title: Multi-unit recording with iridium oxide modified stereotrodes in Drosophila melanogaster.
abstract: BACKGROUND
  Drosophila is a very favorable animal model for the studies of neuroscience. However, it remains a great challenge to employ electrophysiological approaches in Drosophila to study the neuronal assembly dynamics in vivo, partially due to the small size of the Drosophila brain. Small and sensitive microelectrodes for multi-unit recordings are greatly desired.
  
  
  METHODS
  We fabricated micro-scale stereotrodes for electrical recordings in Drosophila melanogaster. The stereotrodes were modified with iridium oxide (IrO2) under a highly controllable deposition procedure to improve their electrochemical properties. Electrical recordings were carried out using the IrO2 stereotrodes to detect spontaneous action potentials and LFPs in vivo.
  
  
  RESULTS
  The IrO2 electrodes exhibited significantly higher capacitance and lower impedance at 1 kHz. Electrical recording with the IrO2 stereotrodes in vivo demonstrated an average signal-to-noise ratio (SNR) of 7.3 and a significantly improved LFP sensitivity. 5 types of different neurons recorded were clearly separated. Electrophysiological responses to visual and odor stimulation were also detected, respectively.
  
  
  CONCLUSIONS
  The most widely used electrodes for electrical recording in Drosophila are glass microelectrode and sharpened tungsten microelectrode, which are typically used for single-unit recordings. Although tetrode technology has been used to record multi-neuronal activities from Drosophila, the fabricated IrO2 stereotrodes possess smaller geometry size but exhibited comparable recording signal-to noise ration and better sorting quality.
  
  
  CONCLUSIONS
  The IrO2 stereotrodes are capable to meet the requirements of multi-unit recording and spike sorting, which will be a useful tool for the electrophysiology-based researches especially in Drosophila and other small animals.
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Wei
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China. Electronic address: luyi@siat.ac.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lu
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.affiliation: Shenzhen Key Lab of Neuropsychiatric Modulation, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China. Electronic address: lp.wang@siat.ac.cn.
authors.forename: Liping
authors.initials: L
authors.lastname: Wang
mesh_terms: D000200:Action Potentials; D000818:Animals; D001921:Brain / Q000502:physiology; D002858:Chromium Alloys; D004331:Drosophila melanogaster / Q000502:physiology*; D025802:Electric Capacitance; D017097:Electric Impedance; D007495:Iridium; D008839:Microelectrodes; D008855:Microscopy, Electron, Scanning; D009474:Neurons / Q000502:physiology; D009812:Odorants; D055696:Olfactory Perception / Q000502:physiology; D010775:Photic Stimulation; D010812:Physical Stimulation; D012815:Signal Processing, Computer-Assisted; D059629:Signal-To-Noise Ratio; D014796:Visual Perception / Q000502:physiology
chemical_list: D002858:Chromium Alloys; C044458:iridium oxide; D007495:Iridium
keywords: Drosophila; Iridium oxide; Multi-unit recording; Stereotrode; Tetrode