title: Local Versus Global Effects of Isoflurane Anesthesia on Visual Processing in the Fly Brain.
abstract: What characteristics of neural activity distinguish the awake and anesthetized brain? Drugs such as isoflurane abolish behavioral responsiveness in all animals, implying evolutionarily conserved mechanisms. However, it is unclear whether this conservation is reflected at the level of neural activity. Studies in humans have shown that anesthesia is characterized by spatially distinct spectral and coherence signatures that have also been implicated in the global impairment of cortical communication. We questioned whether anesthesia has similar effects on global and local neural processing in one of the smallest brains, that of the fruit fly (Drosophila melanogaster). Using a recently developed multielectrode technique, we recorded local field potentials from different areas of the fly brain simultaneously, while manipulating the concentration of isoflurane. Flickering visual stimuli ('frequency tags') allowed us to track evoked responses in the frequency domain and measure the effects of isoflurane throughout the brain. We found that isoflurane reduced power and coherence at the tagging frequency (13 or 17 Hz) in central brain regions. Unexpectedly, isoflurane increased power and coherence at twice the tag frequency (26 or 34 Hz) in the optic lobes of the fly, but only for specific stimulus configurations. By modeling the periodic responses, we show that the increase in power in peripheral areas can be attributed to local neuroanatomy. We further show that the effects on coherence can be explained by impacted signal-to-noise ratios. Together, our results show that general anesthesia has distinct local and global effects on neuronal processing in the fruit fly brain.
authors: School of Psychological Sciences, Monash University , Melbourne 3168, Victoria, Australia.
authors: Dror
authors: 0000-0002-5077-2207
authors: D
authors: Cohen
authors: Queensland Brain Institute, The University of Queensland , Brisbane 4072, Queensland, Australia.
authors: Oressia H
authors: 0000-0002-4267-9491
authors: OH
authors: Zalucki
authors: Queensland Brain Institute, The University of Queensland , Brisbane 4072, Queensland, Australia.
authors: Bruno
authors: B
authors: van Swinderen
authors: School of Psychological Sciences, Monash University, Melbourne 3168, Victoria, Australia; Monash Institute of Cognitive and Clinical Neuroscience, Monash University, Melbourne 3168, Victoria, Australia.
authors: Naotsugu
authors: 0000-0003-4216-8701
authors: N
authors: Tsuchiya
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster; D005074:Evoked Potentials, Visual / Q000187:drug effects; D005260:Female; D007839:Functional Laterality; D007530:Isoflurane / Q000494:pharmacology*; D008839:Microelectrodes; D008959:Models, Neurological; D009043:Motor Activity / Q000187:drug effects; D010775:Photic Stimulation; D012815:Signal Processing, Computer-Assisted; D014796:Visual Perception / Q000187:drug effects* / Q000502:physiology
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane
keywords: SSVEP; anesthesia; consciousness; drosophila; frequency tagging; isoflurane