: 10 (19%)	Responded	No
Type C: 5 (10%)	No	Responded
Type D: 1 (2%)	No	No

A total of 51 task-related neurons were classified into 4 groups. Type A neurons responded to both smooth pursuit and optic flow. Type B responded to smooth pursuit only. Type C responded to optic flow only. One neuron (Type D) showed no distinct discharge modulation during optic flow stimulation and smooth pursuit eye movement despite that it clearly responded to search stimuli (i.e., smooth pursuit with a stationary background pattern).