Developments in autonomic research: a review of the latest literature

In addition to its homeostatic role, the autonomic nervous system is responsible for generating many of the outward signs of our emotions: our tears, our racing heart, our cold sweat. While mental stress causes an increase in heart rate and sweat release, viewing emotionally charged images-especially negative images-causes a decrease in heart rate. Children with autism spectrum disorder show increases in skin conductance (sweat release) when presented with images of faces, but their capacity to recognize faces is compromised. Conversely, children with Williams syndrome, who are very interested in faces and are socially very engaging, show blunted sudomotor responses to faces and show decreases in heart rate. Many studies have used emotionally charged visual stimuli to induce autonomic responses, and changes in electrical skin conductance as a convenient marker of autonomic arousal, to examine the brain structures involved in emotional processes. Such studies have shown that the amygdala is strongly activated during exposure to fearful images, whereas the nucleus accumbens responds strongly to erotic or romantic images (and is deactivated when exposed to negative images). Given that the nucleus accumbens forms part of the reward circuitry, it is perhaps not surprising that it is activated during that most pleasurable of autonomic acts, orgasm.