Review The relationship between the mismatch negativity (MMN) and psycholinguistic models of spoken word processing

Background: The results from previous studies have indicated that a pre‐attentive component of the event‐related potential (ERP), the mismatch negativity (MMN), may be an objective measure of the automatic auditory processing of phonemes and words. Aims: This article reviews the relationship between the MMN data and psycholinguistic models of spoken word processing, in order to determine whether the MMN may be used to objectively pinpoint spoken word processing deficits in individuals with aphasia. Main Contribution: This article outlines the ways in which the MMN data support psycholinguistic models currently used in the clinical management of aphasic individuals. Furthermore, the cell assembly model of the neurophysiological mechanisms underlying spoken word processing is discussed in relation to the MMN and psycholinguistic models. Conclusions: The MMN data support current theoretical psycholinguistic and neurophysiological models of spoken word processing. Future MMN studies that include normal and aphasic populations will further elucidate the role that the MMN may play in the clinical management of aphasic individuals.     

Improved word comprehension in Global aphasia using a modified semantic feature analysis treatment

Limited research has investigated treatment of single word comprehension in people with aphasia, despite numerous studies examining treatment of naming deficits. This study employed a single case experimental design to examine efficacy of a modified semantic feature analysis (SFA) therapy in improving word comprehension in an individual with Global aphasia, who presented with a semantically based comprehension impairment. Ten treatment sessions were conducted over a period of two weeks. Following therapy, the participant demonstrated improved comprehension of treatment items and generalisation to control items, measured by performance on a spoken word picture matching task. Improvements were also observed on other language assessments (e.g. subtests of WAB-R; PALPA subtest 47) and were largely maintained over a period of 12 weeks without further therapy. This study provides support for the efficacy of a modified SFA therapy in remediating single word comprehension in individuals with aphasia with a semantically based comprehension deficit.     

Some anatomo-clinical aspects of phonemic and semantic comprehension disorders in aphasia

60 aphasic patients, affected by localized lesions of the left hemisphere and classed as Broca's, Global, Conduction, Amnestic or Wernicke's aphasia received 1 phoneme discrimination test and 3 semantic-lexical discrimination tests. The aim of the study consisted in investigating the relationships between phoneme and semantic-lexical discrimination disorders, the clinical form of aphasia and the anatomic locus of the cerebral lesion.
The results were not consistent with the claim that comprehension disorders of Wernicke's aphasic patients can be traced back to a phoneme discrimination disorder, since Wernicke's aphasics were not more impaired than other aphasic groups and since patients with lesions localized in the temporal lobe performed quite well in the phoneme discrimination test.
Semantic discrimination disorders were very frequent and severe in patients classified as Wernicke's, Amnesic or Global aphasia, whereas they were much less relevant in patients classified as Broca's or Conduction aphasia.
As for the locus of the lesion, left temporal damage severely impaired semantic-lexical discrimination without affecting phoneme discrimination (a finding which supports the assumption of a selective involvement of the temporal lobe in semantic-lexical memory).
On the other hand, patients with damage localized in the left frontal lobe, obtained poor scores both on semantic-lexical discrimination tasks and on phoneme discrimination tests.     

The impact of phonological versus semantic repetition training on generalisation in chronic stroke aphasia reflects differences in dorsal pathway connectivity

It has been suggested that neuroimaging can be used to inform therapeutic intervention. The current study aimed to determine whether an individual would benefit more from training engaging their intact or their damaged neural pathway. Two males with chronic stroke aphasia participated, with DM showing milder disruption of connectivity along the dorsal language pathway relative to JS, according to distortion corrected diffusion-weighted magnetic resonance imaging. Each patient received two blocks of six repetition training sessions over two weeks, one of which was “phonological” and the other “semantic” in nature. Both phonological and semantic training produced significant gains for both patients for trained items. For the untrained control items, significant gains were specific to training type for each patient. Only phonological training elicited significant generalisation for DM, which was greater than that seen for JS. Conversely, only semantic training elicited significant generalisation for JS, which was greater than that seen for DM. This double dissociation in generalisation effects suggests that a restitutive approach is more effective for patients with milder damage while a compensatory approach may be more effective for those with more severe damage. These results indicate the utility of neuroimaging to optimise relearning strategies and promote generalisation to untrained items.     

Brain regions underlying repetition and auditory-verbal short-term memory deficits in aphasia: Evidence from voxel-based lesion symptom mapping

Background: A deficit in the ability to repeat auditory-verbal information is common among individuals with aphasia. The neural basis of this deficit has traditionally been attributed to the disconnection of left posterior and anterior language regions via damage to a white matter pathway, the arcuate fasciculus. However, a number of lesion and imaging studies have called this notion into question.

Aims: The goal of this study was to identify the neural correlates of repetition and a related process, auditory-verbal short-term memory (AVSTM). Both repetition and AVSTM involve common elements such as auditory and phonological analysis and translation to speech output processes. Based on previous studies, we predicted that both repetition and AVSTM would be most dependent on posterior language regions in left temporo-parietal cortex.

Methods & Procedures: We tested 84 individuals with left hemisphere lesions due to stroke on an experimental battery of repetition and AVSTM tasks. Participants were tested on word, pseudoword, and number-word repetition, as well as digit and word span tasks. Brain correlates of these processes were identified using a statistical, lesion analysis approach known as voxel-based lesion symptom mapping (VLSM). VLSM allows for a voxel-by-voxel analysis of brain areas most critical to performance on a given task, including both grey and white matter regions.

Outcomes & Results: The VLSM analyses showed that left posterior temporo-parietal cortex, not the arcuate fasciculus, was most critical for repetition as well as for AVSTM. The location of maximal foci, defined as the voxels with the highest t values, varied somewhat among measures: Word and pseudoword repetition had maximal foci in the left posterior superior temporal gyrus, on the border with inferior parietal cortex, while word and digit span, as well as number-word repetition, were centred on the border between the middle temporal and superior temporal gyri and the underlying white matter.

Conclusions: Findings from the current study show that (1) repetition is most critically mediated by cortical regions in left posterior temporo-parietal cortex; (2) repetition and AVSTM are mediated by partially overlapping networks; and (3) repetition and AVSTM deficits can be observed in different types of aphasia, depending on the site and extent of the brain injury. These data have implications for the prognosis of chronic repetition and AVSTM deficits in individuals with aphasia when lesions involve critical regions in left temporo-parietal cortex.     

Positive effects of a computerised working memory and executive function training on sentence comprehension in aphasia

Aphasia, the language disorder following brain damage, is frequently accompanied by deficits of working memory (WM) and executive functions (EFs). Recent studies suggest that WM, together with certain EFs, can play a role in sentence comprehension in individuals with aphasia (IWA), and that WM can be enhanced with intensive practice. Our aim was to investigate whether a combined WM and EF training improves the understanding of spoken sentences in IWA. We used a pre–post-test case control design. Three individuals with chronic aphasia practised an adaptive training task (a modified n-back task) three to four times a week for a month. Their performance was assessed before and after the training on outcome measures related to WM and spoken sentence comprehension. One participant showed significant improvement on the training task, another showed a tendency for improvement, and both of them improved significantly in spoken sentence comprehension. The third participant did not improve on the training task, however, she showed improvement on one measure of spoken sentence comprehension. Compared to controls, two individuals improved at least in one condition of the WM outcome measures. Thus, our results suggest that a combined WM and EF training can be beneficial for IWA.     

Behavioral and neurobiological effects of printed word repetition in lexical decision and naming

A series of experiments studied the effects of repetition of printed words on (1) lexical decision (LD) and naming (NAM) behavior and (2) concomitant brain activation. It was hypothesized that subword phonological analysis (assembly) would decrease with increasing word familiarity and the greater decrease would occur in LD, a task that is believed to be less dependent on assembly than naming. As a behavioral marker of assembly, we utilized the regularity effect (the difference in response latency between words with regular versus irregular spelling-sound correspondences). In addition to repetition, stimulus familiarity was manipulated by word frequency and case alternation. Both experiments revealed an initial latency disadvantage for low frequency irregular words suggesting that assembly is the dominant process in both tasks when items are unfamiliar. As items become more familiar with repetition, the regularity effect disappeared in LD but persisted in NAM. Brain activation patterns for repeated words that were observed in fMRI paralleled the behavioral studies in showing greater reductions in activity under lexical decision than naming for regions previously identified as involved in assembly.     

Investigating the effect of a semantic therapy on comprehension in aphasia

Background: While evidence on the use of semantic therapy to improve word retrieval has increased (Whitworth, Webster, & Howard, 2005 Whitworth, A., Webster, J. and Howard, D. 2005. A cognitive neuropsychological approach to assessment and intervention in aphasia, Hove: Psychology Press. [Crossref] , [Google Scholar]), the impact of semantic therapy on comprehension itself has not been studied in depth. This paper reports on a specific semantic therapy, which aims to improve access to semantic information. Data from two participants, JAC and AD, are presented.

Aims: The study aimed to examine the effectiveness of a specific semantic therapy on comprehension of treated and untreated items, and on related tasks, thereby examining generalisation of any improvement to both items and tasks involving semantic processing.

Methods & Procedures: The participants' comprehension was assessed in detail prior to therapy. Measures were repeated over time to ensure any improvement seen could not be due to more general recovery mechanisms. The two participants then took part in therapy which aimed to improve their comprehension, using a picture name verification task. Following therapy, relevant assessments were repeated to examine the effects of therapy. The study uses single case methodology with comparison across two similar cases.

Outcomes & Results: JAC and AD responded differently to the semantic therapy; JAC's auditory comprehension performance improved and this was regardless of whether items had been treated or not. In contrast, despite having a broadly similar profile of language ability, AD's performance did not change. Potential reasons for this are explored within the paper.

Conclusions: This paper provides a much needed demonstration of semantic therapy for comprehension problems. One specific therapy is tested, rather than the combined therapies used in the existing literature. It considers the extent to which therapy generalises to untreated words. It is clear that further research is needed regarding finer differential diagnosis, and ultimately, the impact of therapy on everyday comprehension for these individuals.     

Specialization of phonological and semantic processing in Chinese word reading

The purpose of this study was to examine the neurocognitive network for processing visual word forms in native Chinese speakers using functional magnetic resonance imaging (fMRI). In order to compare the processing of phonological and semantic representations, we developed parallel rhyming and meaning association judgment tasks that required explicit access and manipulation of these representations. Subjects showed activation in left inferior/middle frontal gyri, bilateral medial frontal gyri, bilateral middle occipital/fusiform gyri, and bilateral cerebella for both the rhyming and meaning tasks. A direct comparison of the tasks revealed that the rhyming task showed more activation in the posterior dorsal region of the inferior/middle frontal gyrus (BA 9/44) and in the inferior parietal lobule (BA 40). The meaning task showed more activation in the anterior ventral region of the inferior/middle frontal gyrus (BA 47) and in the superior/middle temporal gyrus (BA 22,21). These findings are consistent with previous studies in English that suggest specialization of inferior frontal regions for the access and manipulation of phonological vs. semantic representations, but also suggest that this specialization extends to the middle frontal gyrus for Chinese. These findings are also consistent with the suggestion that the left middle temporal gyrus is involved in representing semantic information and the left inferior parietal lobule is involved in mapping between orthographic and phonological representations.     

The effects of direct and indirect speech on discourse comprehension in Dutch listeners with and without aphasia

Background: Research on language comprehension in aphasia has primarily focused on comprehension of isolated words and sentences. Even though previous studies have provided insights into comprehension abilities of individuals with aphasia at the word and grammatical level, our understanding of the nature and extent of their language comprehension (dis)abilities is not yet complete. In contrast to the highly restricted semantic and syntactic interpretation of sentences, discourse comprehension requires additional pragmatic and non-linguistic skills.

Aims: The purpose of this study was to assess language comprehension in individuals with and without aphasia at the discourse level. In particular, it addressed the question of whether the use of direct speech, compared to indirect speech, affects comprehension of narrative discourse in Dutch aphasic and non-brain-damaged (NBD) listeners.

Methods & Procedures: The Direct Speech Comprehension (DISCO) test was developed to examine the effects of manipulating direct vs. indirect speech on discourse comprehension. Twenty-three individuals with aphasia and 20 NBD participants were presented with spoken narratives that contained either direct or indirect speech reports. The narratives were presented audio-visually on an iPad, and comprehension was assessed with yes/no questions.

Outcomes & Results: The performance of the participants with aphasia was significantly poorer than that of the NBD participants. Moreover, a main effect for condition type was found, indicating that narratives with direct speech reports were better understood than narratives with indirect speech reports by listeners with and without aphasia. There was no interaction between group and condition type indicating that this main effect held for both the aphasic and the NBD listeners. However, for the participants with aphasia, there was an interaction between condition and Token Test error score indicating that the positive effect of direct speech constructions diminishes for individuals with poorer comprehension.

Conclusions: Direct speech constructions facilitate language comprehension in listeners with and without aphasia. One explanation for this finding is the occurrence of additional “layers” of communication, such as intonation and facial expression, often accompanying direct speech constructions. An alternative account is the degree of grammatical complexity: In Dutch, the syntactic construction of indirect speech requires embedding, whereas in direct speech the introductory sentence and the quote are both main clauses. The finding that the beneficial effect of direct speech on language comprehension diminishes for individuals with severe aphasia may indicate that the DISCO is too difficult for them to reveal an effect of a subtle manipulation such as that of condition type.     

ERP measures of auditory word repetition and translation priming in bilinguals

Motivated by the demonstration of similarly localized adaptation of the hemodynamic response in a first (L1) and second (L2) language, this study examined event-related brain potentials (ERPs) to spoken words in L1 and L2 in 15 English-French bilinguals. We examined whether the temporal pattern of N400 adaptation due to within-language repetitions (i.e., repetition priming) was similar in L1 and L2 and whether the release from adaptation elicited by a within-language word change was similar. Furthermore, using word changes across language, we examined the phonological mismatch negativity (PMN) and N400 components to determine the kind of information activated during translation priming. In contrast to within-language repetition, we expected between-language repetition (i.e., translations) to be characterized by conceptual rather than lexical/phonological word form priming. Overall, the pattern of adaptation and release from adaptation was similar in L1 and L2, with evidence of delayed semantic analysis in L2 in the form of a later N400 effect. A change in language (L1 to L2) elicited a similar pattern of PMN and N400 activity compared to a within-language change in meaning in L1, suggesting that neither word form nor conceptual information was available on-line for the forward translation. In contrast, the presence of strong PMN but minimal N400 effects for L2-to-L1 translations suggests that conceptual but not phonological information is available on-line for backwards translation. L2 proficiency influenced the extent to which conceptual representations were activated by translations. These data are discussed in light of current models of bilingual word processing and suggest modality differences in the pattern of activation of lexical and conceptual information.     

A comparison of drawing and writing on facilitating word retrieval in individuals with aphasia

ABSTRACT

Background: Drawing has long been a focus in aphasia research as a compensatory strategy for improving functional communication in individuals with aphasia, but fewer studies have addressed drawing as a facilitative tool to improve their verbal output.

Aims: The purpose of the current study was to investigate differences in naming accuracy in individuals with aphasia during a drawing versus a writing condition. Two research questions were formed to examine the role of drawing in facilitating naming: 1) Will participants perform better when naming with drawing compared to confrontation naming only or when naming with writing? and 2) Is the quality of the picture drawn related to the naming accuracy?

Methods & Procedures: Across three separate one-hour sessions, fifteen individuals with aphasia (n = 15) aged 44–81 years (M = 61.47, SD = 13.27) were evaluated using two standardized language assessments, the Western Aphasia Battery-Revised and Pyramid and Palm Tree Test, and three naming tasks designed to assess the effect of writing and drawing on naming performance. The three naming conditions consisted of confrontation naming only, naming with drawing, and naming with writing.

Outcomes & Results: A one-way, repeated measures analysis of variance (ANOVA) was computed to analyze the impact of naming conditions on the participants’ naming accuracy. The main effect of naming conditions was statistically significant, F (1, 14) = 5.87, p < 0.05, and Bonferroni correction revealed that the participants performed significantly better in the naming with drawing condition than with writing condition. In addition, no correlation between the quality of the pictures drawn and the participants’ naming performance was found which suggested that the quality of drawing did not affect the accuracy of naming.

Conclusions: When attempting to name a picture along with drawing its representation, the act of drawing may facilitate word retrieval by stimulating the semantic network associated with the word and involving the right cerebral hemisphere in the word retrieval process. Through drawing, these semantic features of the target word are more strongly activated than other related words. When the semantic features are more strongly activated, the probabilities of retrieving the target word may increase. In contrast, writing heavily relies on the left hemisphere and linguistic systems. Thus, naming when attempting to write the associated word may be a more cognitively and linguistically demanding task for individuals with aphasia.     

Functional anatomy of syntactic and semantic processing in language comprehension

A functional magnetic resonance imaging (fMRI) study was conducted to map syntactic and semantic processes onto the brain. Chinese-English bilingual subjects performed two experimental tasks: a syntactic plausibility judgment task in which they decided whether a viewed verb phrase was syntactically legal, and a semantic plausibility judgment task in which they decided whether a viewed phrase was semantically acceptable. A font size judgment task was used as baseline. It is found that a large-scale distributed neural network covering the left mid-inferior frontal and mid-superior temporal cortices was responsible for the processing of Chinese phrases. The right homologue areas of these left cortical sites were also active, although the brain activity was obviously left-lateralized. Unlike previous research with monolingual English speakers that showed that distinct brain regions mediate syntactic and semantic processing of English, the cortical sites contributing to syntactic analysis of Chinese phrases coincided with the cortical sites relevant to semantic analysis. Stronger brain activity, however, was seen in the left middle frontal cortex for syntactic processing (relative to semantic processing), whereas for semantic processing stronger cortical activations were shown in the left inferior prefrontal cortex and the left mid-superior temporal gyri. The overall pattern of results indicates that syntactic processing is less independent in reading Chinese. This is attributable to the linguistic nature of the Chinese language that semantics and syntax are not always clearly demarcated. Equally interesting, we discovered that when our bilingual subjects performed syntactic and semantic acceptability judgments of English phrases, they applied the cerebral systems underlying Chinese reading to the processing of English.     

A comparison of semantic feature analysis and phonological components analysis for the treatment of naming impairments in aphasia

Therapy for naming impairments post-stroke typically involves semantic and/or phonologically-based tasks. However, the relationship between individuals' locus of breakdown in word retrieval and their response to a particular treatment approach remains unclear, and direct comparisons of treatments with different targets (semantics, phonology) yet similar formats are lacking. This study examined eight people with aphasia who each received 12 treatment sessions; half the sessions involved a semantically-based treatment task, Semantic Feature Analysis (SFA), and the other half involved a phonologically-based treatment task, Phonological Components Analysis (PCA). Pre-therapy baseline accuracy scores were compared to naming accuracy post-treatment and at follow-up assessment. Seven of the eight participants showed significant improvements in naming items treated with PCA, with six of these seven participants maintaining improvements at follow-up. Four of the eight participants showed significant improvements for items treated with SFA, with three of the four maintaining improvements at follow-up. The semantic therapy was not beneficial for participants with semantic deficits. In contrast, the phonological therapy was beneficial for most participants, despite differences in underlying impairments. Understanding the relationship between an individual's locus of breakdown in word retrieval and response to different treatment tasks has the potential to optimise targeted treatment.     

脑卒中失语症和阿尔茨海默病的语义记忆损害的研究

目的分析脑卒中失语症和阿尔茨海默病的字词理解障碍的特点,探索语言在脑内的加工过程的神经机制和指导言语康复锻炼。方法采用词画匹配的方法,比较脑卒中失语症患者和阿尔茨海默病患者在呈现时间、语义相关性、字词频率、反应一致性4种条件下的字词理解的成绩。结果呈现时间作用、语义相关性作用影响失语症患者的理解成绩。字词频率是决定阿尔茨海默病患者成绩的一个主要因素。反应不一致性是失语症患者的特点,而在阿尔茨海默病患者中没有观察到反应不一致性。结论脑卒中失语症患者的字词理解障碍,是由于对已存贮的语义表象的再现受损;阿尔茨海默病患者的字词理解障碍,系由于已存贮的语义表象本身缺陷。     

Lexicality effects in word and nonword recall of semantic dementia and progressive nonfluent aphasia

Background: Verbal working memory is an essential component of many language functions, including sentence comprehension and word learning. As such, working memory has emerged as a domain of intense research interest both in aphasiology and in the broader field of cognitive neuroscience. The integrity of verbal working memory encoding relies on a fluid interaction between semantic and phonological processes. That is, we encode verbal detail using many cues related to both the sound and meaning of words. Lesion models can provide an effective means of parsing the contributions of phonological or semantic impairment to recall performance.

Methods & Procedures: We employed the lesion model approach here by contrasting the nature of lexicality errors incurred during recall of word and nonword sequences by three individuals with progressive nonfluent aphasia (a phonological dominant impairment) compared to that of two individuals with semantic dementia (a semantic dominant impairment). We focused on psycholinguistic attributes of correctly recalled stimuli relative to those that elicited a lexicality error (i.e., nonword → word OR word → nonword).

Outcomes & Results: Patients with semantic dementia showed greater sensitivity to phonological attributes (e.g., phoneme length, wordlikeness) of the target items relative to semantic attributes (e.g., familiarity). Patients with PNFA showed the opposite pattern, marked by sensitivity to word frequency, age of acquisition, familiarity, and imageability.

Conclusions: We interpret these results in favour of a processing strategy such that in the context of a focal phonological impairment patients revert to an over-reliance on preserved semantic processing abilities. In contrast, a focal semantic impairment forces both reliance on and hypersensitivity to phonological attributes of target words. We relate this interpretation to previous hypotheses about the nature of verbal short-term memory in progressive aphasia.     

Developmental differences of neurocognitive networks for phonological and semantic processing in Chinese word reading

Developmental differences in the neurocognitive networks for phonological and semantic processing in Chinese word reading were examined in 13 adults and 13 children using functional magnetic resonance imaging (fMRI). Rhyming and semantic association judgments were made to two-character words that were presented sequentially in the visual modality. These lexical tasks were compared with a nonlinguistic control task involving judgment of line patterns. The first main finding was that adults showed greater activation than children in right middle occipital gyrus on both the meaning and rhyming task, suggesting adults more effectively engage right hemisphere brain regions involved in the visual-spatial analysis of Chinese characters. The second main finding was that adults showed greater activation than children in left inferior parietal lobule for the rhyming as compared with the meaning task, suggesting greater specialization of phonological processing in adults. The third main finding was that children who had better performance in the rhyming task on characters with conflicting orthographic and phonological information relative to characters with nonconflicting information showed greater activation in left middle frontal gyrus, suggesting greater engagement of brain regions involved in the integration of orthography and phonology.     

Processing consequences of superfluous and missing prosodic breaks in auditory sentence comprehension

This ERP study investigates whether a superfluous prosodic break (i.e., a prosodic break that does not coincide with a syntactic break) has more severe processing consequences during auditory sentence comprehension than a missing prosodic break (i.e., the absence of a prosodic break at the position of a syntactic break). Participants listened to temporarily ambiguous sentences involving a prosody–syntax match or mismatch. The disambiguation of these sentences was always lexical in nature in the present experiment. This contrasts with a related study by Pauker, Itzhak, Baum, and Steinhauer (2011), where the disambiguation was of a lexical type for missing PBs and of a prosodic type for superfluous PBs. Our results converge with those of Pauker et al. (2011): superfluous prosodic breaks lead to more severe processing problems than missing prosodic breaks. Importantly, the present results extend those of Pauker et al. (2011) showing that this holds when the disambiguation is always lexical in nature. Furthermore, our results show that the way listeners use prosody can change over the course of the experiment which bears consequences for future studies.     

Effects of verb bias and syntactic ambiguity on reading in people with aphasia

Background: The Lexical Bias Hypothesis claims that people with aphasia (PWA) have difficulty understanding sentences when the verb’s argument structure bias conflicts with the sentence structure. This hypothesis can account for comprehension deficits that affect simple sentences, but the role of verb bias has not been clearly demonstrated in temporarily ambiguous sentences.

Aims: This study examined how verb bias affects comprehension of temporarily ambiguous and unambiguous sentences using self-paced reading.

Methods & Procedures: PWA and controls read sentences that contained sentential complements (e.g., The talented photographer accepted (that) the fire could not have been prevented). The main verb was biased to take a direct object (e.g., accepted) or a sentential complement (e.g., admitted). In addition, the sentential complement was either introduced by the complementiser that (i.e., unambiguous) or unmarked (i.e., ambiguous).

Results: The reading times of PWA were affected more by verb bias than by the presence of the complementiser, whereas the control group’s reading times were more affected by the presence or absence of the complementiser.

Conclusions: The results were generally consistent with the Lexical Bias Hypothesis, and showed that a mismatch between verb bias and sentence structure affected the processing of unambiguous and temporarily ambiguous sentences in PWA.