Skin sympathetic nerve activity in humans during exposure to emotionally-charged images: sex differences

Rachael Brown,Vaughan G Macefield

doi:10.3389/fphys.2014.00111

Abstract

While it is known that anxiety or emotional arousal affects skin sympathetic nerve activity (SSNA), the galvanic skin response (GSR) is the most widely used parameter to infer increases in SSNA during stress or emotional studies. We recently showed that SSNA provides a more sensitive measure of emotional state than effector-organ responses. The aim of the present study was to assess whether there are gender differences in the responses of SSNA and other physiological parameters such as blood pressure, heart rate, skin blood flow and sweat release, while subjects viewed neutral or emotionally-charged images from the International Affective Picture System (IAPS). Changes in SSNA were assessed using microneurography in 20 subjects (10 male and 10 female). Blocks of positively-charged (erotica) or negatively-charge images (mutilation) were presented in a quasi-random fashion, following a block of neutral images, with each block containing 15 images and lasting 2 min. Images of both erotica and mutilation caused significant increases in SSNA, with increases being greater for males viewing erotica and greater for females viewing mutilation. The increases in SSNA were often coupled with sweat release and cutaneous vasoconstriction; however, these markers were not significantly different than those produced by viewing neutral images and were not always consistent with the SSNA increases. We conclude that SSNA increases with both positively-charged and negatively-charged emotional images, yet sex differences are present.

Highlights

Human emotion has long been studied, with numerous theories proposed and a diverse range of methods used to investigate emotional reactions and processing
There does remain a continuous development of emotional theories, it is clear that alterations in the activity of organs controlled by the autonomic nervous system (ANS) are involved in emotional state changes (Lacey and Lacey, 1970), such as when cutaneous flushing occurs in the face of a person who blushes when socially embarrassed
In accordance with our previous study (4), when males and females were grouped together, absolute values for blood pressure, heart rate, respiration, cutaneous blood flow, and sweat release showed no significant changes during viewing of emotionally-charged images, compared to viewing neutral images or at rest

Summary

Introduction

Human emotion has long been studied, with numerous theories proposed and a diverse range of methods used to investigate emotional reactions and processing. The activity of the ANS and its broad range of physiological reactions are widely studied during different emotional states or challenges, yet controversy still exists regarding the unambiguous outcome of these investigations (Hare et al, 1970; Callister et al, 1992; Lang et al, 1993; Fox, 2002; Ritz et al, 2005; Carter et al, 2008; Brown et al, 2012). There is emerging evidence of sex differences in emotional processing, with females found to be more emotionally perceptive and experiencing emotions with greater frequency and intensity than males (Whittle et al, 2011), yet there is very little literature exploring sex and emotion. While it is known that there are profound sex differences in the prevalence of emotion dysregulation disorders (Gater et al, 1998), there are mixed results for those studies that have explored sex differences with respect to particular emotional processes (Bradley et al, 2001; McRae et al, 2008; Domes et al, 2010; Lithari et al, 2010; Bianchin and Angrilli, 2012)

Objectives

Methods

Results

Conclusion