The Influence of Oxytocin on Older Adults’ Emotion Processing

Abstract

Emotion processing involves attending to and recognising emotional stimuli, as well as experiencing a feeling of emotion and expressing an emotional reaction. Age-related differences in the processing of emotions are apparent when comparing older (over 60 years) and young (18-30 years) participants. Oxytocin has been shown to increase emotion recognition and some measures that are associated with emotional responses in young adults. The findings are not consistent though, and the effects of oxytocin are often moderated by internal and external factors, such as baseline social proficiency. There is reason to think that oxytocin could improve emotion processing in older adults. This was examined in two studies testing emotion recognition and emotion experience. In the first study, 68 older and 68 young adults were randomly allocated to receive oxytocin nasal spray (20IU) or placebo using a double-blind design. Forty-five minutes after receiving the spray, participants completed a range of tasks to assess accuracy in emotion recognition, including a basic emotion recognition task, the Reading the Mind in the Eyes Test, and an emotion-matching task. During the basic emotion recognition task and the RMET, participants wore an eye-tracking device. The results revealed that oxytocin improved emotion recognition for older males, increased older males’ scanning of the eyes, nose and mouth regions of the face, and changed the way that both older and young adults integrated gaze direction cues with emotion expression to influence emotion recognition. No differences in recognition were found for older females or young adults. In the second study, 68 older adults were randomly allocated to receive oxytocin nasal spray or placebo and watched film clips to induce the experience of certain emotions: anger, disgust, fear, happiness and sadness. They rated their experience of emotion after watching each film clip. While they viewed the films, physiological measures of their heart rate, skin conductance and movement of facial muscles were taken to provide a measure of emotional response. The results indicated that oxytocin did not have any effect on emotion experience in older adults. Older adults did show changes in physiological activity, specifically to the sadness and fear film clips, and changes in facial expressiveness during the film clips. The two studies show that oxytocin can influence older adults’ emotion processing, but has an influence only on the recognition of emotions and not on the experience of emotions. Males and females appear to respond differently to oxytocin, with the largest effects found in older males, showing that gender is an important moderator of oxytocin effects. The mechanisms for declines in emotion processing with age are not fully understood, although could include the structural or functional brain declines that occur with age. This suggests that changes in oxytocin functioning in older males’ brains could be a partial mechanism for emotion recognition difficulties, providing support for the neural model of age-related emotion recognition difficulties.