VEP and PERG acuity in anesthetized young adult rhesus monkeys

Abstract

This study used the swept spatial-frequency method to compare retinal and cortical acuity in anesthetized young adult rhesus monkeys. Visual evoked potentials (VEPs) and pattern electroretinographic responses (PERGs) were recorded from 25 monkeys (age range: 4–12 years) anesthetized with a continuous infusion of propofol. The stimuli were temporally countermodulated sine-wave gratings that increased in spatial frequency within a 10.24-s period. All animals were refracted using acuity estimated from the zero micro-volt intercept of the linear regression of evoked potential amplitude on spatial frequency. Average sweep acuities were 23.7 cycles/deg ± 1.5 S.E.M. and 23.1 cycles/deg ± 1.8 S.E.M. for the PERG and VEP, respectively. VEP and PERG acuities were within the range expected based on acuities estimated from behavioral studies in macaques. PERG and VEP acuities were highly correlated (r = 0.90) and equally sensitive to spherical blur. On a subset of animals, test–retest reliability of animals, and interocular correlations, were high (r = 0.87 and r = 0.83, respectively). Increasing propofol dosage 8-fold did not degrade PERG or VEP acuity. This study demonstrates that high spatial-frequency acuities can be rapidly obtained from young adult rhesus monkeys under a wide dose range of propofol anesthesia using the swept spatial-frequency method.