Maria V. Ivanova

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

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.

A new modified listening span task to enhance validity of working memory assessment for people with and without aphasia

UNLABELLED Deficits in working memory (WM) are an important subset of cognitive processing deficits associated with aphasia. However, there are serious limitations to research on WM in aphasia largely due to the lack of an established valid measure of WM impairment for this population. The aim of the current study was to address shortcomings of previous measures by developing and empirically evaluating a novel WM task with a sentence-picture matching processing component designed to circumvent confounds inherent in existing measures of WM in aphasia. The novel WM task was presented to persons with (n=27) and without (n=33) aphasia. Results demonstrated high concurrent validity of a novel WM task. Individuals with aphasia performed significantly worse on all conditions of the WM task compared to individuals without aphasia. Different patterns of performance across conditions were observed for the two groups. Additionally, WM capacity was significantly related to auditory comprehension abilities in individuals with mild aphasia but not those with moderate aphasia. Strengths of the novel WM task are that it allows for differential control for length versus complexity of verbal stimuli and indexing of the relative influence of each, minimizes metalinguistic requirements, enables control for complexity of processing components, allows participants to respond with simple gestures or verbally, and eliminates reading requirements. Results support the feasibility and validity of using a novel task to assess WM in individuals with and without aphasia. LEARNING OUTCOMES Readers will be able to (1) discuss the limitations of current working memory measures for individuals with aphasia; (2) describe how task design features of a new working memory task for people with aphasia address shortcomings of existing measures; (3) summarize the evidence supporting the validity of the novel working memory task.

Russian normative data for 375 action pictures and verbs

The present article introduces a Russian-language database of 375 action pictures and associated verbs with normative data. The pictures were normed for name agreement, conceptual familiarity, and subjective visual complexity, and measures of age of acquisition, imageability, and image agreement were collected for the verbs. Values of objective visual complexity, as well as information about verb frequency, length, argument structure, instrumentality, and name relation, are also provided. Correlations between these parameters are presented, along with a comparative analysis of the Russian name agreement norms and those collected in other languages. The full set of pictorial stimuli and the obtained norms may be freely downloaded from http://neuroling.ru/en/db.htm for use in research and for clinical purposes.

A tutorial on aphasia test development in any language: Key substantive and psychometric considerations

Background: There are a limited number of aphasia language tests in the majority of the worlds commonly spoken languages. Furthermore, few aphasia tests in languages other than English have been standardised and normed, and few have supportive psychometric data pertaining to reliability and validity. The lack of standardised assessment tools across many of the worlds languages poses serious challenges to clinical practice and research in aphasia. Aims: The current review addresses this lack of assessment tools by providing conceptual and statistical guidance for the development of aphasia assessment tools and establishment of their psychometric properties. Main Contribution: A list of aphasia tests in the 20 most widely spoken languages is included. The pitfalls of translating an existing test into a new language versus creating a new test are outlined. Factors to be considered in determining test content are discussed. Further, a description of test items corresponding to different language functions is provided, with special emphasis on implementing important controls in test design. Next, a broad review of principal psychometric properties relevant to aphasia tests is presented, with specific statistical guidance for establishing psychometric properties of standardised assessment tools. Conclusions: This article may be used to help guide future work on developing, standardising and validating aphasia language tests. The considerations discussed are also applicable to the development of standardised tests of other cognitive functions.

The contribution of working memory to language comprehension: differential effect of aphasia type

Background: Experimental studies of short-term memory and working memory (WM) in aphasia fail to discriminate cognitive impairments of different aphasia types—non-fluent, Broca-type aphasia and fluent, Wernicke-type aphasia. However, based on the varying fundamental features of these two aphasia syndromes, the potentially different underlying mechanisms of impairment and scant preliminary evidence of varying cognitive deficits, a differential relationship between cognitive function and language processing in these two groups can be predicted. Aims: The current study investigates the hypothesis concerning the differential impact of cognitive impairments in individuals with fluent versus non-fluent aphasia types. Methods & Procedures: Participants with fluent (n = 19) and non-fluent (n = 16) aphasia and participants without brain damage (n = 36) were presented with an eye-tracking WM task. Additionally, individuals with aphasia completed two language comprehension tasks. Outcomes & Results: Results revealed significant decrease in WM capacity in individuals with aphasia compared with participants without brain damage. The two aphasia groups performed similarly on the WM and language tasks. Furthermore, for participants with non-fluent aphasia, it was revealed that WM makes a significant contribution to language comprehension, while for fluent individuals this relationship was not significant. Conclusions: Overall, the present data support the claim that there are cognitive deficits in aphasia and that these cognitive deficits tend to exacerbate the language impairments of persons with non-fluent aphasia types. The results are discussed in the context of varying mechanisms of impairment in different types of aphasia. The present findings have important implications both for the assessment and the treatment of individuals with aphasia and for understanding the nature of aphasia.

Sex-related differences in task switching: An fMRI study

Executive functions are the important human ability to program, regulate, and control the implementation of various cognitive processes, such as voluntary task switching. However, sex-related features of this process have not been characterized in sufficient detail. These distinctive features were studied using functional magnetic resonance imaging (fMRI) and neuropsychological examination. Seventy healthy subjects 21–48 years of age (36 men and 34 women) were involved in the study. During an fMRI experiment, the subjects had to shift their attention between two tasks (classifying figures according to their form or number). In neuropsychological examination participants completed a series of visual attention, task switching, and memory tests. The fMRI study revealed that a neuronal network controlling task switching in women includes the dorsolateral prefrontal and inferior parietal cortical areas, as well as the secondary areas of the visual cortex in the left hemisphere (LH) and the right hemisphere (RH), and cortical areas of the left and right hemispheres of the cerebellum. The same areas were activated in men and additional sites of activation were detected in the supplementary motor area, right insula, and left thalamus. Comparison of the groups of men and women revealed significantly stronger activation of the prefrontal areas in both LH and RH, the left parietal lobe, and the right insula in men, and moreover activation of the supplementary motor area was observed in men but not in women. Neuropsychological testing showed that men took significantly more time to perform tasks requiring task switching, searching for stimuli, and arranging them. The data obtained indicate differences in the organization of visual task switching processes in men and women.

Processing lexical ambiguity in sentential context: Eye-tracking data from brain-damaged and non-brain-damaged individuals

The purpose of the present study was to identify general and syndrome-specific deficits in the lexical processing of individuals with non-fluent and fluent aphasia compared to individuals without cognitive, neurological or language impairments. The time course of lexical access, as well as lexical selection and integration was studied using a visual-world paradigm in three groups of Russian speakers: 36 individuals in the control group, 15 individuals with non-fluent aphasia and eight individuals with fluent aphasia. Participants listened to temporarily ambiguous sentences wherein the context biased the interpretation of an ambiguous word toward one of its two meanings. In half of the experimental sentences, a reanalysis was needed upon encountering the disambiguating phrase. The effect of the length of the intervening material between the ambiguous word and the disambiguation point was additionally monitored. All groups of participants showed intact lexical access under slowed speech rate, but non-fluent participants experienced difficulties with timely activation of multiple referents. At later stages of lexical processing, they additionally demonstrated a specific impairment of reanalysis. The deficit in participants with fluent aphasia was not focalized at any specific stage of lexical processing. Rather, the breakdown of lexical processes in fluent aphasia was likely related to difficulties with the inhibition of irrelevant lexical activation, which is further supported by the finding that increased phonological distance between the ambiguous word and ambiguity resolution was influential to the offline performance in this group.

A comparison of two working memory tasks in aphasia

ABSTRACT Background: Overall, there is growing consensus that working memory (WM) should be routinely assessed in individuals with aphasia as it can contribute significantly to their level of language impairment and be an important factor in treatment planning. However, there is still no consensus in the field as to which tasks should be used to assess WM in aphasia. The two main alternatives are adapted complex span tasks and N-back tasks. Both have been used interchangeably in previous studies of WM in aphasia, even though the correspondence between the two tasks has not been properly established. Aims: The current study investigates the relationship between two WM tasks—complex span and N-back tasks—in a large sample of individuals with aphasia. The relationships of these tasks to measures of language comprehension are also explored, as well as differences in performance patterns between individuals with non-fluent and fluent aphasia. Methods & Resources: Forty-four participants with aphasia (non-fluent: n = 27; fluent: n = 13; mixed: n = 4) were examined with a modified listening span task (Ivanova & Hallowell, 2014), an auditory verbal 2-back task, and a standardised Russian language comprehension test. Outcomes & Results: Results revealed a moderate relationship between the two WM measures, but demonstrated a divergence in terms of their relationship to language comprehension. Performance on the modified listening span task was related to language comprehension abilities, but performance on the 2-back task was not, suggesting that the two tasks primarily index different underlying cognitive mechanisms. Furthermore, the relationship between the modified listening span task and language comprehension was significant for individuals with non-fluent aphasia, but not for those with fluent aphasia. Conclusions: Overall, the data demonstrate that while performance of individuals with aphasia was related on the two tasks, the two tasks cannot be substituted for one another without further inquiries into their underlying differences.

Neural Mechanisms of Two Different Verbal Working Memory Tasks: A VLSM Study

ABSTRACT Currently, a distributed bilateral network of frontal‐parietal areas is regarded as the neural substrate of working memory (WM), with the verbal WM network being more left‐lateralized. This conclusion is based primarily on functional magnetic resonance imaging (fMRI) data that provides correlational evidence for brain regions involved in a task. However, fMRI cannot differentiate the areas that are fundamentally required for performing a task. These data can only come from brain‐injured individuals who fail the task after the loss of specific brain areas. In addition to the lack of complimentary data, is the issue of the variety in the WM tasks used to assess verbal WM. When different tasks are assumed to measure the same behavior, this may mask the contributions of different brain regions. Here, we investigated the neural substrate of WM by using voxel‐based lesion symptom mapping (VLSM) in 49 individuals with stroke‐induced left hemisphere brain injuries. These participants completed two different verbal WM tasks: complex listening span and a word 2‐back task. Behavioral results indicated that the two tasks were only slightly related, while the VLSM analysis revealed different critical regions associated with each task. Specifically, significant detriments in performance on the complex span task were found with lesions in the inferior frontal gyrus, while for the 2‐back task, significant deficits were seen after injury to the superior and middle temporal gyri. Thus, the two tasks depend on the structural integrity of different, non‐overlapping frontal and temporal brain regions, suggesting distinct neural and cognitive mechanisms triggered by the two tasks: rehearsal and cue‐dependent selection in the complex span task, versus updating/auditory recognition in the 2‐back task. These findings call into question the common practice of using these two tasks interchangeably in verbal WM research and undermine the legitimacy of aggregating data from studies with different WM tasks. Thus, the present study points out the importance of lesion studies in complementing functional neuroimaging findings and highlights the need to consider task demands in neuroimaging and neuropsychological investigations of WM. HIGHLIGHTSWe determined brain areas required for performance on two common WM tasks using VLSM.The left inferior frontal gyrus was critical for performance on the complex span task.The left superior and middle temporal gyri were crucial for performance on the N‐back task.The two WM tasks depended on distinct neural and cognitive mechanisms.Results emphasize the multi‐dimensional nature of WM.

What do language disorders reveal about brain-language relationships? From classic models to network approaches

Studies of language disorders have shaped our understanding of brain-language relationships over the last two centuries. This article provides a review of this research and how our thinking has changed over the years regarding how the brain processes language. In the 19th century, a series of famous case studies linked distinct speech and language functions to specific portions of the left hemisphere of the brain, regions that later came to be known as Brocas and Wernickes areas. One hundred years later, the emergence of new brain imaging tools allowed for the visualization of brain injuries in vivo that ushered in a new era of brain-behavior research and greatly expanded our understanding of the neural processes of language. Toward the end of the 20th century, sophisticated neuroimaging approaches allowed for the visualization of both structural and functional brain activity associated with language processing in both healthy individuals and in those with language disturbance. More recently, language is thought to be mediated by a much broader expanse of neural networks that covers a large number of cortical and subcortical regions and their interconnecting fiber pathways. Injury to both grey and white matter has been seen to affect the complexities of language in unique ways that have altered how we think about brain-language relationships. The findings that support this paradigm shift are described here along with the methodologies that helped to discover them, with some final thoughts on future directions, techniques, and treatment interventions for those with communication impairments. (JINS, 2017, 23, 741-754).