Effects of neurological damage on production of formulaic language

Acoustic cues associated with Korean sarcastic utterances produced by right- and left-hemisphere damaged individuals

PURPOSE

Sarcasm, prevalent in everyday conversation, refers to the use of words that express negative attitudes toward persons or events. Acoustic cues associated with sarcasm have been reported to vary across studies and the relative importance of particular acoustic parameters for signaling sarcasm has not been fully determined. The hemispheric specialization for the production of acoustic cues has been a matter of controversy. This study investigated the possible prosodic cues associated with Korean sarcastic utterances and the differential effect of left hemisphere damage (LHD) or right hemisphere damage (RHD) on the production of acoustic features of Korean sarcastic utterances.

METHOD

Twenty one native speakers of Korean (7 individuals with LHD, 7 individuals with RHD, and 7 healthy controls (HC)) produced six Korean utterances in two different modes: sarcastic and literal. Utterances validated by sarcasm ratings by native listeners were analyzed acoustically utilizing durational and fundamental frequency (F0) measures.

RESULTS

Listeners' ratings and acoustic analyses indicated that sarcastic utterances in Korean were produced with a combination of multiple acoustic cues. Discriminant function analyses and multiple linear regression showed that LHD and RHD differentially affected the production of acoustic cues associated with sarcasm.

CONCLUSION

LHD negatively affects the production of durational cues, while RHD negatively affects the production of F0 cues.

Age-Dependent Contribution of Domain-General Networks to Semantic Cognition

Aging is characterized by a decline of cognitive control. In semantic cognition, this leads to the paradox that older adults usually show poorer task performance than young adults despite their greater semantic knowledge. So far, the underlying neural changes of these behavioral differences are poorly understood. In the current neuroimaging study, we investigated the interaction of domain-specific and domain-general networks during verbal semantic fluency in young and older adults. Across age groups, task processing was characterized by a strong positive integration within the multiple-demand as well as between the multiple-demand and the default mode network during semantic fluency. However, the behavioral relevance of strengthened connectivity differed between groups: While within-network functional connectivity in both networks predicted greater efficiency in semantic fluency in young adults, it was associated with slower performance in older adults. Moreover, only young adults profited from connectivity between networks for their semantic memory performance. Our results suggest that the functional coupling of usually anticorrelated networks is critical for successful task processing, independent of age, when access to semantic memory is required. Furthermore, our findings lend novel support to the notion of reduced efficiency in the aging brain due to neural dedifferentiation in semantic cognition.

The Role of the Right Hemisphere White Matter Tracts in Chronic Aphasic Patients After Damage of the Language Tracts in the Left Hemisphere

The involvement of the right hemisphere (RH) in language, and especially after aphasia resulting from left hemisphere (LH) lesions, has been recently highlighted. The present study investigates white matter structure in the right hemisphere of 25 chronic post-stroke aphasic patients after LH lesions in comparison with 24 healthy controls, focusing on the four cortico-cortical tracts that link posterior parietal and temporal language-related areas with Broca’s region in the inferior frontal gyrus of the LH: the Superior Longitudinal Fasciculi II and III (SLF II and SLF III), the Arcuate Fasciculus (AF), and the Temporo-Frontal extreme capsule Fasciculus (TFexcF). Additionally, the relationship of these RH white matter tracts to language performance was examined. The patients with post-stroke aphasia in the chronic phase and the healthy control participants underwent diffusion tensor imaging (DTI) examination. The aphasic patients were assessed with standard aphasia tests. The results demonstrated increased axial diffusivity in the RH tracts of the aphasic patients. Patients were then divided according to the extent of the left hemisphere white matter loss. Correlations of language performance with radial diffusivity (RD) in the right hemisphere homologs of the tracts examined were demonstrated for the TFexcF, SLF III, and AF in the subgroup with limited damage to the LH language networks and only with the TFexcF in the subgroup with extensive damage. The results argue in favor of compensatory roles of the right hemisphere tracts in language functions when the LH networks are disrupted.

Subcortical Involvement in Formulaic Language: Studies on Bilingual Individuals With Parkinson's Disease

Purpose An impoverished production of routinized expressions, namely, formulaic language, has been reported for monolingual speakers with Parkinson's disease (PD). Little is known regarding how formulaic expressions might be manifested in individuals with neurological damage who speak more than one language. This study investigated the processing of formulaic language across first language (L1) and second language (L2) in bilingual individuals with PD. Method Eleven Korean-English bilingual speakers with PD, who acquired Korean as L1 and English as L2, were recruited for this study. Two matched control groups composed of 11 healthy Korean-English bilingual individuals and 11 healthy native English speakers were included for comparison. Their performance on three structured tasks (comprehension, completion, and judgment-correction) and conversational speech was measured and compared across groups for analyses. Results The bilingual speakers with PD had significantly impaired comprehension of formulaic language in L1 and had lower proportions of formulaic expressions in their L1 conversational speech compared with the bilingual controls. Regarding L2, both bilingual groups with and without PD were comparable in their English performance across all tasks. Both groups performed significantly poorer in L2 structured tasks than the native English speakers. Spontaneous production of formulaic language in English (L2 for bilingual individuals) was similar across all three groups. Conclusions The results of this study contribute to the growing body of literature on impoverishment of formulaic language production following subcortical dysfunction. Additionally, findings here demonstrate a selective impairment of formulaic language performance in L1 but not L2 for bilinguals with PD, further supporting the role of the basal ganglia in native language.

"You Should Praise" - "You Should Kill": The Contingent Negative Variation Indicates Moral Goodness and Badness

Moral advice (how to behave in life) is often conveyed by short, simple sentence constructions: "You - should - (plus verb with moral meaning)." Yet how moral prescriptions are processed has never been studied from a neurocognitive perspective. The results of this study suggest that the contingent negative variation (CNV) serves as a neural correlate for moral (and immoral) predictive phrases. In step 1, the original CNV paradigm (S1-S2-motor response) was extended using action-demanding three-word phrases taken from everyday contexts (e.g., "Ready-Set-Go"). In step 2, these commands were replaced by abstract words, each phrase then including a verb of moral or immoral meaning (e.g., "You should hope," "You should praise," and "You should lie"). During recording, each phrase type (e.g., moral or immoral) was presented blockwise. The task varied according to block order: Participants (n = 19) had to either listen attentively or respond with a finger tap immediately after the final word of a phrase. Electroencephalogram (EEG) data were bandpass filtered (0.1-30 Hz) and analyzed at the onset of the second word, yielding two independent responses: a bilateral CNV and a bilateral motor-related negativity, both decreasing from anterior to posterior. The results show that the CNV is sensitive to phrase constructions of moral resp. immoral valence. Thus, transfer to remote semantic fields seems possible. Importantly, this transfer is combined with a change of time frames, from restricted and highly pragmatic (as in the original paradigm) to indefinite and vague. Thus, a CNV may indicate not only preparation to action but also general guidelines for social life. An N400 occurring as an additional, task-dependent result cannot be sufficiently explained on the basis of the present data.

Rethinking the Neural Basis of Prosody and Non-literal Language: Spared Pragmatics and Cognitive Compensation in a Bilingual With Extensive Right-Hemisphere Damage

Above and beyond the critical contributions of left perisylvian regions to language, the neural networks supporting pragmatic aspects of verbal communication in native and non-native languages (L1s and L2, respectively) have often been ascribed to the right hemisphere (RH). However, several reports have shown that left-hemisphere activity associated with pragmatic domains (e.g., prosody, indirect speech, figurative language) is comparable to or even greater than that observed in the RH, challenging the proposed putative role of the latter for relevant domains. Against this background, we report on an adult bilingual patient showing preservation of pragmatic verbal skills in both languages (L1: Spanish, L2: English) despite bilateral damage mainly focused on the RH. After two strokes, the patient sustained lesions in several regions previously implicated in pragmatic functions (vast portions of the right fronto-insulo-temporal cortices, the bilateral amygdalae and insular cortices, and the left putamen). Yet, comparison of linguistic and pragmatic skills with matched controls revealed spared performance on multiple relevant tasks in both her L1 and L2. Despite mild difficulties in some aspects of L2 prosody, she showed no deficits in comprehending metaphors and idioms, or understanding indirect speech acts in either language. Basic verbal skills were also preserved in both languages, including verbal auditory discrimination, repetition of words and pseudo-words, cognate processing, grammaticality judgments, equivalent recognition, and word and sentence translation. Taken together, the evidence shows that multiple functions of verbal communication can be widely spared despite extensive damage to the RH, and that claims for a putative relation between pragmatics and the RH may have been overemphasized in the monolingual and bilingual literature. We further discuss the case in light of previous reports of pragmatic and linguistic deficits following brain lesions and address its relation to cognitive compensation in bilingual patients.

Cortical-subcortical production of formulaic language: A review of linguistic, brain disorder, and functional imaging studies leading to a production model

Formulaic language forms about one-fourth of everyday talk. Formulaic (fixed expressions) and novel (grammatical language) differ in important characteristics. The features of idioms, slang, expletives, proverbs, aphorisms, conversational speech formulas, and other fixed expressions include ranges of length, flexible cohesion, memory storage, nonliteral and situation meaning, and affective content. Neurolinguistic observations in persons with focal brain damage or progressive neurological disease suggest that producing formulaic expressions can be achieved by interactions between the right hemisphere and subcortical structures. The known functional characteristics of these structures form a compatible substrate for production of formulaic expressions. Functional imaging using a performance-based analysis supported a right hemisphere involvement in producing conversational speech formulas, while indicating that the pause fillers, uh and um, engage the left hemisphere and function like lexical items. Together these findings support a dual-process model of language, whereby formulaic and grammatical language are modulated by different cerebral structures.

Switching Language Modes: Complementary Brain Patterns for Formulaic and Propositional Language

Language has been modeled as a rule governed behavior for generating an unlimited number of novel utterances using phonological, syntactic, and lexical processes. This view of language as essentially propositional is expanding as a contributory role of formulaic expressions (e.g., you know, have a nice day, how are you?) is increasingly recognized. The basic features of the functional anatomy of this language system have been described by studies of brain damage: left lateralization for propositional language and greater right lateralization and basal ganglia involvement for formulaic expressions. Positron emission tomography (PET) studies of cerebral blood flow (CBF) have established a cortical-subcortical pattern of brain activity predictive of syllable rate during phonological/lexical repetition. The same analytic approach was applied to analyzing brain images obtained during spontaneous monologues. Sixteen normal, right-handed, native English speakers underwent PET scanning during several language tasks. Speech rate for the repetition of phonological/lexical items was predicted by increased CBF in the left inferior frontal region and decreased CBF in the head of the right caudate nucleus, replicating previous results. A complementary cortical-subcortical pattern (CBF increased in the right inferior frontal region and decreased in the left caudate) was predictive of the use of speech formulas during monologue speech. The use of propositional language during the monologues was associated with strong left lateralization (increased CBF at the left inferior frontal region and decreased CBF at the right inferior frontal region). Normal communication involves the integration of two language modes, formulaic and novel, that have different neural substrates.

Listeners' identification and evaluation of Korean idiomatic utterances produced by persons with left- or right-hemisphere damage

This study investigates the effects of left- (LHD) or right-hemisphere damage (RHD) on the production of matched idiomatic or literal expressions by examining healthy listeners' abilities to identify, evaluate and perceptually characterize the utterances. Native speakers of Korean with LHD or RHD and healthy controls (HCs) produced six ditropically ambiguous (idiomatic or literal) sentences in an elicitation and a repetition task. Healthy listeners identified the sentence types and indicated how well each utterance represented the intended meaning. Perceptual ratings of voice quality were performed by expert listeners. The results indicate a negative effect of RHD on listeners' identification and goodness ratings of utterance type. Repetition yielded better speech exemplars than elicitation. Sentence type was associated with selected voice qualities. These findings support previous reports of prosodic information serving to signal idiomatic versus literal meanings as well as a right-hemisphere involvement in formulaic language and the dual process model of language.

Production of Korean Idiomatic Utterances Following Left- and Right-Hemisphere Damage: Acoustic Studies

PURPOSE

This study investigates the effects of left- and right-hemisphere damage (LHD and RHD) on the production of idiomatic or literal expressions utilizing acoustic analyses.

METHOD

Twenty-one native speakers of Korean with LHD or RHD and in a healthy control (HC) group produced 6 ditropically ambiguous (idiomatic or literal) sentences in 2 different speech tasks: elicitation and repetition. Utterances were analyzed using durational and fundamental-frequency (F0) measures. Listeners' goodness ratings (how well each utterance represented its category: idiomatic or literal) were correlated with acoustic measures.

RESULTS

During the elicitation tasks, the LHD group differed significantly from the HC group in durational measures. Significant differences between the RHD and HC groups were seen in F0 measures. However, for the repetition tasks, the LHD and RHD groups produced utterances comparable to the HC group's performance. Using regression analysis, selected F0 cues were found to be significant predictors for goodness ratings by listeners.

CONCLUSIONS

Using elicitation, speakers in the LHD group were deficient in producing durational cues, whereas RHD negatively affected the production of F0 cues. Performance differed for elicitation and repetition, indicating a task effect. Listeners' goodness ratings were highly correlated with the production of certain acoustic cues. Both the acoustic and functional hypotheses of hemispheric specialization were supported for idiom production.

A hypothesis on improving foreign accents by optimizing variability in vocal learning brain circuits

Rapid vocal motor learning is observed when acquiring a language in early childhood, or learning to speak another language later in life. Accurate pronunciation is one of the hardest things for late learners to master and they are almost always left with a non-native accent. Here, I propose a novel hypothesis that this accent could be improved by optimizing variability in vocal learning brain circuits during learning. Much of the neurobiology of human vocal motor learning has been inferred from studies on songbirds. Jarvis (2004) proposed the hypothesis that as in songbirds there are two pathways in humans: one for learning speech (the striatal vocal learning pathway), and one for production of previously learnt speech (the motor pathway). Learning new motor sequences necessary for accurate non-native pronunciation is challenging and I argue that in late learners of a foreign language the vocal learning pathway becomes inactive prematurely. The motor pathway is engaged once again and learners maintain their original native motor patterns for producing speech, resulting in speaking with a foreign accent. Further, I argue that variability in neural activity within vocal motor circuitry generates vocal variability that supports accurate non-native pronunciation. Recent theoretical and experimental work on motor learning suggests that variability in the motor movement is necessary for the development of expertise. I propose that there is little trial-by-trial variability when using the motor pathway. When using the vocal learning pathway variability gradually increases, reflecting an exploratory phase in which learners try out different ways of pronouncing words, before decreasing and stabilizing once the “best” performance has been identified. The hypothesis proposed here could be tested using behavioral interventions that optimize variability and engage the vocal learning pathway for longer, with the prediction that this would allow learners to develop new motor patterns that result in more native-like pronunciation.

You may now kiss the bride: Interpretation of social situations by individuals with right or left hemisphere injury

While left hemisphere damage (LHD) has been clearly shown to cause a range of language impairments, patients with right hemisphere damage (RHD) also exhibit communication deficits, such as difficulties processing prosody, discourse, and social contexts. In the current study, individuals with RHD and LHD were directly compared on their ability to interpret what a character in a cartoon might be saying or thinking, in order to better understand the relative role of the right and left hemisphere in social communication. The cartoon stimuli were manipulated so as to elicit more or less formulaic responses (e.g., a scene of a couple being married by a priest vs. a scene of two people talking, respectively). Participants' responses were scored by blind raters on how appropriately they captured the gist of the social situation, as well as how formulaic and typical their responses were. Results showed that RHD individuals' responses were rated as significantly less appropriate than controls and were also significantly less typical than controls and individuals with LHD. Individuals with RHD produced a numerically lower proportion of formulaic expressions than controls, but this difference was only a trend. Counter to prediction, the pattern of performance across participant groups was not affected by how constrained/formulaic the social situation was. The current findings expand our understanding of the roles that the right and left hemispheres play in social processing and communication and have implications for the potential treatment of social communication deficits in individuals with RHD.

Formulaic Language in Parkinson's Disease and Alzheimer's Disease: Complementary Effects of Subcortical and Cortical Dysfunction

PURPOSE

The production of formulaic expressions (conversational speech formulas, pause fillers, idioms, and other fixed expressions) is excessive in the left hemisphere and deficient in the right hemisphere and in subcortical stroke. Speakers with Alzheimer's disease (AD), having functional basal ganglia, reveal abnormally high proportions of formulaic language. Persons with Parkinson's disease (PD), having dysfunctional basal ganglia, were predicted to show impoverished formulaic expressions in contrast to speakers with AD. This study compared participants with PD, participants with AD, and healthy control (HC) participants on protocols probing production and comprehension of formulaic expressions.

METHOD

Spontaneous speech samples were recorded from 16 individuals with PD, 12 individuals with AD, and 18 HC speakers. Structured tests were then administered as probes of comprehension.

RESULTS

The PD group had lower proportions of formulaic expressions compared with the AD and HC groups. Comprehension testing yielded opposite contrasts: participants with PD showed significantly higher performance compared with participants with AD and did not differ from HC participants.

CONCLUSIONS

The finding that PD produced lower proportions of formulaic expressions compared with AD and HC supports the view that subcortical nuclei modulate the production of formulaic expressions. Contrasting results on formal testing of comprehension, whereby participants with AD performed significantly worse than participants with PD and HC participants, indicate differential effects on procedural and declarative knowledge associated with these neurological conditions.

The formulaic schema in the minds of two generations of native speakers

Schemata are expressions that are fixed except for slots available for novel words (I'm not a ______ person). Our goals were to quantify speakers' knowledge, examine semantic flexibility in open slots, and compare performance data in two generations of speakers using cloze procedures in formulaic expressions, schemata open slots, fixed portions of schemata, and novel sentences. Fewer unique words appeared for the schemata-fixed and formulaic exemplars, reflecting speakers' knowledge of these utterances; the most semantic categories appeared for schemata-open responses. Age groups did not differ. Schemata exemplify creative interplay between novel lexical retrieval and fixed formulaic expression.

Melodic intonation therapy: back to basics for future research

We present a critical review of the literature on melodic intonation therapy (MIT), one of the most formalized treatments used by speech-language therapist in Broca's aphasia. We suggest basic clarifications to enhance the scientific support of this promising treatment. First, therapeutic protocols using singing as a speech facilitation technique are not necessarily MIT. The goal of MIT is to restore propositional speech. The rationale is that patients can learn a new way to speak through singing by using language-capable regions of the right cerebral hemisphere. Eventually, patients are supposed to use this way of speaking permanently but not to sing overtly. We argue that many treatment programs covered in systematic reviews on MIT's efficacy do not match MIT's therapeutic goal and rationale. Critically, we identified two main variations of MIT: the French thérapie mélodique et rythmée (TMR) that trains patients to use singing overtly as a facilitation technique in case of speech struggle and palliative versions of MIT that help patients with the most severe expressive deficits produce a limited set of useful, readymade phrases. Second, we distinguish between the immediate effect of singing on speech production and the long-term effect of the entire program on language recovery. Many results in the MIT literature can be explained by this temporal perspective. Finally, we propose that MIT can be viewed as a treatment of apraxia of speech more than aphasia. This issue should be explored in future experimental studies.

The role of subcortical structures in recited speech: Studies in Parkinson's disease

The role of subcortical structures in language function is complex and dependent on language task, with studies increasingly showing subcortical involvement for the production of formulaic language, including recited speech. Individuals with Parkinson's disease (PD), with (n = 6) and without (n = 7) surgical treatment, deep brain stimulation (DBS), were compared to healthy adults (n = 14) to determine whether individuals with subcortical dysfunction produce more errors during a recitation speech task. Participants were asked to recite poems, prayers, and rhymes familiar to them in order to determine the effects of subcortical disease on recited speech ability. When compared with healthy controls, the DBS-OFF group produced significantly more error words, suggesting that deficits in recitation arise with severe states of subcortical dysfunction. Individuals with DBS in the ON or OFF conditions did not differ significantly during the recited speech task. Results support a model of language where large units of overlearned language are at least partially modulated by subcortical structures.

Formulaic Language in Alzheimer's Disease

BACKGROUND

Studies of productive language in Alzheimer's disease (AD) have focused on formal testing of syntax and semantics but have directed less attention to naturalistic discourse and formulaic language. Clinical observations suggest that individuals with AD retain the ability to produce formulaic language long after other cognitive abilities have deteriorated.

AIMS

This study quantifies production of formulaic expressions in the spontaneous speech of individuals with AD. Persons with early- and late-onset forms of the disease were compared.

METHODS & PROCEDURES

Conversational language samples of individuals with early- (n = 5) and late-onset (n = 6) AD and healthy controls (n = 5) were analyzed to determine whether formulaic language, as measured by the number of words in formulaic expressions, differs between groups.

OUTCOMES & RESULTS

Results indicate that individuals with AD, regardless of age of onset, used significantly more formulaic expressions than healthy controls. The early- and late-onset AD groups did not differ on formulaic language measures.

CONCLUSIONS

These findings contribute to a dual process model of cerebral function, which proposes differing processing principles for formulaic and novel expressions. In this model, subcortical areas, which remain intact into late in the progression of Alzheimer's disease, play an important role in the production of formulaic language. Applications to clinical practice include identifying preserved formulaic language and providing informed counseling to patient and family.

How to engage the right brain hemisphere in aphasics without even singing: evidence for two paths of speech recovery

There is an ongoing debate as to whether singing helps left-hemispheric stroke patients recover from non-fluent aphasia through stimulation of the right hemisphere. According to recent work, it may not be singing itself that aids speech production in non-fluent aphasic patients, but rhythm and lyric type. However, the long-term effects of melody and rhythm on speech recovery are largely unknown. In the current experiment, we tested 15 patients with chronic non-fluent aphasia who underwent either singing therapy, rhythmic therapy, or standard speech therapy. The experiment controlled for phonatory quality, vocal frequency variability, pitch accuracy, syllable duration, phonetic complexity and other influences, such as the acoustic setting and learning effects induced by the testing itself. The results provide the first evidence that singing and rhythmic speech may be similarly effective in the treatment of non-fluent aphasia. This finding may challenge the view that singing causes a transfer of language function from the left to the right hemisphere. Instead, both singing and rhythmic therapy patients made good progress in the production of common, formulaic phrases—known to be supported by right corticostriatal brain areas. This progress occurred at an early stage of both therapies and was stable over time. Conversely, patients receiving standard therapy made less progress in the production of formulaic phrases. They did, however, improve their production of non-formulaic speech, in contrast to singing and rhythmic therapy patients, who did not. In light of these results, it may be worth considering the combined use of standard therapy and the training of formulaic phrases, whether sung or rhythmically spoken. Standard therapy may engage, in particular, left perilesional brain regions, while training of formulaic phrases may open new ways of tapping into right-hemisphere language resources—even without singing.

Language

Noninvasive focal brain stimulation by means of transcranial magnetic stimulation (TMS) has been used extensively in the past 20 years to investigate normal language functions. The picture emerging from this collection of empirical works is that of several independent modular functions mapped on left-lateralized temporofrontal circuits originating dorsally or ventrally to the auditory cortex. The identification of sounds as language (i.e., phonological transformations) is modulated by TMS applied over the posterior-superior temporal cortex and over the caudal inferior frontal gyrus/ventral premotor cortex complex. Conversely, attribution of semantics to words is modulated successfully by applying TMS to the rostral part of the inferior frontal gyrus. Speech production is typically interfered with by TMS applied to the left inferior frontal gyrus, onto the same cortical areas that also contain phonological representations. The cortical mapping of grammatical functions has been investigated with TMS mainly regarding the category of verbs, which seem to be represented in the left middle frontal gyrus. Most TMS studies have investigated the cortical processing of single words or sublexical elements. Conversely, complex elements of language such as syntax have not been investigated extensively, although a few studies have indicated a left temporal, frontal, and parietal system also involving the neocerebellar cortex. Finally, both the perception and production of nonlinguistic communicative properties of speech, such as prosody, have been mapped by TMS in the peri-Silvian region of the right hemisphere.

Dramatic effects of speech task on motor and linguistic planning in severely dysfluent parkinsonian speech

In motor speech disorders, dysarthric features impacting intelligibility, articulation, fluency and voice emerge more saliently in conversation than in repetition, reading or singing. A role of the basal ganglia in these task discrepancies has been identified. Further, more recent studies of naturalistic speech in basal ganglia dysfunction have revealed that formulaic language is more impaired than novel language. This descriptive study extends these observations to a case of severely dysfluent dysarthria due to a parkinsonian syndrome. Dysfluencies were quantified and compared for conversation, two forms of repetition, reading, recited speech and singing. Other measures examined phonetic inventories, word forms and formulaic language. Phonetic, syllabic and lexical dysfluencies were more abundant in conversation than in other task conditions. Formulaic expressions in conversation were reduced compared to normal speakers. A proposed explanation supports the notion that the basal ganglia contribute to formulation of internal models for execution of speech.

Rhythm in disguise: why singing may not hold the key to recovery from aphasia

The question of whether singing may be helpful for stroke patients with non-fluent aphasia has been debated for many years. However, the role of rhythm in speech recovery appears to have been neglected. In the current lesion study, we aimed to assess the relative importance of melody and rhythm for speech production in 17 non-fluent aphasics. Furthermore, we systematically alternated the lyrics to test for the influence of long-term memory and preserved motor automaticity in formulaic expressions. We controlled for vocal frequency variability, pitch accuracy, rhythmicity, syllable duration, phonetic complexity and other relevant factors, such as learning effects or the acoustic setting. Contrary to some opinion, our data suggest that singing may not be decisive for speech production in non-fluent aphasics. Instead, our results indicate that rhythm may be crucial, particularly for patients with lesions including the basal ganglia. Among the patients we studied, basal ganglia lesions accounted for more than 50% of the variance related to rhythmicity. Our findings therefore suggest that benefits typically attributed to melodic intoning in the past could actually have their roots in rhythm. Moreover, our data indicate that lyric production in non-fluent aphasics may be strongly mediated by long-term memory and motor automaticity, irrespective of whether lyrics are sung or spoken.