How To Make Calibration Less Painful. A Proposition Of An Automatic, Reliable And Time-Efficient Procedure.

BackgroundIn neurophysiological pain studies, multiple types of calibration methods are used to quantify the individual pain sensation stimuli that have different modalities. However, such studies often lack calibration procedure implementation, have a vague protocol description, do not provide data quality quantification, or even omit required control for gender pain differences. All this hampers not only study repetition but also interexperimental comparisons. Moreover, typical calibration procedures are long and require a high number of stimulations which may cause participants discomfort and stimuli habituation. MethodTo overcome those shortcomings, we present an automatic staircase pain calibration method for A-delta-specific electrical stimulation adjusted to the magnetoencephalography environment. We provide an in-depth data analysis of the collected self-reports from seventy healthy volunteers (37 males) and propose a method based on a dynamic truncated linear regression model (tLRM). We compare its estimates for the sensation (t), and pain (T) thresholds, as well as for the mid-pain stimulation (MP), with those calculated using a traditional threshold method and standard linear regression models. ResultsCompared to the other threshold methods, tLRM exhibits higher R2 and requires 36% fewer stimuli application and has significantly higher t and lower T and MP intensities. Regarding sex differences, both lower t and T were found for females compared to males, regardless of the calibration method. ConclusionsThe proposed tLRM method quantifies the quality of the calibration procedure, minimizes its duration and invasiveness, as well as provides validation of linearity between stimuli intensity and subjective scores, making it an enabling technique for further studies. Moreover, our results highlight the importance of control for gender in pain studies. SummaryThe purpose of this study was to shorten and automatize the calibration method which is an enabling technique for realizing neurophysiological studies on pain. The proposed method is based on a dynamic truncated linear regression model and was shown to require 36% fewer stimuli application compared to the traditional staircase method. Furthermore, the calibration was adjusted to A-delta specific intraepidermal electrical stimulation, quantifies the quality of the resulting calibration parameters and provides a validation of linearity between stimuli intensity and subjective scores. The results also highlight the importance of control for participant gender in studies where different types of stimulation are used to induce pain sensation.