Prefrontal Lesion Surgery
Objective: To examine the spatial memory functions of the monkey's prefrontal cortex and the effects of unilateral or serial lesions in and around the principal sulcus on oculomotor delayed-response performance and memory-guided eye movements
Protocol Steps
Pre-lesion Training
Train rhesus monkeys on oculomotor delayed-response tasks until they reach criterion performance
Note: Animals must achieve criterion performance before lesion placement
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”
Oculomotor Delayed-Response Task - Cue Presentation
Present peripheral visual cues to the animal while the animal maintains fixation on a central visual target
Note: Cues are presented in the visual field to be tested
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”
Oculomotor Delayed-Response Task - Delay Period
Maintain central fixation during a delay period after cue presentation
Note: Delay period varies from 1.5 to 8 seconds to test delay-dependent effects
View evidence from paper
“during a subsequent 1.5–8 sec delay period”
Oculomotor Delayed-Response Task - Memory-Guided Saccade
Animal makes a memory-guided eye movement to the remembered location of the peripheral visual cue
Note: Performance is measured by accuracy and direction of eye movements
View evidence from paper
“required the animal to remember the spatial location of peripheral visual cues”
Unilateral Prefrontal Lesion Placement
Place a unilateral lesion in and around the principal sulcus of the prefrontal cortex
Note: Lesion is placed after criterion performance is achieved on ODR tasks
View evidence from paper
“Four rhesus monkeys received unilateral or serial prefrontal lesions in and around the principal sulcus”
Post-Unilateral Lesion Testing
Test oculomotor delayed-response performance following unilateral lesion placement
Note: Assess effects on contralateral and ipsilateral visual field performance
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 visually guided eye movement control tasks to assess basic oculomotor function
Note: Controls for sensory or motor deficits independent of memory function
View evidence from paper
“these lesions had little or no effect on performance in visually guided control tasks”
Serial Lesion Placement
Place a second lesion in the opposite hemisphere
Note: Second lesion extends the deficit to include the opposite hemifield
View evidence from paper
“With addition of a second lesion in the opposite hemisphere, the deficit was extended to include the opposite hemifield”
Post-Serial Lesion Testing
Test oculomotor delayed-response performance following bilateral lesion placement
Note: Assess effects on both visual hemifields
View evidence from paper
“With addition of a second lesion in the opposite hemisphere, the deficit was extended to include the opposite hemifield”
Delay-Dependent Analysis
Analyze performance across different delay periods (1.5 to 8 seconds) to determine delay-dependent effects
Note: Performance deficits increase with longer delay periods
View evidence from paper
“The effect of the lesions was delay dependent: performance was rarely altered at the shortest (1.5 sec) delay but became progressively worse as the delay period was lengthened”