Event-related potentials to intranasal trigeminal stimuli change in relation to stimulus concentration and stimulus duration.

Few data are available on the relation of EEG-derived trigeminal event-related potentials (ERPs) to stimulus duration or stimulus concentration. Thus, the aim of this study was to analyze the relation between ERP components and both stimulus duration and stimulus concentration. Twenty healthy young subjects participated. Trigeminal ERPs were recorded after stimulation with CO(2). Five concentrations (45 to 65% volume per volume CO(2)) and five stimulus durations (100 to 300 msec) were used. Trigeminal ERPs were quantified in terms of amplitudes and latencies of its major peaks N(410) (termed N1) and P(622) (termed P3). The relation between stimulus duration, concentration, and amplitudes or latencies of trigeminal ERP components could be described as a model of power, following the formula p = b + k.I g1.D(g2). A linear relationship was found between stimulus concentration, amplitude N1, and amplitude P3, and between stimulus duration and amplitude P3 respectively. Furthermore, a linear relationship was seen between intensity ratings, and stimulus duration and concentration. These data confirm that the different ERP components encode different stimulus characteristics. Specifically, later components of the trigeminal ERP encode not only stimulus concentration but, other than earlier ERP components, also encode stimulus duration. Thus, they reflect the integration of stimuli over relatively long periods of time.