PMID-9350963 A floating microwire technique for multichannel neural recording and stimulation in the awake rat
- sweet electrodes -- attached to glass micropipette with sucrose or saliva.
- Chorover and DeLuca 1972 "A sweet new multiple electrode for chronic single unit recording". {1019}
- 42 implanted rats, 252 implanted wires, 79% yield. 62% of electrodes still working at 5 weeks.
- Targeting an area with really large somas (50um).
- fully-floating 25um microwire ellectrodes.
- platinum iridium, 25um, teflon coated, handled only with silastic-protected pliers & tweezers to prevent damage to the insulation.
- electrode impdance range 200-900kOhms; check insulation by applying -3V to each electrode & looking for hydrogen bubbles.
- soldering hardens platinum iridium alloy (huh).
- (!!!) wires are stiffened for implantation by temporarily attaching them to a micropipette guide with sucrose which subsequently dissolves in the brain!
- the smooth sucrose (40 grams in 50ml of water heated to 118C) coating requires about a week of desiccation to become hard enough for insertion into the brain without premature softening. Sucrose becomes clear like glass once fully desiccated.
- the air above the craniotomy is sufficiently humid to dissolve the sucrose if left there for more than a few seconds.
- used a miniature single-channel FET amplifier as a headstage - only one channel out of 6 could be recorded at once :( Thus their reults only apply to the best of the microwires implanted - not to all of them.
- recorded onto a mac quadra (hahah) 20khz 12 bit
- applying 160ua microstimulation pulses can restore low (200kohm) electrode impedance. Recording quality was generally improved for a few days following stimulation but then returned to an asymptotic level with the impedance at approximately 900kOhm.
- electrodes only seemed to last 5 weeks, whence they declined to about 27% yeild - see figure 8.
- good review of microelectrode recording up to that point (1997).
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