Abstract

In addition to the propositional content of verbal utterances, significant linguistic and emotional information is conveyed by the tone of speech. To differentiate brain regions subserving processing of linguistic and affective aspects of intonation, discrimination of sentences differing in linguistic accentuation and emotional expressiveness was evaluated by functional magnetic resonance imaging. Both tasks yielded rightward lateralization of hemodynamic responses at the level of the dorsolateral frontal cortex as well as bilateral thalamic and temporal activation. Processing of linguistic and affective intonation, thus, seems to be supported by overlapping neural networks comprising partially right-sided brain regions. Comparison of hemodynamic activation during the two different tasks, however, revealed bilateral orbito-frontal responses restricted to the affective condition as opposed to activation of the left lateral inferior frontal gyrus confined to evaluation of linguistic intonation. These findings indicate that distinct frontal regions contribute to higher level processing of intonational information depending on its communicational function. In line with other components of language processing, discrimination of linguistic accentuation seems to be lateralized to the left inferior-lateral frontal region whereas bilateral orbito-frontal areas subserve evaluation of emotional expressiveness.

Introduction

During human communication, multiple channels of information transfer operate simultaneously. Besides explicit encoding by means of the wording and the syntactic structure of verbal utterances, information is conveyed by non-verbal behavior such as facial and body gestures. Speech intonation (prosody) represents a binding element between the verbal and non-verbal level. On the one hand, it is closely related to the phonological structure of verbal utterances since it is characterized by variation of strings of speech sounds in pitch, duration and intensity (Cutler et al., 1997). On the other hand, prosody represents an audible correlate of non-verbal gestures, caused by involuntary modulations of facial and speech muscles (Banse and Scherer, 1996). Speech intonation, thus, can be classified as non-verbal suprasegmental information, superpositioned upon segmental verbal information encoded in phonological units (Cutler et al., 1997). Considering its communicational functions, speech prosody serves different linguistic as well as emotional purposes (Ackermann et al., 1993; Baum and Pell, 1999): It is used to specify linguistic information at the word (content versus content) and sentence level (sentence modus: ‘It is new?’ versus ‘It is new!’; location of sentence focus: ‘He comes back’ versus ‘He comes back’), and conveys information about a speaker's emotional state (happy tone: ‘I have received news from the editor of Cerebral Cortex’).

A variety of lesion and functional imaging studies indicate that lateralization of language competence to the left hemisphere of the human brain might not extend to all aspects of the processing of intonational information (for reviews, see Baum and Pell, 1999; Borod et al., 2001, 2002). It is unsettled, however, whether the presumed right-sided superiority for prosody comprehension is bound to the extraction of specific acoustic properties such as pitch and rhythm (Van Lancker and Sidtis, 1992; Pell and Baum, 1997a; Ivry and Robertson, 1998; Ackermann et al., 2001; Zatorre et al., 2002) or to the processing of emotional as opposed to linguistic information (Heilman et al., 1984; Behrens, 1985; Emmorey, 1987; Pell and Baum 1997b; Geigenberger and Ziegler, 2001; Schirmer et al., 2001; Borod et al., 2002; Charbonneau et al., 2003). To disentangle the functional from the acoustic level, sentences varying in linguistic accentuation (sentence focus) as well as emotional expressiveness were generated by systematic manipulation of the fundamental frequency (Fig. 1). These stimuli were presented pairwise to healthy subjects being asked to perform two different discrimination tasks (referring to either linguistic or emotional aspects of speech intonation) during functional magnetic resonance imaging (fMRI). Since both tasks require evaluation of completely identical acoustic stimuli, comparison of hemodynamic responses obtained during the different task conditions allows for the separation of task-specific responses that are independent of stimulus characteristics. In addition to the identification of cerebral structures specifically related to the discrimination of either linguistic accentuation or emotional expressiveness, each experimental condition was compared to baseline at rest to assess the common network of brain regions contributing to processing of speech intonation under both conditions.

Figure 1.

Systematic manipulation of linguistic (A) and emotional intonation (B). The German sentence ‘Der Schal ist in der Truhe’ (‘the scarf is in the chest’) was digitally resynthesized with various pitch contours. Five different patterns of sentence focus were realized by a stepwise increase of the fundamental frequency on the final word (A). The stress accentuation ranged between an utterance clearly focussed on the second word (bottom line) and one that is focussed on the final word (dotted line). For each of these synthetic sentences, five variations of emotional expressiveness were generated by manipulation of the pitch range across the whole utterance (B). Sentences with broader pitch ranges are perceived as being more excited. As shown for the middle contour of (A) (bold line), the realization of linguistic accents remains constant during manipulation of emotional expressiveness. The sentences of each stimulus pair differed in relative focus accentuation as well as in emotional expressivity.

Figure 1.

Systematic manipulation of linguistic (A) and emotional intonation (B). The German sentence ‘Der Schal ist in der Truhe’ (‘the scarf is in the chest’) was digitally resynthesized with various pitch contours. Five different patterns of sentence focus were realized by a stepwise increase of the fundamental frequency on the final word (A). The stress accentuation ranged between an utterance clearly focussed on the second word (bottom line) and one that is focussed on the final word (dotted line). For each of these synthetic sentences, five variations of emotional expressiveness were generated by manipulation of the pitch range across the whole utterance (B). Sentences with broader pitch ranges are perceived as being more excited. As shown for the middle contour of (A) (bold line), the realization of linguistic accents remains constant during manipulation of emotional expressiveness. The sentences of each stimulus pair differed in relative focus accentuation as well as in emotional expressivity.

Material and Methods

Ten healthy right-handed subjects (six males, four females, age: 20–35 years) without a history of neurological or psychiatric diseases participated in the study. Informed consent was obtained according to the Declaration of Helsinki. The Ethical Committee of the University of Tübingen had approved the investigation. Handedness was determined using the Edinburgh Inventory (Oldfield, 1971). Subjects were asked to perform two different discrimination tasks during pairwise presentation of acoustic stimuli. In two different sessions of the experiment they had to answer one of the following questions: (i) ‘Which of the two sentences is better suited to respond to the question: Where is the scarf?’ (discrimination of linguistic prosody); and (ii) ‘Which of the two sentences sounds more excited?’ (discrimination of emotional expressiveness). Answers were indicated by a touch with the right index finger on a fiber-connected button. 140 pairs of resynthesized variants of a simple declarative sentence served as test materials. Two utterances of the German sentence ‘Der Schal ist in der Truhe’ (= ‘The scarf is in the chest’), produced by a male and a female professional speaker, respectively, were used as a template for the resynthesis of various pitch contours. This sentence can be focussed on the second word, representing an answer to the question ‘What is in the chest?’, or on the final word, providing information about where the scarf is. This prosodic distinction is realized by pitch patterns showing F0-peaks on the accented syllables (Cutler et al., 1997). Based on manually set time marks for F0 edge points, pitch-manipulated versions of this sentence were generated using commercially available software (analysis and resynthesis module of Speech Lab CSL 4300; Kay Elemetrics, USA) in combination with a semi-automatic editing program for generating the pitch contours: First, five F0 contours were produced spanning an acoustic continuum between an utterance that is clearly focused on the second word and one that is focussed on the final word (Fig. 1A). On the basis of each of these five focus patterns, five additional variations were generated differing in pitch range across the whole sentence (Fig. 1B). These global variations of pitch range are perceived as modulations of emotional expressiveness, the sentences with broader F0 range representing the more excited utterances (Banse and Scherer, 1996; Pihan et al., 1997). The entire corpus of stimuli used in the experiment comprised two (male and female speaker) sets of 25 sentences each orthogonally varied on the two prosodic dimensions focus structure and expressiveness. For the fMRI experiment, stimuli were compiled such that each pair comprised differences in accent strength as well as in emotional expressiveness (sentence duration was 1.4 s, the interval between sentences 0.5 s) allowing, thus, completely identical sets of acoustic stimuli to be used under both task conditions.

Participants lay supine in a 1.5 T whole body scanner (Siemens Vision), their eyes being closed and their heads supported by a foam rubber within the head coil. Stimulus presentation was separated to 16 runs of 14 stimuli pairs each. During each run, fMRI data were acquired continuously using a multislice EPI sequence (Klose et al., 1999) covering 28 parallel axial slices (4 mm thickness, 1 mm gap, TR = 3 s, TE = 39 ms, α = 90°, FOV = 192 mm, 64 × 64 matrix). High-resolution images obtained with a T1-weighted 3-D-Turbo-Flash-Sequence served as an anatomical reference. The first five fMRI images acquired during each measurement run were discarded from further analysis in order to exclude measurements preceding T1 equilibrium. Postprocessing of functional images including 3-D motion correction, slice time correction, normalization into MNI (Montreal Neurological Institute) space (Collins et al., 1994), and spatial smoothing (10 mm FWHM) relied on SPM99 (Welcome Department of Cognitive Neurology, London, UK; http//:www.fil.ion.ucl.ac.uk/spm). Statistical evaluation was based on second level random effects analysis (height threshold: P < 0.001, T > 4.30, corrected at cluster level, extent threshold: k > 35 voxels, P < 0.05).

Results

Subjects correctly discriminated 82 ± 14% (mean ± SD) of the sentence pairs with respect to sentence focus and 78 ± 11% with respect to emotional tone. Correct responses did not differ significantly between the two tasks. As compared to the rest condition, both tasks yielded bilateral hemodynamic activation within the supplementary motor area, anterior cingulate gyrus, superior temporal gyrus, frontal operculum, anterior insula, thalamus and cerebellum. Responses within the dorsolateral frontal cortex (BA 9/45/46) showed a rightward lateralization effect whereas activation within the hand area of the primary sensorimotor cortex was limited to the left hemisphere (Fig. 2, Table 1). To identify brain regions specifically contributing to processing of linguistic or emotional intonation, the respective activation patterns were directly compared with each other using a subtraction approach. During the linguistic task, significantly stronger activation was observed within the left inferior frontal gyrus (BA 44/45 = Broca's area). By contrast, the affective condition yielded significant bilateral hemodynamic responses within the orbito-frontal cortex (BA 11/47) as compared to the linguistic task (Fig. 3, Table 1).

Figure 2. Cerebral activation during discrimination of affective and linguistic intonation. Significantly activated areas as compared to rest are projected upon the cortical surface of a template brain and upon an axial slice at the level of the thalamus (z = 9 mm). Both tasks yielded a right-ward lateralization at the level of the dorsolateral frontal cortex and bilateral responses within the superior temporal gyrus, thalamus and cerebellum. Activation of the left primary sensorimotor hand-area is associated with movement of the right index finger, required to answer the discrimination task. (SPM99, random-effect-analysis, T > 4.30, k > 35, P < 0.05, corrected).

Figure 3. Cerebral regions specifically contributing to processing of affective or linguistic intonation. Significantly activated regions, identified by the respective subtraction analysis, are superimposed upon the cortical surface of a template brain and upon an axial slice at the level of the highest activated voxels within each activation cluster. The emotional task (upper row) yielded significant responses within the bilateral orbito-basal frontal cortex (BA 11/47, z = −12 mm), whereas activation of the left inferior frontal gyrus (BA 44/45, z = 3 mm) emerged during discrimination of linguistic prosody (lower row). (SPM99, random-effect-analysis, T > 4.30, k > 35, P < 0.05, corrected).

Figure 2. Cerebral activation during discrimination of affective and linguistic intonation. Significantly activated areas as compared to rest are projected upon the cortical surface of a template brain and upon an axial slice at the level of the thalamus (z = 9 mm). Both tasks yielded a right-ward lateralization at the level of the dorsolateral frontal cortex and bilateral responses within the superior temporal gyrus, thalamus and cerebellum. Activation of the left primary sensorimotor hand-area is associated with movement of the right index finger, required to answer the discrimination task. (SPM99, random-effect-analysis, T > 4.30, k > 35, P < 0.05, corrected).

Figure 3. Cerebral regions specifically contributing to processing of affective or linguistic intonation. Significantly activated regions, identified by the respective subtraction analysis, are superimposed upon the cortical surface of a template brain and upon an axial slice at the level of the highest activated voxels within each activation cluster. The emotional task (upper row) yielded significant responses within the bilateral orbito-basal frontal cortex (BA 11/47, z = −12 mm), whereas activation of the left inferior frontal gyrus (BA 44/45, z = 3 mm) emerged during discrimination of linguistic prosody (lower row). (SPM99, random-effect-analysis, T > 4.30, k > 35, P < 0.05, corrected).

Table 1

Hemodynamic activation during discrimination of emotional and linguistic intonation


 

 
Affective versus rest
 
Linguistic versus rest
 
Affective versus linguistic
 
Linguistic versus affective
 
SMA/ACG (BA 6, 24, 32)  10.95 (−6, 9, 51) 7.58 (0, 18, 42) – – 
DLFC (BA 9, 44–46) left – 6.88 (−60, 15, 12) – 9.72 (−54, 24, 3) 
 right 9.34 (39, 42, 12) 9.60 (36, 45, 24) – – 
FO/ant. INS (BA 6,44,47) left 8.42 (−48, 18, −12) 7.39 (−48, 6, 0) – – 
 right 8.96 (51, 21, −9) 9.78 (54, 21, −6) – – 
OBFC (BA 11, 47) left 8.78 (−21, 42, −12) – 8.13 (−21, 45, −12) – 
 right 6.32 (21, 51, −12) – 6.34 (21, 51, −12) – 
STG (BA 22, 41–42) left 9.00 (−60, −21, 0) 7.54 (−60, −21, 0) – – 
 right 10.42 (63, −21, 6) 12.78 (63, −24, 6) – – 
Motor cortex (BA 4) left 7.72 (−42, −9, 54) 6.90 (−45, −9, 57) – – 
 right – – – – 
Thalamus left 6.82 (−9, −12, 6) 8.74 (−12, −12, 9) – – 
 right 4.86 (9, −12, 0) 6.82 (15, −12, 9) – – 
Cerebellum left 5.20 (−27, −42, −48) 5.94 (−39, −75, −27) – – 

 
right
 
7.63 (33, −57, −39)
 
7.35 (27, −66, −33)
 

 

 

 

 
Affective versus rest
 
Linguistic versus rest
 
Affective versus linguistic
 
Linguistic versus affective
 
SMA/ACG (BA 6, 24, 32)  10.95 (−6, 9, 51) 7.58 (0, 18, 42) – – 
DLFC (BA 9, 44–46) left – 6.88 (−60, 15, 12) – 9.72 (−54, 24, 3) 
 right 9.34 (39, 42, 12) 9.60 (36, 45, 24) – – 
FO/ant. INS (BA 6,44,47) left 8.42 (−48, 18, −12) 7.39 (−48, 6, 0) – – 
 right 8.96 (51, 21, −9) 9.78 (54, 21, −6) – – 
OBFC (BA 11, 47) left 8.78 (−21, 42, −12) – 8.13 (−21, 45, −12) – 
 right 6.32 (21, 51, −12) – 6.34 (21, 51, −12) – 
STG (BA 22, 41–42) left 9.00 (−60, −21, 0) 7.54 (−60, −21, 0) – – 
 right 10.42 (63, −21, 6) 12.78 (63, −24, 6) – – 
Motor cortex (BA 4) left 7.72 (−42, −9, 54) 6.90 (−45, −9, 57) – – 
 right – – – – 
Thalamus left 6.82 (−9, −12, 6) 8.74 (−12, −12, 9) – – 
 right 4.86 (9, −12, 0) 6.82 (15, −12, 9) – – 
Cerebellum left 5.20 (−27, −42, −48) 5.94 (−39, −75, −27) – – 

 
right
 
7.63 (33, −57, −39)
 
7.35 (27, −66, −33)
 

 

 

T-values and MNI-coordinates (in square brackets) of highest activated voxels within each region. SMA = Supplementary motor cortex; ACG = anterior cingulate gyrus; DLFC = dorsolateral frontal cortex; FO / ant. INS = frontal operculum and anterior insula; OBFC = orbito-basal frontal cortex; STG = superior temporal gyrus. Respective Brodmann-Areas (BA) are printed in brackets. SPM99, random-effect analysis, n = 10, P < 0.05 corrected, T > 4.50, k > 35 voxels).

Discussion

The obtained behavioral data demonstrate that participants discriminated patterns of linguistic accentuation and emotional expressiveness at similar levels of accuracy. Therefore, a comparable level of difficulty for both tasks can be assumed. Analysis of hemodynamic responses during task performance involved two complementary steps attempting to, first, delineate the common network of brain regions contributing to the processing of speech prosody irrespective of its communicative function and, second, to identify cerebral regions specifically related to evaluation of either linguistic or emotional aspects of intonation.

Network of Brain Regions Participating in Processing of Linguistic and Emotional Prosody

During perception of each sentence pair, continuous extraction and encoding of the acoustic features of the speech signal as well as transient storage and processing of the respective data within working memory are prerequisites for the discrimination of intonational patterns (Baddeley, 1992; Zatorre et al., 1992, 1994, 2002; Pihan et al., 1997, 2000; Wildgruber et al., 2002). Since verbal utterances were presented during both tasks, phonological (segmental), syntactic and semantic encoding must be expected to some degree, even though the linguistic structure of the stimuli was very simple and linguistic processing was not explicitly required. Furthermore, motor responses were required to indicate a subject's decision on the discrimination task. Both conditions, thus, required several common cognitive and motor operations. Therefore it is not surprising that very similar patterns of cerebral activation were observed during the two different task conditions as compared to rest.

Responses within the central motor system — including the left primary motor hand region, bilateral supplementary motor areas and the cerebellum — presumably reflect control of finger movements required to indicate the decision on the discrimination tasks by button presses after each stimulus pair. A partial contribution of these regions to non-motor aspects common to both conditions, however, can not be ruled out on the basis of our data. Cerebellar activation, for example, has been reported during discrimination of musical rhythms in prior PET experiments (Parsons, 2003). Bilateral hemodynamic responses within the superior temporal cortex and the thalamus during both tasks, indicate activation of the primary and secondary auditory cortices and the respective relay station of the acoustic pathway.

The observed tendency for rightward lateralization of hemodynamic responses within the superior temporal cortex is in accordance with the prominent role of the right temporal cortex for comprehension of intonational information as indicated by the majority of the available lesion data (Heilman et al., 1984; Darby, 1993; Starkstein et al., 1994; Breitenstein et al., 1998; Borod et al., 2002) as well as previous functional imaging studies (Zatorre, 1992, 1994; Meyer et al., 2002; Kotz et al., 2003; Mitchell et al., 2003). The temporal activation clusters bilaterally encroached upon the anterior insular cortex and the frontal operculum (BA 6/44/47). These regions have been linked to extraction of acoustic properties of the speech signal (Ackermann et al., 2001). More specifically, the right insular and frontal-opercular cortex has been assumed to contribute predominantly to pitch extraction whereas the left sided region has been linked to the extraction of segmental units from the speech signal (Meyer et al., 2002). The rather symmetric activation of the insular and fronto-opercular region as observed in the current study, therefore, might reflect extraction of segmental as well as suprasegmental acoustic information under both conditions. Finally, a prominent activation of the right dorsolateral frontal region (BA 9/45/46) emerged during both tasks. Since responses of a similar localization have been observed during discrimination of tonal patterns in previous electrophysiological (Auzou et al., 1995) and PET studies (Zatorre et al., 1992, 1994), this region has been assigned to a pitch working memory system. Discrimination of both linguistic accentuation and emotional expressiveness rely on extraction, storage and comparison of fundamental frequency variations. Therefore, recruitment of a pitch working memory system must be essential for successful performance on either of these tasks. Responses within the right dorsolateral frontal region observed in the current experiment and in prior functional imaging studies during processing of speech prosody (George et al., 1996; Buchanan et al., 2000; Wildgruber et al., 2002; Kotz et al., 2003; Mitchell et al., 2003) presumably reflect engagement of this short-term storage system. In line with this assumption, the clinical observations of impaired prosody comprehension after damage to the right frontal cortex (Breitenstein et al., 1998; Baum and Pell, 1999; Adolphs et al., 2002; Borod et al., 2002) might be caused by a deficit of the pitch working memory system. In this regard, comprehension of intonational information, thus, seems to be lateralized to the right hemisphere independent of its communicational function.

Task-specific Activation Patterns (Affective Prosody versus Linguistic Prosody)

As its main goal, the present study aimed at the identification of brain regions specifically related to the evaluation of either emotional or linguistic aspects of speech intonation. The specificity of hemodynamic responses obtained during experimental conditions depends upon the reference chosen (Newman et al., 2001). Using the resting state of the brain as baseline has been observed to reduce, eliminate, or even reverse the sign of the activity during task conditions (Stark and Squire, 2001). On the other hand, hierarchical task decomposition attempting to isolate specific cognitive components of complex tasks may yield divergent results, depending on slight changes in task-control matching (Poeppel, 1996; Newman et al., 2001). Presentation of completely identical stimuli under two highly specified conditions, therefore, might provide the most appropriate reference condition to evaluate cerebral responses related to specific cognitive operations independent from subsidiary aspects of task performance (i.e. extraction of stimulus characteristics, working memory processes, motor control mechanisms). In the present study, the comparison of activation patterns obtained during discrimination of linguistic accentuation and emotional expressiveness revealed that evaluation of these different aspects of speech prosody is to some extent subserved by distinct cerebral regions.

Comprehension of linguistic prosody requires analysis of the lexical, semantic and syntactic relevance of pitch modulation patterns. Activation of the left inferior frontal cortex (Broca's area) linked to discrimination of linguistic accentuation indicates that such operations might be housed within this region. In line with this assumption, native speakers of Thai, a tone language, showed activation of the left inferior frontal region during discrimination of linguistically relevant pitch patterns in Thai words. This activity was absent in English speaking subjects listening to identical stimuli (Gandour et al., 1998). Based on a variety of PET experiments on language processing, it has been assumed that Broca's area contributes to the verbal working memory system (Poeppel, 1996). It might be argued, therefore, that activation of this region simply reflects increased demands on the verbal working memory capacity during discrimination of linguistically relevant intonational features. This possibility can not completely be ruled out on the basis of our findings. Clinical observations, however, rather support the assumption of a specific contribution of the left hemisphere to comprehension of linguistic aspects of intonation. Heilman et al. (1984) found that patients suffering from focal left-sided brain lesions made significantly more errors in a linguistic prosody identification task as compared to comprehension of affective intonation whereas damage to the right hemisphere was associated with similar impairments on both tasks. Furthermore, Emmorey (1987) observed impaired discrimination of stress contrasts between noun compounds and noun phrases after damage to the left hemisphere whereas patients with right-sided lesions performed as well as normal control subjects. Predominant disturbance of linguistic prosody comprehension concomitant with relatively preserved processing of emotional intonation in patients with lesions of the left hemisphere has also been reported by Pell and Baum (1997b) and Geigenberger and Ziegler (2001).

Discrimination of emotional expressiveness yielded a significant increase of hemodynamic responses within the bilateral orbito-frontal cortex (BA 11/47) as compared to the linguistic task, thus, indicating a specific contribution of this region to the evaluation of emotional aspects of verbal utterances conveyed by the tone of speech. On the basis of neuro-anatomical considerations, e.g. reciprocal fiber connections to sensory cortices and limbic regions, this region might serve as a substrate for the integration of multimodal sensory information with affective reactions (Price, 1999). Accordingly, activation of the orbito-basal frontal cortex has been observed in prior functional imaging studies during perception of emotional intonation (George et al., 1996; Wildgruber et al., 2002), emotional facial expressions (Blair et al., 1999; Nakamura et al., 1999) and affective gustatory judgements (Small et al., 2001). Moreover, patients suffering from unilateral circumscribed lesions to this area showed impaired identification of emotional face and voice expressions whereas performance in non-emotional control tasks (i.e. discrimination of unfamiliar voices and recognition of environmental sounds) was found uncompromised (Hornak et al., 1996, 2003). As concerns linguistic information, disordered assignment of emotional states to story protagonists and identification of violations of social behavior concomitant with preservation of executive functions, reasoning and attribution of mental states in non-emotional contexts have been described (Blair and Cipolotti, 2000). The results of the present study provide further evidence for the assumption of a critical involvement of the orbito-frontal cortex in the processing of emotional information conveyed by various communicational channels. Regarding lateralization of responses within this region, right-sided superiority for the evaluation of emotional information has been reported by several investigations (George et al., 1996; Nakamura et al., 1999). It might be argued, therefore, that the bilateral activation as observed in the present study could be related to inter-hemispheric information transfer via activation of homologue regions within the contralateral hemisphere required for control of right index finger responses. The assumption of a bilateral involvement of this region in processing of emotional information independent of motor control demands, however, is supported by various clinical and experimental studies (Hornak et al., 1996, 2003; Gorno-Tempini et al., 2001; Maratos et al., 2001; Beer et al., 2003). A recent lesion study, moreover, found the most significant changes in social behavior to be bound to bilateral orbito-frontal damage (Hornak et al., 2003).

Conclusion

Extraction and comparison of pitch patterns, as required for the evaluation of linguistic as well as emotional aspects of intonation, was found associated with a bilateral, but partially rightward lateralized hemodynamic activation pattern within dorsolateral frontal cortex, frontal operculum, anterior insula and superior temporal cortex. In contrast, hemispheric specialization of subsequent higher-level processing of intonation contours depends on the functional role of the acoustic signals within the communication process: comprehension of linguistic aspects of speech intonation relies predominantly upon left-sided language areas whereas the evaluation of emotional tone is bound to bilateral orbito-frontal regions. These differences in hemispheric lateralization might explain the rare occurrence of severe impairments in non-verbal emotional communication as compared to relatively frequent language disabilities observed after focal brain lesions.

This study was supported by the ‘Junior science program of the Heidelberger Academy of Sciences and Humanities’ and the German Research Foundation (DFG-SPP ‘Sprachproduktion’).

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Author notes

1Department of General Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Germany and 2Section MR of CNS, Department of Neuroradiology, University of Tübingen, Germany