The effect of dopamine on the comprehension of spectrally-shifted noise-vocoded speech: a pilot study

Objectives: Cochlear implantation has proven beneficial in restoring hearing. However, success is variable, and there is a need for a simple post-implantation therapy that could significantly increase implantation success. Dopamine has a general role in learning and in assigning value to environmental stimuli. We tested the effect of dopamine in the comprehension of spectrally-shifted noise-vocoded (SSNV) speech, which simulates, in hearing individuals, the signal delivered by a cochlear implant (CI). Design and study sample: Thirty-five participants (age = 38.0 +/- 10.1 SD) recruited from the general population were divided into three groups. We tested SSNV speech comprehension in two experimental sessions. In one session, a metabolic precursor of dopamine (L-DOPA) was administered to participants in two of the groups; a placebo was administered in the other session. Results: A single dose of L-DOPA interacted with training to improve perception of SSNV speech, but did not significantly accelerate learning. Conclusions: These findings are a first step in exploring the use of dopamine to enhance speech understanding in CI patients. Replications of these results using SSNV in individuals with normal hearing, and also in CI users, are needed to determine whether these effects can translate into benefits in everyday language comprehension.