Facilitated acquisition of the classically conditioned eyeblink response in females is augmented in those taking oral contraceptives

Abstract

Sex differences in attentional processing and new motor learning remain controversial, and are complicated by the influence of endogenous and exogenous gonadal hormones. Facilitated acquisition of a classically conditioned eyeblink response in oral contraceptive-using women has been reported, as have menstrual cycle-dependent changes in pre-pulse inhibition (PPI). The current study sought to replicate and extend these findings by comparing acquisition of the conditioned eyeblink response and PPI in women currently taking oral contraceptives (OCs), women not taking OCs, as well as men. Women were assigned to participate either during their follicular or luteal menstrual cycle phase. Acquisition was assessed in a two-tone discrimination delay paradigm (500-ms conditional stimulus (CS); 100-ms airpuff unconditional stimulus (US)). PPI was lower in males and OC-users depending on stimulus intensity. Consistent with early classical conditioning research, females acquired an eyeblink conditioned response faster than males. Faster acquisition was associated with larger unconditional responses. Women taking OCs demonstrated accelerated conditioned response acquisition compared to women not taking OCs and males although unconditional responses were comparable to males. Facilitated acquisition of new motor learning in OC-users was replicated in a college-aged population of women and was not secondary to enhanced reactivity to sensory stimuli.