Energetic and informational masking place dissociable demands on listening effort: Evidence from simultaneous electroencephalography and pupillometrya).

The task of processing speech masked by concurrent speech/noise can pose a substantial challenge to listeners. However, performance on such tasks may not directly reflect the amount of listening effort they elicit. Changes in pupil size and neural oscillatory power in the alpha range (8-12 Hz) are prominent neurophysiological signals known to reflect listening effort; however, measurements obtained through these two approaches are rarely correlated, suggesting that they may respond differently depending on the specific cognitive demands (and, by extension, the specific type of effort) elicited by specific tasks. This study aimed to compare changes in pupil size and alpha power elicited by different types of auditory maskers (highly confusable intelligible speech maskers, speech-envelope-modulated speech-shaped noise, and unmodulated speech-shaped noise maskers) in young, normal-hearing listeners. Within each condition, the target-to-masker ratio was set at the participant's individually estimated 75% correct point on the psychometric function. The speech masking condition elicited a significantly greater increase in pupil size than either of the noise masking conditions, whereas the unmodulated noise masking condition elicited a significantly greater increase in alpha oscillatory power than the speech masking condition, suggesting that the effort needed to solve these respective tasks may have different neural origins.

Strength of target source segregation cues affects the outcome of speech-on-speech masking experiments.

In speech-on-speech listening experiments, some means for designating which talker is the "target" must be provided for the listener to perform better than chance. However, the relative strength of the segregation variables designating the target could affect the results of the experiment. Here, we examine the interaction of two source segregation variables-spatial separation and talker gender differences-and demonstrate that the relative strengths of these cues may affect the interpretation of the results. Participants listened to sentence pairs spoken by different-gender target and masker talkers, presented naturally or vocoded (degrading gender cues), either colocated or spatially separated. Target and masker words were temporally interleaved to eliminate energetic masking in either an every-other-word or randomized order of presentation. Results showed that the order of interleaving had no effect on recall performance. For natural speech with strong talker gender cues, spatial separation of sources yielded no improvement in performance. For vocoded speech with degraded talker gender cues, performance improved significantly with spatial separation of sources. These findings reveal that listeners may shift among target source segregation cues contingent on cue viability. Finally, performance was poor when the target was designated after stimulus presentation, indicating strong reliance on the cues.

Speech intelligibility and talker gender classification with noise-vocoded and tone-vocoded speech.

Vocoded speech provides less spectral information than natural, unprocessed speech, negatively affecting listener performance on speech intelligibility and talker gender classification tasks. In this study, young normal-hearing participants listened to noise-vocoded and tone-vocoded (i.e., sinewave-vocoded) sentences containing 1, 2, 4, 8, 16, or 32 channels, as well as non-vocoded sentences, and reported the words heard as well as the gender of the talker. Overall, performance was significantly better with tone-vocoded than noise-vocoded speech for both tasks. Within the talker gender classification task, biases in performance were observed for lower numbers of channels, especially when using the noise carrier.

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

Acoustic beamforming has been shown to improve identification of target speech in noisy listening environments for individuals with sensorineural hearing loss. This study examined whether beamforming would provide a similar benefit for individuals with aphasia (acquired neurological language impairment). The benefit of beamforming was examined for persons with aphasia (PWA) and age- and hearing-matched controls in both a speech masking condition and a speech-shaped, speech-modulated noise masking condition. Performance was measured when natural spatial cues were provided, as well as when the target speech level was enhanced via a single-channel beamformer. Because typical psychoacoustic methods may present substantial experimental confounds for PWA, clinically guided modifications of experimental procedures were determined individually for each PWA participant. Results indicated that the beamformer provided a significant overall benefit to listeners. On an individual level, both PWA and controls who exhibited poorer performance on the speech masking condition with spatial cues benefited from the beamformer, while those who achieved better performance with spatial cues did not. All participants benefited from the beamformer in the noise masking condition. The findings suggest that a spatially tuned hearing aid may be beneficial for older listeners with relatively mild hearing loss who have difficulty taking advantage of spatial cues.

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

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 cognitive-linguistic 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.

Between-session and within-session intra-individual variability in attention in aphasia.

Persons with aphasia (PWA) have been found in many previous studies to exhibit impaired performance on attention processing tasks, even when these tasks do not contain linguistic stimuli. There is also some evidence that as individuals, PWA may show more intra-individual variability (i.e. time-based fluctuations) in attention than healthy controls. The current study systematically examines two types of intra-individual variability in attention in aphasia, between-session intra-individual variability (BS-IIV) and within-session intra-individual variability (WS-IIV), looking in particular at how task demands impact these dimensions of performance. We administered five novel attention tasks with varying processing demands, three non-linguistic and two linguistic, to 20 PWA and 20 similar-aged healthy controls. Results showed that PWA exhibited higher levels of WS-IIV than controls but that levels of BS-IIV were similar between the two groups. Increased task demands were found to result in increased BS-IIV and WS-IIV for both groups, and there was some evidence suggesting that the addition of language demands may further increase both WS-IIV and BS-IIV in the PWA group. In addition to these group differences, substantial inter-individual variability in WS-IIV and BS-IIV was observed within the PWA group. These findings have implications for better understanding attentional fluctuations in aphasia, as well as how it relates to language deficits in this population, and potentially for better understanding language treatment outcomes.

Does Naming Therapy Make Ordering in a Restaurant Easier? Dynamics of Co-Occurring Change in Cognitive-Linguistic and Functional Communication Skills in Aphasia.

PURPOSE: This study was conducted to investigate the static and dynamic relationships between impairment-level cognitive-linguistic abilities and activity-level functional communication skills in persons with aphasia (PWA). METHOD: In Experiment 1, a battery of standardized assessments was administered to a group of PWA (N = 72) to examine associations between cognitive-linguistic ability and functional communication at a single time point. In Experiment 2, impairment-based treatment was administered to a subset of PWA from Experiment 1 (n = 39) in order to examine associations between change in cognitive-linguistic ability and change in function and associations at a single time point. RESULTS: In both experiments, numerous significant associations were found between scores on tests of cognitive-linguistic ability and a test of functional communication at a single time point. In Experiment 2, significant treatment-induced gains were seen on both types of measures in participants with more severe aphasia, yet cognitive-linguistic change scores were not significantly correlated with functional communication change scores. CONCLUSIONS: At a single time point, cognitive-linguistic and functional communication abilities are associated in PWA. However, although changes on standardized assessments reflecting improvements in both types of skills can occur following an impairment-based therapy, these changes may not be significantly associated with each other.

Evaluating Treatment and Generalization Patterns of Two Theoretically Motivated Sentence Comprehension Therapies.

Purpose: The current study examined treatment outcomes and generalization patterns following 2 sentence comprehension therapies: object manipulation (OM) and sentence-to-picture matching (SPM). Findings were interpreted within the framework of specific deficit and resource reduction accounts, which were extended in order to examine the nature of generalization following treatment of sentence comprehension deficits in aphasia. Method: Forty-eight individuals with aphasia were enrolled in 1 of 8 potential treatment assignments that varied by task (OM, SPM), complexity of trained sentences (complex, simple), and syntactic movement (noun phrase, wh-movement). Comprehension of trained and untrained sentences was probed before and after treatment using stimuli that differed from the treatment stimuli. Results: Linear mixed-model analyses demonstrated that, although both OM and SPM treatments were effective, OM resulted in greater improvement than SPM. Analyses of covariance revealed main effects of complexity in generalization; generalization from complex to simple linguistically related sentences was observed both across task and across movement. Conclusions: Results are consistent with the complexity account of treatment efficacy, as generalization effects were consistently observed from complex to simpler structures. Furthermore, results provide support for resource reduction accounts that suggest that generalization can extend across linguistic boundaries, such as across movement type.

The effect of a sentence comprehension treatment on discourse comprehension in aphasia.

BACKGROUND: While it is well understood that individuals with aphasia have difficulty with discourse comprehension, very few studies have examined the nature of discourse comprehension deficits in aphasia and the potential for improvement in discourse comprehension after rehabilitation. To address the first goal, we previously developed the Test of Syntactic Effects on Discourse Comprehension (TSEDC), which provides a measure of the extent to which a participant's sentence comprehension ability aids in comprehending passages (Levy et al., 2012). AIMS: The goal of this study was to examine the effect of a sentence comprehension treatment on the TSEDC to assess if training participants to understand sentences of different syntactic complexity would improve their ability to understand passages that vary by their level of syntactic complexity. METHODS & PROCEDURES: Forty participants with aphasia received sentence comprehension treatment using one of two syntactic comprehension tasks: object manipulation (OM) or sentence to picture matching (SPM). The dependent measure was improved sentence comprehension of one sentence type in one task-related protocol, with the order of task and structure counterbalanced across participants. Before and after treatment, participants also completed a self-paced auditory story comprehension task which involved 9 passages that contained either semantically reversible canonical sentences (simple passages) or semantically reversible noncanonical sentences (complex passages). At the end of each passage, participants were asked explicit or implicit questions about the story. Accuracy and reaction times were measured for each patient for each story before and after treatment. OUTCOMES & RESULTS: Analysis of the treatment data revealed that participants improved in their ability to understand trained sentences (both in terms of effect size and percent change on trained structure), irrespective of whether the trained task was SPM or OM. There was no significant relationship between treatment improvements on the SPM/OM treatment (even when the task targeted in treatment was controlled for) and changes in performance on the TSEDC. Also, there was no significant improvement in TSEDC accuracy after treatment, even when various aspects of the narrative passages, including passage complexity (simple/complex), the nature of sentence type (semantically constrained/semantically reversible) and the nature of questions asked (explicit or implicit) were accounted for. CONCLUSIONS: Inherent differences between the sentence comprehension treatment and the TSEDC may have precluded generalization.

Between-session intra-individual variability in sustained, selective, and integrational non-linguistic attention in aphasia.

A number of studies have identified impairments in one or more types/aspects of attention processing in patients with aphasia (PWA) relative to healthy controls; person-to-person variability in performance on attention tasks within the PWA group has also been noted. Studies using non-linguistic stimuli have found evidence that attention is impaired in this population even in the absence of language processing demands. An underlying impairment in non-linguistic, or domain-general, attention processing could have implications for the ability of PWA to attend during therapy sessions, which in turn could impact long-term treatment outcomes. With this in mind, this study aimed to systematically examine the effect of task complexity on reaction time (RT) during a non-linguistic attention task, in both PWA and controls. Additional goals were to assess the effect of task complexity on between-session intra-individual variability (BS-IIV) in RT and to examine inter-individual differences in BS-IIV. Eighteen PWA and five age-matched neurologically healthy controls each completed a novel computerized non-linguistic attention task measuring five types of attention on each of four different non-consecutive days. A significant effect of task complexity on both RT and BS-IIV in RT was found for the PWA group, whereas the control group showed a significant effect of task complexity on RT but not on BS-IIV in RT. Finally, in addition to these group-level findings, it was noted that different patients exhibited different patterns of BS-IIV, indicating the existence of inter-individual variability in BS-IIV within the PWA group. Results may have implications for session-to-session fluctuations in attention during language testing and therapy for PWA.

Development of a theoretically based treatment for sentence comprehension deficits in individuals with aphasia.

PURPOSE: Two new treatments, 1 based on sentence to picture matching (SPM) and the other on object manipulation (OM), that train participants on the thematic roles of sentences using pictures or by manipulating objects were piloted. METHOD: Using a single-subject multiple-baseline design, sentence comprehension was trained on the affected sentence type in 1 task-related protocol in 15 participants with aphasia. The 2 tasks were SPM and OM; the treatment stimuli were object relatives, object clefts, passives, and unaccusatives, as well as two control structures-object relatives with a complex noun phrase (NP) and active sentences with three NPs. RESULTS: The criteria for efficacious treatment was an increase in the level of performance from the pretreatment probes to the posttreatment probes for the treated structure such that accuracy rose from at or below chance to above chance and either (a) accuracy rose by 33% or (b) the effect size was 2.6. Based on these criteria, the success rate for training the target structure was 2/6 participants in the SPM condition and 4/7 participants in the OM condition. CONCLUSION: The outcome of this study illustrates the utility of this theoretically motivated and efficacious treatment for sentence comprehension deficits in individuals with aphasia.