Validity of an eye-tracking method to index working memory in people with and without aphasia

Abstract

Background: Working memory (WM) is essential to auditory comprehension; thus understanding of the nature of WM is vital to research and clinical practice to support people with aphasia. A key challenge in assessing WM in people with aphasia is related to the myriad deficits prevalent in aphasia, including deficits in attention, hearing, vision, speech, and motor control of the limbs. Eye-tracking methods augur well for developing alternative WM tasks and measures in that they enable researchers to address many of the potential confounds inherent in tasks traditionally used to study WM. Additionally, eye-tracking tasks allow investigation of trade-off patterns between storage and processing in complex span tasks, and provide on-line response measures.

Aims: The goal of the study was to establish concurrent and discriminative validity of a novel eye movement WM task in individuals with and without aphasia. Additionally we aimed to explore the relationship between WM and general language measures, and determine whether trade-off between storage and processing is captured via eye-tracking measures.

Methods & Procedures: Participants with (n = 28) and without (n = 32) aphasia completed a novel eye movement WM task. This task, incorporating natural response requirements, was designed to circumvent potential confounds due to concomitant speech, motor, and attention deficits. The task consisted of a verbal processing component intermixed with presentation of colours and symbols for later recall. Performance on this task was indexed solely via eye movements. Additionally, participants completed a modified listening span task that served to establish concurrent validity of the eye-tracking WM task.

Outcomes & Results: Performance measures of the novel eye movement WM task demonstrated concurrent validity with another established measure of WM capacity: the modified listening span task. Performance on the eye-tracking task discriminated effectively between participants with and without aphasia. No consistent relationship was observed between WM scores and Western Aphasia Battery aphasia quotient and subtest scores for people with aphasia. Additionally, eye-tracking measures yielded no trade-off between processing and storage for either group of participants.

Conclusions: Results support the feasibility and validity of employing a novel eye-tracking method to index WM capacity in participants with and without aphasia. Further research is required to determine the nature of the relationship between WM, as indexed through this method, and specific aspects of language impairments in aphasia.

Keywords:

• Working memory
• Working memory assessment
• Eye-tracking
• Aphasia
• Cognitive processing
• Complex span tasks

Acknowledgments

This work was supported in part by an Ohio University Graduate Fellowship in the Communication Sciences and Disorders, International Graduate Student Award from the American Speech-Language and Hearing Foundation, Original Work Grant from the Graduate Student Senate at Ohio University, and funding from the National Institutes of Health/National Institute on Deafness and Other Communication Disorders and the National Science Foundation Biomedical Engineering Research to Aid Persons with Disabilities Program.

We thank Dr Jim Montgomery, Dr Jennifer Horner, Dr Alexander Sergeev, and Dr Danny Moates for their invaluable suggestions regarding study design, task development, and data analysis. We are grateful to Yoonsoo Lee for the development of the graphic stimuli. We express sincere gratitude to Dr Hans Kruse for prompt and extensive modification of eye-tracking and data analysis software. We thank Emily Boyer and JoLynn Vargas for assistance with data collection, and Sabine Heuer for her help and support with various stages of the project. We are sincerely grateful to Darlene Williamson, Melissa Richman, and the Stroke Comeback Center for assistance with participant recruitment.

Notes

¹ We performed all the primary analyses described in the results section with and without participants with visual field deficits. All the results remained unchanged.