Relations between Short-term Memory Deficits, Semantic Processing, and Executive Function

BACKGROUND: Previous research has suggested separable short-term memory (STM) buffers for the maintenance of phonological and lexical-semantic information, as some patients with aphasia show better ability to retain semantic than phonological information and others show the reverse. Recently, researchers have proposed that deficits to the maintenance of semantic information in STM are related to executive control abilities. AIMS: The present study investigated the relationship of executive function abilities with semantic and phonological short-term memory (STM) and semantic processing in such patients, as some previous research has suggested that semantic STM deficits and semantic processing abilities are critically related to specific or general executive function deficits. METHOD AND PROCEDURES: 20 patients with aphasia and STM deficits were tested on measures of short-term retention, semantic processing, and both complex and simple executive function tasks. OUTCOME AND RESULTS: In correlational analyses, we found no relation between semantic STM and performance on simple or complex executive function tasks. In contrast, phonological STM was related to executive function performance in tasks that had a verbal component, suggesting that performance in some executive function tasks depends on maintaining or rehearsing phonological codes. Although semantic STM was not related to executive function ability, performance on semantic processing tasks was related to executive function, perhaps due to similar executive task requirements in both semantic processing and executive function tasks. CONCLUSIONS: Implications for treatment and interpretations of executive deficits are discussed.     

Effects of phonological and semantic deficits on facilitative and inhibitory consequences of item repetition in spoken word comprehension

Repeating a word can have both facilitative and inhibitory effects on subsequent processing. The present study investigated these dynamics by examining the facilitative and inhibitory consequences of different kinds of item repetition in two individuals with aphasia and a group of neurologically intact control participants. The two individuals with aphasia were matched on overall aphasia severity, but had deficits at different levels of processing: one with a phonological deficit and spared semantic processing, the other with a semantic deficit and spared phonological processing. Participants completed a spoken word-to-picture matching task in which they had to pick which of four object images matched the spoken word. The trials were grouped into pairs such that exactly two objects from the first trial in a pair were present on screen during the second trial in the pair. When the second trial's target was the same as the first trial's target, compared to control participants, both participants with aphasia exhibited equally larger repetition priming effects. When the second trial's target was one of the new items, the participant with a phonological deficit exhibited a significantly more negative effect (i.e., second trial response slower than first trial response) than the control participants and the participant with a semantic deficit. Simulations of a computational model confirmed that this pattern of results could arise from (1) normal residual activation being functionally more significant when overall lexical processing is slower and (2) residual phonological activation of the previous trial's target having a particularly strong inhibitory effect specifically when phonological processing is impaired because the task was phonologically-driven (the spoken input specified the target). These results provide new insights into perseveration errors and lexical access deficits in aphasia.     

Mixed language dominance: insights from a case of unexpected fluent aphasia with semantic jargon resulting from massive left perisylvian lesion

We report a right-handed patient with a massive lesion in left perisylvian language cortex, who unexpectedly presented with fluent aphasia with semantic jargon. Language deficits were assessed with a comprehensive battery of language tests. Comprehension, naming, reading, and writing were severely impaired, and verbal expression was moderately fluent with semantic jargon. Although the patient’s lesion included brain areas typically essential for motor speech coordination, he was neither nonfluent nor apraxic. He exhibited strikingly unexpected aphasia with semantic jargon and prominent comprehension deficits, suggesting that this is a case of mixed dominance: the right hemisphere likely controls motor speech and basic syntactic skills, while the severely damaged left hemisphere controls semantic processing, predictably severely impaired.     

Linguistic deficits in the acute phase of stroke

Background and Purpose For the diagnosis of aphasia early after stroke, several screening tests are available to support clinical judgment.None of these tests enables the clinician to assess the underlying linguistic deficits, i. e. semantic, phonological and syntactic deficits, which provides indispensable information for early therapeutic decisions. The ScreeLing was designed as a screening test to detect semantic, phonological and syntactic deficits. The ScreeLings sensitivity, specificity and accuracy in detecting aphasia and semantic, phonological and syntactic deficits were determined.Methods The ScreeLing was validated in an acute stroke population against a combined reference diagnosis of aphasia (aphasia according to at least two of the following measures:ne urologists judgment, linguists judgment, Tokentestscore). The three ScreeLing subtests were validated in the aphasic population against the presence or absence of a semantic, phonological and/or syntactic deficit according to an experienced clinical linguist.Results From a consecutive series of 215 stroke patients, 63 patients were included. The ScreeLing was an accurate test for the detection of aphasia (0.92),with a sensitivity of 86% and specificity of 96%. Sensitivity of subtests was 62 % for semantics, 54 % for phonology and 42 % for syntax. Specificity was 100 % for semantics and phonology and 80 % for syntax, and accuracy 0.84 for semantics, 0.87 for phonology and 0.64 for syntax.Conclusions The ScreeLing is an accurate test that can be easily administered and scored to detect aphasia in the first weeks after stroke. Furthermore, the ScreeLing is suitable for revealing underlying linguistic deficits, especially semantic and phonological deficits.     

Effects of working memory load on processing of sounds and meanings of words in aphasia

BACKGROUND: Language performance in aphasia can vary depending on several variables such as stimulus characteristics and task demands. This study focuses on the degree of verbal working memory (WM) load inherent in the language task and how this variable affects language performance by individuals with aphasia. AIMS: The first aim was to identify the effects of increased verbal WM load on the performance of judgments of semantic similarity (synonymy) and phonological similarity (rhyming). The second aim was to determine if any of the following abilities could modulate the verbal WM load effect: semantic or phonological access, semantic or phonological short-term memory (STM) and any of the following executive processing abilities: inhibition, verbal WM updating, and set shifting. METHOD AND PROCEDURES: Thirty-one individuals with aphasia and 11 controls participated in this study. They were administered a synonymy judgment task and a rhyming judgment task under high and low verbal WM load conditions that were compared to each other. In a second set of analyses, multiple regression was used to identify which factors (as noted above) modulated the verbal WM load effect. OUTCOME AND RESULTS: For participants with aphasia, increased verbal WM load significantly reduced accuracy of performance on synonymy and rhyming judgments. Better performance in the low verbal WM load conditions was evident even after correcting for chance. The synonymy task included concrete and abstract word triplets. When these were examined separately, the verbal WM load effect was significant for the abstract words, but not the concrete words. The same pattern was observed in the performance of the control participants. Additionally, the second set of analyses revealed that semantic STM and one executive function, inhibition ability, emerged as the strongest predictors of the verbal WM load effect in these judgment tasks for individuals with aphasia. CONCLUSIONS: The results of this study have important implications for diagnosis and treatment of aphasia. As the roles of verbal STM capacity, executive functions and verbal WM load in language processing are better understood, measurements of these variables can be incorporated into our diagnostic protocols. Moreover, if cognitive abilities such as STM and executive functions support language processing and their impairment adversely affects language function, treating them directly in the context of language tasks should translate into improved language function.     

Phonological short-term memory in conduction aphasia

Background: Within cognitive neuropsychological models conduction aphasia has been conceptualised as a phonological buffer deficit. It may affect the output buffer, the input buffer, or both. The phonological output buffer is a short-term storage, responsible for the short-term maintenance of phonological units until their articulation, as well as for phonological and morphological composition. The phonological input buffer holds input strings until they are identified in the input lexicon. Thus the phonological buffers are closely related to phonological short-term memory (pSTM), and hence it is important to assess pSTM in conduction aphasia. Because the input and output buffers play different roles, impairment in each of them predicts different impairments in the patient's ability to understand certain sentences, to learn new words and names, and to remember and recall lists of words and numbers for short time periods.

Aims: This study explored in detail pSTM in individuals with conduction aphasia, comparing individuals with input and output deficits, recall and recognition tasks, and stimuli of various types. It also tested pSTM in six age groups of healthy individuals, assessing the effect of age on various types of stimuli. This paper presents a new battery of 10 recall and recognition span tests, designed to assess pSTM in aphasia and to measure spans and effects on spans.

Methods & Procedures: The participants were 14 Hebrew-speaking individuals with conduction aphasia, 12 with input or input-output phonological buffer deficit, and 2 with only output deficit, and 296 healthy individuals.

Outcomes & Results: The analyses of the spans and effects on pSTM in the 10 tests indicated that all the participants with conduction aphasia had limited pSTM, significantly poorer than that of the control participants, and no semantic STM impairment. They had shorter spans, smaller length and similarity effects, and larger sentential effect than the controls. The individuals with conduction aphasia who had an impairment in the phonological input buffer showed deficit in both the recall and recognition span tasks. The individuals with the output conduction aphasia showed impairment only in the recall tasks. The healthy individuals showed age effect on span tasks involving words, but no effect of age on span tasks of nonwords.

Conclusions: pSTM is impaired in conduction aphasia, and different pSTM impairments characterise different types of conduction aphasia. Output conduction aphasia causes difficulties only when verbal output is required, whereas input conduction aphasia also causes a deficit when only recognition is required. This suggests that rehearsal can take place without the phonological output buffer. Age differentially affects pSTM for words and nonwords in healthy adults: whereas the encoding of words changes, the ability to remember nonwords is unchanged.     

Treatment of word retrieval deficits with contextual priming

Background: Repetition priming is often a component of treatments for word‐finding disorders. It can facilitate or interfere with naming success depending on a number of factors. Here we investigate the effectiveness of massed priming coupled with semantic or phonological context as a treatment for naming impairments arising from semantic and phonological deficits. Aims: We aimed to determine whether (1) this procedure, used previously in a short‐term facilitation study, would effectively improve word retrieval in a treatment study, and (2) the pattern of facilitation or interference observed in the facilitation study would carry over to the treatment programme. Methods & Procedures: We used a single subject multiple baseline design. There were two participants: LP with a phonological encoding deficit and AS with both semantic and phonological deficits. Treatment involved identifying and repeating the names of words that were related semantically or phonologically, or unrelated. Pre and post measures of naming were used to assess overall effectiveness of the treatment. Acquisition, maintenance, and generalisation were measured with baseline tests at the start of each session. Correct responses and errors on within‐training naming probes were used to measure sensitivity to priming in a particular context. Outcomes & Results: LP benefited from this procedure regardless of the training context. AS showed interference in the semantic context during training and only modest short‐term gains. These outcomes were predicted by their performance on an earlier facilitation study. Conclusions: Contextual repetition priming has different effects on naming and these differences appear to be related to the context of training (semantic or phonological) and the primary source of an individual's naming impairment (semantic or phonological). This procedure is most effective when semantic processing of words is relatively spared.     

Understanding semantic and phonological processing deficits in adults with aphasia: effects of category and typicality

Background: Semantic and phonological processing deficits are often present in aphasia. The degree of interdependence between the deficits has been widely studied with variable findings. Semantic variables such as category and typicality have been found to influence semantic processing in healthy individuals and persons with aphasia (PWA), but their influence on phonological processing is unknown.

Aims: This study examined the nature of semantic and phonological access in aphasia by comparing adults with aphasia to healthy control participants. Semantic and phonological tasks were used to assess the difference in processing requirements between and within each group as well as examine the effects of category and typicality on different stages of semantic and phonological processing.

Methods & Procedures: Thirty-two PWA and 10 neurologically healthy adults were administered nine tasks: Category Superordinate, Category Coordinate, Semantic Feature, Rhyme Judgment (No-Name), Syllable Judgment (No-Name), Phoneme Verification (No-Name), Rhyme Judgment (Name-Provided), Syllable Judgment (Name-Provided), and Phoneme Verification (Name-Provided). Accuracy and reaction time (RT) data were collected for each of these tasks and between-group and within-group differences were analysed via MANOVA/MANCOVA and hierarchical clustering analyses.

Outcomes & Results: PWA performed with significantly lower accuracy than controls on phonological tasks but performed comparably on semantic tasks. Participants with aphasia were significantly slower than controls on all semantic and phonological tasks. Clustering of the nine tasks by accuracy revealed different processing requirements in the participants with aphasia compared to the control group while clustering by RT revealed similar trends in both groups in that phonological (no-name) items required the most processing time. Significant effects of category and typicality were noted in the semantic tasks but not in any of the phonological tasks.

Conclusions: Individuals with aphasia demonstrated overall impaired phonological processing with relatively preserved semantic processing as compared to controls. Per accuracy and RT measures, distinct trends in processing load for semantic tasks versus phonological tasks were seen in the individuals with aphasia whereas only speed of processing and not accuracy was impacted by phonological processing load in the control group. The results align most closely with discrete serial processing models of lexical processing as category and typicality effects were robust in the semantic tasks but not in any of the phonological tasks. Alternative explanations for these results also are discussed.     

On the nature of naming difficulties in aphasia.

An extensive naming battery was administered to ten patients representing classical aphasia syndromes. The battery included traditional performance measures and error scoring, phonological cuing, multiple-choice tasks tapping semantic and phonological knowledge, and word repetition tests. Differences in the patients' performance profiles were interpreted as reflecting lexical-phonological, phoneme assembly or multiple deficits. The results suggest that the hypothesized naming deficits have complex relationships to classical aphasia syndromes.     

Reduced short-term memory span in aphasia and susceptibility to interference: Contribution of material-specific maintenance deficits

Semantic short-term memory (STM) deficits have been traditionally defined as an inability to maintain semantic representations over a delay (Martin et al., 1994b). Yet some patients with semantic STM deficits make numerous intrusions of items from previously presented lists, thus presenting an interesting paradox: why should an inability to maintain semantic representations produce an increase in intrusions from earlier lists? In this study, we investigated the relationship between maintenance deficits and susceptibility to interference in a group of 20 aphasic patients characterized with weak semantic or weak phonological STM. Patients and matched control participants performed a modified item-recognition task designed to elicit semantic or phonological interference from list items located one, two, or three trials back (Hamilton & Martin, 2007). Controls demonstrated significant effects of interference in both versions of the task. Interference in patients was predicted by the type and severity of their STM deficit; that is, shorter semantic spans were associated with greater semantic interference and shorter phonological spans were associated with greater phonological interference. We interpret these results through a new perspective, the reactivation hypothesis, and we discuss their importance for accounts emphasizing the contribution of maintenance mechanisms for STM impairments in aphasia as well as susceptibility to interference.     

Executive function ability in persons with aphasia

Background: There is an increasing recognition that the communication problems one observes in persons with aphasia extend beyond verbal deficits and that the myriad of symptoms observed are not solely due to a faulty linguistic system. Rather, there exists a coalition of causal elements resulting in a wide range of communicative deficits. There is some preliminary evidence suggesting that communicative success of clients with aphasia may depend on the integrity of executive function skills. Executive functions are called into play when an individual is involved in a complex, novel activity. They allow us to plan, sequence, organise, and monitor goal-directed activities in a flexible manner as demanded by situational and environmental changes. When linguistic skills are impaired, individuals need to rely on other cognitive skills in order to communicate. Aims: The purpose of this study was to explore executive functioning ability in persons with aphasia. Methods & Procedures: A total of 15 individuals with aphasia and 12 healthy control subjects participated in this study. Three dimensions of performance were examined (accuracy, speed, and efficiency) in the context of neuropsychological tests designed to examine cognitive flexibility and goal-directed planning (Wisconsin Card Sorting Test, Porteus Maze Test, Tower of London, and Tower of Hanoi). Outcomes & Results: Results indicated that the two groups performed with similar levels of accuracy on two of the four tests. However, significant differences were found on all speed and efficiency variables, suggesting decreased executive functioning skills in the group of individuals with aphasia. Conclusions: It is important to consider executive functioning ability in clients with aphasia and attempt to determine the influence of executive function skill on communicative performance. Understanding the cognitive abilities as well as the linguistic abilities of these clients may ultimately help clinicians determine which patients are better candidates for intervention as well as which treatment approaches would be most efficient and beneficial.     

Treatment of verbal akinesia in a case of transcortical motor aphasia

Abstract

Patients with transcortical motor aphasia frequently demonstrate an ‘akinesia of speech’ resulting in decreased word fluency, reduced syntactic complexity, and diminished speech initiative. A treatment protocol targeting verbal generativity in terms of communicative expansion was instituted in this case study to address the patient's deficit area—deficient linguistic planning and goal setting. The patient demonstrated adequate lexical and syntactic skills and improved sentence generation performance as a result of treatment. However, treatment effects were short-lived as the patient returned to pre-treatment levels on the generalization measures three months post-discharge.     

Verbal short-term memory in individuals with congenital articulatory disorders: new empirical data and review of the literature

Background To investigate the nature of the articulatory rehearsal mechanism of the Articulatory Loop in Baddeley's Working Memory model, it seems particularly important to study individuals who developed a deficit (dysarthria) or total abolition (anarthria) of the ability to articulate language following a cerebral lesion. Method In this study, a forced‐choice recognition procedure for word sequences of increasing length was used to evaluate verbal short‐term memory in nine individuals with severe congenital motor and verbal disabilities (seven anarthric and two severely dysarthric) and associated intellectual disability (ID) and 30 normal children of comparable mental age. Results The normal children exhibited classical phonological similarity effects (better performance on acoustically dissimilar than on similar word lists), word length (greater accuracy on two‐syllable than on four‐syllable word lists) and frequency of occurrence (an advantage of high‐frequency over low‐frequency words). Instead, all of these effects were lacking in the experimental group. Conclusions These data suggest that persons with congenital anarthria/dysarthria and ID present defective maturation at many levels of the Articulatory Loop and reduced contribution of semantic‐lexical processing in the temporary retention of phonological sequences. It is likely that in these individuals both communicative deficits and ID play a role in the impaired development of verbal short‐term memory abilities.     

Validation of the Italian version of the American Speech-Language and Hearing Association—Functional Assessment of Communication Skills for adults (I-ASHA-FACS)

Background: Impairment of communicative-linguistic and cognitive functions is common after stroke and traumatic brain injury (TBI). While assessment of language function is usually performed in clinical practice, standardised assessment of pragmatic, functional, and communicative competences is less common, even though suggested by many recent national and international guidelines. The “American Speech-Language and Hearing Association—Functional Assessment of Communication Skills for adults” (ASHA-FACS) is a measure of communication disability that investigates functional communication. It has been translated and adapted into Italian in 2001, but psychometric properties of Italian version of ASHA-FACS (I-ASHA-FACS) have not yet been investigated.

Aims: To investigate psychometric properties of the I-ASHA-FACS scale and provide normative data.

Methods & Procedures: Participants included 100 healthy adult persons without neurological disorders nor communicative-cognitive deficits and 80 post-acute outpatients with aphasia following stroke (n = 60) or TBI (n = 20). Mini Mental State Examination (MMSE) was used to exclude control participants with cognitive decline (MMSE > 24). I-ASHA-FACS was completed for all participants. All patients were also assessed with Functional Independent Measure (FIM) and either Aachener Aphasie Test (AAT) for persons with aphasia due to stroke or Levels of Cognitive Functions scale (LCF) for TBI persons. I-ASHA-FACS internal consistency, inter- and intra-rater reliability and construct validity were calculated; normative data were also calculated for healthy controls stratified by age and education. Cronbach’s alpha was used for internal consistency analysis. Spearman’s test was used to correlate I-ASHA-FACS and FIM, AAT, and LCF scores.

Outcomes & Results: I-ASHA-FACS showed good internal consistency (α > .84) and strong intra- and inter-rater reliability (r > .97 and >.89). All healthy persons showed very high level of functional communication abilities in all domains of communication independence (higher than 6, on a 7-point scale) and all qualitative dimensions scores (higher than 4, on a 5-point scale). Correlations between I-ASHA-FACS scores and FIM were strong in aphasic persons, particularly in problem solving (r > .71) and comprehension (r > .73) subscales. Correlations between I-ASHA-FACS and AAT were generally from moderate to strong (r values ranging from r = .31 to r = .81), and particularly strong in spontaneous speech subtest (r > .70). Correlations between I-ASHA-FACS and LCF did not reach statistical significance.

Conclusions: I-ASHA-FACS shows good internal consistency, strong intra- and inter-rater reliability and satisfactory validity. The application of I-ASHA-FACS to the Italian population of patients with communicative deficits due to aphasia or TBI is recommended.     

Neuropsychological characteristics of five children with the Landau-Kleffner syndrome: dissociation of auditory and phonological discrimination.

The Landau-Kleffner Syndrome (LKS) is characterized by acquired receptive aphasia and EEG abnormality with onset between the ages of 3 and 8 years. This study presents neuropsychological assessments in 5 children with LKS. The aims were (1) to specify the neuropsychological deficits characteristic of these children; and (2) to clarify the nature of the receptive aphasia by comparing nonverbal and verbal auditory discrimination. Receptive aphasia was present in all children. Retardation, poor motor coordination, hyperkinesia, and conduct problems were frequent but variable. All children exhibited a dissociation between the discrimination of environmental sounds and phonological auditory discrimination, the latter being more impaired than the former. This suggests that the primary deficit of the receptive aphasia is an impairment of auditory phonological discrimination rather than a generalized auditory agnosia.     

Crossed anomic aphasia: mild naming deficits following right brain damage in a dextral patient.

A detailed case study is reported of crossed aphasia (CA) in a dextral patient, bearing upon such controversial issues as intrahemispheric localisation of language function and hemispheric reversal of nonverbal function. DA, a man aged 37, developed a mild naming problem due to right temporal lobe haematoma. Apart from a mild acquired stutter, his continuous speech was fluent and had a normal proportion of open to closed class lexical items. His naming deficit appears to originate in the 'blocking' or 'disconnection' of the phonological lexicon: he could usually give a functional definition of un-named items and retrieve them with the help of a phonemic cue. Lexical retrieval appears his only language deficit, as he had no comprehension or phonological discrimination deficits. DA showed no visuo-spatial or auditory-nonverbal deficits, suggesting the complete reversal of hemispheric specialisation.     

Contrasting effects of errorless naming treatment and gestural facilitation for word retrieval in aphasia

We compared the effects of two treatments for aphasic word retrieval impairments, errorless naming treatment (ENT) and gestural facilitation of naming (GES), within the same individuals, anticipating that the use of gesture would enhance the effect of treatment over errorless treatment alone. In addition to picture naming, we evaluated results for other outcome measures that were largely untested in earlier ENT studies. In a single participant crossover treatment design, we examined the effects of ENT and GES in eight individuals with stroke-induced aphasia and word retrieval impairments (three semantic anomia, five phonological anomia) in counterbalanced phases across participants. We evaluated effects of the two treatments for a daily picture naming/gesture production probe measure and in standardised aphasia tests and communication rating scales administered across phases of the experiment. Both treatments led to improvements in naming of trained words (small-to-large effect sizes) in individuals with semantic and phonological anomia. Small generalised naming improvements were noted for three individuals with phonological anomia. GES improved use of corresponding gestures for trained words (large effect sizes). Results were largely maintained at one month post-treatment completion. Increases in scores on standardised aphasia testing also occurred for both ENT and GES training. Both ENT and GES led to improvements in naming measures, with no clear difference between treatments. Increased use of gestures following GES provided a potential compensatory means of communication for those who did not improve verbal skills. Both treatments are considered to be effective methods to promote recovery of word retrieval and verbal production skills in individuals with aphasia.     

Aphasia severity,semantics, and depression predict functional communication in acquired aphasia

Background: The functional communication deficits that result from aphasia are well known, although contributing factors have not been systematically studied. Although overall aphasia severity is directly related to communication ability, the contribution of cognitive and mood factors is less understood.

Aims: This study attempted to identify predictors of functional communication in patients with acquired aphasia at various points post‐unilateral left hemisphere stroke.

Methods & Procedures: A total of 57 patients with aphasia due to left hemisphere stroke completed a comprehensive battery of aphasia diagnostic, neuropsychological, mood, and functional communication measures. Significant predictors of functional communication were identified with multiple hierarchical regression analysis.

Outcomes & Results: Over and above the contribution of aphasia severity, depression (sadness and anger), semantic processing, and reading comprehension accounted for a significant amount of variance in functional communication. Working memory, phonologic processing, and other mood states were not predictive.

Conclusions: Aphasia severity, depression, semantic impairment, and reading comprehension may be most relevant to functional communication in people with acquired aphasia.