Magnetic and electrical responses to CO2 stimulation of the nasal mucosa were recorded in 4 subjects. The magnetic responses peaked at 350-400 msec, coinciding with the negative vertex potential. The field pattern suggested neural activation in the upper bank of the sylvian fissure near the lateral end of the central sulcus, i.e., at or near SII. The results also suggest that this area contributes to the generation of the electrical vertex potential.