Effects of Acquired Aphasia on the Recognition of Speech Under Energetic and Informational Masking Conditions

Abstract

Persons with aphasia (PWA) often report difficulty understanding spoken language in noisy environments that require listeners to identify and selectively attend to target speech while ignoring competing background sounds or "maskers." This study compared the performance of PWA and age-matched healthy controls (HC) on a masked speech identification task and examined the consequences of different types of masking on performance. Twelve PWA and 12 age-matched HC completed a speech identification task comprising three conditions designed to differentiate between the effects of energetic and informational masking on receptive speech processing. The target and masker speech materials were taken from a closed-set matrix-style corpus, and a forced-choice word identification task was used. Target and maskers were spatially separated from one another in order to simulate real-world listening environments and allow listeners to make use of binaural cues for source segregation. Individualized frequency-specific gain was applied to compensate for the effects of hearing loss. Although both groups showed similar susceptibility to the effects of energetic masking, PWA were more susceptible than age-matched HC to the effects of informational masking. Results indicate that this increased susceptibility cannot be attributed to age, hearing loss, or comprehension deficits and is therefore a consequence of acquired cognitivelinguistic impairments associated with aphasia. This finding suggests that aphasia may result in increased difficulty segregating target speech from masker speech, which in turn may have implications for the ability of PWA to comprehend target speech in multitalker environments, such as restaurants, family gatherings, and other everyday situations.

Assessing the benefit of acoustic beamforming for listeners with aphasia using modified psychoacoustic methods

“…Additionally, assessing the benefit of acoustic beamforming in PWA may provide information about the factors that facilitate or hinder the ability of PWA to understand speech in complex acoustic environments. While our previous work has found that PWA perform more poorly than controls under a condition where maskers consist of intelligible speech spatially separated from the target ( Villard and Kidd, 2019 ), the precise reason(s) for this are not yet known. Because beamforming provides the listener with both a distinct advantage (an improved TMR) and a distinct disadvantage (removal of binaural spatial cues), relative to a natural listening condition, it may allow us to learn more about what drives PWA performance.…”

“…(2017) for a series of recent reviews], has high relevance for everyday communication, as real-world conversations often take place in settings that are acoustically complex. While the majority of past research on receptive speech processing in persons with aphasia (PWA) has focused on auditory language comprehension in quiet settings, several recent studies have directly investigated the ability of persons with aphasia (PWA) to selectively attend to and understand speech in the presence of auditory maskers [e.g., Rankin et al (2014) and Villard and Kidd (2019) ]. These studies have provided evidence that PWA—even, in some cases, PWA with milder aphasia types thought to be characterized primarily by expressive language deficits—require higher target-to-masker ratios (TMRs) than do age-matched controls in order to successfully understand target speech.…”

“…Our recent study on the respective effects of EM and IM in PWA found that when simple target sentences were masked by speech-shaped, speech envelope-modulated noise—a high-EM, low-IM condition—PWA and age-matched controls performed similarly. However, when the same sentences were masked by intelligible speech—a high-IM, low-EM condition—PWA required significantly higher TMRs in order to comprehend the target sentences ( Villard and Kidd, 2019 ). These results suggest that PWA experience a particular difficulty in perceptually segregating target speech from masker speech and/or selectively attending to target speech.…”

“…The first and primary aim was simply to determine whether acoustic beamforming could provide a benefit for PWA in understanding speech in acoustically complex environments. Although prior work had demonstrated that beamforming can provide a benefit for listeners with SNHL, it could not be assumed that PWA would receive a similar benefit, despite the evidence suggesting that persons with SNHL and PWA both experience difficulty understanding speech in complex acoustic environments [e.g., Kidd et al (2019) and Villard and Kidd (2019) ]. This is because the factors underlying these two groups' difficulties almost certainly differ, particularly in terms of whether the limitation on performance is predominantly peripheral or central in origin.…”

“…Notably, because aphasia is more common in older individuals, many PWA may also have some age-related peripheral hearing loss, and thus may also experience increased EM. However, the limited evidence available has shown that additional, centrally based processing problems likely are present ( Villard and Kidd, 2019 ), potentially resulting in a mixed peripheral-central processing deficit. As discussed earlier, the extent to which PWA can utilize various sound source segregation cues currently is not known and the extent to which enhancing specific cues—such as segregation of competing speech sounds by level from a single-channel beamformer—is beneficial also is not clear.…”