Oxytocin can impair memory for social and non-social visual objects: a within-subject investigation of oxytocin's effects on human memory

Abstract

Oxytocin is important to social behavior and emotion regulation in humans. Oxytocin's role derives in part from its effect on memory performance. More specifically, previous research suggests that oxytocin facilitates recognition of social (e.g., faces), but not of non-social stimuli (e.g., words, visual objects). We conducted the first within-subject study to this hypothesis in a double-blind, placebo-controlled design. We administered oxytocin (24IU) and placebo (saline) in two separate sessions and in randomized order to healthy men. To obtain a baseline measure for session-dependent memory effects, which are caused by proactive interference, an additional group of male subjects in each session received placebo unbeknownst to them and the experimenter. After administration, participants studied faces and houses. Exactly one day after each study session, participants were asked to make memory judgments of new and old items. In the first study-test session, participants administered with oxytocin showed reduced recollection of previously studied faces and houses. Oxytocin also interacted with proactive-interference effects. By impeding memory in the first session, it reduced proactive interference in the second. But oxytocin contributed additionally to the memory-reducing effect of proactive interference when administered in the second session. These results demonstrate that oxytocin can have a memory-impairing effect on both social and non-social visual objects. The present study also emphasizes the necessity of including a non-treated, baseline group in within-subject designs when investigating oxytocin's effects on human memory.

Figure 1

Schematic of the experimental design and examples for stimuli. Group abbreviations refer to the administrated nasal spray (O for oxytocin, P for placebo) and indicate the order in which it was received (e.g., OP indicates that oxytocin was received in Study Session 1 and placebo in Study Session 2).

Figure 2

Discrimination index for recollection measured as hits minus false alarms for faces and houses in Test Sessions 1 and 2 for all three experimental groups (OP for oxytocin first/placebo second, PP for placebo in first and second session, PO for placebo first/oxytocin second). Error bars indicate standard error.

Figure 3

Hit rates of accurate “recollect” judgments for studied (i.e., old) faces and houses in Test Sessions 1 and 2 for all three experimental groups (OP for oxytocin first/placebo second, PP for placebo in first and second session, PO for placebo first/oxytocin second). Error bars indicate standard error.

Figure 4

Effects of test session measured as performance in Test Session 1 minus Test Session 2 for the discrimination index of recollection (i.e., hits minus false alarms) for faces and houses for all three experimental groups (OP for oxytocin first/placebo second, PP for placebo in first and second session, PO for placebo first/oxytocin second). Error bars indicate standard error.

Figure 5

Effects of test session measured as performance in Test Session 1 minus Test Session 2 for the hit rates of accurate “recollect” judgments for studied (i.e., old) faces and houses for all three experimental groups (OP for oxytocin first/placebo second, PP for placebo in first and second session, PO for placebo first/oxytocin second). Error bars indicate standard error.