Eur Arch Otorhinolaryngol DOI 10.1007/s00405-013-2810-8

OTOLOGY

Brain voice processing with bilateral cochlear implants: a positron emission tomography study Arnaud Coez • Monica Zilbovicius • Evelyne Ferrary • Didier Bouccara Isabelle Mosnier • Emmanue`le Ambert-Dahan • Eric Bizaguet • Jean-Luc Martinot • Yves Samson • Olivier Sterkers



Received: 9 September 2013 / Accepted: 3 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013

Abstract Most cochlear implantations are unilateral. To explore the benefits of a binaural cochlear implant, we used water-labelled oxygen-15 positron emission tomography. Relative cerebral blood flow was measured in a binaural implant group (n = 11), while the subjects were passively listening to human voice sounds, environmental sounds non-voice or silence. Binaural auditory stimulation in the cochlear implant group bilaterally activated the temporal voice areas, whereas monaural cochlear implant stimulation only activated the left temporal voice area. Direct comparison of the binaural and the monaural cochlear implant stimulation condition revealed an additional right temporal activation during voice processing in the binaural condition and the activation of a right fronto-parietal cortical network during sound processing that has been implicated in attention. These findings provide evidence that a bilateral cochlear implant stimulation enhanced the spectral cues associated with sound perception and

improved brain processing of voice stimuli in the right temporal region when compared to a monaural cochlear implant stimulation. Moreover, the recruitment of sensory attention resources in a right fronto-parietal network allowed patients with bilateral cochlear implant stimulation to enhance their sound discrimination, whereas the same patients with only one cochlear implant stimulation had more auditory perception difficulties.

A. Coez  M. Zilbovicius  J.-L. Martinot CEA-Inserm U1000 Neuroimaging and Psychiatry, Service Hospitalier Fre´de´ric Joliot, IFR49, 91401 Orsay, France

E. Ferrary  D. Bouccara  I. Mosnier  O. Sterkers Universite´ Paris, 7 Denis Diderot, Paris, France

A. Coez  M. Zilbovicius  J.-L. Martinot  Y. Samson CEA, DRM, DSV, Service Hospitalier Fre´de´ric-Joliot, 91401 Orsay, France A. Coez (&)  E. Bizaguet Laboratoire de Correction Auditive, Eric Bizaguet, 20, rue The´re`se, 75001 Paris, France e-mail: [email protected] E. Ferrary  D. Bouccara  I. Mosnier  O. Sterkers UMR-S 867, Inserm, 75018 Paris, France E. Ferrary  D. Bouccara  E. Ambert-Dahan  O. Sterkers Service d’ORL et de Chirurgie Cervico-Faciale, AP-HP, Hoˆpital Beaujon, 92110 Clichy, France

Keywords Binaural hearing  Brain imaging  Cochlear implant  Deafness  Positron emission tomography  Temporal voice area

Introduction Hearing loss is an auditory perception disorder that induces deficits in oral communication due to an ability to perceive

E. Ferrary  D. Bouccara  I. Mosnier  O. Sterkers Institut Fe´de´ratif de Recherche Claude Bernard Physiologie et Pathologie, IFR02, 75018 Paris, France I. Mosnier  O. Sterkers Service d’ORL et de Chirurgie Cervico-Faciale, AP-HP, Hoˆpital Louis Mourier, 92700 Colombes, France Y. Samson Service Urgences Ce´re´bro-Vasculaires, AP-HP, Hoˆpital Pitie´-Salpe´trie`re, 75013 Paris, France Y. Samson Universite´ Paris, 6 Pierre et Marie Curie, Paris, France

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acoustical cues important for speech production and understanding. Patients with hearing loss have difficulty in distinguishing speech and voices from other sounds such as environmental noises. Individuals with hearing loss may benefit from cochlear implantation to improve voice and speech cue transduction. Most current cochlear implants (CI) are multichannel devices that provide intra-cochlear stimulation, exploiting the tonotopic organisation of the cochlea and the central auditory pathways. Psychophysical experiments have demonstrated that stimulating different cochlear electrodes elicits auditory perception of different pitches and that the identification of consonants, vowels and words significantly improved as the number of bands increased [1]. The functional results ranged from the restoration of sound perception to full speech intelligibility and voice recognition [2]. The outcome of implantation depended on the implant signal, its coupling to the central auditory system and the ability of the auditory system and other related brain systems to learn how to most efficiently obtain information from the signal [3]. Monaural or binaural cochlear implantation Although binaural perception is important for normal hearing, recent clinical studies have demonstrated that bilateral perception improves speech intelligibility and sound localisation in complex, noisy environments [4]. The majority of the 120,000 patients [2] who have benefited from cochlear implantation only have one cochlear implant. Binaural information (interaural time and level differences) and the spectral shaping of sounds by the pinna are used for sound source localisation and to increase the ability to distinguish background noise [5]. The overall increase in sound quality is attributed to the head shadow effect, the squelch effect and the diotic summation effect [6]. It is still unknown whether two CI compared to one CI could enhance voice and speech perception and whether their response properties differ in the two brain hemispheres. Cochlear implants and neuroimaging Functional neuroimaging studies provide an insight into the cortical changes that take place in patients with cochlear implant (see review [7]), and especially in bilateral cochlear implant users [8, 9]. Recent (H15 2 O) positron emission tomography (PET) activation studies [10, 11] have suggested that PET is an effective method to explore the benefit of cochlear implants and that improvements in speech intelligibility can be linked to the activation of the temporal voice area (TVA), which is located bilaterally along the upper bank of the superior temporal sulcus (STS). In adults, the cerebral processing of vocal sounds is known to engage TVAs that are primarily located along the middle

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and anterior parts of the STS. Functional magnetic resonance imaging (fMRI) studies have shown increased activity in the TVA in response to voices (speech and nonspeech vocalisations, such as laughs and coughs) when compared to natural non-vocal sounds (environmental and musical sounds) or to amplitude- or frequency-matched acoustical control sounds [12]. A previous study [12] examined how the activation of voice-sensitive areas and the subjects’ performance on voice-perception tasks are affected by modifying the spectral structure of the stimuli. Sets of vocal and non-vocal sounds were presented during scanning, and spectral filtering removed either the high or low frequencies. The mean activity in the TVA was enhanced by vocal stimuli in comparison to non-vocal stimuli, but the activity was significantly decreased by spectral filtering. A CI was used as one method of spectral filtering [1]. To measure the benefit of two independent sites of cochlear stimulation provided by a bilateral CI, we used PET (H15 2 O) to study TVA activation. We hypothesised that an improvement in spectral cue transmission by bilateral CI stimulation would produce stronger TVA activation when compared to a unilateral implant stimulation.

Materials and methods Subjects Eleven male patients with bilateral cochlear implants and an average age of 56 years ± 9 (mean ± SD, n = 11) were studied during binaural or monaural stimulation. Written informed consent was obtained from all subjects. The Xavier-Bichat Hospital Ethics Committee approved the protocol. Patients had bilateral progressive (n = 8), otosclerosis (n = 2), or meningitis (n = 1) post-lingual deafness. They were bilaterally implanted between 2003 and 2006 with Opus 2 cochlear implants containing 12 active electrodes (Medel Inc, Innsbruck, Austria), and they had 3 years ± 1 (mean ± SD, n = 11) of cochlear implant experience. The CI was used more than 8 h a day. The mean auditory threshold (average of auditory thresholds at 500 Hz, 1, 2 and 4 kHz) measured in the free field with warble tones was 23 dB ± 7 (mean ± SD, n = 11). The average intelligibility score on the Lafon monosyllabic task at 65 dB in the free field of the binaural condition was 75 % ± 23, which was higher than in the monaural condition (54 ± 28 %, p \ 0.05). Task and stimuli The subjects were scanned while passively listening to voice sounds (30 % speech sounds, 70 % non-speech vocal

Eur Arch Otorhinolaryngol

sounds) or to only non-voice stimuli (19 % nature, 24 % animals, 47 % modern human environment, and 10 % musical instruments). The same stimuli were used in the original fMRI study [12]. Twelve PET (ECAT-EXACTHR?; Siemens AG, Erlangen, Germany) acquisitions after an intravenous bolus of (H15 2 O) (333 MBq per injection) were obtained at 10-min intervals during passive listening: four measurements occurred during passive listening to the voice condition (two during a binaural stimulation, two during a monaural stimulation), four occurred during passive listening to a non-voice condition (two during a binaural stimulation, two during a monaural stimulation), and four occurred during passive listening in silence. The listening blocks were presented to the patient in random order at a mean sound pressure level of 65 dB through KOSS electrostatic headphones. Patients were asked to listen carefully to the sounds with their eyes closed and while awake, which was systematically checked during the exam. At the end of the PET exam, the patients were asked to report what they had heard. PET acquisition The rCBF was determined from the distribution of radioactivity measured with the PET (ECAT-EXACT-HR?, Siemens AG, Erlangen, Germany) after intravenous H15 2 O bolus injections [13]. Listeners received 12 H15 2 O injections (333 MBq per injection) corresponding to the 12 rCBF measurements that were performed at 10-min intervals. The first scan corresponded to a silent condition. There was a fixed period of 30 s between the bolus infusion and the presentation of the stimuli. The attenuation-corrected data were reconstructed into 63 axial slices (2.25 mm thick) with a resulting resolution of 4.5 mm full width at half maximum after reconstruction [14]. Data analyses The rCBF images were analysed using statistical parametric mapping software (SPM99) that was used for image realignment, transformation into standard stereotaxic anatomical space [15], smoothing (12 mm) and statistical analyses [16]. The state-dependent differences in global flow were covaried using proportional scaling. Comparisons across conditions were made using a t test that was subsequently transformed into normally distributed z statistics using a multi-study design. The resulting z map threshold was at p \ 0.001. Three statistical analyses of activation were performed in the monaural and binaural conditions: a comparison of activation for listening to voice and non-voice sounds versus the silent condition (p = 0.001; corrected for multiple comparisons to p = 0.05) and a comparison between

voice stimuli and non-voice stimuli (p = 0.00005). These analyses were then examined by a between-condition comparison relative to the results obtained in the CI monaural and binaural stimulation conditions for the voice and non-voice stimuli (p = 0.001) and for the voice and non-voice conditions compared to the silent condition (p = 0.0001).

Results Comparing voice to non-voice stimuli during monaural and binaural conditions Activation was observed bilaterally in the TVA in the binaural CI stimulation condition. In contrast, in the monaural condition, patients only showed left TVA activation without right TVA activation (Fig. 1, left upper panel; Table 1). When comparing the binaural condition to the monaural condition, the CI showed a significantly greater right activation along the upper bank of the right STS in the former condition than in the latter one (Fig. 1, left lower panel; Table 2). When comparing the monaural condition to the binaural one, no activation was found. Comparing the whole sound stimuli to silence during the monaural and binaural conditions When comparing the listening condition (pooled voice and non-voice conditions) to the silence condition, binaural and monaural stimulations by the CI led to a bilateral temporal pattern of activation (Fig. 1, right upper panel; Table 3). Activation peaks were similarly located in both right and left STS, during the binaural and monaural stimulations. Activation of a right fronto-parietal network was observed in the binaural condition when compared to the monaural one (Fig. 1, right lower panel; Table 4). No additional temporal activation was found in the binaural condition as compared to the monaural one.

Discussion Bilateral cochlear implant and TVA activation Listening to the voice stimuli compared to listening to nonvoice stimuli, a bilateral TVA activation was found during bilateral CI stimulation. Only the left TVA was activated during unilateral CI stimulation. When compared to monaural stimulation, binaurally stimulated patients had an additional right temporal activation with their CI. Patients also had a better intelligibility score with two cochlear

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Fig. 1 Localisation of activation peaks. Left upper panel voice versus non-voice group analysis. The location of activation peaks to compare ‘voice’ versus ‘non-voice’ in each condition (binaural and monaural condition with bilateral CI at p = 0.00005) shown in a lateral view of both hemispheres. Right upper panel voice and non-voice versus silence group analysis. The location of activation peaks comparing the ‘voice ? non-voice’ versus ‘silence’ conditions [binaural and monaural conditions with bilateral CI at p \ 0.001 and then corrected for multiple comparisons (p = 0.05)] are shown in a lateral view of both

hemispheres. Lower panel direct comparison of a monaural and a binaural stimulation using a CI. The localisation of the activation peaks are shown in a glass brain view. Left lower panel voice versus non-voice (at p = 0.001). The location of activation peaks comparing the ‘voice’ versus ‘non-voice’ in the binaural versus the monaural stimulation (upper panel) is shown. Right lower panel voice and nonvoice versus silence (at p = 0.0001). The location of activation peaks comparing the ‘voice ? non-voice’ versus ‘silence’ in the binaural versus the monaural stimulation is shown. CI cochlear implant

implants. As shown in previous studies [10, 11], we found that the subjects’ rCBF response to the stimuli paralleled their intelligibility score performance. With a different PET paradigm design, using word stimuli, binaural stimulation through cochlear implants appeared also advantageous when compared with the monaural at the neurofunctional level because the pattern of brain activation was closer to the normal one [9]. The paradigm of the present study allowed a direct comparison of a binaural stimulation to a monaural one by cochlear implants. Although, some studies suggested a dissociation in the dynamic of functional recuperation of speech and voice processing [17], binaural cochlear users had in this study an immediate degradation of speech intelligibility when using only one cochlear implant and they had concomitantly a different pattern of brain networks when listening to voices. Moreover, in adults, the TVAs are sensitive to voices and highly selective. The enhanced responses to voice stimuli as compared to a range of control sounds, even after spectral filtering of voice and non-voice stimuli [12], allowed showing that the TVA’s preference is driven by low-level acoustical parameters.

Bilateral cochlear implant and perception of spectral acoustical cues

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A weaker brain response with increased spectral filtering was found in a group of normal hearing adults [12, 18]. In vocoding, a process that mimics the effects of a cochlear implant processor, global temporal information is preserved, while the fine spectral structure is degraded (1). The difference between monaural and binaural CI stimulation reflects the impact of a reduced number of independent peripheral sites of stimulation in the cochlea obtained with a single CI when compared to a strict binaural effect with two cochlear implants. Actually, no more than 4–8 independent sites are available in the speechprocessor context using the present electrode designs due to substantial overlap in the electric fields from adjacent electrodes [19]. The use of two CI allowed for an increase in the number of independent ear stimulation sites and improved the ability to discriminate the features of two different sounds that could allow the patient to have a stronger discrimination of voice sounds as compared to other sounds.

Eur Arch Otorhinolaryngol Table 1 Coordinates, size and Z score of areas activated by voice compared to non-voice conditions in the CI group Area

Voice versus non-voice x

y

z

Z

t

Cluster size

Table 3 Coordinates, size and Z score of areas activated by voice and non-voice conditions compared to silent conditions in the CI groups in the monaural and the binaural condition at p \ 0.001 corrected for multiple comparison (p = 0.05) Area

Voice ? non-voice versus silence x

y

z

Z

t

Cluster size

5,455

Binaural CI stimulation STS, anterior (BA21)

66

-2

-6

4.38

4.48

27

STS, middle (BA22)

68

-14

4

4.06

4.14

15

STS, middle (BA21)

-60

-10

-4

4.10

4.18

66

STS, posterior (BA22)

-64

-22

4

4.17

4.25

Monaural CI stimulation STS, middle (BA21)

-58

-12

0

5.66

5.87

STS, posterior (BA22)

-64

-22

2

4.98

5.12

517

Approximate Brodmann numbers (BA) associated with anatomical regions of the superior temporal sulcus (STS) are given in parentheses. Coordinates (in standard stereotaxic space [15]) of voxels correspond to local maxima of Z value, above Z = 4.0 (p = 0.00005) within each focus of activation. x: distance (mm) to right (?) or left (-) of the midsagittal line; y: distance anterior (?) or posterior (-) to vertical plane through the anterior commissure; z: distance above (?) or below (-) the intercommissural (AC-PC) line. The cluster size refers to the number (k) of voxels in a given cluster (voxel size, in mm: 2 9 2 9 2); for statistical parametric mapping, SPM(Z) maps were thresholded at t = 3.96 (p \ 0.00005, uncorrected)

Table 2 Monaural and binaural CI stimulation comparison Area

Voice versus non-voice x

y

Binaural CI stimulation STS, posterior (BA22)

62

-24

6 [10

16.76

STS anterior (BA21)

64

-6

-6 [10

14.50

STS posterior (BA 22)

-60

-22

6 [10

11.48

STS posterior (BA42)

-46

-24

6 [10

10.74

Monaural CI stimulation STS, posterior (BA22)

66

-22

4 [10

18.12

STS, anterior (BA21)

62

-4

-4 [10

12.28

STS, posterior (BA22)

-58

-30

8 [10

12.37

STS, middle (BA21)

-48

-12

-4 [10

10.99

3,280

4,811 4,250

Approximate Brodmann numbers (BA) associated with anatomical regions of the superior temporal sulcus (STS) are given in parentheses. Coordinates (in standard stereotaxic space [15]) of voxels correspond to local maxima of Z value, above Z [ 10 (p \ 0.001) within each focus of activation. x: distance (mm) to right (?) or left (-) of the midsagittal line; y: distance anterior (?) or posterior (-) to vertical plane through the anterior commissure; z: distance above (?) or below (-) the intercommissural (AC-PC) line. The cluster size refers to the number (k) of voxels in a given cluster (voxel size, in mm: 2 9 2 9 2); for statistical parametric mapping, SPM(Z) maps were thresholded at t = 4.65 (p \ 0.001, uncorrected) and then corrected for multiple comparisons (p = 0.05)

z

Z

t

Cluster size

STS superior temporal sulcus

12

3.24

3.28

4

damage to the right superior temporal cortex, but not to the left primary auditory areas, affects a variety of other tonal or spectral processing tasks [23, 24]. In this study, patients had no cerebral lesions, and the supplementary right temporal activation should reflect stronger bottom-up sound perception from spectral cues when two cochlear implants were functioning.

Binaural versus monaural CI stimulation STS, middle (BA42) Monaural CI stimulation

72

-14

No significant differences

Coordinates, size and Z score of areas activated by voice compared to non-voice conditions Approximate Brodmann numbers (BA) associated with anatomical regions of the superior temporal sulcus (STS) are given in parentheses. Coordinates (in standard stereotaxic space [15]) of voxels correspond to local maxima of Z value, above Z = 3.0 (p = 0.001) within each focus of activation. x: distance (mm) to right (?) or left (-) of the midsagittal line; y: distance anterior (?) or posterior (-) to vertical plane through the anterior commissure; z: distance above (?) or below (-) the intercommissural (AC-PC) line. The cluster size refers to the number (k) of voxels in a given cluster (voxel size, in mm: 2 9 2 9 2); for statistical parametric mapping, SPM(Z) maps were thresholded at t = 3.13 (p = 0.001, uncorrected)

Specifically, several studies have examined the spectral and temporal acoustical cues present in the stimuli, which were shown to be important factors for determining the recruitment of the left and/or right auditory cortex [20]. Many PET and fMRI experiments [21, 22] have shown an enhanced sensitivity to temporal rate by the left auditory cortex and to pitch by the right auditory cortex. In general,

Bilateral cochlear implant and brain sound discrimination networks rCBF increases in the right temporal lobe have been previously correlated with subjects’ performance in a speaker identification task [25] or with their ability to direct attention to vocal identity [26, 27]. By comparing the binaural to monaural conditions when listening to voice and non-voice stimuli versus silence, we observed the activation of a supplementary right fronto-parietal network in the binaural CI stimulation condition. This right frontoparietal network activation has been found in other studies on selective or sustained attention to sound intensity discrimination [28] or to sound duration [29]. In these two

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Eur Arch Otorhinolaryngol Table 4 Monaural and binaural CI stimulation comparison Area

Voice ? non-voice versus silence x

y

z

Z

t

Cluster size

Binaural versus monaural CI stimulation Precentral Gyrus (BA4)

52

-12

58

4.24

4.32

32

Inferior parietal lobule (BA40)

40

-44

42

4.19

4.27

30

Inferior frontal Gyrus (BA47)

40

30

-18

4.17

4.25

13

Monaural versus binaural CI stimulation

No significant differences

Coordinates, size and Z score of areas activated by voice and nonvoice condition compared to silent condition Approximate Brodmann numbers (BA) associated with anatomical regions of the STS are given in parentheses. Coordinates (in standard stereotaxic space [15]) of voxels correspond to local maxima of Z value, above Z = 4.16 (p = 0.0001) within each focus of activation. x: distance (mm) to right (?) or left (-) of the midsagittal line; y: distance anterior (?) or posterior (-) to vertical plane through the anterior commissure; z: distance above (?) or below (-) the intercommissural (AC-PC) line. The cluster size refers to the number (k) of voxels in a given cluster (voxel size, in mm: 2 9 2 9 2); for statistical parametric mapping, SPM(Z) maps were thresholded at t = 3.78 (p = 0.0001, uncorrected)

studies, comparable peaks (mean location: x, y, z) of activation [(48, 0, 48), (44, -48, 50) and (42, 28, 4)] were found. This non-specific cortical network is associated with sound discrimination ability. This neuro-functioning observation supports the conclusion that with two CI, patients have better sound discrimination abilities and they have to pay less attention because of a lack of auditory perception when compared to one CI. We could speculate that while the involvement of auditory areas reflected the processing of acoustic contributors to voice sounds activity in frontal regions reflected the overall perceived attractiveness of sounds despite their lack of linguistic content [30]. The results obtained with two cochlear implants compared to one may suggest the influence of hidden non-linguistic aspects of signals on cerebral activity that needs further investigations. It is currently important to determine the utility of bilateral cochlear implants. The TVA PET activation studies examined a group of patients to objectively demonstrate the binaural advantages resulting from improvements in the peripheral spectral representation of the stimuli. The number of independent channels was an important characteristic. We found an enhanced cortical representation of the voice when using both CI, but the activation of a right fronto-parietal attention network could also facilitate spectral sound discrimination.

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Acknowledgments We thank the Beaujon Hospital clinical team for their assistance and the patients for their participation in this study. This work was supported by the Institut National de la Sante´ et de la Recherche Me´dicale, Inserm, France, and the Commissariat a` l’Energie Atomique, CEA, France. The authors declare that they have no competing financial interests. Conflict of interest

No duality of interest to declare.

References 1. Shannon RV, Zeng FG, Kamath V, Wygonski J, Ekelid M (1995) Speech recognition with primarily temporal cues. Science 270:303–304 2. Wilson BS, Dorman MF (2008) Cochlear implants: a remarkable past and a brilliant future. Hear Res 242:3–21 3. Moore DR, Shannon RV (2009) Beyond cochlear implants: awakening the deafened brain. Nat Neurosci 12:686–691 4. Mosnier I, Sterkers O, Bebear JP, Godey B, Robier A et al (2009) Speech performance and sound localization in a complex noisy environment in bilaterally implanted adult patients. Audiol Neurootol 14:106–114 5. Bronkhorst AW, Plomp R (1988) The effect of head-induced interaural time and level differences on speech intelligibility in noise. J Acoust Soc Am 83:1508–1516 6. Dillion H (2001) Binaural and bilateral considerations in hearing aid fitting. In: Thie`me NY (ed) Hearing aids. Boomerang Press, Sydney, pp 370–403 7. Aggarwal R, Green KM (2012) Cochlear implants and positron emission tomography. J Laryngol Otol 126:1200–1203 8. Green KM, Julyan PJ, Hastings DL, Ramsden RT (2011) Cortical activations in sequential bilateral cochlear implant users. Cochlear Implants Int 12:3–9 9. Strelnikov K, Rouger J, Eter E, Lagleyre S, Fraysse B et al (2011) Binaural stimulation through cochlear implants in postlingual deafness: a positron emission tomographic study of word recognition. Otol Neurotol 32:1210–1217 10. Coez A, Zilbovicius M, Ferrary E, Bouccara D, Mosnier I et al (2008) Cochlear implant benefits in deafness rehabilitation: PET study of temporal voice activations. J Nucl Med 49:60–67 11. Coez A, Zilbovicius M, Ferrary E, Bouccara D, Mosnier I et al (2009) Processing of voices in deafness rehabilitation by auditory brainstem implant. Neuroimage 47:1792–1796 12. Belin P, Zatorre RJ, Lafaille P, Ahad P, Pike B (2000) Voiceselective areas in human auditory cortex. Nature 403:309–312 13. Fox PT, Mintun MA, Raichle ME, Herscovitch P (1984) A noninvasive approach to quantitative functional brain mapping with H2 (15)O and positron emission tomography. J Cereb Blood Flow Metab 4:329–333 14. Bendriem B, Dahlbom M, Trebossen R (1996) Evaluation of the ECAT EXACT HR?: a new positron camera with 2D/3D acquisition capabilities and nearly isotropic spatial resolution [abstract]. J Nucl Med 37(suppl):170P 15. Talairach J, Tournoux P (eds) (1988) Co-planar stereotaxic atlas of the human brain: 3-dimensional proportional system—an approach to cerebral imaging. Thieme Medical, New York 16. Friston KJ, Worsley KJ, Poline JB, Frith CD, Frackowiak RS (1995) Statistical parametric maps in functional imaging: a general linear approach. Hum Brain Mapp 2:189–210 17. Massida Z, Belin P, James C, Rouger J, Fraysse B et al (2011) Voice discrimination in cochlear-implanted deaf subjects. Hear Res 275:120–129

Eur Arch Otorhinolaryngol 18. Strelnikov K, Massida Z, Rouger J, Belin P, Barone P (2011) Effects of vocoding and intelligibility on the cerebral response to speech. BMC Neurosci 12:122 19. Friesen LM, Shannon RV, Baskent D, Wang X (2001) Speech recognition in noise as a function of the number of spectral channels: comparison of acoustic hearing and cochlear implants. J Acoust Soc Am 110:1150–1163 20. Zatorre RJ, Gandour JT (2008) Neural specializations for speech and pitch: moving beyond the dichotomies. Philos Trans R Soc Lond B Biol Sci 363:1087–1104 21. Schonwiesner M, Rubsamen R, von Cramon DY (2005) Spectral and temporal processing in the human auditory cortex—revisited. Ann N Y Acad Sci 1060:89–92 22. Zatorre RJ, Belin P (2001) Spectral and temporal processing in human auditory cortex. Cereb Cortex 11:946–953 23. Sidtis JJ, Volpe BT (1988) Selective loss of complex-pitch or speech discrimination after unilateral lesion. Brain Lang 34:235–245 24. Zatorre RJ (1985) Discrimination and recognition of tonal melodies after unilateral cerebral excisions. Neuropsychologia 23:31–41

25. Nakamura K, Kawashima R, Sugiura M, Kato T, Nakamura A et al (2001) Neural substrates for recognition of familiar voices: a PET study. Neuropsychologia 39:1047–1054 26. von Kriegstein K, Eger E, Kleinschmidt A, Giraud AL (2003) Modulation of neural responses to speech by directing attention to voices or verbal content. Brain Res Cogn Brain Res 17:48–55 27. Belin P, Zatorre RJ (2003) Adaptation to speaker’s voice in right anterior temporal lobe. Neuroreport 14:2105–2109 28. Belin P, McAdams S, Smith B, Savel S, Thivard L et al (1998) The functional anatomy of sound intensity discrimination. J Neurosci 18:6388–6394 29. Belin P, McAdams S, Thivard L, Smith B, Savel S et al (2002) The neuroanatomical substrate of sound duration discrimination. Neuropsychologia 40:1956–1964 30. Bestelmeyer PE, Latinus M, Bruckert L, Rouger J, Crabbe F et al (2012) Implicitly perceived vocal attractiveness modulates prefrontal cortex activity. Cereb Cortex 22:1263–1270

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Brain voice processing with bilateral cochlear implants: a positron emission tomography study.

Most cochlear implantations are unilateral. To explore the benefits of a binaural cochlear implant, we used water-labelled oxygen-15 positron emission...
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