Attentional Bias Modification Training for Itch: A Proof-of-Principle Study in Healthy Individuals

Neural mechanisms underlying attentional bias modification in fibromyalgia patients: a double-blind ERP study

There is a growing interest in the potential benefits of attentional bias modification (ABM) training in chronic pain patients. However, studies examining the effectiveness of ABM programs in fibromyalgia patients have demonstrated inconclusive effects on both behavioral indices and clinical symptoms. Additionally, underlying neural dynamics of ABM effects could yield new insights but remain yet unexplored. Current study, therefore, aims to investigate the effects of ABM training on known neural electrophysiological indicators of attentional bias to pain (P2, N2a). Thirty-two fibromyalgia patients were enrolled and randomly assigned to an ABM training (N = 16) or control (N = 16) condition (2 weeks duration). Within the ABM training condition participants performed five sessions consisting of a modified version of the dot-probe task in which patients were trained to avoid facial pain expressions, whereas in the control group participants performed five sessions consisting of a standard version of the dot-probe task. Potential ABM training effects were evaluated by comparing a single pre- and post-treatment session, in which event-related potentials (ERPs) were recorded in response to both facial expressions and target stimuli. Furthermore, patients filled out a series of self-report questionnaires assessing anxiety, depression, pain-related worrying, fear of pain, fatigue and pain status. After training, results indicated an overall reduction of the amplitude of the P2 component followed by an enhancement of N2a amplitude for the ABM condition compared to control condition. In addition, scores on anxiety and depression decreased in patients assigned to the training condition. However, we found no effects derived from the training on pain-related and fatigue status. Present study offers new insights related to the possible neural mechanisms underlying the effect of ABM training in fibromyalgia. Clinical trial (TRN: NCT05905159) retrospectively registered (30/05/2023).

Subliminal attentional bias modification training for itch

Introduction

Itch is unpleasant and induces the urge to scratch. This is adaptive to remove the itch-inducing stimulus from the skin. Accordingly, itch draws attention to protect our bodily integrity. Recent studies investigated whether attention is preferentially drawn towards its location, i.e., attentional bias (AB), and also whether this bias could be changed in healthy individuals. So far, results are mixed concerning the existance of an attentional bias towards itch stimuli in healthy individuals as well as the impact of modifications. However, available studies have typically focused on conscious processing and might miss preconscious aspects of attention and potential biases at these stages.

Methods

This study included 117 healthy individuals who underwent a subliminal Attentional Bias Modification (ABM)- training for itch based on a dot-probe paradigm with itch- related pictures. Participants were randomly assigned to a training towards itch group, a training away from itch group and a control group. This was done by manipulating the itch-target congruency of the dot-probe task during a training block. Pre- and post-training assessments were regular dot-probe tasks. Exploratorily, also attentional inhibition, cognitive flexibility and itch-related cognitions were assessed. Lastly, participants received an itchy stimulus on the inner forearm before and after the ABM-training to assess potential effects on itch sensitivity.

Results

Results showed no AB towards itch across groups at baseline, i.e., pre-training, but an AB away from itch, hence, avoidance of itch, post-training. Further analyses showed that this effect was driven by an attentional bias away from itch in the control group, while there were no significant effects in the experimental groups. There was no effect on itch sensitivity.

Conclusion

These findings are in line with recent studies on conscious ABM-training for itch and pain that also did not find significant training effects. Therefore, it is suggested that the field of AB might need to reconsider the current assessment of AB. Moreover, AB is probably a dynamic process that is highly dependent on current itch-related goals and relevance of itch in a specific situation. This suggests that processes probably differ in patients with chronic itch and that also ABM-training might work differently in these populations.

Clinical trial registration

https://trialsearch.who.int/Trial2.aspx?TrialID=NTR7561, identifier NTR7561.

The prelimbic cortex regulates itch processing by controlling attentional bias

Itch is a complex and unpleasant sensory experience. Recent studies have begun to investigate the neural mechanisms underlying the modulation of sensory and emotional components of itch in the brain. However, the key brain regions and neural mechanism involved in modulating the attentional processing of itch remain elusive. Here, we showed that the prelimbic cortex (PrL) is associated with itch processing and that the manipulation of itch-responsive neurons in the PrL significantly disrupted itch-induced scratching. Interestingly, we found that increasing attentional bias toward a distracting stimulus could disturb itch processing. We also demonstrated the existence of a population of attention-related neurons in the PrL that drive attentional bias to regulate itch processing. Importantly, itch-responsive neurons and attention-related neurons significantly overlapped in the PrL and were mutually interchangeable in the regulation of itch processing at the cellular activity level. Our results revealed that the PrL regulates itch processing by controlling attentional bias.