Repeatable, low-drift recordings in behaving nonhuman primates using flexible microelectrodes

Neurophysiological recordings from nonhuman primates rely on rigid microelectrode arrays whose mechanical mismatch with brain tissue causes neuronal drift and unstable single-unit recordings. Here we present a flexible microelectrode platform for repeated recordings in awake rhesus macaques. We fabricated a 32-channel, 7-μm-thick Parylene-C array and developed a telescopic insertion method using concentric guide tubes and a retractable microwire shuttle to repeatedly deliver free-floating arrays through intact dura using standard recording chambers. Across two animals, we optimized the electrode geometry and insertion to achieve an 80% single-unit recording success rate. During an oculomotor delayed response task, we recorded stable task-responsive neurons from prefrontal and posterior parietal cortex. Compared with rigid probes in the same animals and recording chambers, flexible arrays achieved a comparable single-unit yield while reducing drift from hundreds to tens of micrometers. Our work establishes flexible microelectrodes as a practical and high-performing technology for primate neuroscience.