- Email: [email protected]
Opposite hemispheric asymmetries for pitch identification in absolute pitch and non-absolute pitch musicians
Neuropsychologia 47 (2009) 2937–2941
Contents lists available at ScienceDirect
Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia
Opposite hemispheric asymmetries for pitch identification in absolute pitch and non-absolute pitch musicians Alfredo Brancucci ∗ , Milena di Nuzzo, Luca Tommasi Department of Biomedical Sciences and Institute for Advanced Biomedical Technologies, University “G. d’Annunzio”, Chieti, Italy
a r t i c l e
i n f o
Article history: Received 12 January 2009 Received in revised form 16 June 2009 Accepted 19 June 2009 Available online 27 June 2009 Keywords: Absolute pitch Relative pitch Musicians Dichotic listening Laterality Left/right hemisphere Pitch Musical tones
a b s t r a c t The aim of the present study is to investigate functional laterality for pitch identification in subjects with absolute pitch (AP) and without absolute pitch (NAP). Forty-four musicians were divided into two groups (AP and NAP) on the basis of their performance in a preliminary standard AP-test. They were subsequently presented with an AP-test designed for dichotic listening, a neuropsychological technique which allows the investigation of functional hemispheric asymmetries. Dependent variables were accuracy and reaction time. It was observed that AP and NAP subjects exhibit opposite hemispheric specialization for pitch identification, AP subjects showing a bias towards the left hemisphere and NAP subjects showing a bias towards the right hemisphere. Results are discussed in the context of neuroimaging evidence of structural and functional asymmetries related to AP. © 2009 Elsevier Ltd. All rights reserved.
1. Introduction Absolute pitch (AP) refers to the ability to identify the correct label of any note in the absence of a reference or of a musical context (Levitin & Rogers, 2005; Miyazaki, 1988; Takeuchi & Hulse, 1993; Zatorre, 2003). AP possessors report commonly that the identification of the correct pitch of a tone does require no cognitive effort, rather, it appears a so natural and immediate skill to them that they assume everyone else should possess it. Previous work has demonstrated the presence of a high correlation between AP manifestation and early exposure to music (Krumhansl, 1991; Ohnishi et al., 2001) and it has been suggested that AP appears mainly in a critical developmental period (Gregersen, Kowalsky, Kohn, & Marvin, 2001). In addition, there is also evidence that genetic factors play a fundamental role in AP (Baharloo, Johnston, Service, Gitschier, & Freimer, 1998; Baharloo, Service, Risch, Gitschier, & Freimer, 2000; Drayna, 1998). The investigation of the neural bases of AP is of high interest for cognitive neuroscience as AP is a clean example of an ability which arises relatively separately from other cognitive functions, providing thus an useful paradigm for understanding how specialized abilities are linked to brain function. However, as regards the per-
∗ Corresponding author at: Via dei Vestini, 29 Blocco A, University of Chieti, 66013 – Chieti (CH), Italy. Tel.: +39 0871 355 4206. E-mail address: [email protected] (A. Brancucci). 0028-3932/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2009.06.021
ceptual and neural mechanisms underlying this particular ability, many aspects remain unclear. In particular, perceptual asymmetries have not been investigated in AP and the mutual role of the two hemispheres is not clearly disentangled yet. Two structural neuroimaging studies (Keenan, Thangaraj, Halpern, & Schlaug, 2001; Schlaug, Jäncke, Huang, & Steinmetz, 1995) have shown that in AP possessors there is an enhanced leftward asymmetry in the size of the planum temporale (PT). However, if compared with NAP possessors (both musicians and musically naïve subjects) the asymmetry was determined by a smaller extent of the right planum temporale (PT) rather than by a larger extent of the left PT. The absolute size of the right and not of the left PT turned out to be the better predictor of AP, indicating a possible pruning of the right PT rather than expansion of the left as the basis of the increased asymmetry in AP. However, the results of a positron emission tomography study (Zatorre, Perry, Beckett, Westbury, & Evans, 1998) suggest the left dorsolateral prefrontal cortex as a possible crucial area involved in AP processing. This area plays a role in conditional associative memory and was recruited when naming tones by AP possessors but not by musicians without AP. These findings raise a question about the relation between anatomical, physiological and perceptual hemispheric asymmetries in pitch identification. Is the hemispheric specialization driven by the peculiar morphology of the right PT or by the leftward asymmetry of the dorsolateral prefrontal cortex? The aim of the present study is to investigate hemispheric specialization for pitch identification in musicians with AP and
2938
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
musicians without AP (NAP). The hypothesis is that AP and NAP subjects show perceptual asymmetries during pitch identification as a consequence of structural and functional hemispheric asymmetries. To pursue our aim, we used dichotic listening (DL), the most employed neuropsychological technique for the study of functional hemispheric asymmetries or perceptual laterality in the auditory domain. DL is a simple, fully non-invasive technique consisting in the simultaneous presentation of two different auditory stimuli via headphones, one at the left and the other at the right ear. It allows testing the two hemispheres separately because when the two auditory pathways convey (unnaturally) incongruent information to the auditory cortices the ipsilateral pathways are suppressed, thus allowing the two stimuli reaching mainly the contralateral auditory cortices. This view has received both neuropsychological and neurophysiological support (Brancucci et al., 2004; Della Penna et al., 2007; Kimura, 1967). According to these studies, testing the right ear during DL means, with a good approximation, testing the left hemisphere and testing the left ear means testing the right hemisphere (Hugdahl et al., 1999; Tervianemi & Hugdahl, 2003). 2. Materials and methods 2.1. Subjects Forty-four healthy subjects (15 females and 29 males) were recruited. Mean age was 26.0 (s.e.m. = ±1.4). All of them were musicians (recruited at the music conservatories of Bari and Pescara, Italy) and most of them claimed to possess AP when informally interviewed. Subjects declared to have no auditory impairment, but they were recruited only when the hearing threshold difference between left and right ear was lower than 5 dBA. This was assessed by means of audiometric testing. In the audiometric test subjects were presented with a series of complex tones (fundamental frequency: 264 and 395 Hz) with increased intensities (steps of 2.5 dBA) starting with sub-threshold intensity, and had to press a button when the tone, which was presented monaurally via earphones, became perceivable. Mean handedness index was 48.4 (s.e.m. = ±6.1) as measured with the Italian revised version of the Edinburgh Handedness Inventory (Salmaso & Longoni, 1985). Scores were distributed as follows: 27 subjects scored ≥50, 13 subjects scored ≥0 and <50, and 4 subjects scored <0. Subjects were assigned to two groups on the basis of their performance on a preliminary standard AP-test, which was borrowed from Robert J. Zatorre at BRAMS (www.brams.org). The test consisted of 108 trials in which subjects had to identify the name of the presented musical tone, that changed at every trial. The response was given by mouse click on the perceived note label selected among the 12 note labels displayed on the computer screen. Tone height ranged from a3 to a5, tone duration was 1 s, and intensity could be 67, 70, or 73 dBA. Of note, it is in principle impossible to assess whether a subject has or has not AP in a dichotomous way, as everyone has at least some degree of AP. Half of the subjects scoring the lowest distance from target (in semitones) were assigned to the AP group, the other half were assigned to the NAP group. Mean ± s.e.m. performance in the AP group was 8.24 ± 1.78 semitones errors (out of 108 items), whereas the mean performance in the NAP group was 49.71 ± 10.86 semitones error. In both groups (see Fig. 1) the mode of the distribution was zero, indicating that more correct note-name responses were given than responses at more distant points, even in the NAP group. However, the response distribution of AP musicians had a much smaller variance than that of NAP musicians, indicating the presence of precise fixed-pitch categories in the AP but not in the NAP group. Table 1 summarizes descriptive data from the two groups. 2.2. Stimuli Tones corresponded to all notes comprised in the range from A3 (220.00 Hz) to B5 (987.77 Hz). The duration of the tones was 400 ms and the intensity level 70 dBA. Spectral composition was harmonic, with eight spectral components having the following relative amplitudes: 1, 0.7, 0.5, 0.2, 0.15, 0.05, 0.02, 0.01. One dichotic pair consisted in one of the tones and contralateral white noise. The white noise was presented at 75 dBA and had the same duration of the contralateral tone. The sam-
Table 1 Descriptive data from the AP and NAP groups.
AP NAP
Age (years)
Musical practice (years)
Handedness
M
F
N
25.4 ± 2.0 26.5 ± 1.8
16.3 ± 1.5 17.5 ± 1.5
51.1 ± 8.3 46.0 ± 8.8
18 11
4 11
22 22
Fig. 1. Distribution of group responses in the preliminary AP-test plotted as absolute distance from target, in semitones.
pling rate of each sound was 44,100 kHz and amplitude resolution 16 bit. Amplitude envelope of both tones and white noise contained 50 ms rise and fall times. To obtain a dichotic pair, a tone and white noise were aligned on the two auditory channels by means of the CSound programming language (Vercoe, 1992). An example stimulus is illustrated in Fig. 2. 2.3. Procedure Subjects were presented with a dichotic AP-test with focused attention (Jäncke, Specht, Shah, & Hugdahl, 2003). The test consisted in a sequence of 120 dichotic pairs composed of a musical tone presented at one ear and white noise presented at the other ear (see above). In each trial, after the presentation of the dichotic pair, the task of the subject was to indicate with the mouse the note perceived at the ear receiving the musical tone (Fig. 2). The note names Do, Do#/Reb, Re, Re#/Mib, Mi, Fa, Fa#/Solb, Sol, Sol#/Lab, La, La#/Sib, and Si (fixed do solmization) were presented on the computer monitor arranged in a circle in which the note name “Do” was at the top, Fa#/Solb at the bottom, Re#/Mib on the right and La on the left (Fig. 2). The mouse arrow was automatically positioned at the centre of the circle at the beginning of each trial. The 120 trials were grouped into 20 blocks of 6 trials each. The blocks were separated by a 4-s interval and each block was preceded by a beep (2000 Hz, 200 ms), which was presented monaurally to the ear that was about to receive the target stimuli in that block. Subjects were instructed to direct their attention to the side of the monaural beep in the subsequent block and were informed that tones would be delivered to that side. In half of the trials (blocks) tones were presented to the right ear and white noise to the left, in the other half vice versa. Tones were allocated to blocks on a pseudorandom basis. The side (ear) of presentation of the target stimulus changed at every block. Subjects were familiarized with the test by listening to a sample sequence consisting of 10 dichotic pairs. The format of the test was chosen because it allowed controlling the direction of attention, i.e. fluctuations of attention from one to other ear were minimized. The experiment was completely automated by means of an ad hoc software written in Microsoft Visual Basic. Stimuli were processed by means of a PC with Sound Blaster audio card (Creative, Model AWE 32). Subjects wore headphones (Sennheiser HD 202) and sat comfortably in front of a computer monitor with one hand laying on the computer mouse which was used to indicate on the screen the name of the note which was perceived in each dichotic pair. Half of the subjects used the right hand and half used the left hand to move the mouse. Subjects were instructed to look at the note circle in the centre of the screen in front of them and to avoid shifting their gaze laterally during the experiment. The intensity level of the sounds was the same at both earphones, as measured by a phonometer. However, in order to keep maximal control on the intensity level of the stimuli presented at the ears, after 60 trials (middle of test) subjects reversed the two earphones (the initial position of the headphone was counterbalanced across subjects). Selected note names and latency of response were automatically stored for later analysis. Each experimental session lasted approximately 12 min.
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
2939
categorized, respectively, as small, moderate, and large (Cohen, 1977). 3.1. Preliminary analyses Preliminary statistical analyses indicated that the headphone position at the beginning of the test (upright or reversed), the sex of the participants, and the hand which was used to give the response by moving the mouse did not influence laterality scores (i.e. they showed no significant interactions with the factor ‘ear’). These variables were therefore not included in the subsequent analyses. Yates-corrected 2 × 2 2 -test on gender distribution in the AP and NAP groups showed that the number of males and females in the two groups was not statistically significant (2 = 4.96, p = 0.06), but there was a clear tendency towards significance. However, previous studies have shown that substantially males and females do not differ in perceptual asymmetries, especially when presented with DL of non-verbal sounds (Hiscock, Inch, Jacek, Hiscock-Kalil, & Kalil, 1994; McRoberts & Sanders, 1992; Munro & Govier, 1993). In addition, literature indicates that AP occurs equally in males and females (Athos et al., 2007; Drayna, 2007). 3.2. Main analyses A 2 × 2 measure ANOVA with Group (AP, NAP) as an independent factor and Ear of input (left, right) as a repeated factor was carried out for both dependent variables. Results are illustrated in Fig. 3. For the accuracy variable, the ANOVA showed a significant main effect of Group (F = 35.02; p < 0.001), due to a better general performance of the AP group, no main effect of the Ear of input, and a significant interaction Group × Ear of input (F = 9.06; p = 0.004). Duncan post hoc analysis showed that the effect of the Ear of
Fig. 2. Structure of one trial. After receiving the dichotic pair composed of a musical tone presented at one ear and a white noise burst presented at the other ear (lasting both 400 ms), subject had to indicate the perceived note on the computer monitor, responding with the mouse.
3. Results The dependent variables were (a) accuracy, computed as the distance in semitones from the correct response and (b) reaction time, measured as the median latency of correct responses. Data analysis was performed according to previous studies (Brancucci & San Martini, 1999, 2003; Brancucci, D’Anselmo, Martello, Tommasi, 2008; Brancucci, Babiloni, Rossini, & Romani, 2005). Statistical effects were evaluated by mixed analysis of variance (ANOVA) design at a significance level of p = 0.05. Since preliminary observation of the data distributions indicated that they met ANOVA criteria concerning normality and homogeneity, untransformed scores were used for the statistical analyses. A laterality index (LI) was calculated as follows: LI = (R − L)/(R + L) × 100, where R is the accuracy score (or the reaction time) of the right ear and L is the accuracy score (or the reaction time) of the left ear. For the statistically significant results we calculated the effect size (Cohen’s d). This parameter is the difference between the mean values of two samples divided by the standard deviation of both samples taken together. The effect size is an index of the magnitude of the difference between groups. It can be useful to compare effects across studies, as it does not depend on sample size. Effect sizes of about 0.2, 0.5, and 0.8 are
Fig. 3. Means and standard errors for accuracy (y-axis represents errors measured as absolute distance from target, in semitones, where low distance from target means high accuracy) and reaction time in the AP and NAP groups. Both dependent variables showed a statistically significant Group × Ear interaction.
2940
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
input was significant in both the AP (p = 0.048, right ear advantage) and NAP (p < 0.001, left ear advantage) group. The effect size of the ear asymmetry for accuracy was ‘moderate’ in the AP group (Cohen’s d = 0.46) and between ‘small’ and ‘moderate’ in the NAP group (d = 0.25). In the AP group, 15 subjects showed a right ear advantage (positive laterality index), 4 subjects showed a left ear advantage (negative laterality index) and 3 subjects showed no advantage (mean LIacc ± s.e.m. was 21.6 ± 7.7). In the NAP group, 8 subjects showed a right ear advantage and 14 subjects showed a left ear advantage (mean LIacc ± s.e.m. was −6.0 ± 4.2). Yates-corrected 2 × 2 2 -contingency test indicated that the frequency distribution of ear advantage in the two groups was significantly different (2 = 5.88, p = 0.015). For the reaction time variable, the ANOVA showed no main effects, but a significant interaction Group × Ear of input (F = 4.82; p = 0.034). Duncan’s post hoc analysis showed that the effect of the Ear of input was significant in the NAP (p = 0.047, left ear advantage) but not in the AP group, which showed a non-significant right ear advantage. In the AP group, 15 subjects showed a right ear advantage and 7 subjects showed a left ear advantage (mean LIRT ± s.e.m. was 2.1 ± 1.4). In the NAP group, 7 subjects showed a right ear advantage and 15 subjects showed a left ear advantage (mean LIRT ± s.e.m. was −4.4 ± 2.8). Yates-corrected 2 × 2 2 -contingency test indicated that the frequency distribution of ear advantage in the two groups was significantly different (2 = 4.45, p = 0.035). 4. Discussion The results of the present study show a right ear advantage in AP subjects and an opposite, left ear advantage in NAP subjects for pitch identification. This claim is based on a statistically significant interaction between the factors group and ear which was observed consistently for both accuracy and reaction time. For the accuracy variable the claim is further supported by significant post hoc results. According to the literature (Brancucci et al., 2004; Della Penna et al., 2007; Hugdahl et al., 1999; Kimura, 1967) the right ear advantage can be interpreted as a left hemispheric specialization and the left ear advantage as a right hemispheric specialization. This indicated that AP subjects recruit a mainly leftlateralized neural network during pitch identification, whereas NAP subjects recruit a mainly right-lateralized neural network. Analyzing specifically the means observed with both accuracy and reaction time, it can be speculated that most of the difference between the groups can be ascribed to the right ear. This would support the hypothesis that the principal centres of AP ability are located in the left hemisphere, in agreement with evidence from both structural neuroimaging studies (Keenan et al., 2001; Schlaug et al., 1995) showing that AP possessors have enhanced leftward asymmetry in the size of the planum temporale (PT) and functional neuroimaging studies (Bermudez & Zatorre, 2005; Zatorre et al., 1998) suggesting that also the left dorsolateral prefrontal cortex plays a role in AP. The present results agree also with the findings of a recent study (Wilson, Lusher, Wan, Dudgeon, & Reutens, 2009) which showed that the activation of the left planum temporale was AP-skill dependent. Significant activation associated with this region appeared dependent on high levels of skill expertise, with less skilled performance engaging a right hemisphere network including pitch working memory structures. This points to the involvement of the left planum temporale in pitch naming ability. At a first glance, the present results run against those of a study by Itoh, Miyazaki, and Nakada (2003) whose main purpose was to investigate left–right asymmetry in the central processing of musical consonance and in which, as a requirement of the experimental design, AP possessors were tested. Results showed no statistical significant effects of ear asymmetry. One possible cause of the
lack of laterality effect could be ascribed to the method used to measure ear performance, which was based on an absolute correct/incorrect criterion rather than magnitude of error (i.e. number of semitones distance from target, more widely used and more precise, Zatorre, 2003). Moreover, if one looks at the mean performance level reached by the subjects in that study and compares it with the performance obtained by the two groups tested in the present one, it can be observed that performance of the subjects tested by Itoh and coworkers was located between the performances of the AP and NAP groups tested in the present study. According to our results, it would be expected that left–right asymmetries in a group of subjects with such an AP ability level would disappear as a consequence of the opposite asymmetry observed in subjects with lower AP ability (the present NAP group). Once established that the main neural mechanisms underlying AP are in the left hemisphere, future investigations could answer the question of whether the role of the right hemisphere is beneficial or detrimental during pitch identification in AP subjects. One could hypothesize that the activation of the right hemisphere in parallel to the left hemispheric-based neural mechanisms devoted to pitch labelling could cause interference. In this case, an inhibition of the right hemisphere would be required in order to develop high-level AP. This could be done by comparing the performance of the two ears in a test similar to the present one with the performance obtained by the same subjects in a variant of the classical AP-test in which tones and white noise are delivered simultaneously and binaurally, in order to control task difficulty. Comparison of the performance obtained with the left ear, the right ear and binaurally could answer the above question. Acknowledgements This research is part of the project EDCBNL (Evolution and Development of Cognitive, Behavioural and Neural Lateralization, 2006–2010), supported by the Commission of the European Communities within the framework of the specific research and technological development programme “Integrating and strengthening the European Research Area” (initiative “What it means to be human”), through a financial grant to LT. We thank Professor Robert J. Zatorre for allowing us to use the BRAMS software. References Athos, E. A., Levinson, B., Kistler, A., Zemansky, J., Bostrom, A., Freimer, N., et al. (2007). Dichotomy and perceptual distortions in absolute pitch ability. Proceedings of the National Academy of Sciences USA, 104(37), 14795–14800. Baharloo, S., Johnston, P. A., Service, S. K., Gitschier, J., & Freimer, N. B. (1998). Absolute pitch: An approach for identification of genetic and nongenetic components. American Journal of Human Genetics, 62, 224–231. Baharloo, S., Service, S. K., Risch, N., Gitschier, J., & Freimer, N. B. (2000). Familial aggregation of absolute pitch. American Journal of Human Genetics, 67, 755– 758. Bermudez, P., & Zatorre, R. J. (2005). Conditional associative memory for musical stimuli in nonmusicians: Implications for absolute pitch. The Journal of Neuroscience, 25, 7718–7723. Brancucci, A., Babiloni, C., Babiloni, F., Galderisi, S., Mucci, A., Tecchio, F., et al. (2004). Inhibition of auditory cortical responses to ipsilateral stimuli during dichotic listening: Evidence from magnetoencephalography. European Journal of Neuroscience, 19, 2329–2336. Brancucci, A., Babiloni, C., Rossini, P. M., & Romani, G. L. (2005). Right hemisphere specialization for intensity discrimination of musical and speech sounds. Neuropsychologia, 43, 1916–1923. Brancucci, A., D’Anselmo, A., Martello, F., & Tommasi, L. (2008). Left hemisphere specialization for duration discrimination of musical and speech sounds. Neuropsychologia, 46(7), 2013–2019. Brancucci, A., & San Martini, P. (1999). Laterality in the perception of temporal cues of musical timbre. Neuropsychologia, 37, 1445–1451. Brancucci, A., & San Martini, P. (2003). Hemispheric asymmetries in the perception of rapid (timbral) and slow (nontimbral) amplitude fluctuations of complex tones. Neuropsychology, 17, 451–457. Cohen, J. (1977). Statistical power analysis for the behavioral sciences. New York: Academic Press., pp. 48–49
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941 Della Penna, S., Brancucci, A., Babiloni, C., Franciotti, R., Pizzella, V., Rossi, D., et al. (2007). Lateralization of dichotic speech stimuli is based on specific auditory pathway interactions: Neuromagnetic evidence. Cerebral Cortex, 17, 2303–2311. Drayna, D. (1998). Genetics tunes in. Nature Genetics, 18(2), 96–97. Drayna, T. (2007). Absolute pitch: A special group of ears. Proceedings of the National Academy of Sciences USA, 104, 14549–14550. Gregersen, P. K., Kowalsky, E., Kohn, N., & Marvin, E. W. (2001). Early childhood music education and predisposition to absolute pitch: Teasing apart genes and environment. American Journal of Medical Genetics, 98(3), 280–282. Hiscock, M., Inch, R., Jacek, C., Hiscock-Kalil, C., & Kalil, K. M. (1994). Is there a sex difference in human laterality? I. An exhaustive survey of auditory laterality studies from six neuropsychology journals. Journal of Clinical and Experimental Neuropsychology, 16(3), 423–435. Hugdahl, K., Bronnick, K., Kyllingsbaek, S., Law, I., Gade, A., & Paulson, O. B. (1999). Brain activation during dichotic presentations of consonant–vowel and musical instrument stimuli: A 15O-PET study. Neuropsychologia, 37, 431–440. Itoh, K., Miyazaki, K., & Nakada, T. (2003). Ear advantage and consonance of dichotic pitch intervals in absolute-pitch possessors. Brain & Cognition, 53(3), 464– 471. Jäncke, L., Specht, K., Shah, J. N., & Hugdahl, K. (2003). Focused attention in a simple dichotic listening task: An fMRI experiment. Cognitive Brain Research, 16(2), 257–266. Keenan, J. P., Thangaraj, V., Halpern, A. R., & Schlaug, G. (2001). Absolute pitch and planum temporale. Neuroimage, 14, 1402–1408. Kimura, D. (1967). Functional asymmetry of the brain in dichotic listening. Cortex, 3, 163–168. Krumhansl, C. L. (1991). Music psychology: Tonal structures in perception and memory. Annual Reviews of Psychology, 42, 277–303. Levitin, D. J., & Rogers, S. E. (2005). Absolute pitch: Perception, coding, and controversies. Trends in Cognitive Sciences, 9, 26–33.
2941
McRoberts, G. W., & Sanders, B. (1992). Sex differences in performance and hemispheric organization for a nonverbal auditory task. Perception & Psychophysics, 51(2), 118–122. Miyazaki, K. (1988). Musical pitch identification by absolute pitch possessors. Perception & Psychophysics, 44(6), 501–512. Munro, P., & Govier, E. (1993). Dynamic gender-related differences in dichotic listening performance. Neuropsychologia, 31(4), 347–353. Ohnishi, T., Matsuda, H., Asada, T., Aruga, M., Hirakata, M., Nishikawa, M., et al. (2001). Functional anatomy of musical perception in musicians. Cerebral Cortex, 11, 754–760. Salmaso, D., & Longoni, A. M. (1985). Problems in the assessment of hand preference. Cortex, 21(4), 533–549. Schlaug, G., Jäncke, L., Huang, Y., & Steinmetz, H. (1995). In vivo evidence of structural brain asymmetry in musicians. Science, 267, 699–701. Takeuchi, A. H., & Hulse, S. H. (1993). Absolute pitch. Psychological Bulletin, 113, 345–361. Tervianemi, M., & Hugdahl, K. (2003). Lateralization of auditory-cortex functions. Brain Research Reviews, 43, 231–246. Vercoe, B. L. (1992). A manual for the audio processing system and supporting programs with tutorials. Cambridge, MA: Massachusetts Institute of Technology Media Labs. Wilson, S. J., Lusher, D., Wan, C. Y., Dudgeon, P., & Reutens, D. C. (2009). The neurocognitive components of pitch processing: insights from absolute pitch. Cerebral Cortex, 19(3), 724–732. Zatorre, R. J., Perry, D. W., Beckett, C. A., Westbury, C. F., & Evans, A. C. (1998). Functional anatomy of musical processing in listeners with absolute pitch and relative pitch. Proceedings of the National Academy of Sciences USA, 95, 3172–3177. Zatorre, R. J. (2003). Absolute pitch: A model for understanding the influence of genes and development on neural and cognitive function. Nature Neuroscience, 6, 692–695.
Contents lists available at ScienceDirect
Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia
Opposite hemispheric asymmetries for pitch identification in absolute pitch and non-absolute pitch musicians Alfredo Brancucci ∗ , Milena di Nuzzo, Luca Tommasi Department of Biomedical Sciences and Institute for Advanced Biomedical Technologies, University “G. d’Annunzio”, Chieti, Italy
a r t i c l e
i n f o
Article history: Received 12 January 2009 Received in revised form 16 June 2009 Accepted 19 June 2009 Available online 27 June 2009 Keywords: Absolute pitch Relative pitch Musicians Dichotic listening Laterality Left/right hemisphere Pitch Musical tones
a b s t r a c t The aim of the present study is to investigate functional laterality for pitch identification in subjects with absolute pitch (AP) and without absolute pitch (NAP). Forty-four musicians were divided into two groups (AP and NAP) on the basis of their performance in a preliminary standard AP-test. They were subsequently presented with an AP-test designed for dichotic listening, a neuropsychological technique which allows the investigation of functional hemispheric asymmetries. Dependent variables were accuracy and reaction time. It was observed that AP and NAP subjects exhibit opposite hemispheric specialization for pitch identification, AP subjects showing a bias towards the left hemisphere and NAP subjects showing a bias towards the right hemisphere. Results are discussed in the context of neuroimaging evidence of structural and functional asymmetries related to AP. © 2009 Elsevier Ltd. All rights reserved.
1. Introduction Absolute pitch (AP) refers to the ability to identify the correct label of any note in the absence of a reference or of a musical context (Levitin & Rogers, 2005; Miyazaki, 1988; Takeuchi & Hulse, 1993; Zatorre, 2003). AP possessors report commonly that the identification of the correct pitch of a tone does require no cognitive effort, rather, it appears a so natural and immediate skill to them that they assume everyone else should possess it. Previous work has demonstrated the presence of a high correlation between AP manifestation and early exposure to music (Krumhansl, 1991; Ohnishi et al., 2001) and it has been suggested that AP appears mainly in a critical developmental period (Gregersen, Kowalsky, Kohn, & Marvin, 2001). In addition, there is also evidence that genetic factors play a fundamental role in AP (Baharloo, Johnston, Service, Gitschier, & Freimer, 1998; Baharloo, Service, Risch, Gitschier, & Freimer, 2000; Drayna, 1998). The investigation of the neural bases of AP is of high interest for cognitive neuroscience as AP is a clean example of an ability which arises relatively separately from other cognitive functions, providing thus an useful paradigm for understanding how specialized abilities are linked to brain function. However, as regards the per-
∗ Corresponding author at: Via dei Vestini, 29 Blocco A, University of Chieti, 66013 – Chieti (CH), Italy. Tel.: +39 0871 355 4206. E-mail address: [email protected] (A. Brancucci). 0028-3932/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.neuropsychologia.2009.06.021
ceptual and neural mechanisms underlying this particular ability, many aspects remain unclear. In particular, perceptual asymmetries have not been investigated in AP and the mutual role of the two hemispheres is not clearly disentangled yet. Two structural neuroimaging studies (Keenan, Thangaraj, Halpern, & Schlaug, 2001; Schlaug, Jäncke, Huang, & Steinmetz, 1995) have shown that in AP possessors there is an enhanced leftward asymmetry in the size of the planum temporale (PT). However, if compared with NAP possessors (both musicians and musically naïve subjects) the asymmetry was determined by a smaller extent of the right planum temporale (PT) rather than by a larger extent of the left PT. The absolute size of the right and not of the left PT turned out to be the better predictor of AP, indicating a possible pruning of the right PT rather than expansion of the left as the basis of the increased asymmetry in AP. However, the results of a positron emission tomography study (Zatorre, Perry, Beckett, Westbury, & Evans, 1998) suggest the left dorsolateral prefrontal cortex as a possible crucial area involved in AP processing. This area plays a role in conditional associative memory and was recruited when naming tones by AP possessors but not by musicians without AP. These findings raise a question about the relation between anatomical, physiological and perceptual hemispheric asymmetries in pitch identification. Is the hemispheric specialization driven by the peculiar morphology of the right PT or by the leftward asymmetry of the dorsolateral prefrontal cortex? The aim of the present study is to investigate hemispheric specialization for pitch identification in musicians with AP and
2938
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
musicians without AP (NAP). The hypothesis is that AP and NAP subjects show perceptual asymmetries during pitch identification as a consequence of structural and functional hemispheric asymmetries. To pursue our aim, we used dichotic listening (DL), the most employed neuropsychological technique for the study of functional hemispheric asymmetries or perceptual laterality in the auditory domain. DL is a simple, fully non-invasive technique consisting in the simultaneous presentation of two different auditory stimuli via headphones, one at the left and the other at the right ear. It allows testing the two hemispheres separately because when the two auditory pathways convey (unnaturally) incongruent information to the auditory cortices the ipsilateral pathways are suppressed, thus allowing the two stimuli reaching mainly the contralateral auditory cortices. This view has received both neuropsychological and neurophysiological support (Brancucci et al., 2004; Della Penna et al., 2007; Kimura, 1967). According to these studies, testing the right ear during DL means, with a good approximation, testing the left hemisphere and testing the left ear means testing the right hemisphere (Hugdahl et al., 1999; Tervianemi & Hugdahl, 2003). 2. Materials and methods 2.1. Subjects Forty-four healthy subjects (15 females and 29 males) were recruited. Mean age was 26.0 (s.e.m. = ±1.4). All of them were musicians (recruited at the music conservatories of Bari and Pescara, Italy) and most of them claimed to possess AP when informally interviewed. Subjects declared to have no auditory impairment, but they were recruited only when the hearing threshold difference between left and right ear was lower than 5 dBA. This was assessed by means of audiometric testing. In the audiometric test subjects were presented with a series of complex tones (fundamental frequency: 264 and 395 Hz) with increased intensities (steps of 2.5 dBA) starting with sub-threshold intensity, and had to press a button when the tone, which was presented monaurally via earphones, became perceivable. Mean handedness index was 48.4 (s.e.m. = ±6.1) as measured with the Italian revised version of the Edinburgh Handedness Inventory (Salmaso & Longoni, 1985). Scores were distributed as follows: 27 subjects scored ≥50, 13 subjects scored ≥0 and <50, and 4 subjects scored <0. Subjects were assigned to two groups on the basis of their performance on a preliminary standard AP-test, which was borrowed from Robert J. Zatorre at BRAMS (www.brams.org). The test consisted of 108 trials in which subjects had to identify the name of the presented musical tone, that changed at every trial. The response was given by mouse click on the perceived note label selected among the 12 note labels displayed on the computer screen. Tone height ranged from a3 to a5, tone duration was 1 s, and intensity could be 67, 70, or 73 dBA. Of note, it is in principle impossible to assess whether a subject has or has not AP in a dichotomous way, as everyone has at least some degree of AP. Half of the subjects scoring the lowest distance from target (in semitones) were assigned to the AP group, the other half were assigned to the NAP group. Mean ± s.e.m. performance in the AP group was 8.24 ± 1.78 semitones errors (out of 108 items), whereas the mean performance in the NAP group was 49.71 ± 10.86 semitones error. In both groups (see Fig. 1) the mode of the distribution was zero, indicating that more correct note-name responses were given than responses at more distant points, even in the NAP group. However, the response distribution of AP musicians had a much smaller variance than that of NAP musicians, indicating the presence of precise fixed-pitch categories in the AP but not in the NAP group. Table 1 summarizes descriptive data from the two groups. 2.2. Stimuli Tones corresponded to all notes comprised in the range from A3 (220.00 Hz) to B5 (987.77 Hz). The duration of the tones was 400 ms and the intensity level 70 dBA. Spectral composition was harmonic, with eight spectral components having the following relative amplitudes: 1, 0.7, 0.5, 0.2, 0.15, 0.05, 0.02, 0.01. One dichotic pair consisted in one of the tones and contralateral white noise. The white noise was presented at 75 dBA and had the same duration of the contralateral tone. The sam-
Table 1 Descriptive data from the AP and NAP groups.
AP NAP
Age (years)
Musical practice (years)
Handedness
M
F
N
25.4 ± 2.0 26.5 ± 1.8
16.3 ± 1.5 17.5 ± 1.5
51.1 ± 8.3 46.0 ± 8.8
18 11
4 11
22 22
Fig. 1. Distribution of group responses in the preliminary AP-test plotted as absolute distance from target, in semitones.
pling rate of each sound was 44,100 kHz and amplitude resolution 16 bit. Amplitude envelope of both tones and white noise contained 50 ms rise and fall times. To obtain a dichotic pair, a tone and white noise were aligned on the two auditory channels by means of the CSound programming language (Vercoe, 1992). An example stimulus is illustrated in Fig. 2. 2.3. Procedure Subjects were presented with a dichotic AP-test with focused attention (Jäncke, Specht, Shah, & Hugdahl, 2003). The test consisted in a sequence of 120 dichotic pairs composed of a musical tone presented at one ear and white noise presented at the other ear (see above). In each trial, after the presentation of the dichotic pair, the task of the subject was to indicate with the mouse the note perceived at the ear receiving the musical tone (Fig. 2). The note names Do, Do#/Reb, Re, Re#/Mib, Mi, Fa, Fa#/Solb, Sol, Sol#/Lab, La, La#/Sib, and Si (fixed do solmization) were presented on the computer monitor arranged in a circle in which the note name “Do” was at the top, Fa#/Solb at the bottom, Re#/Mib on the right and La on the left (Fig. 2). The mouse arrow was automatically positioned at the centre of the circle at the beginning of each trial. The 120 trials were grouped into 20 blocks of 6 trials each. The blocks were separated by a 4-s interval and each block was preceded by a beep (2000 Hz, 200 ms), which was presented monaurally to the ear that was about to receive the target stimuli in that block. Subjects were instructed to direct their attention to the side of the monaural beep in the subsequent block and were informed that tones would be delivered to that side. In half of the trials (blocks) tones were presented to the right ear and white noise to the left, in the other half vice versa. Tones were allocated to blocks on a pseudorandom basis. The side (ear) of presentation of the target stimulus changed at every block. Subjects were familiarized with the test by listening to a sample sequence consisting of 10 dichotic pairs. The format of the test was chosen because it allowed controlling the direction of attention, i.e. fluctuations of attention from one to other ear were minimized. The experiment was completely automated by means of an ad hoc software written in Microsoft Visual Basic. Stimuli were processed by means of a PC with Sound Blaster audio card (Creative, Model AWE 32). Subjects wore headphones (Sennheiser HD 202) and sat comfortably in front of a computer monitor with one hand laying on the computer mouse which was used to indicate on the screen the name of the note which was perceived in each dichotic pair. Half of the subjects used the right hand and half used the left hand to move the mouse. Subjects were instructed to look at the note circle in the centre of the screen in front of them and to avoid shifting their gaze laterally during the experiment. The intensity level of the sounds was the same at both earphones, as measured by a phonometer. However, in order to keep maximal control on the intensity level of the stimuli presented at the ears, after 60 trials (middle of test) subjects reversed the two earphones (the initial position of the headphone was counterbalanced across subjects). Selected note names and latency of response were automatically stored for later analysis. Each experimental session lasted approximately 12 min.
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
2939
categorized, respectively, as small, moderate, and large (Cohen, 1977). 3.1. Preliminary analyses Preliminary statistical analyses indicated that the headphone position at the beginning of the test (upright or reversed), the sex of the participants, and the hand which was used to give the response by moving the mouse did not influence laterality scores (i.e. they showed no significant interactions with the factor ‘ear’). These variables were therefore not included in the subsequent analyses. Yates-corrected 2 × 2 2 -test on gender distribution in the AP and NAP groups showed that the number of males and females in the two groups was not statistically significant (2 = 4.96, p = 0.06), but there was a clear tendency towards significance. However, previous studies have shown that substantially males and females do not differ in perceptual asymmetries, especially when presented with DL of non-verbal sounds (Hiscock, Inch, Jacek, Hiscock-Kalil, & Kalil, 1994; McRoberts & Sanders, 1992; Munro & Govier, 1993). In addition, literature indicates that AP occurs equally in males and females (Athos et al., 2007; Drayna, 2007). 3.2. Main analyses A 2 × 2 measure ANOVA with Group (AP, NAP) as an independent factor and Ear of input (left, right) as a repeated factor was carried out for both dependent variables. Results are illustrated in Fig. 3. For the accuracy variable, the ANOVA showed a significant main effect of Group (F = 35.02; p < 0.001), due to a better general performance of the AP group, no main effect of the Ear of input, and a significant interaction Group × Ear of input (F = 9.06; p = 0.004). Duncan post hoc analysis showed that the effect of the Ear of
Fig. 2. Structure of one trial. After receiving the dichotic pair composed of a musical tone presented at one ear and a white noise burst presented at the other ear (lasting both 400 ms), subject had to indicate the perceived note on the computer monitor, responding with the mouse.
3. Results The dependent variables were (a) accuracy, computed as the distance in semitones from the correct response and (b) reaction time, measured as the median latency of correct responses. Data analysis was performed according to previous studies (Brancucci & San Martini, 1999, 2003; Brancucci, D’Anselmo, Martello, Tommasi, 2008; Brancucci, Babiloni, Rossini, & Romani, 2005). Statistical effects were evaluated by mixed analysis of variance (ANOVA) design at a significance level of p = 0.05. Since preliminary observation of the data distributions indicated that they met ANOVA criteria concerning normality and homogeneity, untransformed scores were used for the statistical analyses. A laterality index (LI) was calculated as follows: LI = (R − L)/(R + L) × 100, where R is the accuracy score (or the reaction time) of the right ear and L is the accuracy score (or the reaction time) of the left ear. For the statistically significant results we calculated the effect size (Cohen’s d). This parameter is the difference between the mean values of two samples divided by the standard deviation of both samples taken together. The effect size is an index of the magnitude of the difference between groups. It can be useful to compare effects across studies, as it does not depend on sample size. Effect sizes of about 0.2, 0.5, and 0.8 are
Fig. 3. Means and standard errors for accuracy (y-axis represents errors measured as absolute distance from target, in semitones, where low distance from target means high accuracy) and reaction time in the AP and NAP groups. Both dependent variables showed a statistically significant Group × Ear interaction.
2940
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941
input was significant in both the AP (p = 0.048, right ear advantage) and NAP (p < 0.001, left ear advantage) group. The effect size of the ear asymmetry for accuracy was ‘moderate’ in the AP group (Cohen’s d = 0.46) and between ‘small’ and ‘moderate’ in the NAP group (d = 0.25). In the AP group, 15 subjects showed a right ear advantage (positive laterality index), 4 subjects showed a left ear advantage (negative laterality index) and 3 subjects showed no advantage (mean LIacc ± s.e.m. was 21.6 ± 7.7). In the NAP group, 8 subjects showed a right ear advantage and 14 subjects showed a left ear advantage (mean LIacc ± s.e.m. was −6.0 ± 4.2). Yates-corrected 2 × 2 2 -contingency test indicated that the frequency distribution of ear advantage in the two groups was significantly different (2 = 5.88, p = 0.015). For the reaction time variable, the ANOVA showed no main effects, but a significant interaction Group × Ear of input (F = 4.82; p = 0.034). Duncan’s post hoc analysis showed that the effect of the Ear of input was significant in the NAP (p = 0.047, left ear advantage) but not in the AP group, which showed a non-significant right ear advantage. In the AP group, 15 subjects showed a right ear advantage and 7 subjects showed a left ear advantage (mean LIRT ± s.e.m. was 2.1 ± 1.4). In the NAP group, 7 subjects showed a right ear advantage and 15 subjects showed a left ear advantage (mean LIRT ± s.e.m. was −4.4 ± 2.8). Yates-corrected 2 × 2 2 -contingency test indicated that the frequency distribution of ear advantage in the two groups was significantly different (2 = 4.45, p = 0.035). 4. Discussion The results of the present study show a right ear advantage in AP subjects and an opposite, left ear advantage in NAP subjects for pitch identification. This claim is based on a statistically significant interaction between the factors group and ear which was observed consistently for both accuracy and reaction time. For the accuracy variable the claim is further supported by significant post hoc results. According to the literature (Brancucci et al., 2004; Della Penna et al., 2007; Hugdahl et al., 1999; Kimura, 1967) the right ear advantage can be interpreted as a left hemispheric specialization and the left ear advantage as a right hemispheric specialization. This indicated that AP subjects recruit a mainly leftlateralized neural network during pitch identification, whereas NAP subjects recruit a mainly right-lateralized neural network. Analyzing specifically the means observed with both accuracy and reaction time, it can be speculated that most of the difference between the groups can be ascribed to the right ear. This would support the hypothesis that the principal centres of AP ability are located in the left hemisphere, in agreement with evidence from both structural neuroimaging studies (Keenan et al., 2001; Schlaug et al., 1995) showing that AP possessors have enhanced leftward asymmetry in the size of the planum temporale (PT) and functional neuroimaging studies (Bermudez & Zatorre, 2005; Zatorre et al., 1998) suggesting that also the left dorsolateral prefrontal cortex plays a role in AP. The present results agree also with the findings of a recent study (Wilson, Lusher, Wan, Dudgeon, & Reutens, 2009) which showed that the activation of the left planum temporale was AP-skill dependent. Significant activation associated with this region appeared dependent on high levels of skill expertise, with less skilled performance engaging a right hemisphere network including pitch working memory structures. This points to the involvement of the left planum temporale in pitch naming ability. At a first glance, the present results run against those of a study by Itoh, Miyazaki, and Nakada (2003) whose main purpose was to investigate left–right asymmetry in the central processing of musical consonance and in which, as a requirement of the experimental design, AP possessors were tested. Results showed no statistical significant effects of ear asymmetry. One possible cause of the
lack of laterality effect could be ascribed to the method used to measure ear performance, which was based on an absolute correct/incorrect criterion rather than magnitude of error (i.e. number of semitones distance from target, more widely used and more precise, Zatorre, 2003). Moreover, if one looks at the mean performance level reached by the subjects in that study and compares it with the performance obtained by the two groups tested in the present one, it can be observed that performance of the subjects tested by Itoh and coworkers was located between the performances of the AP and NAP groups tested in the present study. According to our results, it would be expected that left–right asymmetries in a group of subjects with such an AP ability level would disappear as a consequence of the opposite asymmetry observed in subjects with lower AP ability (the present NAP group). Once established that the main neural mechanisms underlying AP are in the left hemisphere, future investigations could answer the question of whether the role of the right hemisphere is beneficial or detrimental during pitch identification in AP subjects. One could hypothesize that the activation of the right hemisphere in parallel to the left hemispheric-based neural mechanisms devoted to pitch labelling could cause interference. In this case, an inhibition of the right hemisphere would be required in order to develop high-level AP. This could be done by comparing the performance of the two ears in a test similar to the present one with the performance obtained by the same subjects in a variant of the classical AP-test in which tones and white noise are delivered simultaneously and binaurally, in order to control task difficulty. Comparison of the performance obtained with the left ear, the right ear and binaurally could answer the above question. Acknowledgements This research is part of the project EDCBNL (Evolution and Development of Cognitive, Behavioural and Neural Lateralization, 2006–2010), supported by the Commission of the European Communities within the framework of the specific research and technological development programme “Integrating and strengthening the European Research Area” (initiative “What it means to be human”), through a financial grant to LT. We thank Professor Robert J. Zatorre for allowing us to use the BRAMS software. References Athos, E. A., Levinson, B., Kistler, A., Zemansky, J., Bostrom, A., Freimer, N., et al. (2007). Dichotomy and perceptual distortions in absolute pitch ability. Proceedings of the National Academy of Sciences USA, 104(37), 14795–14800. Baharloo, S., Johnston, P. A., Service, S. K., Gitschier, J., & Freimer, N. B. (1998). Absolute pitch: An approach for identification of genetic and nongenetic components. American Journal of Human Genetics, 62, 224–231. Baharloo, S., Service, S. K., Risch, N., Gitschier, J., & Freimer, N. B. (2000). Familial aggregation of absolute pitch. American Journal of Human Genetics, 67, 755– 758. Bermudez, P., & Zatorre, R. J. (2005). Conditional associative memory for musical stimuli in nonmusicians: Implications for absolute pitch. The Journal of Neuroscience, 25, 7718–7723. Brancucci, A., Babiloni, C., Babiloni, F., Galderisi, S., Mucci, A., Tecchio, F., et al. (2004). Inhibition of auditory cortical responses to ipsilateral stimuli during dichotic listening: Evidence from magnetoencephalography. European Journal of Neuroscience, 19, 2329–2336. Brancucci, A., Babiloni, C., Rossini, P. M., & Romani, G. L. (2005). Right hemisphere specialization for intensity discrimination of musical and speech sounds. Neuropsychologia, 43, 1916–1923. Brancucci, A., D’Anselmo, A., Martello, F., & Tommasi, L. (2008). Left hemisphere specialization for duration discrimination of musical and speech sounds. Neuropsychologia, 46(7), 2013–2019. Brancucci, A., & San Martini, P. (1999). Laterality in the perception of temporal cues of musical timbre. Neuropsychologia, 37, 1445–1451. Brancucci, A., & San Martini, P. (2003). Hemispheric asymmetries in the perception of rapid (timbral) and slow (nontimbral) amplitude fluctuations of complex tones. Neuropsychology, 17, 451–457. Cohen, J. (1977). Statistical power analysis for the behavioral sciences. New York: Academic Press., pp. 48–49
A. Brancucci et al. / Neuropsychologia 47 (2009) 2937–2941 Della Penna, S., Brancucci, A., Babiloni, C., Franciotti, R., Pizzella, V., Rossi, D., et al. (2007). Lateralization of dichotic speech stimuli is based on specific auditory pathway interactions: Neuromagnetic evidence. Cerebral Cortex, 17, 2303–2311. Drayna, D. (1998). Genetics tunes in. Nature Genetics, 18(2), 96–97. Drayna, T. (2007). Absolute pitch: A special group of ears. Proceedings of the National Academy of Sciences USA, 104, 14549–14550. Gregersen, P. K., Kowalsky, E., Kohn, N., & Marvin, E. W. (2001). Early childhood music education and predisposition to absolute pitch: Teasing apart genes and environment. American Journal of Medical Genetics, 98(3), 280–282. Hiscock, M., Inch, R., Jacek, C., Hiscock-Kalil, C., & Kalil, K. M. (1994). Is there a sex difference in human laterality? I. An exhaustive survey of auditory laterality studies from six neuropsychology journals. Journal of Clinical and Experimental Neuropsychology, 16(3), 423–435. Hugdahl, K., Bronnick, K., Kyllingsbaek, S., Law, I., Gade, A., & Paulson, O. B. (1999). Brain activation during dichotic presentations of consonant–vowel and musical instrument stimuli: A 15O-PET study. Neuropsychologia, 37, 431–440. Itoh, K., Miyazaki, K., & Nakada, T. (2003). Ear advantage and consonance of dichotic pitch intervals in absolute-pitch possessors. Brain & Cognition, 53(3), 464– 471. Jäncke, L., Specht, K., Shah, J. N., & Hugdahl, K. (2003). Focused attention in a simple dichotic listening task: An fMRI experiment. Cognitive Brain Research, 16(2), 257–266. Keenan, J. P., Thangaraj, V., Halpern, A. R., & Schlaug, G. (2001). Absolute pitch and planum temporale. Neuroimage, 14, 1402–1408. Kimura, D. (1967). Functional asymmetry of the brain in dichotic listening. Cortex, 3, 163–168. Krumhansl, C. L. (1991). Music psychology: Tonal structures in perception and memory. Annual Reviews of Psychology, 42, 277–303. Levitin, D. J., & Rogers, S. E. (2005). Absolute pitch: Perception, coding, and controversies. Trends in Cognitive Sciences, 9, 26–33.
2941
McRoberts, G. W., & Sanders, B. (1992). Sex differences in performance and hemispheric organization for a nonverbal auditory task. Perception & Psychophysics, 51(2), 118–122. Miyazaki, K. (1988). Musical pitch identification by absolute pitch possessors. Perception & Psychophysics, 44(6), 501–512. Munro, P., & Govier, E. (1993). Dynamic gender-related differences in dichotic listening performance. Neuropsychologia, 31(4), 347–353. Ohnishi, T., Matsuda, H., Asada, T., Aruga, M., Hirakata, M., Nishikawa, M., et al. (2001). Functional anatomy of musical perception in musicians. Cerebral Cortex, 11, 754–760. Salmaso, D., & Longoni, A. M. (1985). Problems in the assessment of hand preference. Cortex, 21(4), 533–549. Schlaug, G., Jäncke, L., Huang, Y., & Steinmetz, H. (1995). In vivo evidence of structural brain asymmetry in musicians. Science, 267, 699–701. Takeuchi, A. H., & Hulse, S. H. (1993). Absolute pitch. Psychological Bulletin, 113, 345–361. Tervianemi, M., & Hugdahl, K. (2003). Lateralization of auditory-cortex functions. Brain Research Reviews, 43, 231–246. Vercoe, B. L. (1992). A manual for the audio processing system and supporting programs with tutorials. Cambridge, MA: Massachusetts Institute of Technology Media Labs. Wilson, S. J., Lusher, D., Wan, C. Y., Dudgeon, P., & Reutens, D. C. (2009). The neurocognitive components of pitch processing: insights from absolute pitch. Cerebral Cortex, 19(3), 724–732. Zatorre, R. J., Perry, D. W., Beckett, C. A., Westbury, C. F., & Evans, A. C. (1998). Functional anatomy of musical processing in listeners with absolute pitch and relative pitch. Proceedings of the National Academy of Sciences USA, 95, 3172–3177. Zatorre, R. J. (2003). Absolute pitch: A model for understanding the influence of genes and development on neural and cognitive function. Nature Neuroscience, 6, 692–695.