Transcript Target in Field Search: Distractor in Field - Smith

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.