Hum bug 50 60 hz

The peroneal nerve was stimulated by a 2 disc bar electrode (3 cm spacing between discs) filled with conductive gel. It was positioned inferior to the fibular head with the cathode distal, and secured in place with an elastic strap [24 ]. The pulse duration was set to 1 ms to be consistent with our patient studies. In some patients, the maximal output of the stimulator (50 mA) was insufficient to evoke a supramaximal CMAP when pulse duration was less than 1 ms. Preliminary experiments revealed that MScan responses evoked by peroneal nerve stimulation at the ankle were uncomfortable; thus, stimulation at the fibular head was used for definitive MScan recordings.
Stimulation and recording were controlled by QTracS software (© Professor H. Bostock, Institute of Neurology, London). Pulses generated by computer were converted to current via a constant current stimulator (DS5, Digitimer Ltd., Welwyn Garden City, Hertfordshire, UK). EMG activity was amplified (x500) and bandpass filtered (10 Hz to 3 kHz) (Astro-Medical, model P511, West Warwick, Rhode Island). A noise eliminator (Hum Bug 50/60 Hz, Digitimer Ltd) removed line frequency noise. EMG was digitized at a sampling rate of 10 kHz with a 16-bit converter (NI-USB6221; National Instruments; Austin, Texas).

After sectioning, slices were placed in a Haas-type interface recording chamber and allowed to equilibrate for an hour at the interface between aCSF and moist 95%O₂–5%CO₂ (300 cm³/min). Slices were constantly perfused with aCSF at a flow rate of ∼2 ml/min; the temperature was maintained at 32°C. Slices were visualised with a stereo-microscope (Leica MZ8, Micro Instruments, Long Hanborough, Oxon, UK) mounted above the interface chamber. Extracellular microelectrodes were pulled from thick-walled borosilicate glass capillaries (1.2 mm O.D.×0.69 mm I.D.; Harvard apparatus, Edenbridge, Kent, UK) using a P-97 puller (Sutter Instrument Co, Novato, CA). Electrodes were filled with aCSF and had a typical resistance of 2–4 MΩ. Extracellular potentials were recorded using an Axoclamp 2B amplifier (Molecular Devices, Sunnyvale, CA), low pass Bessel filtered at 1 kHz (NL-125, Digitimer Ltd, Welwyn Garden City, UK) and digitized at 10 kHz by a Power 1401 (CED Ltd, Cambridge, UK). Additionally, a Humbug 50/60 Hz (Digitimer) was used to remove noise locked to the electrical mains supply. Stimulation and data acquisition were controlled using Spike 2 software (v6.12; CED). Data were stored for subsequent off-line analysis using Spike 2.