Multielectrode recordings from auditory neurons in the brain of a small grasshopper.
BACKGROUND
Grasshoppers have been used as a model system to study the neuronal basis of insect acoustic behavior. Auditory neurons have been described from intracellular recordings. The growing interest to study population activity of neurons has been satisfied so far with artificially combining data from different individuals.


METHODS
We for the first time used multielectrode recordings from a small grasshopper brain. We used three 12μm tungsten wires (combined in a multielectrode) to record from local brain neurons and from a population of auditory neurons entering the brain from the thorax. Spikes of the recorded units were separated by sorting algorithms and spike collision analysis.


RESULTS
The tungsten wires enabled stable recordings with high signal to noise ratio. Due to the tight temporal coupling of auditory activity to the stimulus spike collisions were frequent and collision analysis retrieved 10-15% of additional spikes. Marking the electrode position was possible using a fluorescent dye or electrocoagulation with high current. Physiological identification of units described from intracellular recordings was hard to achieve.


METHODS
12μm tungsten wires gave a better signal to noise ratio than 15μm copper wires previously used in recordings from bees' brains. Recording the population activity of auditory neurons in one individual prevents interindividual and trial-to-trial variability which otherwise reduce the validity of the analysis. Double intracellular recordings have quite low success rate and therefore are rarely achieved and their stability is much lower than that of multielectrode recordings which allows sampling of data for 30min or more.
Georg-August-University of Göttingen, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Department of Cellular Neurobiology, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany. Electronic address: mbhavsa@gwdg.de.
Mit Balvantray
MB
Bhavsar
Georg-August-University of Göttingen, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Department of Cellular Neurobiology, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
Ralf
R
Heinrich
Georg-August-University of Göttingen, Johann-Friedrich-Blumenbach-Institute for Zoology and Anthropology, Department of Cellular Neurobiology, Julia-Lermontowa-Weg 3, D-37077 Göttingen, Germany.
Andreas
A
Stumpner
D000200:Action Potentials; D000465:Algorithms; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology; D001307:Auditory Perception / Q000502:physiology*; D001921:Brain / Q000502:physiology; D003300:Copper; D004594:Electrophysiology / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D006110:Grasshoppers / Q000502:physiology*; D042541:Intracellular Space / Q000502:physiology; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013995:Time; D014414:Tungsten
D003300:Copper; D014414:Tungsten
Brain; Hearing; Insect; Spike collisions; Spike sorting; Tetrode