Effects of Lexical Variables on Silent Reading Comprehension in Individuals With Aphasia: Evidence From Eye Tracking

Eye Fixation Behaviors and Processing Time of People With Aphasia and Neurotypical Adults When Reading Narratives With and Without Text-to-Speech Support

BACKGROUND

Researchers have used eye-tracking technology to investigate eye movements in neurotypical adults (NAs) when reading. The technology can provide comparable information about people with aphasia (PWA). Eye fixations occurring when PWA do and do not have access to text-to-speech (TTS) technology are of interest because the support improves reading comprehension and decreases processing time for at least some PWA.

AIMS

This study's purpose was to examine forward, regressive, and off-track eye fixations when PWA and NAs read narratives in read-only (RO) and TTS conditions. A secondary aim was to examine the influence of eye fixations on processing time.

METHOD AND PROCEDURE

A Tobii Dynavox Pro Spectrum eye tracker recorded eye movements of nine PWA and nine NAs while reading narratives in two conditions. Movements of interest were forward fixations; within-word, within-sentence, and previous-sentence regressive fixations; and off-track fixations.

OUTCOMES AND RESULTS

PWA exhibited significantly more forward and regressive fixations in the RO than TTS condition, whereas NAs showed opposite behaviors. NAs had significantly more off-track fixations in the TTS than RO condition, whereas PWA exhibited no difference across conditions. PWA took significantly longer to process content in the RO condition, whereas NAs took longer in the TTS condition.

CONCLUSIONS

PWA and NAs differ in important ways when processing texts with and without TTS support. Examining eye-tracking data provides a means of gaining insight into the decoding and reading comprehension challenges of PWA and helps elucidate how assistive technology can mediate these challenges.

Eye Tracking Measures for Studying Language Comprehension Deficits in Aphasia: A Systematic Search and Scoping Review

Aim The aim of this scoping review is to identify the eye tracking paradigms and eye movement measures used to investigate auditory and reading comprehension deficits in persons with aphasia (PWA). Method MEDLINE via PubMed, Cochrane, CINAHL, Embase, PsycINFO, OTseeker, Scopus, Google Scholar, Grey Literature Database, and ProQuest Search (Dissertations & Theses) were searched for relevant studies. The Covidence software was used to manage the initial and full-text screening process for the search. Results and Discussion From a total of 1,803 studies, 68 studies were included for full-text screening. In addition, 418 records from gray literature were also screened. After full-text screening, 16 studies were included for this review-12 studies for auditory comprehension in PWA and four studies for reading comprehension in PWA. The review highlights the use of common eye tracking paradigms used to study language comprehension in PWA. We also discusse eye movement measures and how they help in assessing auditory and reading comprehension. Methodological challenges of using eye tracking are discussed. Conclusion The studies summarized in this scoping review provide evidence that the eye tracking methods are beneficial for studying auditory and reading comprehension in PWA.

Effects of animacy and sentence type on silent reading comprehension in aphasia: An eye-tracking study

The present study examined how healthy aging and aphasia influence the capacity for readers to generate structural predictions during online reading, and how animacy cues influence this process. Non-brain-damaged younger (n =24) and older (n =12) adults (Experiment 1) and individuals with aphasia (IWA; n =11; Experiment 2) read subject relative and object relative sentences in an eye-tracking experiment. Half of the sentences included animate sentential subjects, and the other half included inanimate sentential subjects. All three groups used animacy information to mitigate effects of syntactic complexity. These effects were greater in older than younger adults. IWA were sensitive to structural frequency, with longer reading times for object relative than subject relative sentences. As in previous work, effects of structural complexity did not emerge on IWA's first pass through the sentence, but were observed when IWA reread critical segments of the sentences. Thus, IWA may adopt atypical reading strategies when they encounter low frequency or complex sentence structures, but they are able to use animacy information to reduce the processing disruptions associated with these structures.

Setting the midpoint of sentences: The role of the left hemisphere

The human brain has a remarkable capacity to focus processing resources based on the features and the relevance of the task at hand. The two cerebral hemispheres contribute differentially to this capacity, with the left hemisphere linguistic and right hemisphere visuo-spatial abilities each offering unique contributions. For example, previous research has established that healthy participants set the subjective mid-point of written sentences more leftwards of center, compared to unpronounceable letter strings or simple lines. Remarkably, patients with right hemisphere damage exhibiting unilateral spatial neglect also show this pattern, even though, as well known in the literature, they tend toward a rightward- bias for non-linguistic stimuli. This evidence suggests that the leftward bias for sentential material is due to linguistic, mainly left-hemisphere mediated processes, which are largely unimpaired in right brain-damaged patients, and intact in heathy participants. To test this hypothesis, we compared sentence bisection performance to that of letter strings and simple lines in left brain-damaged patients (with and without aphasia). If the larger leftward bias in the bisection of sentential material is based on linguistic processes, then the left brain-damaged patients should show a reduction or absence of a leftward bias in sentence bisection. We tested twenty-four left brain-damaged patients (12 with aphasia and 12 without aphasia), and 24 age-matched elderly participants (patients and controls were all right-handed). Participants were asked to bisect 240 stimuli, comprising: (i) affirmative and interrogative clauses, (ii) sentences with lexical and syntactic violations, (iii) letter strings and (iv) simple lines. As predicted, neurologically intact participants showed larger leftward biases in bisecting written readable sentences compared to strings of letters. In contrast, the left hemispheredamaged patients (both with and without aphasia) showed no differences in bisecting sentences and letter strings or lines. These findings indicate that the larger leftward bias exhibited by healthy participants in the bisection of sentences is likely due to ortho-phonological coding taking place implicitly during the bisection task. This ortho-phonological coding is impaired with left brain damage - also in absence of apparent aphasia - leading to the left hemispheredamaged patients showing a reduced leftward bias in sentence bisection. These findings support the hypothesis that the leftward bias in the bisection of written sentences is the result of ortho-phonological influences rather than visual-spatial biases.

Perceptual span in individuals with aphasia

BACKGROUND

Perceptual span refers to the field of effective vision during reading comprehension. It is determined by many factors, including reading proficiency. No studies have investigated the perceptual span in people with reading comprehension impairments due to aphasia.

AIMS

The present study examined whether perceptual span is smaller in individuals with aphasia than controls.

METHODS AND PROCEDURES

The task was a gaze-contingent moving windows paradigm during silent reading using an eye tracker. Data from 11 individuals with aphasia and 15 neurotypical controls were analyzed.

OUTCOMES AND RESULTS

Perceptual span in individuals with aphasia was the fixated word plus one word to the right of fixation, whereas perceptual span in controls was the fixated word plus two words to the right of fixation.

CONCLUSION

Individuals with aphasia have a smaller perceptual span than controls, which likely reflects increased effort during reading comprehension.

The eyes reveal uncertainty about object distinctions in semantic variant primary progressive aphasia

At least three distinct variants of primary progressive aphasia (PPA) have been described, but they are difficult to distinguish early in the course, when individuals experience primarily anomia. People with svPPA are often the hardest to care for, because they have impaired comprehension of words and objects and often have negative changes in comportment. We sought to identify an early marker of semantic variant primary progressive aphasia (svPPA) and to enhance the understanding of the semantic deficit in svPPA. We hypothesized that the pattern of eye tracking in a word picture matching task can differentiate svPPA from other variants and can predict which participants with unclassifiable PPA will progress to svPPA. We tested 19 individuals with PPA on a word picture matching task with eye tracking. We found that individuals with svPPA were less accurate than other variants when the foils were semantic coordinates (horse-cow) or schematically related (horse-saddle), but not when they were thematically related (saw-horse) or unrelated. Moreover, even in the condition in which they were highly accurate (unrelated foils) they looked much more often to the foils and for longer, than other variants or controls. Unclassifiable PPA participants who eventually developed svPPA showed the same pattern. This abnormal pattern was associated with atrophy in bilateral temporal poles.