Respiratory Sinus Arrhythmia and Emotion: Effects of pictorial stimuli and state anxiety

Sammanfattning: Respiratory sinus arrhythmia (RSA) refers to heart rate variations due to respiration, which results from parasympathetic nervous system activity mediated via the tenth cranial nerve, the vagus. Thus, the magnitude of RSA is considered as an index of cardiac vagal tone. This thesis explored RSA during emotional responding in healthy women and men. In the first two studies fear-relevant pictorial stimuli were contrasted with fear-irrelevant ones. In the third study, RSA was related to differences in subjective ratings of state anxiety. In paper I, RSA was examined in women and men who were being shown pictures of angry and happy faces. Since prior research has indicated that emotional information may be processed even at a preattentive level, the pictures were presented both subliminally and supraliminally. The results showed that angry faces concurred with greater RSA than happy faces. Moreover, no interaction effect between exposure time and facial expression was found, indicating that the pictures induced emotional activation both subliminally and supraliminally. These results were, however, obtained for men only. In paper II, RSA was examined in women and men who were being shown film-clips. Films containing spiders or snakes were considered as fear relevant stimuli, scenic views represented neutral stimuli, and films of dogs, puppies, cats and kittens were considered as positively valenced stimuli. RSA was found to be linearly related to the emotional valence of the films, that is, greater RSA in response to fear relevant films, and lower RSA to the positive films. It has been suggested that fear relevant pictorial stimuli might be regarded as potential threats, rather than actual threats. Furthermore, actual threats result in fear relevant behaviour, whereas potential threats result in anxiety related behaviour. Therefore, in paper III RSA was related to subjective ratings of state anxiety. Based on median split women and men were grouped into low, and high state anxious groups. RSA was recorded while the participants were resting in a quiet and relaxed mood. Higher RSA was found in those who rated them selves higher on state anxiety than in those who rated themselves lower on state anxiety. To summarize, increased RSA magnitude was found in response to fear- relevant stimuli, and in individuals with higher state anxiety. These findings were interpreted as indexing behavioural and motor inhibition, and increased attention.