Readout of Higher-level Processing in the Discharge of Superior Colliculus Cells Edward L. Keller, Kyoung-Min Lee and Robert M. McPeek The Smith-Kettlewell Eye Research Institute San Francisco, CA and Seoul National University, Seoul, Korea Delayed-saccade paradigm Fixation point Delay Target Eye From Basso and Wurtz 1998: Correlation with prior probability Visual Search Task Search: Target in Field Single Target Second burst Search: Distractor in Field Time from stimulus onset (ms) Delayed Saccade: Target in Field Time from stimulus onset (ms) Search: Target in Field Search: Distractor in Field Area Under ROC Curve Earliest Discrimination Threshold • 33 ga. Injection cannula with attached micro-electrode • Location on SC map determined by recording and stimulation • Injected Lidocaine (2%; 0.25 - 1.25 ul) or muscimol (0.5 ug/ul; 0.25 - 1 ul) • Test target selection and motor execution pre-injection, post-injection, and after recovery Choice response task Targets Masks Cue Time Two choice response task RF 4 Fixation point Cue 4 Conclusions Most neurons in the deeper layers of the SC show activity aligned with the visual input and the motor response in single-target tasks. Many of these same neurons show additional discharge that is correlated with higherlevel decision processes in more natural visual tasks. In the case of pop-out search the SC has been shown to be functionally involved in the decision processes. The cue aligned activity in SC in the choice response task is surprising because no transient visual stimulus appeared in the response field of the neuron. It remains to show whether this cue aligned activity is functionally related to choice response.