title: Covariation of pupillary and auditory cortical activity in rats under isoflurane anesthesia.
abstract: Very slow fluctuations of spontaneous activities significantly influence not only behavioral performance in a conscious state, but also neural activities in an unconscious state. Covariation of pupil and cortical activities may lend important insights into the state-dependent modulation of stimulus encoding, yet this phenomenon has received little attention, especially with regard to non-visual cortices. In the present study, we investigated co-fluctuation of pupil size and neural activity in the auditory cortex of rats under isoflurane anesthesia. Pupil fluctuation consisted of longitudinal irregular shifts, and 1-min cyclic modulations. Both spontaneous and auditory-evoked potentials (AEPs) covaried with the longitudinal fluctuation of pupil size, but not with the 1-min cycle. Pupil size exhibited a positive correlation with spontaneous activity and negative correlation with AEP amplitude, particularly when the pupil size was beyond the normal range. Stimulus-specific adaptation characterized using an oddball paradigm was less dependent on pupil size than AEP. In contrast to the cortical activity, heart rate covaried with pupil size with the 1-min oscillatory component, but not the non-oscillatory component. Furthermore, light exposure induced the pupil reflex through the autonomic system, but did not modify cortical activity, indicating that autonomic activity was not causing the cortical modulation. These results together suggest that cortical activities spontaneously covary with pupillary activity through central cholinergic modulation that triggers sympathetic nerve activation. Such a state-dependent property may be a confounding factor in cortical electrophysiology studies.
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan. Electronic address: takahashi@i.u-tokyo.ac.jp.
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Tokushige
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: T I
authors.initials: TI
authors.lastname: Shiramatsu
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Noda
authors.affiliation: Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Kanzaki
mesh_terms: D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001303:Auditory Cortex / Q000187:drug effects* / Q000502:physiology*; D001307:Auditory Perception / Q000187:drug effects / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000187:drug effects / Q000502:physiology; D007839:Functional Laterality; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D009929:Organ Size; D010507:Periodicity; D011680:Pupil / Q000187:drug effects* / Q000502:physiology*; D017208:Rats, Wistar; D012025:Reflex, Pupillary / Q000187:drug effects / Q000502:physiology
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane
keywords: auditory cortex; auditory-evoked potential (AEP); isoflurane; pupil; spontaneous activity; stimulus-specific adaptation (SSA)