NONINVASIVE MULTIELECTRODE ARRAY FOR HIGH-RESOLUTION SAMPLING OF SCALP-RECORDED POTENTIAL FIELDS

A new non-invasive electrode array has been devised to record electric al signals on the scalp. The electrodes are arranged every 10 mm in a 4 X 8 grid, thus totalling 32. Electrical coupling is assured by a col umn of conductor gel with a diameter of 2 mm. The electrode array has been used to record multichannel scalp potentials evoked by stimulatio n of the median nerve at the wrist. It was positioned on the parietal region with the midline corresponding to the external acoustic meatus. The high spatial resolution of this device allows a detailed spatial sampling of the scalp potential field where the electrical activity ar ising from the parietal and premotor cortex is predominant. Scalp pote ntials with the system are compared with those with the 10/20 system. The improved spatial resolution allows more precise localization of mi nimum and maximum of the potential field, though the overall distortio n introduced by aliasing in the 10/20 system is not striking. Instead, the amplitudes of fields are considerably affected by insufficient sp atial sampling.