Extracranial and digital vascular events: an analysis of methods in BVP amplitude and biofeedback research.

The purpose of the present study was to assess and compare the effects of within and between-session exposure to environmental context on left temporal artery pulse amplitude, right temporal artery pulse amplitude, and left digital pulse amplitude. Subjects were individually tested for 20 min daily over a period of eight consecutive days. A significant interaction was found for Position X Interval. These results show that exposure to the experimental context occurs with diametrically opposite effects on temporalis and digital pulse amplitude within session. Moreover, these results would support the hypothesis that controversial findings within the headache and biofeedback literature may be partially attributable to methodological differences where, for example, different authors use different transducer locations and/or evaluate pulse amplitude at different points within or among sessions. Indeed, research on the effects or lack thereof of therapeutic manipulations may have little or nothing to do with the intervention or experimental manipulations themselves. These effects may be masked or augmented by subject and methodological confounds during baseline and testing conditions.