Effect of Stimulus Duration on the Electrogustometric Threshold

Electrogustometry (EGM)-the psychophysical measurement of human taste function by the application of weak electric currents to taste bud fields-has proved useful in clinical and research settings. Although EGM detection thresholds have been reported to be sensitive to stimulus duration, studies differ on this point and have not been definitive. Most have employed too few subjects, electrogustometers incapable of presenting very low currents, and non-forced-choice tests that confound sensitivity with the response criterion.

Anodal single-staircase EGM detection thresholds were determined for 50 healthy subjects at 0.5, 1.0, 1.5, and 2.0 s stimulus durations using an electrogustometer capable of producing currents as low as 0.25 µA (-30 dB) and a unique bipolar electrode that confined current to the lingual surface. Means were compared using analysis of variance. Stimulus duration trials were counterbalanced in order.

The EGM threshold values were remarkably stable and did not differ across stimulus durations ranging from 0.5 to 2 s (p = 0.941, η ² = 0.003). Women exhibited lower thresholds than men [respective mean (95% CI) threshold values = 2.53 µA (1.90, 3.36) vs. 4.17 µA (3.69, 6.46); p = 0.007, η ² = 0.123] and thresholds increased monotonically with age (p = 0.005, η ² = 0.139). No influences of tongue side (p = 0.779, η ² = 0.002) were evident.

Employing state-of-the-art EGM and a sizable sample size, we definitively demonstrate that EGM threshold values are equivalent for stimulus durations ranging from 0.5 to 2 s. This clarifies the discrepant literature on this point and makes direct comparisons across a number of studies possible.