Background
Willfully not responding to auditory stimuli hampers accurate behavioral measurements. An objective measure of covert manual suppression recorded during response tasks may be useful to assess the veracity of responses to stimuli.

Purpose
To investigate whether the Lateralized Readiness Potential (LRP), an electrophysiological measure of corticomotor response and suppression, may be of use in determining when subjects hear but do not respond to pure tones.

Research Design
Within-subject repeated measures with a Go-NoGo paradigm.

Study Sample
Five males and five females (mean age=38.8, SD=8.8) underwent electrophysiology testing. All had normal hearing, except one.

Intervention
Subjects were tested in a condition where they consistently responded to tonal stimuli, and in a condition where intensity cued whether they should respond or not. Scalp-recorded cortical potentials and behavioral responses were recorded, along with a question that probed the perceived effort required to suppress responses to the stimuli.

Data Collection and Analysis
Electrophysiology data was processed with Independent Component Analysis and epoch-based artifact rejection. Averaged group and individual LRPs were calculated.

Results
Group averaged waveforms show that suppressed responses, cued by NoGo stimuli, diverge positively at approximately 300 ms poststimulus, when compared to performed (Go) responses. LRPs were comparable when Go responses were recorded in a separate condition in which subjects responded to all stimuli, and when Go and NoGo trials were included in the same condition. The LRP was not observed in one subject.

Conclusions
Subsequent to further investigation, the LRP may prove suitable in assessing the suppression of responses to audiometric stimuli, and thereby useful in cases where functional hearing loss is suspected.


Keywords: functional hearing loss; electrophysiology; lateralized readiness potential

Abbreviations: EEG= Electroencephalography; kΩ=kilo ohms; LRP=Lateralized Readiness Potential; μV=micro Volts