All eyes on us?: Validation of an addiction-associated picture-set for the use in high-resolution eye-tracking research

Introduction:

According to the well-known "incentive sensitization" theory of Robinson and Berridge (1993) the repeated intake of addiction-causing drugs leads to an association of previously neutral, but with the addiction associated stimuli, with the rewarding effects of the substance itself by sensitizing the dopaminergic activity of the Striatum. As a result, addiction-associated stimuli appear attractive and can direct the attention of the individual ("attentional bias"). Studies have confirmed this theoretical assumption. It could be shown that the presentation of addiction-associated stimuli leads to shorter response times to a subsequent target stimulus than the presentation of neutral stimuli. These findings have been demonstrated in smokers, alcohol-addicted patients and individuals with obesity. However, picture-sets available so far have not been optimized for eye-tracking-devices. In order to increase the significance of eye-tracking examinations various picture-variables are of high relevance, such as brightness, contrast and complexity.

Methods:

The arbitrary and non-arbitrary reactions to the image-stimuli are recorded with the help of a stationary Eyelink 1000 Plus eye-tracker. The eye-tracking system is able to non-invasivly record the eye movements (fixations, saccades, pupil diameter) and reaction times of the subjects, as well as the subjective evaluation of the image-stimuli during the processing of two tasks. The examination is performed on four groups of subjects: 1.) Alcohol-addicted patients, 2.) nicotine-addicted patients, 3.) overweight patients, 4.) healthy, normal-weight subjects in a pseudo-randomized scheme of the picture-sequence on the basis of an attentional-bias (dotprobe-task with addiction-associated stimuli and neutral stimuli) and a cue-reactivity-paradigm with pictures of the four stimulus-categories: Alcohol, tobacco, food, neutral.

Results:

The preliminary results of the study showed that there was a correlation between the objectively measured eye movements and the subjectively stated assessment measures, depending on the experimental-group affiliation compared to the control-group. There were differences depending on the stimulus-categories and subject-affiliation during cue-reactivity, as well as differences in the response time during the attentional-bias-dotprobe-paradigm, too.

Conclusion:

The results of the study allow a better characterization of the connections between the subjective perception of addiction-associated and neutral image stimuli with objective measures of eye movement (fixation, pupil size, saccades) on certain stimulus characteristics (context, complexity) as well as the temporal course of attention directed to these stimuli. By identifying the mechanisms that have a specific influence on the development of attention-focusing and craving in addicted patients, an improved care of patients (e.g. by improving existing cue-exposure procedures with optimized image material) and a long-term reduction of the probability of a possible relapse can be achieved.