ELECTROCUTANEOUS SPATIAL INTEGRATION AT SUPRATHRESHOLD LEVELS - AN ADDITIVE NEURAL MODEL

The effects of cathode size on estimates of the magnitude of electrocu taneous stimulation were studied. The 24 Ss made magnitude estimates f or combinations of 6 cathode sizes (2.5-30 mm diameter) and 5 currents (1.5-3.3 times the threshold). Estimates for small cathodes were cons istently smaller but grew more rapidly than those for intermediate and large cathodes. From the results, contours were constructed showing h ow area and current trade off to maintain apparent intensity. These ar ea-current contours suggest that supersummation prevails at low estima tion levels and complete summation takes place at high levels. An addi tive neural model is proposed to account for the results and is also a pplied to other somatosensory systems.