In 7 of 12 normal subjects 40-60 mcg. LSD orally produced autonomic, psychic and EEG responses. In 4 subjects only 1 or 2 of these responses were observed. In 1 case LSD had no effect. The effects are considered to be an expression of neuronic hyperexcitability (shortening of refractory period) and a reduction in the "filtering" of impulses through nervous centers.
