The neurodyne: a simple mains-powered constant-current stimulus isolator

Electrical stimulation of neuronal tissue is a fundamental part of many experiments in neuroscience. It is now widely accepted that to minimise stimulus artefacts stimulators need to be both constant-current devices and also electrically isolated from ground. This difficult combination of parameters is usually only obtained with battery-powered devices. Here we describe a fully isolated and constant-current mains-powered stimulus interface ('Neurodyne') which is based around a toroidal transformer. It is simple to construct and has the ability to deliver analogue signals as stimuli as well as pulses. The signal amplitude can be up to 20 mA and has a voltage compliance of over 100 V. The device has been shown to perform satisfactorily when applied to a brain slice preparation in vitro.