Psychophysiological and subjective responses to acquisition, extinction (three sub-phases), recall, and renewal of fear at pre- and post-intervention. Neither a SCRs nor b expectancy ratings of the unconditioned stimulus (electrical stimulation) were modulated by colonic SCFA administration. SCRs (µS) skin conductance responses in microSiemens, Acq acquisition, Ext extinction, Rec recall, Ren renewal. Graphs show means ± SE.