No preconscious attentional bias towards itch in healthy individuals

Abstract

Rapidly attending towards potentially harmful stimuli to prevent possible damage to the body is a critical component of adaptive behavior. Research suggests that individuals display an attentional bias, i.e., preferential allocation of attention, for consciously perceived bodily sensations that signal potential threat, like itch or pain. Evidence is not yet clear whether an attentional bias also exists for stimuli that have been presented for such a short duration that they do not enter the stream of consciousness. This study investigated whether a preconscious attentional bias towards itch-related pictures exists in 127 healthy participants and whether this can be influenced by priming with mild itch-related stimuli compared to control stimuli. Mild itch was induced with von Frey monofilaments and scratching sounds, while control stimuli where of matched modalities but neutral. Attentional bias was measured with a subliminal pictorial dot-probe task. Moreover, we investigated how attentional inhibition of irrelevant information and the ability to switch between different tasks, i.e., cognitive flexibility, contribute to the emergence of an attentional bias. Attentional inhibition was measured with a Flanker paradigm and cognitive flexibility was measured with a cued-switching paradigm. Contrary to our expectations, results showed that participants attention was not biased towards the itch-related pictures, in facts, attention was significantly drawn towards the neutral pictures. In addition, no effect of the itch-related priming was observed. Finally, this effect was not influenced by participants’ attentional inhibition and cognitive flexibility. Therefore, we have no evidence for a preconscious attentional bias towards itch stimuli. The role of preconscious attentional bias in patients with chronic itch should be investigated in future studies.

Subliminal attentional bias modification training for itch

“…Attentional bias towards itch was measured with a dot-probe paradigm ( 9–11 ). Forty pairs of two pictures were used, one being itch-related and one being neutral (i.e., 20 stimuli presenting neutral skin and 20 presenting a neutral object), validated and used in earlier studies ( 10 , 13 ). An itch-related picture showed someone scratching their own body.…”

“…Awareness of the subliminally presented pictures during the ABM-training, was checked by two subjective awareness questions and an objective awareness check in line with an earlier study ( 13 ). Subjective awareness was assessed by directly asking whether participants noticed something special during the task (question 1) and if this was answered with yes, whether they noticed any pictures (question 2).…”

“…Descriptive statistics are given as mean ( M ) and standard deviation ( SD ) if not stated otherwise. Reliability of the dot-probe pre- and post-training was calculated with the package “splithalfr” ( 38 ) in line with earlier studies ( 13 , 16 ).…”

“…Furthermore, it has been researched whether visual itch-related stimuli draw attention towards their location, i.e., an attentional bias towards itch, which resulted in mixed findings so far ( 9–11 ). These studies have shown that attention for itch might differ between conscious and preconscious processing stages: while some studies found heightened conscious attention towards itch ( 9 ), others could not replicate this finding ( 10 , 11 ) and a recent finding suggests preconscious avoidance of itch-related stimuli ( 13 ). The importance of fast processing of itch is also supported by contagious itch which suggests very fast and maybe unconscious processing of itch-related gestures, e.g., scratching, which then induces itchiness in the observer ( 14 , 15 ).…”

“…Because attention is a continuum, including first orienting towards a stimulus, actual selective attention to a stimulus and eventual disengagement ( 23–25 ), attention can be biased at different stages of attentional processing ( 26 ) which is suggested by the inconsistend findings on attentional bias towards itch so far at different processing stages, e.g., conscious engagement and disengagement vs. preconscious orienting ( 9–11 , 13 ). However, preconscious ABM-trainings are scarce and actually lacking in itch.…”