title: Implicit Memory in Monkeys: Development of a Delay Eyeblink Conditioning System with Parallel Electromyographic and High-Speed Video Measurements.
abstract: Delay eyeblink conditioning, a cerebellum-dependent learning paradigm, has been applied to various mammalian species but not yet to monkeys. We therefore developed an accurate measuring system that we believe is the first system suitable for delay eyeblink conditioning in a monkey species (Macaca mulatta). Monkey eyeblinking was simultaneously monitored by orbicularis oculi electromyographic (OO-EMG) measurements and a high-speed camera-based tracking system built around a 1-kHz CMOS image sensor. A 1-kHz tone was the conditioned stimulus (CS), while an air puff (0.02 MPa) was the unconditioned stimulus. EMG analysis showed that the monkeys exhibited a conditioned response (CR) incidence of more than 60% of trials during the 5-day acquisition phase and an extinguished CR during the 2-day extinction phase. The camera system yielded similar results. Hence, we conclude that both methods are effective in evaluating monkey eyeblink conditioning. This system incorporating two different measuring principles enabled us to elucidate the relationship between the actual presence of eyelid closure and OO-EMG activity. An interesting finding permitted by the new system was that the monkeys frequently exhibited obvious CRs even when they produced visible facial signs of drowsiness or microsleep. Indeed, the probability of observing a CR in a given trial was not influenced by whether the monkeys closed their eyelids just before CS onset, suggesting that this memory could be expressed independently of wakefulness. This work presents a novel system for cognitive assessment in monkeys that will be useful for elucidating the neural mechanisms of implicit learning in nonhuman primates.
authors.affiliation: Department of Neurobiophysics, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kishimoto
authors.affiliation: Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu, Japan.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yamamoto
authors.affiliation: Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu, Japan.
authors.forename: Kazutaka
authors.initials: K
authors.lastname: Suzuki
authors.affiliation: Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu, Japan.
authors.forename: Haruyoshi
authors.initials: H
authors.lastname: Toyoda
authors.affiliation: Department of Neurophysiology, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kano
authors.affiliation: Central Research Laboratory, Hamamatsu Photonics K.K., Hamakita-ku, Hamamatsu, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Tsukada
authors.affiliation: Department of Neurobiophysics, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kirino
mesh_terms: D000818:Animals; D001767:Blinking; D003214:Conditioning, Classical; D004576:Electromyography; D008253:Macaca mulatta; D008297:Male; D008568:Memory; D011930:Reaction Time; D014741:Video Recording