Microelectrode arrays for stimulation of neural slice preparations

A planar 6×6 array of iridium electrodes with four reference electrodes has been developed for use with neural tissue preparations. Precise knowledge of the relative locations of the array elements allows for spatial neurophysiological analyses. The 10 μm diameter platinized iridium electrodes on a 100 μm pitch have been used to stimulate acutely prepared slices of spinal cord from free-ranging rodents. An intracellular recording from a single neuron in the substantia gelatinosa (SG) using the whole-cell, tight-seal technique allowed low noise, high resolution studies of excitatory or inhibitory electrical responses of a given neuron to inputs from the primary afferent fibers or from stimulation by individual electrodes of the array. The resulting maps of responses provide an indication of the interconnectivity of neural processes. The pattern emerging is that of limited interconnectivity in the SG from areas surrounding a recorded neuron but with strong excitatory or inhibitory effects from those oriented in a longitudinal (rostral–caudal) direction relative to the neuron. The observations to date suggest the neurons of the SG are arranged in sets of independent networks, possibly related to sensory modality and input from particular body regions.