Oculomotor Delayed-Response Task
Objective: To examine the spatial memory functions of the monkey's prefrontal cortex by testing oculomotor delayed-response performance, measuring the ability to remember peripheral visual cue locations while maintaining central fixation during cue presentation and delay periods
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Equipment1
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Protocol Steps
Pre-lesion Training to Criterion
Train animals on oculomotor delayed-response tasks until they reach criterion performance level
Note: Animals must achieve criterion performance before proceeding to lesion surgery
View evidence from paper
“Four rhesus monkeys received unilateral or serial prefrontal lesions in and around the principal sulcus after they reached criterion performance on the ODR tasks”
Cue Presentation Phase
Present peripheral visual cues while animal maintains fixation on a central visual target
Note: Animal must maintain central fixation during cue presentation
View evidence from paper
“required the animal to remember the spatial location of peripheral visual cues, while maintaining fixation on a central visual target during the presentation of each cue”
Delay Period
Maintain central fixation during the delay period after cue offset before memory-guided saccade response
Note: Delay period varies from 1.5 to 8 seconds; performance is delay-dependent
View evidence from paper
“during a subsequent 1.5–8 sec delay period”
Memory-Guided Saccade Response
Animal makes eye movement to the remembered location of the peripheral visual cue
Note: Saccadic reaction times and velocities are measured
View evidence from paper
“memory-guided eye movements to spatial cues in the visual field contralateral to the hemisphere”
Surgical Lesion Placement
Create unilateral or serial prefrontal lesions in and around the principal sulcus
Note: Lesions placed after criterion performance achieved; some lesions extended into frontal eye field region of arcuate sulcus
View evidence from paper
“Four rhesus monkeys received unilateral or serial prefrontal lesions in and around the principal sulcus”
Post-lesion ODR Testing
Repeat oculomotor delayed-response task testing after lesion placement to assess performance changes
Note: Test across multiple delay periods (1.5-8 sec) to assess delay-dependent effects
View evidence from paper
“Unilateral lesions disrupted the performance of memory-guided eye movements to spatial cues in the visual field contralateral to the hemisphere in which the lesion was placed”
Visually Guided Control Task
Perform control task with visually guided eye movements to assess sensory and motor function independent of memory
Note: Lesions had little or no effect on visually guided control task performance
View evidence from paper
“these lesions had little or no effect on performance in visually guided control tasks”