title: Adaptive changes in firing of primary auditory cortical neurons following illumination shift from light to dark in freely moving guinea pigs.
abstract: Some animals are forced to rely more on non-visual signals, such as audition or olfaction, than on vision when a bright environment becomes dark. By recording from a primary-like auditory cortex (field A) in freely moving guinea pigs, possible changes in the responsiveness of single units were explored in association with illumination changes. For a subset of units, we found that robust decreases (off-decrease) or increases (off-increase) in baseline discharge (BsD) were initiated soon after room light was silently extinguished. These neuronal changes were accompanied by the initiation of explorative locomotion, possibly reflecting a changed internal brain state. Preferred acoustic stimuli evoked salient excitatory responses against the reduced BsD level in the dark for the off-decrease units, and salient inhibitory responses against the increased BsD level for the off-increase units. Histological verification indicated that the units showing such BsD changes were located predominantly in layer V or its vicinity. These results are discussed in the context of the effects of the brainstem neuromodulatory systems that are activated during behavioral adaptation to new environments.
authors.affiliation: Cognitive Neurobiology, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo, Tokyo 113-8549, Japan. yojima.cnb@tmd.ac.jp
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Ojima
authors.forename: Miki
authors.initials: M
authors.lastname: Taoka
authors.forename: Atsushi
authors.initials: A
authors.lastname: Iriki
mesh_terms: D000161:Acoustic Stimulation; D000200:Action Potentials / Q000502:physiology*; D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001303:Auditory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D001306:Auditory Pathways / Q000033:anatomy & histology / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D001931:Brain Mapping; D003623:Dark Adaptation / Q000502:physiology; D003624:Darkness; D004594:Electrophysiology; D005260:Female; D006168:Guinea Pigs; D008027:Light; D008029:Lighting; D008297:Male; D009068:Movement / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009483:Neuropsychological Tests; D010470:Perceptual Masking / Q000502:physiology*; D010775:Photic Stimulation; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*