The ability of right- and left-hemisphere-damaged individuals to produce and interpret prosodic cues marking phrasal boundaries

A systematic review on production and comprehension of linguistic prosody in people with acquired language and communication disorders resulting from unilateral brain lesions

BACKGROUND

Prosody serves central functions in language processing including linguistic functions (linguistic prosody), like structuring the speech signal. Impairments in production and comprehension of linguistic prosody have been described for persons with unilateral right (RHDP) or left hemisphere damage (LHDP). However, reported results differ with respect to the characteristics and severities of these impairments AIMS: We conducted a systematic literature review focusing on production and comprehension of linguistic prosody at the prosody-syntax interface (i.e., phrase or sentence level) in LHDP and RHDP.

METHODS & PROCEDURES

In a systematic literature search we included: (i) empirical studies with (ii) adult RHDP and/or LHDP (iii) investigating production and/or comprehension of linguistic prosody at the (iv) phrase or sentence level (v) reporting quantitative data on prosodic measures. We excluded overview papers; studies involving participants with dysarthria, apraxia of speech, foreign accent syndrome, psychiatric diseases, and/or neurodegenerative diseases; studies focusing primarily on emotional prosody; and on lexical stress / word level; studies of which no full text was available and/or that were published in a language other than English. We searched the databases BIOSIS, MEDLINE, EMBASE, PubMed, Web of Science, CINAHL, Cochrane Library, PSYNDEX, PsycINFO and speechBITE, last searched on January 13^th 2022.We found 2,631 studies without duplicates. We identified 43 studies which were included into our systematic review. For data extraction and synthesis of results, we grouped studies by (i) modality (production vs. comprehension), (ii) function (syntactic structure vs. information structure), and (iii) by experiment task. For production studies, outcome measures were defined as the productive use of the different prosodic cues (lengthening, pause, f0, amplitude). For comprehension studies, performance measures (accuracy and reaction times) were defined as outcome measures. In accordance with the PRISMA 2020 statement (Page et al., 2021), we conducted a quality check to assess study risk of bias. Our review was pre-registered with PROSPERO (CRD42019120308).

OUTCOMES & RESULTS

Of the 43 studies reviewed, 30 studies involved RHDP (n = 309), assessing production in 15 studies and focusing on comprehension of prosody in 16 studies (one study investigated production and comprehension). LHDP (n = 438) were included in 35 studies of which 15 studied production and 21 evaluated comprehension of prosody (one study investigated production and comprehension). Despite the heterogeneity of results in the studies reviewed, our synthesis of results suggests that both LHDP and RHDP show limitations, but no complete impairment, in their production and/or comprehension of linguistic prosody. Prosodic limitations are evident in different areas of processing linguistic prosody, like syntactic disambiguation or the distinction between sentence types. There is a tendency towards more severe limitations in LHDP as compared to RHDP.

CONCLUSIONS

We only included published studies into our review and did not perform an assessment of risk of reporting bias as well as systematic certainty assessments of the outcomes. Despite these limitations, we conclude that both groups show deficits in production and comprehension of linguistic prosody, but neither LHDP nor RHDP are completely impaired in their prosodic processing. This suggests that prosody is a relevant communicative resource for LHDP and RHDP worth being addressed in speech-language-therapy.

Production and Comprehension of Prosodic Boundary Marking in Persons With Unilateral Brain Lesions

PURPOSE

Persons with unilateral brain damage in the right hemisphere (RH) or left hemisphere (LH) show limitations in processing linguistic prosody, with yet inconclusive results on their ability to process prosodically marked structural boundaries for syntactic ambiguity resolution. We aimed at systematically investigating production and comprehension of three prosodic cues (f ₀ range, final lengthening, and pause) at structural boundaries in coordinate sequences in participants with right hemisphere brain damage (RHDP) and participants with left hemisphere brain damage (LHDP).

METHOD

Twenty RHDP and 15 LHDP participated in our study. Comprehension experiment: Participants and a control group listened to coordinate name sequences with internal grouping by a prosodically marked structural boundary (grouped condition, e.g., "(Gabi und Leni) # und Nina") or without internal grouping (ungrouped condition, e.g., "Gabi und Leni und Nina") and had to identify the target condition. The strength and combinations of prosodic cues in the stimuli were manipulated. Production experiment: Participants were asked to produce coordinate sequences in the two conditions (grouped, ungrouped) in two different tasks: a Reading Aloud and a Repetition experiment. Accuracy of participants' productions was subsequently assessed in a rating study and productions were analyzed with respect to use of prosodic cues.

RESULTS

In the Comprehension experiment, RHDP and LHDP had overall lower identification accuracies than unimpaired control participants and LHDP were found to have particular problems with boundary identification when the pause cue was reduced. In production, LHDP and RHDP employed all three prosodic cues for boundary marking, but struggled to clearly mark prosodic boundaries in 28% of all productions. Both groups showed better performance in reading aloud than in repetition. LHDP relied more on using f ₀ range and pause duration to prosodically mark structural boundaries, whereas RHDP employed final lengthening more vigorously than LHDP in reading aloud.

CONCLUSIONS

We conclude that processing of linguistic prosody is affected in RHDP and LHDP, but not completely impaired. Therefore, prosody can serve as a relevant communicative resource. However, it should also be considered as a target area for assessment and treatment in both groups.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21637505.

Aprosodia Following Focal Brain Damage: What's Right and What's Left?

PURPOSE

Hemispheric specialization for the comprehension and expression of linguistic and emotional prosody is typically attributed to the right hemisphere. This study used techniques adapted from meta-analysis to critically examine the strength of existing evidence for hemispheric lateralization of prosody following brain damage.

METHOD

Twenty-one databases were searched for articles published from 1970 to 2020 addressing differences in prosody performance between groups defined by right hemisphere damage and left hemisphere damage. Hedges's g effect sizes were calculated for all possible prosody comparisons. Primary analyses summarize effects for four types: linguistic production, linguistic comprehension, emotion comprehension, and emotion production. Within each primary analysis, Hedges's g values were averaged across comparisons (usually from a single article) based on the same sample of individuals. Secondary analyses explore more specific classifications of comparisons.

RESULTS

Out of the 113 articles investigating comprehension and production of emotional and linguistic prosody, 62 were deemed appropriate for data extraction, but only 21 met inclusion criteria, passed quality reviews, and provided sufficient information for analysis. Evidence from this review illustrates the heterogeneity of research methods and results from studies that have investigated aprosodia. This review provides inconsistent support for selective contribution of the two cerebral hemispheres to prosody comprehension and production; however, the strongest finding suggests that right hemisphere lesions disrupt emotional prosody comprehension more than left hemisphere lesions.

CONCLUSION

This review highlights the impoverished nature of the existing literature; offers suggestions for future research; and highlights relevant clinical implications for the prognostication, evaluation, and treatment of aprosodia.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20334987.

Aprosodia Subsequent to Right Hemisphere Brain Damage: A Systematic Review and Meta-Analysis

OBJECTIVE

To identify which aspects of prosody are negatively affected subsequent to right hemisphere brain damage (RHD) and to evaluate the methodological quality of the constituent studies.

METHOD

Twenty-one electronic databases were searched to identify articles from 1970 to February 2020 by entering keywords. Eligibility criteria for articles included a focus on adults with acquired RHD, prosody as the primary research topic, and publication in a peer-reviewed journal. A quality appraisal was conducted using a rubric adapted from Downs and Black (1998).

RESULTS

Of the 113 articles appraised as eligible and appropriate for inclusion, 71 articles were selected to undergo data extraction for both meta-analyses of population effect size estimates and qualitative synthesis. Across all domains of prosody, the effect estimate was g = 2.51 [95% CI (1.94, 3.09), t = 8.66, p < 0.0001], based on 129 contrasts between RHD and non-brain-damaged healthy controls (NBD), indicating a significant random effects model. This effect size was driven by findings in emotional prosody, g = 2.48 [95% CI (1.76, 3.20), t = 6.88, p < 0.0001]. Overall, studies of higher quality (r_pb = 0.18, p < 0.001) and higher sample size/contrast ratio (r_pb = 0.25, p < 0.001) were more likely to report significant differences between RHD and NBD participants.

CONCLUSIONS

The results confirm consistent evidence for emotional prosody deficits in the RHD population. Inconsistent evidence was observed across linguistic prosody domains and pervasive methodological issues were identified across studies, regardless of their prosody focus. These findings highlight the need for more rigorous and sufficiently high-powered designs to examine prosody subsequent to RHD, particularly within the linguistic prosody domain.

A Systematic Review of Expressive and Receptive Prosody in People With Dementia

Purpose This review was designed to provide a systematic overview of prosody in people with a primary diagnosis of dementia (PwD) and evaluate the potential use of prosodic features for diagnosis of dementia. Method A systematic search of five databases was conducted using Medical Subject Headings and keywords. Studies included in the review were evaluated for their methodological quality using the modified Joanna Briggs Institute checklist. Results A total of 14 articles were identified as being relevant for this review. Among the 14 articles, the methodological quality ranged, with eight rated as weak, four rated as moderate, and two rated as strong. Ten of the 14 articles had people with Alzheimer's disease (AD) as participants, and the remaining four had people with frontotemporal dementia as participants. Four articles focused on receptive prosody, another six focused on expressive prosody, and the remaining four articles were investigations into both. The 14 articles presented inconsistent findings, and various tasks were used to measure prosodic features in PwD in the articles. Prosody was studied as a diagnostic tool for dementia in four of the articles, all of which were based on expressive prosody in individuals with AD. Among the four articles, three proposed the use of automatic speech analysis for diagnosis of AD. Conclusions This review demonstrates that prosody in PwD is an underinvestigated area. In particular, it was concerning that most articles were of weak methodological quality. Nevertheless, it was found that prosody may be a potential diagnostic tool for assessing dementia. More studies that replicate the existing studies and those with stronger methodology are needed to confirm that receptive and/or expressive prosody can be used for dementia diagnosis.

How do persons with apraxia of speech deal with morphological stress in Spanish? A preliminary study

Equal stress across adjacent syllables and extended syllable durations are amongst the most salient features of acquired Apraxia of Speech (AOS). Most studies conclude that there is a deficit in durational cue processing, whereas the other acoustic stress correlates remain relatively unimpaired. Spanish is a free-stress language in which stress patterns are contrastive, especially in verbal forms (e.g. lavo /'labo/ '[I] wash' vs lavó /la'bo/ '[He/she] washed'). The aim of this preliminary study is to determine whether persons with AOS are able to make the intended stress pattern identifiable and, if so, to determine which acoustic cues they use to avoid the 'equal stress' phenomenon. The results show that, for each parameter considered (duration, intensity, fundamental frequency), apraxic participants' productions differed from those of controls to varying degrees depending on the task. However, 91.7% of the apraxic participants' realisations were perceived as corresponding to the intended tense and person. These results are interpreted as deriving from a motoric deficit affecting morphological stress processing by subjects with AOS combined with an idiosyncratic compensatory use of the stress cues in order to avoid 'equal stress'.

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.

Acute Ischemic Lesions Associated with Impairments in Expression and Recognition of Affective Prosody

PURPOSE

We aimed to: (a) review existing data on the neural basis of affective prosody;(b) test the hypothesis that there are double dissociations in impairments of expression and recognition of affective prosody; and (c) identify areas of infarct associated with impaired expression and/or recognition of affective prosody after acute right hemisphere (RH) ischemic stroke.

METHODS

Participants were tested on recognition of emotional prosody in content-neutral sentences. Expression was evaluated by measuring variability in fundamental frequency. Voxel-based symptom mapping was used to identify areas associated with severity of expressive deficits.

RESULTS

We found that 9/23 patients had expressive prosody impairments; 5/9 of these patients also had impaired recognition of affective prosody; 2/9 had selective deficits in expressive prosody; recognition was not tested in 2/9. Another 6/23 patients had selective impairment in recognition of affective prosody. Severity of expressive deficits was associated with lesions in right temporal pole; patients with temporal pole lesions had deficits in expression and recognition.

CONCLUSIONS

Expression and recognition of prosody can be selectively impaired. Damage to right anterior temporal pole is associated with impairment of both, indicating a role of this structure in a mechanism shared by expression and production of affective prosody.

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.

The nature of hemispheric specialization for linguistic and emotional prosodic perception: a meta-analysis of the lesion literature

It is unclear whether there is hemispheric specialization for prosodic perception and, if so, what the nature of this hemispheric asymmetry is. Using the lesion-approach, many studies have attempted to test whether there is hemispheric specialization for emotional and linguistic prosodic perception by examining the impact of left vs. right hemispheric damage on prosodic perception task performance. However, so far no consensus has been reached. In an attempt to find a consistent pattern of lateralization for prosodic perception, a meta-analysis was performed on 38 lesion studies (including 450 left hemisphere damaged patients, 534 right hemisphere damaged patients and 491 controls) of prosodic perception. It was found that both left and right hemispheric damage compromise emotional and linguistic prosodic perception task performance. Furthermore, right hemispheric damage degraded emotional prosodic perception more than left hemispheric damage (trimmed g=-0.37, 95% CI [-0.66; -0.09], N=620 patients). It is concluded that prosodic perception is under bihemispheric control with relative specialization of the right hemisphere for emotional prosodic perception.

Use of prosodic cues in the production of idiomatic and literal sentences by individuals with right- and left-hemisphere damage

The neural bases of prosody during the production of literal and idiomatic interpretations of literally plausible idioms was investigated. Left- and right-hemisphere-damaged participants and normal controls produced literal and idiomatic versions of idioms (He hit the books.) All groups modulated duration to distinguish the interpretations. LHD patients, however, showed typical speech timing difficulties. RHD patients did not differ from the normal controls. The results partially support a differential lateralization of prosodic cues in the two cerebral hemispheres [Van Lancker, D., & Sidtis, J. J. (1992). The identification of affective-prosodic stimuli by left- and right-hemisphere-damaged subjects: All errors are not created equal. Journal of Speech and Hearing Research, 35, 963-970]. Furthermore, extended final word lengthening appears to mark idiomaticity.

The production of linguistic prosody in subjects with aphasia

This study investigated the production of linguistic prosody in subjects with left hemisphere damage (LHD). Three experiments involving the production of lexical stress in nouns vs verbs, compound nouns vs tag constructions, and echo questions vs statements were conducted. Acoustic measurements (fundamental frequency (F(0)), duration and amplitude) of the prosodic structures were examined and naive listeners were asked to identify the meanings of the utterances. The results of the acoustic measurements indicated that LHD subjects did not produce prosodic structures that were comparable to control subjects to convey different linguistic meanings in all three experiments. Naive listeners had greater difficulty identifying the intended meanings of the utterances produced by the LHD subjects than control subjects in all three experiments. The results suggest that the left hemisphere plays a role in the production of linguistic prosody.

Processing Prosodic Boundaries in Natural and Hummed Speech: An fMRI Study

Speech contains prosodic cues such as pauses between different phrases of a sentence. These intonational phrase boundaries (IPBs) elicit a specific component in event-related brain potential studies, the so-called closure positive shift. The aim of the present functional magnetic resonance imaging study is to identify the neural correlates of this prosody-related component in sentences containing segmental and prosodic information (natural speech) and hummed sentences only containing prosodic information. Sentences with 2 IPBs both in normal and hummed speech activated the middle superior temporal gyrus, the rolandic operculum, and the gyrus of Heschl more strongly than sentences with 1 IPB. The results from a region of interest analysis of auditory cortex and auditory association areas suggest that the posterior rolandic operculum, in particular, supports the processing of prosodic information. A comparison of natural speech and hummed sentences revealed a number of left-hemispheric areas within the temporal lobe as well as in the frontal and parietal lobe that were activated more strongly for natural speech than for hummed sentences. These areas constitute the neural network for the processing of natural speech. The finding that no area was activated more strongly for hummed sentences compared with natural speech suggests that prosody is an integrated part of natural speech.

Neural substrates of linguistic prosody: evidence from syntactic disambiguation in the productions of brain-damaged patients

The present investigation focussed on the neural substrates underlying linguistic distinctions that are signalled by prosodic cues. A production experiment was conducted to examine the ability of left- (LHD) and right- (RHD) hemisphere-damaged patients and normal controls to use temporal and fundamental frequency cues to disambiguate sentences which include one or more Intonational Phrase level prosodic boundaries. Acoustic analyses of subjects' productions of three sentence types-parentheticals, appositives, and tags-showed that LHD speakers, compared to RHD and normal controls, exhibited impairments in the control of temporal parameters signalling phrase boundaries, including inconsistent patterns of pre-boundary lengthening and longer-than-normal pause durations in non-boundary positions. Somewhat surprisingly, a perception test presented to a group of normal native listeners showed listeners experienced greatest difficulty in identifying the presence or absence of boundaries in the productions of the RHD speakers. The findings support a cue lateralization hypothesis in which prosodic domain plays an important role.

Auditory location in the irrelevant sound effect: The effects of presenting auditory stimuli to either the left ear, right ear or both ears

Two experiments used both irrelevant speech and tones in order to assess the effect of manipulating the spatial location of irrelevant sound. Previous research in this area had produced inconclusive results (e.g., Colle, 1980). The current study demonstrated a novel finding, that sound presented to the left ear produces the greatest level of disruption. These results were explained in terms of hemispheric specialisation for processing of some supra-linguistic components in the unattended sound. Results also supported previous research by demonstrating that both forms of irrelevant sound disrupted performance on serial memory tasks (Bridges & Jones, 1996; Colle & Welsh, 1976; Jones, Alford, Bridges, Tremblay, & Macken, 1999; Jones, Miles, & Page, 1990).

Temporal parameters as cues to phrasal boundaries: a comparison of processing by left- and right-hemisphere brain-damaged individuals

Two experiments were conducted to examine the ability of left- (LHD) and right-hemisphere-damaged (RHD) patients and normal controls to use temporal cues in rendering phrase grouping decisions. The phrase "pink and black and green" was manipulated to signal a boundary after "pink" or after "black" by altering pre-boundary word durations and pause durations at the boundary in a stepwise fashion. Stimuli were presented to listeners auditorily along with a card with three alternative groupings of colored squares from which to select the presented alternative. Results revealed that normal controls were able to use both temporal cues to identify the intended grouping. In contrast, LHD patients required longer than normal pause durations to consistently identify the intended grouping, suggesting a higher than normal threshold for perception of temporal prosodic cues. Surprisingly, the RHD patients exhibited great difficulty with the task, perhaps due to the limited acoustic cues available in the stimuli.

Sensitivity to prosodic structure in left- and right-hemisphere-damaged individuals

An experiment was conducted in order to determine whether left- (LHD) and right-hemisphere-damaged (RHD) patients exhibit sensitivity to prosodic information that is used in syntactic disambiguation. Following the work of, a cross-modal lexical decision task was performed by LHD and RHD subjects, as well as by adults without brain pathology (NC). Subjects listened to sentences with attachment ambiguities with either congruent or incongruent prosody, while performing a visual lexical decision task. Results showed that each of the unilaterally damaged populations differed from each other, as well as from the NCs in terms of sensitivity regarding prosodic cues. Specifically, the RHD group was insensitive to sentence prosody as a whole. This was in contrast to the LHD patients, who responded to the prosodic manipulation, but in the unexpected direction. Results are discussed in terms of current hypotheses regarding the hemispheric lateralization of prosodic cues.

Temporal integration of speech prosody is shaped by language experience: an fMRI study

Differences in hemispheric functions underlying speech perception may be related to the size of temporal integration windows over which prosodic features (e.g., pitch) span in the speech signal. Chinese tone and intonation, both signaled by variations in pitch contours, span over shorter (local) and longer (global) temporal domains, respectively. This cross-linguistic (Chinese and English) study uses functional magnetic resonance imaging to show that pitch contours associated with tones are processed in the left hemisphere by Chinese listeners only, whereas pitch contours associated with intonation are processed predominantly in the right hemisphere. These findings argue against the view that all aspects of speech prosody are lateralized to the right hemisphere, and promote the idea that varying-sized temporal integration windows reflect a neurobiological adaptation to meet the 'prosodic needs' of a particular language.

Hemispheric specialization of linguistic pitch patterns

Pitch is used to signal different aspects of language such as speaker identity, intonation, emphatic stress, and word identity (as signaled by lexical tones). This article reviews research studies investigating hemispheric specialization of these pitch patterns in the context of two competing hypotheses. The functional hypothesis states that pitch patterns are lateralized to different hemispheres of the brain depending on their functions. Those pitch patterns that carry a greater linguistic load (e.g., lexical tones) are lateralized to the left hemisphere, while those that carry a less linguistic load (e.g., intonation patterns signaling affective moods) are lateralized to the right hemisphere. The alternative hypothesis, the acoustic hypothesis, states that all pitch patterns, regardless of their functions, are lateralized to one hemisphere (the right hemisphere in particular). Although most researchers support the functional hypothesis, a comprehensive review, which includes lesion, dichotic-listening, and functional imaging studies of different types of pitch patterns, does not support this view. Moreover, little evidence exists for the alternative hypothesis. Possible methodological problems of these studies, alternative hypotheses, and considerations for future research are noted.

Production of stress retraction by left- and right-hemisphere-damaged patients

An acoustic-perceptual investigation of a phonological phenomenon in which stress is retracted in double-stressed words (e.g., thirTEEN vs THIRteen MEN) was undertaken to identify the locus of functional impairments in speech prosody. Subjects included left-hemisphere-damaged (LHD) and right-hemisphere-damaged (RHD) patients and nonneurological controls. They were instructed to read sentences containing double-stressed target words in the presence of a clause boundary or its absence. Whereas all three groups of subjects were capable of manipulating the acoustic parameters that signal a shift in stress, there were some differences between the performance of the patient groups and that of the normal controls. Further, stress production deficits were more severe in LHD aphasic patients than in RHD patients. LHD speakers exhibited deficits in the control of both temporal and F0 cues. Their F0 disturbance appears to be secondary to a primary deficit in temporal control at the phase or sentence level, as an increased number of continuation rises found for the LHD patients seemed to arise from lengthy pauses within sentences. Findings are highlighted to address the nature of breakdown in speech prosody and the competing views of prosodic lateralization.

Prosodic facilitation in the resolution of syntactic ambiguities in subjects with left and right hemisphere damage

The purpose of this study was to determine if prosody facilitates the comprehension of sentences containing temporary syntactic ambiguities in control, and left (LHD) and right hemisphere damaged (RHD) subjects. To test for effects of prosodic facilitation, sentences were created where prosodic boundaries coincided with (cooperating), were absent (baseline), or conflicted (conflicting) with syntactic boundaries in three response times (RTs) experiments. Despite differences in overall RTs and response accuracy for each group, all three groups responded faster and more accurately to sentences in the cooperating than in the baseline and conflicting conditions across experiments, indicating that prosody facilitates syntactic parsing in brain-damaged subjects just as it does with normal control subjects. Results are discussed in relation to psycholinguistic theories of syntactic parsing and neurolinguistic theories of hemispheric specialization in processing the acoustic properties of prosodic structures.

Gender and the integration of acoustic dimensions of prosody: implications for clinical studies

This study was conducted to detect the existence of a relationship between spectral and temporal prosodic cues and to examine gender differences in any such relationship. The rationale for the investigation was to gain a greater understanding of normal prosody and the requirements for control groups in clinical studies of prosody. Ten male and 10 female speakers with no known speech or neurological deficits participated in the study. They performed a reading task which involved delivering 10 sentences first with a declarative and then repeated with an interrogative intonation (20 sentences per speaker). Intrasubject and intersubject analyses of the speech data revealed a dependence of pitch on duration that differed between male and female speakers. Significant differences between the genders were also found in speech rate, pitch range, and pitch slope. The findings suggest that an integrated treatment of acoustic cues may provide a more invariant feature of normal prosody against which clinical groups may be compared. The data also imply that in clinical studies of the production of prosody gender should be carefully controlled.

Contextual influences on phonetic identification in aphasia: the effects of speaking rate and semantic bias

Two experiments examined the influence of context on stop-consonant voicing identification in fluent and nonfluent aphasic patients and normal controls. Listeners were required to label the initial stop in a target word varying along a voice onset time (VOT) continuum as either voiced or voiceless ([b]/[p] or [d]/[t]). Target stimuli were presented in sentence contexts in which the rate of speech of the sentence context (Experiment 1) or the semantic bias of the context (Experiment 2) was manipulated. The results revealed that all subject groups were sensitive to the contextual influences, although the extent of the context effects varied somewhat across groups and across experiments. In addition, a number of patients in both the fluent and nonfluent aphasic groups could not consistently identify even endpoint stimuli, confirming phonetic categorization impairments previously shown in such individuals. Results are discussed with respect to the potential reliance by aphasic patients on higher level context to compensate for phonetic perception deficits.

Lateralization of prosody during language production: a lesion study

To examine brain lateralization of prosody during speech, the sentence production of six right-hemisphere-lesion patients and five left-hemisphere-lesion patients was compared to that of seven normal controls using a question-answer paradigm. The task required the prosodic realization of two different syntactic structures under conditions of wide and narrow focus. Acoustical analyses were carried out on F0 and time structure. These analyses revealed a preserved ability in patients to express differences in syntactic structure via prosody. However, there were deficits in distinguishing narrow focus from wide focus. Whereas both right- and left-hemisphere lesions caused impairments in the realization of F0, time structure was mainly impaired in left-hemisphere patients. Therefore, the present results from language production support functional as well as cue-dependent hypotheses of the lateralization of prosodic processing in the brain.

Speech timing in Thai left- and right-hemisphere-damaged individuals

An acoustic analysis of syllable duration in short Thai phrases was conducted to evaluate the effects of focal brain damage on the control of speech timing. Almost all 35 of the subjects had participated in each of four previous companion studies: 13 left-brain-damaged (6 nonfluent aphasics; 7 fluent aphasics), 14 right-brain-damaged patients, and 8 normal controls. Somewhat surprisingly, results revealed relatively normal timing patterns in 3-syllable phrases in all subject groups. A comparison of the current study and the four others, however, led us to conclude that Thai-speaking nonfluent aphasics exhibit a speech timing deficit regardless of the linguistic level of representation, whereas timing deficits in fluent aphasics appear to be restricted to units larger than a syllable. Speech timing, on the other hand, appears to be intact across the board in right-brain-damaged individuals. Findings are brought to bear on theories of temporal control in brain-damaged patients.

The temporal organization of affective and non-affective speech in patients with right-hemisphere infarcts

To evaluate the right hemisphere's role in encoding speech prosody, an acoustic investigation of timing characteristics was undertaken in speakers with and without focal right-hemisphere damage (RHD) following cerebrovascular accident. Utterances varying along different prosodic dimensions (emphasis, emotion) were elicited from each speaker using a story completion paradigm, and measures of utterance rate and vowel duration were computed. Results demonstrated parallelism in how RHD and healthy individuals encoded the temporal correlates of emphasis in most experimental conditions. Differences in how RHD speakers employed temporal cues to specify some aspects of prosodic meaning (especially emotional content) were observed and corresponded to a reduction in the perceptibility of prosodic meanings when conveyed by the RHD speakers. Findings indicate that RHD individuals are most disturbed when expressing prosodic representations that vary in a graded (rather than categorical) manner in the speech signal (Blonder, Pickering, Heath et al., 1995; Pell, 1999a).

Fundamental frequency encoding of linguistic and emotional prosody by right hemisphere-damaged speakers

To illuminate the nature of the right hemisphere's involvement in expressive prosodic functions, a story completion task was administered to matched groups of right hemisphere-damaged (RHD) and nonneurological control subjects. Utterances which simultaneously specified three prosodic distinctions (emphatic stress, sentence modality, emotional tone) were elicited from each subject group and then subjected to acoustic analysis to examine various fundamental frequency (F(0)) attributes of the stimuli. Results indicated that RHD speakers tended to produce F(0) patterns that resembled normal productions in overall shape, but with significantly less F(0) variation. The RHD patients were also less reliable than normal speakers at transmitting emphasis or emotional contrasts when judged from the listener's perspective. Examination of the results across a wide variety of stimulus types pointed to a deficit in successfully implementing continuous aspects of F(0) patterns following right hemisphere insult.

Effect of sentence length on the production of linguistic stress by left- and right-hemisphere-damaged patients

An acoustical/perceptual study of phonemic stress (e.g., HOTdog vs. hot DOG) was conducted to evaluate the effect of sentence length on stress production after brain damage. Productions of phonemic stress pairs were elicited in sentence contexts of increasing length from eight left-hemisphere-damaged nonfluent (LHD-NFL), fluent LHD-FL), right-hemisphere-damaged (RHD), and normal speakers (n = 32). Tape recordings of subjects' productions were presented to naïve listeners for perceptual identification of stress placement. Acoustic analysis focused on fundamental frequency, duration, and intensity of the initial and final syllables as well as pause duration between syllables. Perceptual tests indicated that regardless of sentence length, all brain-damaged groups exhibited an impairment in the production of linguistic stress when compared to normals. The LHD-NFL group experienced the greatest difficulty in signaling stress contrasts, followed in order by the LHD-FL and RHD groups. In medium-length sentences, the LHD-FL group's performance was degraded by comparison to short-length sentences. Acoustic analysis showed that pause duration was the strongest predictor of phonemic stress for all groups. Acoustic profiles of the RHD group were similar qualitatively to those of normals, but differed quantitatively in terms of magnitude of effect associated with shifts in stress patterns. Findings are brought to bear on the nature of the stress production deficit after unilateral brain damage, the role of the right hemisphere in linguistic prosody, and the concept of "subtle phonetic deficit" in fluent aphasia.

Speech timing subsequent to brain damage: effects of utterance length and complexity

Acoustic analyses of syllable durations were conducted in order to address several hypotheses concerning deficits in the control of speech timing subsequent to focal brain damage. Groups of nonfluent and fluent aphasics, right-hemisphere-damaged patients, and normal controls produced monosyllabic root syllables in medial and final position in the context of short and long sentences and syntactically simple and complex sentences. Durations of the target syllable as a proportion of the utterance were compared across contexts and groups. Somewhat surprisingly, the results revealed relatively normal temporal patterns in all subject groups, with the main exception emerging for the nonfluent aphasic patients who failed to demonstrate normal phrase-final lengthening effects. Implications of the findings for theories of temporal control in brain-damaged patients are considered.