Elsevier

Behavioural Brain Research

Volume 216, Issue 1, 1 January 2011, Pages 301-307
Behavioural Brain Research

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

https://doi.org/10.1016/j.bbr.2010.08.008Get rights and content

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.

Research highlights

▶ Females exhibit faster new motor learning than males. ▶ Oral contraceptives facilitate new motor learning.

Section snippets

Participants

Seventy-two participants were recruited from Seton Hall University as a one credit hour requirement for an introductory psychology course. Participant ages and years of education ranged from 18–23 to 12–16, respectively. Women with irregular menstrual cycles were excluded from the study. Informed consent was obtained in accordance with procedures approved by the Seton Hall University Institutional Review Board.

Materials and apparatus

The equipment used for stimulus delivery and assessment of eyelid electromyographic

Acoustic startle responding and pre-pulse inhibition

Regarding the startle response data, a 4 (group) × 2 (intensity) mixed-design ANOVA yielded only a main effect of intensity, F(1,57) = 144.33, p < .001. As expected, larger eyeblink responses were observed in response to the higher intensity acoustic stimulus. As for PPI, a 4 (group) × 2 (IPI) × 2 (intensity) mixed-design ANOVA was conducted. A significant IPI × intensity interaction, F(1,57) = 13.79, was qualified by the triple interaction of group × IPI × intensity, F(3,57) = 4.56, all ps < .001 (see Table 1). For

Discussion

The present study examined associative learning in females currently taking oral contraceptives, females not taking oral contraceptives, and males. The results show that during a classical eyeblink conditioning task, there is a significant sex difference in associative learning acquisition, with females generally learning the CS/US association faster than males and reaching higher asymptotic performance. This difference was driven by the OC group, which demonstrated the highest percentage of

Acknowledgements

The present manuscript was in partial fulfillment of the requirements for a Masters degree from Seton Hall University. The primary author wishes to thank Dr. Janine Buckner for guidance in the study design, approval and execution. Michael T. Bergen and Robert DeMarco helped in the equipment setup and signal processing. Research supported by Department of Veterans Affairs Medical Research Funds and the Stress & Motivated Behavior Institute.

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