Abstract
Visual orienting of attention in healthy human males was examined following the administration of testosterone (T). In males, T has been found to influence the dopaminergic system which has been found to change the efficiency of various cognitive functions such as stimulus identification and inhibition of response output. Similarly, high levels of Estrogen associated with a female's ovulatory phase have been linked to higher dopaminergic activity and then larger inhibition effects during paradigms involving reflexive orienting of attention. Overall, individual differences in visual attention are potentially due to both distinct neural structures and variations in hormone levels. In this study, the influence of T on reflexive and volitional orienting of visual attention was investigated. Sixteen participants completed both an exogenous and an endogenous cueing task on two days of testing that were separated by two weeks. On each day, participants were administered either T or a placebo. The expected inhibition of return (IOR) was observed in the exogenous task, F(1, 15) = 39.05, p< 0.001. However, T did not moderate IOR (p= 0.266). Participants also demonstrated the expected cueing effects during the endogenous task, F(2, 30) = 25.5, p< 0.001. However, following T administration, there was a much longer delay responding to a target after an invalid cue, F(2, 30) = 5.65, p< 0.008. The results indicate that hormone levels can influence visual orienting of attention in a state specific manner. The data support the notion that individual differences in inhibitory control are dependent upon hormonal levels and/or neural-structural variation.Acknowledgments: SH supported by CFI. JMC supported by NSERC.