Role of personality and expectations for itch and scratching induced by audiovisual itch stimuli.

Itch is an unpleasant, bodily sensation, which--similar to pain--evokes behavioral reactions. As a response to itch, people start scratching. There are different ways to provoke itch and subsequent scratching in experimental settings. A non-invasive method to induce itch and scratching is the presentation of itch-related (audio-) visual stimulus material, like slide-supported lectures on skin diseases or crawling insects. Also, watching videos showing other people scratching provokes itch and the desire to scratch. In this review, we focus on psychological factors, which were shown to be associated with itch and scratching provoked by (audio-) visual itch stimuli. First, we summarize the findings on the relationship between personality characteristics and (audio-) visually induced itch. Agreeableness and self-consciousness were shown to be associated with induced itch and scratching in patients with chronic skin diseases, while neuroticism was linked to induced itch in healthy subjects. Second, we present results of a recent study, in which we altered the expectations towards audio-visually induced itch and scratching by changing the information given on upcoming itch stimuli. It was shown that subjects being informed about itch stimuli in a neutral way displayed a shorter scratch duration in itch inducing situations than subjects having catastrophizing expectations. Also, the increase in scratch duration and in the number of scratch movements induced by audiovisual itch stimuli was higher when the patients were not informed about itch induction. Thus, in itch patients neither catastrophizing nor trivializing symptoms seems to be helpful.

The role of cardiac and vascular components in blood pressure variability during voluntary apnea in snoring subjects.

The aim of this study was to evaluate the cardiovascular response to the activation of arterial chemoreceptors during voluntary apnea in snoring subjects. Fifty five men were enrolled in the study: 33 snorers and 22 non-snorers (control group). The majority of snorers were overweight and hypertensive. The experimental session consisted of 20 voluntary inspiratory apneas interspersed with 1 min free breathing periods, and 20 min recovery. The following parameters were recorded noninvasively: blood pressure, ECG, and arterial oxygen saturation. Data analysis was based on the Smietanowski procedure, written in the 4-th generation script language of MATLAB environment, which allows assessing the relative contribution of cardiac and vascular components to blood pressure variability. The results indicate that repetitive apneas led to significantly greater increases in blood pressure in the snorers. In this group, the domination of vascular influences during apnea periods reached 67 +/-2.0%, which was greater than the 56 +/-1.8% in the non-snorers (P<0.01). In contrast, the contribution of the cardiac component in the blood pressure response to apnea was greater in the non-snorers: 33 +/-3% vs. 20 +/-2% in the snorers (P<0.01). We conclude that activation of carotid chemoreceptors during voluntary apnea evokes a greater cardiovascular response in snorers, related to the reflex increase in total peripheral vascular resistance, and, consequently, a greater increase in blood pressure.