A Proposed Speech Discrimination Assessment Methodology Based on Event-Related Potentials to Visual Stimuli

Abstract

Objective and quantitative assessment methods are needed for the fitting of hearing aid parameters. This paper proposes a novel speech discrimination assessment method using electroencephalograms (EEGs). The method utilizes event-related potentials (ERPs) to visual stimuli instead of the conventionally used auditory stimuli. A spoken letter is played through a speaker as an initial auditory stimulus. The same letter can then be visually displayed on a screen as a match condition, or a different letter is displayed (mismatch condition). The participant determines whether the two stimuli represent the same letter or not. The P3 component or late positive potential (LPP) component are elicited when a participant detects either a match or mismatch between the auditory and visual stimuli, respectively. The hearing ability of each participant can be estimated objectively via analysis of these ERP components.

Automatic Speech Discrimination Assessment Methods Based on Event-Related Potentials (ERP)

“…Figure 2 shows the sequence of each trial in Methods 2 and 3. Method 2 was slightly adjusted from the method that was proposed by Morikawa et al [ 26 ]. Each trial started by playing a word through the laptop speaker for 500 ms then showing a picture for 1000 ms.…”

“…To test speech discrimination using an MMN-based method, the participants would be required to undergo many rounds of oddball tasks with different standard and deviant stimuli which would be time-consuming and repetitive. These limitations have led to various improvements and alternatives being proposed such as variations to the oddball paradigm [ 15 , 22 ], different analysis approaches [ 23 , 24 ], or an alternative method or marker [ 25 , 26 ].…”

“…Morikawa et al [ 26 ] proposed an alternative speech discrimination assessment method that utilized visual ERP that was induced by visual stimuli that was associated with an auditory stimuli instead of auditory ERP. In their method, the participants listened to a sound corresponding to a Japanese letter and then were shown a picture of a Japanese letter.…”

“…LPP was assumed to be similar to the P3b component [ 28 , 30 ] and was elicited when there was a mismatch between the expectation and feedback. To classify between the match and mismatch conditions, Morikawa et al [ 26 ] calculated a feature value from the average amplitude difference between the intervals where P3 and LPP were observed. This feature value was compared to a predetermined threshold value to separate between cases with successful and unsuccessful discrimination.…”

“…However, as mentioned, this method might be time-consuming as many rounds of oddball task are needed in order to get an assessment that covers all the meaningful contrasts in a language. A possible alternative to an MMN-based method is a visual-ERP-based method that was proposed by Morikawa et al [ 26 ] which was reported to have high accuracy. However, the use of Japanese letters limited the use of this method to literate patients only.…”