Fundamental Frequency , Language Processing, Linguistic Structure in Wernicke

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BRAIN AND LANGUAGE 19, l-24 (1983) Fundamental Frequency, Language Processing, and Linguistic Structure in Wernicke’s Aphasia MARTHA DANLY AND WILLIAM E. COOPER AND BARBARA SHAPIRO Five Wernicke’s aphasics and five normal control subjects were tested in order to assess several aspects of fundamental frequency (F,,) in speech production. The clinical impression of normal prosody in Wernicke’s aphasia is correct inasmuch as these patients generally exhibited F,, declination. However, F,, dec- lination ranged over shorter domains than in normal speech. Moreover. the increased use of F,) continuation rises by the Wernicke’s aphasics indicated their inability to maintain a single F,) contour over constituents which are normally integral. The hypermelodic quality of F,, in the speech of Wernicke’s aphasics further supported the notion that speech prosody was not strictly normal. F,) attributes tended to be normal when they corresponded to the global linguistic variable of sentence length, while they were abnormal when they corresponded to the processing of syntactic structure. No evidence was found that paraphasias and neologisms directly affected the programming of F,). The results are discussed in terms of speech processing abilities and limitations in Wernicke’j aphasia. This research was supported by NIH Grants NS 06029, NS 11408, NS 13028, and NS 15059, and a Dissertation Research Award to the first author from the Department of Psychology and Social Relations, Harvard University. The authors gratefully acknowledge Suzanne Hamby for assistance in testing subjects: John M. Sorensen for consulting on acoustical matters; Kenneth N. Stevens for making available the computer facilities of the Speech Communication Group, Research Laboratory of Electronics, MIT; Kyle R. Cave for advice on text editing; and Sheila E. Blumstein. Roger W. Brown, Jill G. de Villiers. Susan F. Ehrlich, Charles M. Judd. Edgar B. Zurif, and two anonymous reviewers for helpful comments on the manuscript. Please address reprint requests to: Martha Danly. Psychology Service 116-B. Aphasia Research Center, Boston Veterans Administration Medical Center. I50 South Huntington Avenue. Boston. MA 02130. I 0093-934X183 $3.00 Cop\r,ght c IYU? hy Acadcn,,c Prcr,. Ini All rIghi\ 01 rcprmlucr~on an <in> lwm ,r\cr\ed

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Transcript of Fundamental Frequency , Language Processing, Linguistic Structure in Wernicke

  • BRAIN AND LANGUAGE 19, l-24 (1983)

    Fundamental Frequency, Language Processing, and Linguistic Structure in Wernickes Aphasia

    MARTHA DANLY AND WILLIAM E. COOPER

    AND

    BARBARA SHAPIRO

    Five Wernickes aphasics and five normal control subjects were tested in order to assess several aspects of fundamental frequency (F,,) in speech production. The clinical impression of normal prosody in Wernickes aphasia is correct inasmuch as these patients generally exhibited F,, declination. However, F,, dec- lination ranged over shorter domains than in normal speech. Moreover. the increased use of F,) continuation rises by the Wernickes aphasics indicated their inability to maintain a single F,) contour over constituents which are normally integral. The hypermelodic quality of F,, in the speech of Wernickes aphasics further supported the notion that speech prosody was not strictly normal. F,) attributes tended to be normal when they corresponded to the global linguistic variable of sentence length, while they were abnormal when they corresponded to the processing of syntactic structure. No evidence was found that paraphasias and neologisms directly affected the programming of F,). The results are discussed in terms of speech processing abilities and limitations in Wernickej aphasia.

    This research was supported by NIH Grants NS 06029, NS 11408, NS 13028, and NS 15059, and a Dissertation Research Award to the first author from the Department of Psychology and Social Relations, Harvard University. The authors gratefully acknowledge Suzanne Hamby for assistance in testing subjects: John M. Sorensen for consulting on acoustical matters; Kenneth N. Stevens for making available the computer facilities of the Speech Communication Group, Research Laboratory of Electronics, MIT; Kyle R. Cave for advice on text editing; and Sheila E. Blumstein. Roger W. Brown, Jill G. de Villiers. Susan F. Ehrlich, Charles M. Judd. Edgar B. Zurif, and two anonymous reviewers for helpful comments on the manuscript. Please address reprint requests to: Martha Danly. Psychology Service 116-B. Aphasia Research Center, Boston Veterans Administration Medical Center. I50 South Huntington Avenue. Boston. MA 02130.

    I 0093-934X183 $3.00

    Cop\r,ght c IYU? hy Acadcn,,c Prcr,. Ini All rIghi\ 01 rcprmlucr~on an lwm ,r\cr\ed

  • DANLY, COOPER, AND SHAPIRO

    INTRODUCTION

    In recent years, speech prosody has become an increasingly useful medium for the study of language representation and processing in normal speech production (for reviews, see Cooper & Paccia-Cooper, 1980; Cooper & Sorensen, 1981). Speech prosody refers to variations in three acoustic properties of the speech wave: duration, amplitude, and fun- damental frequency (FO). The perceptual correlates of these attributes include speech rate and timing, stress, and intonation (Lehiste, 1970; Lieberman, 1967). Because elements of speech prosody systematically correspond to features of linguistic structure, such as sentence length, syntactic boundaries, and semantic reference, we can acquire knowledge about the underlying structure and processing of language by measuring such prosodic elements. In this paper we are primarily concerned with the acoustical analysis of speech produced by patients with Wernickes aphasia in order to provide a description of its F0 patterns. We will use the F,, patterns to examine similarities and differences between aphasic and normal speakers in terms of linguistic structure and sentence production strategies.

    Clinically, patients with Wernickes aphasia demonstrate several types of language comprehension deficits, which fall into semantic, syntactic, phonemic, and lexical domains (e.g., Rinnert & Whitaker, 1973; Parisi & Pizzamiglio, 1970; Blumstein, 1973; Zurif & Caramazza, 1976; re- spectively). In contrast, the language production of Wernickes aphasics has few overt signs of syntactic difficulty, but contains frequent errors of word and phoneme selection, termed verbal and phonemic paraphasias, respectively (Green, 1969; Buckingham & Kertesz, 1974). The resulting paraphasic speech, when combined with neologisms, yields semantically empty though fluent speech (Goodglass & Geschwind, 1976).

    Speech prosody in Wernickes aphasia is considered to remain intact (Hecaen & Albert, 1978). In fact, the intonational contour or melodic line of speech is used as a factor in the assessment of aphasia, as exemplified by the Boston Diagnostic Aphasia Examination (Goodglass & Kaplan, 1972). According to this view, Brocas and Wernickes aphasics are contrasted not only in terms of verbal fluency but in their ability to maintain an intonational contour throughout an entire sentence. Whereas the contour is limited to short phrases or is absent altogether in Brocas aphasia, Wernickes aphasics appear able to produce an intonational contour that spans an entire sentence. We suggest that this claim needs to be systematically evaluated by acoustically measuring F,,. In doing so we circumvent some of the limitations and biases inherent in perceptual judgments of this attribute. In a study of Brocas aphasics, Danly and Shapiro (1982) showed that under limited syntactic domains, some- though certainly not all-attributes of F,, can remain intact despite the clinical impression of dysprosody. Although the melodic line in Wernickes

  • WERNICKES APHASIA 3

    aphasia sounds quite normal to the clinician, it may contain certain abnormalities.

    In a preliminary study of the oral reading of five Wernickes aphasics, Cooper, Danly, and Hamby (1979) did, in fact, find a number of systematic impairments in FO. Both the normal and abnormal F,, attributes may be used to demonstrate the role of sentential and syntactic factors in sentence planning in Wernickes aphasia. The purpose of the present study, then, is to investigate these findings further and to examine their implications for psycholinguistic models of sentence processing. We also discuss the relationships among FO, speech timing, and paraphasia in order to investigate the interaction of speech prosody and lexical selection. Below we define the F,, attributes on which this study is focused and outline the experimental hypotheses corresponding to each.

    F,, Declination

    It is a well-established finding in the speech communication literature that F,, values tend to decrease throughout the course of a declarative sentence (Bolinger, 1964; Cohen & tHart, 1967; Maeda, 1976). This phenomenon, known as FO declination, is depicted in Fig. 1.

    While several descriptions of F, declination have been proposed (e.g., OShaughnessy, 1976; Pierrehumbert, 1979), the Topline Rule as developed by Sorensen and Cooper (1980) is particularly useful for our purposes here, because it can be used to reflect the sensitivity of F, to syntactic boundaries. The Topline Rule predicts peak F, values, which appear as local F,, maxima on the stressed syllables of content words for normal, nonemphatic speech (shown as PI-4 in Fig. 1).

    The presence of F,, declination in Wernickes aphasia would allow us to assess the following: (1) the speakers ability to plan and execute F.

    TIME (secl

    FIG. I. Fundamental frequency contour and Topline Rule predictions for the four-peak sentence, The book on the table wa.7 a gift ,frorn my mother. (P 1 = book; P2 = table: P3 = gift; P4 = mother.) The Topline Rule is not used to predict the first peak of the contour, because PI consistently occurs above the declination line (Olive. 1975: Maeda. 1976: Cooper & Sorensen. 1981).

  • 4 DANLY, COOPER, AND SHAPIRO

    patterns over relevant linguistic domains, and (2) the speakers ability to control F0 despite paraphasias and neologisms.

    F,, Resetting

    In normal speech, a single declination line typically spans an entire single-clause sentence. Within a given sentence with an established dec- lination function, we define F, resetting as occurring at an observed F. peak which is higher than the peak preceding it. For resetting to occur, F, declination must be present both before and after resetting; in this way, we exclude local perturbations in declination such as stress height- ening. Resetting of the declination function normally occurs between sentences or at clause boundaries of a multiclause sentence. As can be seen in Fig. 2, F. resetting occurs on the word asleep, following the relative clause. Note that the observed value of P3 is greater than the value predicted on the basis of a single-function Topline Rule (solid line), indicating F, resetting. For this sentence, it can be seen that F, values are better predicted by two declination functions (broken lines) rather than one.

    Once established, F. declination can be used as a means to determine the scope of linguistic planning in the following way. Since the F. declination function requires some preplanning in order for the speaker to initiate the sentence with an appropriate F. value, we may infer the organization of linguistic units that coincide with the F, contour. For utterances in which an intonation contour extends over the entire sentence, the pre- programming of the initial F,, value and declination indicates that, at least

    160 -

    70 I I I I I 1.0 2.0 30 4.0 5.0

    TIME (set)

    FIG. 2. Fundamental frequency contour for the sentence, The car that Sally owned was asleep on the large branch in the bee. (Pl = cat; P2 = owned; P3 = asleep; P4 = branch; PS = tree.) The solid line represents the Topline Rule predictions for a single F, declination function. Observe that P3 occurs above its predicted value, indicating F(, resetting. The broken lines represent the Topline Rule predictions for two declination functions. Note also the continuation rise on the word owned at the end of the relative clause.

  • WERNICKES APHASIA 5

    at some level, the sentence has been planned in an integral manner. In contrast, if F0 resetting occurs within a sentence, we cannot necessarily claim that the entire sentence has been preplanned; rather, the syntactic phrases or clauses that the PO contours span are more likely to be the basic planning units. We hypothesize that the linguistic impairments in Wernickes aphasia may be reflected in the occurrence of F,, resetting in sentences that normally do not require resetting.

    We might also expect F, resetting in Wernickes aphasia to differ from normal patterns in two other respects. In normal speech, one determinant of F,, resetting is the strength of syntactic boundaries, as defined by the number of phrase structure nodes intervening between two words in a surface structure tree diagram (OShaughnessy, 1979; Cooper & Sorensen, 1981). Given the syntactic comprehension deficits in Wernickes aphasia, a faulty syntactic component may be reflected as a failure in speech production to distinguish between boundaries differing in strength. For example, in normal speech we typically find more F,, resetting after a sentence-internal relative clause than after a prepositional phrase. This distinction may be lost in Wernickes aphasia, as is the case in Brocas aphasia (Danly & Shapiro, 1982). Moreover, there are certain syntactic configurations at which resetting rarely occurs in normal speech, such as minor boundaries within clauses. We might expect to find inappropriate or indiscriminate use of resetting by Wernickes aphasics in such locations, again demonstrating an underlying deficit in syntactic structure and processing.

    Continuution Rises

    Often accompanying F, resetting, the continuation rise is a second prosodic phenomenon sensitive to the variables of sentence length and syntactic boundary strength. Occurring on the last syllable preceding a syntactic boundary, a continuation rise is a 5 to 10 Hz increase in F,, (Cooper & Sorensen, 1977; OShaughnessy, 1976, 1979). In Fig. 2, the final rise on the word owned is a typical continuation rise, both in its location and size. By measuring the frequency, location, and magnitude of continuation rises in normal and Wernickes subjects, we will determine the influence of sentence length and syntactic boundaries on their use. The logic used to interpret the findings for continuation rises is similar to that used for PO resetting. Because they signal the end of major constituents, continuation rises may reveal differences in syntactic or- ganization between normal and aphasic speakers.

    The PI Ejfect

    Normal speakers take into account the general length of a sentence when programming the value of the first PO peak (Pl), such that longer sentences are produced with higher Pl values (McAllister, 1971; Sorensen

  • 6 DANLY, COOPER, AND SHAPIRO

    & Cooper, 1980). Because the final peak of sentences occurs at approx- imately the same value and the F,, declination slope remains fairly constant in single-clause sentences, a higher Pl in long sentences allows the speaker an adequate range for the declination of F0 values. The PI effect is examined in this study to establish whether overall sentence length, declination, and F0 programming are properly coordinated in the speech of Wernickes aphasics.

    Sentence-Final F. Fall

    In declarative sentences, the largest F, fall on a given word occurs on the sentence-final word (Lea, 1973; Maeda, 1976). Not only does this F. fall indicate the end of the utterance, but the minor falls which precede it reveal the speakers intention to continue the utterance. As a dem- onstration that Brocas aphasics plan speech in units larger than the single word, Danly and Shapiro (1982) showed that Brocas aphasics produce the largest F. fall in sentence-terminal position. A similar analysis will be undertaken here in order to examine the scope of speech planning in Wernickes aphasia.

    F. Variability and Speech Rate

    To study further the degree to which Wernickes speech is prosodically normal, we will determine whether normal subjects and Wemickes aphasics exhibit similar valley-peak-valley change in F,, (F,, variability). These measurements are taken by summing the F,, change from each measured words initial F. value (valley) to its greatest value (peak) to its final value (valley); any additional variation due to a continuation rise is also included. Acoustical analysis may reveal a difference between normal and aphasic subjects that cannot be detected in subjective analysis.

    As for speech rate, two recent studies have shown that speech fluency (Kreindler, Mihailescu, & Fradis, 1980) and verbal rate (Deloche, Jean- Louis, & Seron, 1979) call for more complex measures than simply the number of words uttered per unit of time. They argue that in order to characterize adequately the various forms of aphasia, a unidimensional measure of speech rate is insufficient. Consideration of variables such as overall speaking time, total number of words, number of silent pauses, and mean duration of silent pauses is also required to provide a model of speech rate that properly differentiates the types of aphasia. In the present study we will relate the above observations to the relevant acoustic data on speech timing in the reading of Wernickes aphasics. In addition, we will comment on the relationship between speech timing and paraphasia. As Butterworth (1979) has documented, paraphasias and neologisms are more likely than real words to follow hesitation pauses in the spontaneous speech of a jargon aphasic, indicating word-finding difficulty; we will determine whether this finding extends to the present subject population using a practiced reading paradigm.

  • WERNICKES APHASIA 7

    Subjects

    METHOD

    A total of IO subjects participated in this study. These included 5 right-handed male Wernickes aphasics. ranging in age from 47 to 61. All subjects were tested at the Boston Veterans Administration Hospital: they were the same subjects for which preliminary results were reported in Cooper et al. (1979). Diagnoses were based on the Boston Diagnostic Aphasia Examination (BDAE) (Goodglass & Kaplan, 1972). Each diagnosis was verified by a CT scan which, for all 5 aphasics, showed a localized lesion in the left posterior cerebral hemisphere due to an infarction of the brain tissue in the territory of the middle cerebral artery. The degree of linguistic impairment in the aphasic subjects revealed a range of severity from moderately to severely disordered. In oral reading, the least impaired subject produced paraphasias and neologisms in 1% of the content words. while the most impaired subject produced paraphasias and neologisms in about 90% of the content words.

    Five normal male subjects were also tested. Matched in age, educational level. and handedness to the experimental subjects, they were Boston-area residents who volunteered to participate in a variety of psychology experiments. In addition, we tested five patients with either anterior or posterior right-hemisphere damage. Our aim was to study neurological control subjects whose brain damage was in the nondominant hemisphere. However, upon analyzing the F,, patterns produced by the right-hemisphere patients, it was evident that they exhibited certain gross abnormalities of prosody that would require explanations distinct from those within the scope of this paper. Hence. the data gathered from these subjects will receive separate treatment (Danly. Gardner. & Shapiro. 1982).

    Sentence Materiuls The sentences listed in Table I, taken from Cooper and Sorensen (lY81), were designed

    to test the hypotheses outlined in the Introduction. The italicized key words were measured to test F,) declination and F,, resetting. In sentences l-4 we measured three peaks, in sentences 5-8 four peaks, and in sentences Y-12 five peaks. These sentences were designated as short, medium. and long sentences, respectively. Notice that the three-peak and five- peak sentences are paired to test the PI effect for short vs. long sentences. The order of

    TABLE I

    I. The deer could be .ree,r from the car.

    2. The /lost could have packed all the p/ares.

    3. The car was asleep in the tree.

    4. The fox has escaped from his cage.

    5. The book on the table was a gift from my mother.

    6. The lnan in the truck sent roses to his niec,e.

    7. The students on the bus threw ~u,n at the teacher

    8. The ducks in the park will eat popcorn and peanuts

    9. The deer by the canyon could be Seen from the ;c+doM, of the car

    10. The host at the parry could have packed all the glusses with the plafes.

    II. The cat that Sally ottaned was asleep on the large branch in the free.

    12. The fox that Sidney cauxhr had escaped sometime last night from his cage.

  • 8 DANLY, COOPER, AND SHAPIRO

    the sentences was randomized; the sentences were then presented to subjects with different pseudorandom orders shown to alternate subjects. Two filler sentences appeared as the first and last sentences of each list to eliminate the possibility of starting and finishing effects. The sentences contained no punctuation other than sentence-final periods.

    Procedure The subjects were tested individually in a sound-insulated room. At the beginning of

    each session, the experimenter told the subject that he would be given a list of sentences to read first silently to himself and then aloud. After a practice oral reading of each sentence, during which the experimenter monitored the recording levels and checked for emphatic or contrastive stress, the subject read the sentence aloud for recording. On occasion, particularly for the more disordered aphasics, the first recorded token included words that were emphatically or contrastively stressed. If so, the experimenter asked the subject to repeat the sentence, providing a verbal model of the sentence without such stress; the subject was then asked to produce the sentence a second time for recording. The Wernickes subjects appeared unable to avoid the use of stress in some sentence tokens despite their ability to repeat single words in isolation without emphasis. In such cases we analyzed the sentence token containing the least emphatic or contrastive stress.

    Paraphasias and neologisms produced by the Wernickes subjects were not corrected by the experimenter, as we were particularly interested in capturing F,) patterns in the context of paraphasic and neologistic output. The subjects read each sentence aloud until at least one clearly articulated version of the completed sentence was produced. All utterances were recorded onto a Sony TC106A tape recorder via a Sony F-25 microphone.

    Acoustical Analysis Employing a computerized procedure used in previous studies of normal speech, we

    analyzed the utterances for FO, timing, and amplitude. The F0 values were determined using Dr. W. L. Henkes FPRD program implemented on a PDP-9 computer at MITs Research Laboratory of Electronics. The program digitized the amplitude-over-time speech waveform and measured the durations of individual glottal cycles in voiced portions of speech at a sampling rate of 10 kHz. The glottal-cycle durations were then inverted to provide an estimate of F(,, which was plotted on a visual display accompanied by an amplitude trace of the speech signal. (For a more detailed description of this procedure, see Cooper & Sorensen, 1981.)

    Measurements were recorded for the initial, peak, and final F,, and time of occurrence for each key word. In addition to obtaining the above F,, measurements, we noted the use of continuation rises and made a phonemic transcription of each utterance. Paraphasias and neologisms did not hinder the experimenters ability to make the correct assignment of the produced word to its target in the typed sentence. Even for the most paraphasic subject, there was invariably a one-to-one correspondence between the number of words in the produced and intended sentences. Moreover, the function words tended to remain intact more often than the content words, thereby easing the task of mapping the output utterance onto its target.

    RESULTS

    Summarized in Table 2 are the results of the F, measures for the normal and Wernickes subjects. Below we report the findings with respect to each of the measures.

  • WERNICKES APHASIA 9

    TABLE 2 SUMMARY OF F,, MEASURES FOR NORMAL SUBJECTS AND WERNICKES APHASICS

    F,) measure

    I. F,, declination

    2. F,, resetting Short sentences Medium sentences Long sentences

    Prepositional phrase boundary Relative clause boundary

    Subject-predicate boundary Other boundaries

    3. Continuation rises Short sentences Medium sentences Long sentences

    Prepositional phrase boundary Relative clause boundary

    Subject-predicate boundary Other boundaries Magnitude

    4. PI effect Pl. short sentences PI, long sentences

    5. Sentence-final F,, fall (four-peak sentences)

    F,, fall, key word I F,, fall, key word 2 F,) fall, key word 3 F,, fall, key word 4

    6. F,, variability

    F, Declination

    Normal subjects (N = 5)

    12.7 Hz/peak

    Wernickes aphasics (N = 5)

    9.9 Hz/peak

    0% 5% 0% 55%

    60% SO%

    30% 50% 90% 50%

    N = 12 N = 22 N=2 N = 18

    0% S%

    50%

    30% 70%

    N = II N = 2

    6.2 Hz

    17% 45% 68%

    80% 50%

    N = 26 N = 25 15.0 Hz

    139.6 Hz 146.8 Hz 145.4 Hz 152.6 Hz

    - 13.2 Hz 17.6 Hz 12.0 Hz 11.6 Hz 13.0 Hz 6.0 Hz 26.4 Hz 45.6 Hz

    22.8 Hz 45.8 Hz

    The first property of FO studied was declination, in part because it is a primary feature of F, and also because it must be established prior to the examination of F,, resetting.

    To establish whether Wernickes aphasics produce F,, declination, we initially intended to calculate the least-squares linear regressions of F,, on time for the three-peak, four-peak, and five-peak sentences in order

  • 10 DANLY, COOPER, AND SHAPIRO

    to compare the slopes and goodness-of-fit measures with those for normal subjects. But since the speech rate of normal subjects was almost twice that of the aphasic subjects (the aphasics took an average of 6.54 set to produce each sentence, while the normals took 3.35 set), we considered a direct comparison of the declination slopes to be inappropriate. To avoid the bias due to speech rate differences, we instead regressed F, on the key words (peaks), thereby neutralizing the factor of time.

    Generalizing across sentence length, we found that the Wernickes aphasics produced a significant declination slope, of 9.9 Hz/peak: t(53) = 8.87, p < .OOl, r = .77. For the normal subjects, the declination slope was 12.7 Hz/peak (t(53) = 14.70, p < .OOl, Y = .90), which does not differ significantly from the Wernickes declination slope (t( 115) = 1.38, p = .17, Y = .13). These results indicate that Wernickes aphasics adequately program F. declination over sentence strings and that the total decrease in F. is comparable to normal declination. This particular finding coincides with the clinical impression that Wernickes aphasics do not suffer from a disorder of speech prosody.

    While the Wernickes aphasics, taken together, exhibited F. declination, it is noteworthy that this effect is primarily attributable to four of the five aphasic subjects (SM, WH, LMc, and ES), whose declination slopes ranged from 10.2 to 17.0 Hz/peak. The fifth subject, RD, who was the most severely aphasic of the group, produced virtually no declination whatsoever, at 0.9 Hz/peak: t(9) = .78, p > .40, Y = .25. From this observation we may conclude that F, declination is spared in Wernickes aphasia, except perhaps in the severest of cases.

    Having established F, declination in the aphasic subjects, we now turn to the role of paraphasia in the programming of Fo. One might consider that a disorder in the lexical selection process, exhibited as a paraphasia or neologism, might disrupt the maintenance of F. declination. In keeping with such a claim is the fact that RD, the most severely aphasic of the group, produced virtually no declination and was almost entirely paraphasic and neologistic (88% of the words). However, since practically all of RDs content words were either paraphasic or neologistic, his speech does not allow us to directly test the effect of paraphasia on declination; likewise there is a similar lack of variability in subjects ES, WH, and SM, whose paraphasias contributed to no more than 10% of their output. Therefore, we focused on the speech of LMc, who produced verbal paraphasias and neologisms in approximately half (54%) of the content words. We considered two possible ways in which these errors might affect declination: (1) the paraphasias and neologisms are consistently accompanied by F, peaks that fall either above or below the declination line (but not both), or (2) F. peaks of errors generally miss the declination function more than the peaks of correct words. For this analysis, we combined verbal paraphasias with neologisms into a single category of

  • WERNICKES APHASIA II

    lexical selection errors, which we will call paraphasia in this analysis for the sake of brevity.

    To test these hypotheses we performed two sets of multiple regressions. For the first, we regressed the F0 of each key word produced by LMc on peak number, sentence length, and paraphasia. The results showed that, when the other two independent variables are controlled for, para- phasias had no consistent additive or subtractive effect on F, (b = -7.9 Hz, t(44) = - 1.63, p > .lO). The second analysis was implemented in two steps. We first regressed the F, of each key word on peak number and sentence length. The resultant residuals were squared to eliminate the negative values and then regressed on paraphasia. If the second hypothesis were true, we would expect to find the large residuals paired with the paraphasic words. Yet this second analysis revealed that the paraphasias were no more inaccurately programmed for F,, than correct words (t(46) = 1.23, p > .20, r = . IS). This last result suggests that, at least in terms of F,, declination programming, errors in lexical selection do not adversely affect intonation.

    The Topline Rule as a predictor of F, is useful at this point in the analysis. Having demonstrated F, declination and its lack of interaction with paraphasia, we now turn to a more subtle comparison of F,, patterns in normal and Wernickes subjects. As mentioned in the Introduction, the Topline Rule mathematically describes the relation between F0 and time and is used to predict F, peak values between the initial and final peaks of a given sentence. One use of the Topline Rule has been to test the invariance of F, across a wide range of speaking variables. such as speakers sex, speaking rate, and grammatical category of the measured words (Cooper & Sorensen, 1981). The rules utility is also seen in the analysis of F, resetting, which occurs when observed peak values are greater than those predicted on the basis of the Topline Rule. However, the Topline Rule presupposes declination as a property of the F,, peaks: therefore it is not an ideal test of the declination slope per se.

    Figure 3 shows the Topline Rule predictions for the four-peak and five-peak sentences, along with the actual peak values produced by both groups of subjects. Observe that F, resetting appears to occur at the subject-predicate boundary (between P2 and P3) for both the Wernickes and normal subjects in the five-peak sentences, yet only for the aphasic

    It also should be noted that despite the relationship noted between extreme paraphasia and the loss of declination in patient RD. the individual declination slopes of the remaining four aphasic subjects were unrelated to the number of paraphasias that each subject produced.

    The declination slope for an N-peak sentence as defined by the Topline Rule is: 213 [(PN - Pl)/(TN - TI)]. From this formula it is clear that if PI equals PN, the slope of the declination line is zero. Thus the Topline Rule cannot be used to establish whether or not the peaks in a given utterance actually decline: rather, it is used to predict peaks intermediate to the initial and final peaks.

  • 12 DANLY, COOPER, AND SHAPIRO

    160 -

    150 -

    ;; 140 -

    5 130 -

    G E 120 -

    z 110 -

    ks &I. 100 -

    2 160 -

    2 150 -

    ii Q 140 -

    2 3 130 - Y

    120 -

    II0 -

    100 -

    4-PEAK SENTENCES

    :\

    Wernickes Aphasics

    Normal Subjects

    5-PEAK SENTENCES

    \

    Y\

    h;;\zts Subjects

    PI P2 P3 P4 P5

    PEAK NUMBER

    FIG. 3. F0 declination functions for the four-peak and five-peak sentences produced by normal speakers and Wernickes aphasics. The Topline Rule indicates similar declination slopes for the two groups of subjects. In addition, note that F,) resetting occurs at P3 for both the Wernickes aphasics and the normal speakers in the long sentences, but only for the aphasic subjects in the medium-length sentences (see text).

    subjects in the four-peak sentences. This difference in resetting is examined in more depth in the following section.

    F. Resetting

    Our three questions concerning F,, resetting may be summarized as follows: (1) As in normal speech, does sentence length determine the probability of F. resetting at the subject-predicate boundary (Cooper & Sorensen, 1981); and if so, do Wernickes aphasics maintain an F. contour over comparable amounts of material? (2) Do syntactic boundaries differing in strength trigger distinct amounts of resetting for the Wernickes subjects? (3) Do Wernickes aphasics maintain the distinction between boundaries for which resetting is either appropriate or inappropriate?

    The first question concerning sentence length and F0 resetting is answered by the data graphed in Fig. 4. Analyzing the results using a repeated- measures two-way ANOVA (subject type x sentence length), we found a significant main effect for sentence length, showing that F. resetting was more likely to occur between the subject and predicate of long rather than short sentences (F(2, 16) = 16.55, p < .OOl, q* = .67).3 The

    Eta, symbolized 7. is an effect size estimator (providing an estimate of the proportion of variance accounted for by the independent variable). which can be computed from the following formula (Freidman. 1968: Fleiss. 1969): SS,,,,,,/(SS,,,,,, + SS,,,,,,). Eta provides

  • WERNICKES APHASIA

    Normal Speakers

    Wernickes Aphasics

    /

    short medium long

    SENTENCE LENGTH

    FIG. 4. The percentage of F,, resetting at the subject-predicate boundaries of short, medium, and long sentences for normal speakers and Wernickes aphasics.

    Wernickes aphasics produced approximately equal amounts of resetting as the normal subjects in short and long sentences, but they produced more resetting in the medium-length sentences, as revealed by a statistically significant interaction between subject category and sentence length: (F(2, 16) = 6.95, p < .Ol, $ = .47). We interpret this finding as follows. Although Wernickes aphasics exhibit sensitivity to overall sentence length as a determinant of F, resetting, the use of resetting in medium-length sentences shows that their intonation contours span shorter-than-normal domains.

    Adding to the above finding, the aphasic subjects were unable to dif- ferentiate prosodically between two types of syntactic boundaries. While the normal subjects reset at 60% of the subject-predicate boundaries in the five-peak sentences, this value can be divided into two categories, with 90% resetting for boundaries preceded by relative clauses (sentences 11 and 12) vs. 30% resetting for boundaries preceded by prepositional phrases (sentences 9 and 10). This distinction was not present for the Wernickes aphasics, who reset in equal amounts following relative clauses and prepositional phrases (see Fig. 5). Tested as an interaction between subject type and boundary type in a two-way repeated-measures ANOVA, we found a significant interaction between the independent variables (F( 1, 8) = 6.00, p < .05, nz = .42). Like the resetting differences in medium- length sentences, this contrast between normal and aphasic subjects

    an estimate of the effect size, the sample size notwithstanding. Because we are performing significance tests at relatively low power with only 10 subjects. it may be useful to take 7 into account along with the probability values for each statistic when interpreting the analyses.

  • 14 DANLY, COOPER, AND SHAPIRO

    100 - 7 E _ z p 00- Normal L

    Speakers

    E a 60

    2

    ;/

    -- ----q

    b 40 Wernickes Aphasics

    z it? 2 20 2 E

    O- , , Prepositional Phrase Relative Clause BOUNDARY TYPE

    FIG. 5. The percentage of F0 resetting following prepositional phrases (sentences 9, 10) vs. relative clauses (sentences 11, 12) for normal speakers and Wernickes aphasics.

    shows that, when subjected to acoustical analysis, the speech of Wernickes aphasics exhibits a systematic deficit in FO.

    In the third analysis of F0 resetting, we observed that resetting occurred at atypical sentence locations in the aphasic subjects. To test the hypothesis that resetting occurred more frequently at inappropriate locations, we compared the frequency of resetting for subject-predicate boundaries (appropriate) and other locations (inappropriate) for both groups of subjects. Shown in Table 2, the results indicate a significant difference in the proportion of appropriate vs. inappropriate F,, resettings produced by the normal and Wernickes subjects (f(8) = 2.92, p < .02, r = .72).

    Continuation Rises

    Parallel to our analysis of F0 resetting, we examined the influence of sentence length and syntactic boundaries on F0 continuation rises. The results, graphed in Fig. 6, show a significant effect of sentence length on the probability of continuation rises occurring at the subject-predicate boundary. This effect was tested in a two-way repeated-measures ANOVA (subject type x sentence length): F(2, 16) = 19.44, p < .OOl, q2 = .94. The main effect for subject type approached significance (F(1, 8) = 4.60, p = .06, n2 = .36), indicating that the Wernickes aphasics tended to use continuation rises more frequently in general. This increased use of continuation rises by the brain-damaged subjects occurred regardless of sentence length, as shown by a nonsignificant interaction effect (F(2, 16) = 1.22, p > .30, v2 = .13). These analyses suggest that the Wernickes aphasics consider the length of constituents in planning and executing speech by placing continuation rises following and preceding lengthier phrases. Moreover, the increased use of continuation rises by the aphasic

  • WERNICKES APHASIA

    = BO- 6 _ F ; 60-

    F

    6

    u 40- /

    / /

    Wernickes Aphasics

    / /

    / -Normal / Speakers

    /

    short medium I

    long

    SENTENCE LENGTH

    FIG. 6. The percentage of F0 continuation rises preceding the subject-predicate boundaries of short, medium, and long sentences for normal speakers and Wernickes aphasics.

    subjects indicates that they are generally more likely than normal speakers to intonationally break up constituents.

    Evidence for the aphasics lack of syntactic differentiation is shown in Fig. 7 by the frequency of continuation rises in contrasting boundaries. Examining the occurrence of continuation rises at prepositional and relative clause boundaries in the five-peak sentences, it is evident that normal speakers produced more continuation rises at the larger of the two syntactic boundaries (the relative clause), whereas the Wernickes aphasics did not. This interaction was tested in a two-way repeated-measures ANOVA (subject type x boundary type), which revealed that the normal and

    2 100 -

    2 - vr

    a BO- \ NOVlKll Speakers

    k! -

    ::

    E o- 1 I

    Prepositional Phrase Relative Clause

    BOUNDARY TYPE

    FIG. 7. The percentage of F. continuation rises following prepositional phrases (sentences 9, 10) vs. relative clauses (sentences II, 12) for normal speakers and Wernickes aphasics.

  • 16 DANLY, COOPER, AND SHAPIRO

    aphasic subjects tended to treat the contrast between the two boundaries in different manners: F(1, 8) = 3.92, p = .08, n2 = .35. While this interaction is not significant at (Y = .05, the effect size is relatively large.

    Continuation rises, like F0 resetting, rarely occur at clause-internal locations in normal speech. When they consistently occur at such locations, they may reflect a defect in or the absence of a syntactic analysis of the sentence. Table 2 compares the number of continuation rises normal and aphasic subjects produce at the subject-predicate boundary (appropriate) vs. other locations (inappropriate). The Wernickes aphasics were sig- nificantly more likely than normal subjects to produce continuation rises at minor, within-clause boundaries (t(8) = 2.92, p < .02, Y = .72). This finding allows two interpretations. One, the aphasics produced more continuation rises at smaller though reasonable boundaries; that is, their threshold for production of continuation rises is lower than normal, although some syntactic hierarchy of boundaries exists, however rudi- mentary. Two, continuation rises occurred randomly within sentences, without regard to syntactic boundary strength. For the five-peak sentences, there was a total of 20 measured words, 16 of which occurred in positions at which it is reasonable to produce continuation rises-that is, nonsentence- final position. Of these 16 key words, 4 (25%) occur between the subject and predicate, the strongest syntactic boundary. In these five-peak sen- tences, the Wernickes aphasics produced a total of 25 continuation rises, 14 (56%) of which occurred at the subject-predicate boundary, more often than predicted by random placement. A matched-pairs t test com- paring the frequency of continuation rises at major vs. minor boundaries showed that they were significantly more likely to occur at the major boundary (t(4) = 2.81, p < .05, Y = .64). In a parallel analysis of F0 resetting, we found that the Wernickes aphasics also reset intonation contours significantly more often at the largest syntactic boundary of the five-peak sentences: t(4) = 7.50, p < .Ol, r = .81. Thus, the findings for F0 resetting and continuation rises, taken together, show that Wernickes aphasics produce F0 patterns that reflect the distinction between major and minor syntactic boundaries, though clear deficits exist in the processing of complex structure.

    The PI Effect

    The results of the test of the PI effect revealed that the Wernickes aphasics were able to combine the factors of sentence length and declination in order to produce higher values of Pl for longer sentences. Both the control and aphasic subjects produced PI values that were 5.8 Hz higher for the long vs. the short sentences, which is a significant main effect for sentence length in a two-way repeated-measures ANOVA (sentence

  • WERNICKES APHASIA 17

    length x subject type): F(1, 8) = 11.33, p < .Ol, r) = .59. As we have seen for F0 declination, resetting, and continuation rises, fundamental frequency remains intact when it depends on the purely sentential factor of length.

    Sentence-Final F,, Full

    We measured the magnitude of F, fall in sentence-final position in order to compare it with F. fall in nonfinal key words. Table 2 lists the mean word-final contours of Pl-4 in the four-peak sentences. A two- way repeated-measures ANOVA (word position x subject type), yielded a significant main effect for word position: F(3, 12) = 6.99, p < .Ol, q = .64. A t test comparing the final contour with the second largest nonfinal contour showed that the final contour was indeed the largest F(, fall in the four-peak sentences: t(4) = 4.77, p < .Ol, Y = $8.5. Analyses of the three-peak and five-peak sentences yielded similar results: three- peak: t(4) = 5.06, p < .Ol, I = .86; five-peak: t(4) = 4.93, p < .Ol , t = .86. The presence of the sentence-final contour in conjunction with the nonappearance of large F,, falls earlier in the sentence, lends support to the notion that Wernickes aphasics plan speech in units larger than the single word. And since the sentence-final F,, fall is intact, we document another spared feature of F, in Wernickes aphasia. However, note that the magnitude of the final F. fall for the aphasic subjects in the four- peak sentences averaged 46 Hz, greater than the normal fall of 26 Hz. Similar results were obtained for the three-peak and five-peak sentences, with the final fall averaging 48 Hz for the aphasic speakers and 24 Hz for the normal speakers. In the following section we report the differences between normal and aphasic speakers in terms of F,, variability.

    F, Variability and Speech Rate

    A certain amount of F,, fluctuation between peaks and valleys is normal (23 Hz/word in the present sample). But acoustical analysis of the Wer- nickes speech reveals that they produced twice as much F,, variability, 46 Hz/word, as the normal subjects. An ANOVA comparing F,, variability in the two groups of subjects showed a highly significant difference in the group means: F(l, 8) = 47.74, ,LJ < .OOl, q2 = .86. As mentioned above in the discussion of the sentence-terminal contour, the Wernickes aphasic subjects produced a much larger F,, fall in sentence-final position than the normal subjects. A t test revealed this difference to be significant:

    The present result is in contrast with the negative finding for the PI effect reported in the preliminary study (Cooper et al.. 1979). This difference stems from the following methodological change: Originally. we tested IO control subjects, all MIT undergraduates. whose PI effect was 13.5 Hz-larger than the .5.8-Hz PI effect of the current control subjects. This difference in results is most likely due to the fact that the current control subjects are better matched in both age and educational level to the experimental subjects.

  • 18 DANLY, COOPER, AND SHAPIRO

    t(8) = 5.60, p < .OOl, r = .89. Moreover, the magnitude of continuation rises averaged 15 Hz for the Wernickes aphasics, compared to only 6 Hz for the normal subjects. This difference was also statistically significant: t(8) = 4.84, p < .Ol, r = .88. These differences in the magnitude of F0 variability, sentence-terminal contour, and continuation rises suggest that Wernickes aphasics generally exaggerate within-word F, fluctuation. In contrast, the comparable declination slopes for the normal and aphasic subjects suggest that across-word F,, patterns are not emphasized.

    As reported above, the Wernickes aphasics produced each sentence in 6.47 set vs. 3.35 set for the normal subjects. While this difference is significant (t(8) = 6.06, p < .OOl, r = .91), it should be remembered that this result does not necessarily imply that the Wernickes aphasics were nonfluent. Because we employed a practiced reading paradigm in which the subjects were required to conform to a prespecified set of utterances, the resultant speech rate cannot be directly compared to established rates for spontaneous speech (e.g., Howes, 1964). The Wer- nickes subjects pauses accounted for almost three times as much of the total speaking time as the normal subjects pauses, whereas word durations were approximately 50% longer. For both the phonation time and silent intervals these differences were significant (phonation: t(8) = 3.84, p < .Ol, r = .80; silence: t(8) = 3.41, p < .Ol, Y = .77).

    The number of paraphasias produced by each aphasic subject was significantly correlated with speech rate: r(3) = .972, p < .Ol. Butterworth (1979) has shown that paraphasic and neologistic utterances were more likely to be preceded by pauses in a jargon aphasic, a finding that is consistent with the above statistic and the following correlation. For the three-peak sentences, paraphasias were significantly correlated with in- terpeak latency (r(38) = .48, p < .Ol), pointing more directly to paraphasias as a possible source of slow speech rate in Wernickes aphasia. However, it may be that both of these correlations are entirely due to between- subjects effects. The more rapid speech and shorter interpeak latencies may have been produced by the three mildly paraphasic subjects, ES, WH, and SM; similarly, the slow speech and long interpeak latencies may be attributable to the severely paraphasic subject, RD. This latter hypothesis is supported by the lack of correlation of paraphasia to interpeak latency in a within-subject analysis of LMc: t(46) = .96, p > .20, r = - .14. Nor does an analysis of LMcs hesitation pauses (following But- terworth, 1979), yield any relationship between paraphasias and hesitation pauses: x(1) = .25, p > .20, 4 = .08. Thus at least for the present testing paradigm and subject population, we are unable to establish a direct effect of paraphasia on speech timing.

    Yet, as noted by Butterworth, neologisms rather than paraphasias are more likely to be associated with hesitation pauses, leading to an analysis of hesitation pauses and neologisms in the speech of LMc. Butterworths

  • WERNICKES APHASIA 19

    observation matches our findings for this subject. Compared to real words, neologisms were significantly more likely to be preceded by pauses of 250 msec or greater: x2(1) = 4.80; p < .05; 4 = .38. We therefore replicate Butterworths finding for neologisms with a Wernickes aphasic in the practiced reading paradigm. Moreover, we establish a dissociation between the programming of two prosodic features: speech timing and F0 declination (upon which neologisms apparently had no effect).S This difference between the two prosodic features indicates the independence of their relationships to lexical selection in Wernickes aphasia.

    DISCUSSION

    From the constellation of F. attributes discussed above, it is clear that Wernickes aphasics exhibit systematic patterns of F-some intact, others impaired. Therefore, strictly speaking, the clinical impression of normal prosody is incorrect, though the deviations from normal prosody may be imperceptible. Yet many elements of F, are spared, which may be summarized as follows.

    When less severely disordered, Wemickes aphasics produce a significant F0 declination. However, we detected no declination in the speech of the most impaired aphasic subject. The Wernickes aphasics produce higher starting F0 values for longer sentences than for shorter ones, consistent with the PI effect found for normal speakers. This finding indicates the speakers ability to combine information about sentence length and declination slope in order to correctly program the appropriate F0 value for the first peak. We note the contrast between Wernickes and Brocas aphasics in this regard. Despite the presence of limited F, declination, Brocas aphasics do not exhibit the PI effect (Danly & Shapiro, 1982). It is likely that this difference in the two subject populations is due to the tenuous presence of F,, declination in the Brocas aphasics. We found that the declination slope was correlated with the severity of language disorder, and a normal slope was present in only one of the five Brocas aphasics. In contrast, four of the five Wernickes aphasics in the present study produced F,, declination, the slope of which was unrelated to the degree of impairment, as assessed by the BDAE. Since the Pl effect is dependent on declination, we consider the contrast between the two populations to be a logical outcome of their declination differences.

    Three other F0 properties are spared in Wernickes aphasia: sentence- final F, fall and the sentential aspects of F,, resetting and continuation rises. As in normal speech, sentence length determines the likelihood of

    This finding was established by computing the following regressions using subject LMc: After regressing F,) on peak number, initial peak. syntactic boundary. and sentence length, neither the resulting residuals nor their squares were correlated to neologism (for neologisms and the residuals. ~(27) = .02, p > .SO: for neologisms and the squared residuals, r(27) = .14, p > ,401.

  • 20 DANLY, COOPER, AND SHAPIRO

    F0 resetting and continuation rises at the subject-predicate boundary. Taken together, the presence of F0 declination, the Pl effect, sentence- final F, fall, F0 resetting, and continuation rises, indicate that Wernickes aphasics produce normal F0 patterns, in particular when F0 is governed by global, sentential factors.

    The impaired prosodic features reveal interesting abnormalities in the sentence production strategies and in the use of syntactic structure in Wernickes aphasia. The abnormal F,, patterns include the occurrence of F0 resetting in shorter sentences and at minor syntactic boundaries, increased use of continuation rises (which also occur at minor syntactic boundaries), and increased F0 variability. In addition, Wernickes aphasics fail to use F, to signal the difference between syntactic boundaries whose constituent structures are different. These findings demonstrate the lim- itations of perceptual rather than acoustical studies of speech prosody (e.g., Duchon, Stengel, & Oliva, 1980), in which either absent, impaired, or exaggerated F0 properties may remain undetected.

    The relationship between the clinical profiles and F,, measures of the subjects studied here suggests that many F,, deficits are not apparent to the listener. All five Wernickes aphasics received the highest possible score on the BDAE in the categories of grammatical form (normal range), articulatory agility (never impaired), and phrase length (seven cards). Four of the five subjects received the highest rating for the category of melodic line (YWZZS through the entire sentence), including subject RD, who did not produce F0 declination at all. From these clinical observations we remark that subtle F0 impairments are difficult to detect without the aid of acoustical instruments. Moreover, these impaired F0 attributes enable more precise judgments to be made about phrase length and grammatical form.

    We link the impaired F0 measures to three distinct sources. One cause, impaired language processing capacity, would lead to shorter domains of F, declination. Wernickes aphasic speakers divide sentences into smaller processing units than normal speakers do, as evidenced by the finding that F, resetting occurs more often within sentences of only moderate length, while its occurrence in such locations is rare in normal speech. It is possible that this effect is not present in spontaneous speech but is actually due to an eye-voice span limitation in the reading of Wernickes aphasics (e.g., Gibson & Levin, 1975). Further study of spontaneous speech should reveal whether frequent F, resetting is merely a methodological artifact. Even if this were the case, syntactic or planning deficits would not necessarily be ruled out, since the eye-voice span is dependent on such factors as syntactic competence and memory (Gibson & Levin, 1975).

    Wernickes aphasics generally produce continuation rises more often than normal speakers. Since continuation rises occur only following major

  • WERNICKES APHASIA 21

    constituents in normal speech (assuming that continuation rises serve the same function in aphasic speech), we may conclude that Wernickes aphasics have a more limited capacity for sentence processing. As further evidence of the increased segmentation of sentences, we find that aphasic speakers are more likely to produce F, resetting and continuation rises at minor syntactic boundaries. In other words, aphasic speakers pro- sodically divide sentences at appropriate boundaries, though more fre- quently than normal speakers; they also reset F, and produce continuation rises at minor syntactic boundaries, which is atypical of normal speech.

    A second cause of faulty F,,, impaired syntactic competence, may lead to the failure of Wernickes aphasics to distinguish between two types of syntactic boundaries. While normal speakers reset F0 and produce continuation rises more often following sentence-internal relative clauses than prepositional phrases, the aphasics consistently failed to do so. It is impossible to account for the Wernickes aphasics lack of F, differ- entiation in their inability to use either of the two prosodic features, since sentence length clearly determines the probability of both F,, resetting and continuation rises in these subjects. Therefore, we infer that similar amounts of resetting and continuation rises reflect a faulty syntactic representation of the sentences.

    A third possible factor underlying F0 abnormality in Wernickes aphasia is impaired articulatory control of F,, in sentence production. Kreindler. Calvarezo, and Mihailescu (1971, cited in Lesser, 1978) claim that one jargon aphasics excessive use of rhythm and rhyme reflected the patients inability to structure sentences semantically. While this explanation of F, impairment is plausible, it alone does not directly account for increased F, variability per se. We suggest that the Wernickes aphasics use of emphatic stress leads to increased F,, variability. Although Wernickes aphasics are perceptually able to detect stress patterns (as evidenced in research by Blumstein & Goodglass (1972) and the present subjects response to the experimenters instructions), they are unable to reduce emphatic stress when producing sentences. As Lehiste (1970) notes, stressed words are accompanied by higher F,) values, which could pre- sumably increase F, variability. This observation is supported by the fact that the Wernickes subjects tended either to overly stress content words or to initiate sentences with very high levels of amplitude. However, the stress account for increased F, variability does not explain the ex- aggeration of sentence-final contours and continuation rises, which do not necessarily occur on stressed syllables. Although the aphasic subjects F,, was approximately 10 Hz higher than the normal subjects F,,, the final peak of sentences produced by Wernickes aphasics was not so much greater as to explain the 23-Hz difference in the magnitude of normal and aphasic sentence-final contours. To understand fully the hy- permelodic quality of speech in Wernickes aphasia may require further

  • 22 DANLY, COOPER, AND SHAPIRO

    study of the factors that influence FO variability in normal speech; in addition, the explanation is likely to relate to interdependencies in the control of the three aspects of speech prosody, F,, timing, and amplitude.

    Having argued that limited speech planning and abnormal syntactic structure are related to F, deficits, we wish to consider the scope of these impairments. Given the well-documented speech production abilities of Wernickes aphasics (Goodglass & Kaplan, 1972; Goodglass & Gesch- wind, 1976; Hecaen & Albert, 1978), it is obvious that they retain significant abilities in the domains of planning and syntax. Supporting the notion of speech planning, we find that for normal and aphasic speech the largest F,, fall occurs in sentence-final position. We claim that the smaller FO falls on previous words indicate that the speaker intends to continue the utterance. In terms of syntax, Wernickes aphasics ably demonstrate that the major syntactic division in sentences occurs at the subject-predicate boundary, despite their lack of F, resetting and continuation rises in accordance with more complex syntactic boundaries. Therefore, in both domains-speech planning and syntactic structure-we find that Wernickes aphasics express basic characteristics in conjunction with systematic impairments.

    Despite difficulties encountered in lexical selection, Wernickes aphasics do not exhibit any observable deficits in F,, when producing paraphasias and neologisms. We note, however, that neologisms are likely to follow hesitation pauses, in agreement with Butterworths (1979) claim. This finding points to the independence of the mechanisms underlying FO programming and speech timing, observed for Brocas aphasics (Danly & Shapiro, 1982). These statements are based on a within-subject analysis of a moderately impaired Wernickes aphasic; it is possible that FO is dependent on paraphasias and neologisms, though in different subtypes or severities of aphasia (Lecours & Rouillon, 1976).

    This investigation demonstrates that the acoustical analysis of FO can serve as a useful instrument in the study of aphasia. Both normal and abnormal FO patterns give insight into the structure and function of language. The conclusions reached here could well be amended or augmented by the study of different subject populations, an increase in the sample size, the examination of F,, in spontaneous speech, and the combined study of sentence comprehension and FO production. In conclusion, it is clear that Wernickes aphasics produce FO configurations which reveal shorter- than-normal domains of speech planning and certain syntactic limitations.

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  • WERNICKES APHASIA 23

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