Abstract

The sympathetic innervation of the skin primarily subserves thermoregulation, but the system has also been commandeered as a means of expressing emotion. While it is known that the level of skin sympathetic nerve activity (SSNA) is affected by anxiety, the majority of emotional studies have utilized the galvanic skin response as a means of inferring increases in SSNA. The purpose of the present study was to characterize the changes in SSNA when showing subjects neutral or emotionally charged images from the International Affective Picture System (IAPS). SSNA was recorded via tungsten microelectrodes inserted into cutaneous fascicles of the common peroneal nerve in ten subjects. Neutral images, positively charged images (erotica) or negatively charged images (mutilation) were presented in blocks of fifteen images of a specific type, each block lasting 2 min. Images of erotica or mutilation were presented in a quasi-random fashion, each block following a block of neutral images. Both images of erotica or images of mutilation caused significant increases in SSNA, but the increases in SSNA were greater for mutilation. The increases in SSNA were often coupled with sweat release and cutaneous vasoconstriction; however, these markers were not always consistent with the SSNA increases. We conclude that SSNA, comprising cutaneous vasoconstrictor and sudomotor activity, increases with both positively charged and negatively charged emotional images. Measurement of SSNA provides a more comprehensive assessment of sympathetic outflow to the skin than does the use of sweat release alone as a marker of emotional processing.

Highlights

  • IntroductionThe complexities of human emotion, in particular negative emotion or mental stress have been widely studied, with physiological responses such as blood pressure, heart rate, cutaneous blood flow, and sweat release commonly being measured during cognitive stress (such as the Stroop color-word conflict test or mental arithmetic) and perceived stress (viewing of negatively charged emotional images) (Hare et al, 1970; Frijda, 1986; Ellsworth, 1991; Callister et al, 1992; Fox, 2002; Kern et al, 2002; Carter et al, 2008)

  • The aim of the present study was to characterize the changes in skin sympathetic nerve activity (SSNA) using microneurography while showing subjects neutral or emotionally charged images from the International Affective Picture System (IAPS), which is a widely recognized stimulus system that is used to study the effects of emotion on human subjects (Lang et al, 1997)

  • It is apparent that the latter indirect measures of skin sympathetic outflow are sluggish and long-lasting, correlating poorly with the actual bursts of SSNA that bring about the cutaneous vasoconstriction and sweat release

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Summary

Introduction

The complexities of human emotion, in particular negative emotion or mental stress have been widely studied, with physiological responses such as blood pressure, heart rate, cutaneous blood flow, and sweat release commonly being measured during cognitive stress (such as the Stroop color-word conflict test or mental arithmetic) and perceived stress (viewing of negatively charged emotional images) (Hare et al, 1970; Frijda, 1986; Ellsworth, 1991; Callister et al, 1992; Fox, 2002; Kern et al, 2002; Carter et al, 2008). One study has examined the effects of MSNA while viewing negatively charged images (Carter et al, 2008), with no reported studies on the effect of SSNA while viewing any emotionally charged images (negative or positive).

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