Implicit attention to itch: an exploratory study

The mechanisms underlying chronic pain are assumed to be based on altered
signal processing and central sensitization processes. These processes lead to
pain responses that are exaggerated, prolonged and spread widely. Similar
mechanisms of altered signal processing and central sensitization are supposed
to underlie chronic itch symptoms.
One of the key mechanisms in the perception of somatosensory sensations, e.g.,
itch and pain, are attentional processes. Attentional processes determine the
prioritization of signal processing, e.g., of somatosensory stimuli, by
exerting the function of a gatekeeper that processes signals by their saliency,
for example when signals are relevant and/or threatening. Focusing attention on
somatosensory stimuli is protective in the case of physical threat when
attentional focusing leads to faster detection and more accurate discrimination
of for example pain. However, in chronic pain the fear-driven unintentional
process of attending (i.e. hypervigilance) can aggravate the pain symptoms. In
view of the similarities between pain and itch, similar mechanisms of
attentional processes might also be relevant to itch. However, the role of
attention in itch has not yet been investigated systematically.

The objective of the study is to experimentally investigate attentional
focusing on itch. The primary focus will be on an automatic level of attending
to somatosensory itch stimuli. Secondary, automatic attentional focusing on
itch will also be investigated by use of visual itch stimuli in the dot-probe
task and modified Stroop task. In addition, attentional focusing will be
investigated on an intentional level (i.e., of which one is aware) by use of
questionnaires.

This is an experimental study in which two tasks are used to investigate
automatic attentional focusing on itch. The first task, the somatosensory
attention task for itch, is based on the sensory spatial cueing task, which has
been used by our collaborating partners from Ghent University with respect to
pain. The second task is the dot-probe computer task, which has frequently been
applied to measure attentional focusing to pain. Feasibility of these for itch
adapted tasks will be investigated in healthy subjects. In addition, a modifed
Stroop task for itch will be used to measure attentional focusing on itch words
and validated questionnaires measuring attentional focusing on bodily
sensations will be administered.

Potential participants will first complete a screening questionnaire (10 min).
Participants will then visit the lab at the Faculty of Social and Behavioural
Sciences of Leiden University once for approximately 70 minutes. For the
somatosensory attention task for itch (which has frequently been used for pain
by our collaborating partners from Ghent University), itch will be induced
non-invasively by means of electrical stimulation, according to a method that
has been validated by our research group and frequently been applied the past
years. The dot-probe computer task has frequently been used in previous
research, e.g., in relation to pain. The modified Stroop task for itch is
currently being used in other studies of our research group and patients and
healthy participants, who experienced the task as not-burdensome. The tasks are
not difficult, but only require concentration. Moreover, a series of validated
questionnaires will be administered to assess relevant individual
characteristics. No risks are involved with participation in this study.