Dynamics of nasal irritation from pulsed homologous alcohols

Abstract

Relatively, few studies have focused on how nasal irritation changes over time. To simulate the rhythm of natural respiration, subjects received 3-s pulses of volatile organic compounds interspersed with 3-s pulses of clean air. Each trial, subjects received 9 pulses of a chemical vapor over about 1 min. Subjects rated nasal irritation from each pulse using magnitude estimation. Within a trial, compound and concentration were fixed. Compound (ethanol, n-butanol, or n-hexanol) and concentration (4 levels for each compound) varied across trials. For all stimuli, rated irritation decreased over time (adaptation). Plots of log-rated intensity versus elapsed time were approximately linear (intensity decreased by a fixed ratio per unit time). Interestingly, the slopes of intensity versus time functions differed very little: Regardless of concentration and compound, rated irritation decreased by about 32% over the 9 pulses. The basic mechanism of short-term adaptation may be the same for the 3 alcohols studied. Regardless, these data suggest that very simple models might be able to describe some aspects of perceptual dynamics quite well.

Figure 1

Time course of a trial. Trials lasted 54 s, with cycles of 3 s of VOC-laden air followed by 3 s of clean air (or, for blanks, 3 s of clean air followed by 3 s of clean air). Subjects rated the intensity of nasal irritation from each VOC pulse via magnitude estimation.

Figure 2

Ratings of intensity as a function of pulse number (elapsed time) and concentration. x axis: pulse number (elapsed time). y Axis: log-rated intensity (“2” is the value assigned to a standard of 12.5% v/v ethanol). (A) Ethanol. (B) n-Butanol. (C) n-hexanol. In each graph, the 4 data series represent different stimulus concentrations. The lines represent linear fits (least squares regression) to functions of log intensity versus pulse number. Error bars represent standard errors of the means.