Perception and Cognition in Absolute Pitch: Distinct Yet Inseparable

The Journal of Neuroscience, July 24, 2019 • 39(30):5839–5841 • 5839

Journal Club

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Perception and Cognition in Absolute Pitch: Distinct yet Inseparable

X Simon Leipold, XMarielle Greber, and XStefan Elmer Division of Neuropsychology, Department of Psychology, University of Zurich, 8050 Zurich, Switzerland Review of McKetton et al.

Absolute pitch (AP) refers to the rare abil- groups were well matched for demo- delineated these core areas of auditory ity to effortlessly identify and/or produce graphic characteristics, and the two musi- cortex and calculated their respective vol- the pitch of a sound without a reference cian groups were additionally matched for umes using morphometric techniques. pitch (Deutsch, 2013). Since AP has been their primary instruments, age of onset of The McKetton et al. (2019) analyses re- proposed to constitute an ideal model for musical training, and number of training vealed an interesting constellation of re- investigating the joint influences of genes hours per week. The authors used fMRI sults: First, the authors observed overall and environment on the development of a during acoustic stimulation with ascend- larger bilateral Heschl’s gyri in AP musi- highly specific ability and its neural un- ing and descending pure tone sweeps cians compared with both non-AP derpinnings, it has intrigued researchers (“chirps”) to map neural responses in the musicians and controls, and these en- in music science, neuroscience, psychol- primary auditory cortex (A1), the rostral largements were found in A1, R, and RT. ogy, and genetics (Zatorre, 2003). Over part of auditory cortex (R), and the Second, and contrary to the authors’ orig- the last 25 years, because of the advent of rostral-temporal part of auditory cortex inal hypothesis of sharper frequency tun- structural and functional neuroimaging, (RT). All of these areas are part of Heschl’s ing in AP musicians, the larger volumes an increasing number of studies have be- gyrus located on the supratemporal plane. were paralleled by broader frequency gun to uncover the neural substrates of AP Importantly, evidence from both humans tuning in A1 and R in AP musicians com- by comparing AP musicians with non-AP and monkeys suggests that A1, R, and RT pared with non-AP musicians. The au- musicians. Nevertheless, our knowledge show tonotopic gradients, characterized thors concluded that the enlarged core about the neural mechanisms underlying by spatially organized neuronal popula- areas form the anatomical basis for the en- AP is still limited. tions, which are particularly sensitive to gagement of a larger number of neuronal A recent Journal of Neuroscience article specific sound frequencies (i.e., center fre- populations during sound processing in set forth to shed more light on the neural quency). Moreover, neuronal popula- AP musicians (McKetton et al., 2019). mechanisms that allow AP musicians to tions in these regions show a characteristic However, an important question that re- categorize tones as easily as most people tuning width determined by their fre- mains largely unanswered is how these name the colors of objects (McKetton et quency selectivity. In particular, popula- findings are related to previous studies al., 2019). The study included 20 AP mu- tions with a broad tuning width respond demonstrating structural and functional sicians, 20 non-AP musicians, and 20 to many frequencies, whereas populations alterations in AP and non-AP musicians. non-musician control subjects. The three with a sharper tuning width respond to Many of the previous studies on brain fewer frequencies (Moerel et al., 2014). structure in AP and non-AP musicians Received March 22, 2019; accepted May 25, 2019. McKetton et al. (2019) computationally found alterations in regions related to S.L. and M.G. were supported by Swiss National Science Foundation Grant320030_163149(toLutzJa¨ncke).WethankProfessorLutzJa¨nckefor modeled the neural responses using lower-level auditory perception. For ex- support; Chantal Oderbolz for critical reading of the manuscript; and Isabel population receptive field mapping (Du- ample, Wengenroth et al. (2014) observed Hotz for assistance in creating the figure. moulin and Wandell, 2008) to create indi- an increased volume of the right Heschl’s The authors declare no competing financial interests. vidual tonotopic maps of A1, R, and RT, gyrus in AP musicians compared with Correspondence should be addressed to Simon Leipold at [email protected]. determining both center frequencies and non-AP musicians. Moreover, earlier https://doi.org/10.1523/JNEUROSCI.0653-19.2019 tuning sharpness of single voxels within studies showed a substantially larger an- Copyright © 2019 the authors these areas. In addition, they manually teromedial area of bilateral Heschl’s gyri, 5840 • J. Neurosci., July 24, 2019 • 39(30):5839–5841 Leipold et al. • Journal Club which corresponds approximately to core area A1, in non-AP musicians compared with controls (Schneider et al., 2002). Apart from primary auditory areas, the planum temporale, a secondary auditory region located immediately posterior to Heschl’s gyrus, has been prominently linked to AP. In a seminal study, Schlaug et al. (1995) discovered a stronger left- ward asymmetry of the planum temporale in AP compared with non-AP musicians. Subsequent studies have found that this asymmetry is mainly driven by a smaller right planum temporale in AP musicians (e.g., Keenan et al., 2001). Findings of a larger Heschl’s gyrus and a smaller planum temporale in AP musicians can be easily reconciled with the notion that AP and non-AP musicians differ in their dis- tribution of cortical volume rather than the absolute volume itself (Wengenroth et al., 2014). Here, McKetton et al. (2019) make an important contribution in ex- plaining the perceptual function underlying enlarged Heschl’s gyrus areas in AP Figure 1. Ventral and dorsal streams in absolute pitch processing. Brain regions that have previously been associated with musicians, namely, the broader frequency absolute pitch might be integrated in the context of dual-stream models of auditory processing. Apart from larger cortical tuning of neuronal populations in re- volumes and broader frequency tuning in core areas of Heschl’s gyrus (HG), absolute pitch-specific structural and functional sponse to acoustic stimulation. alterationshavebeenidentifiedintheplanumtemporale(PT)andtheplanumpolare(PP),butalsoinhigher-orderregions,such Previous studies on brain function in astheinferiorfrontalgyrus(IFG)andtheDLPFC.Theventralstreammightunderliepitchcategorizationinabsolutepitch,whereas the dorsal stream might facilitate access to verbal codes necessary for pitch labeling. A1 ϭ primary auditory cortex; R ϭ rostral AP and non-AP musicians found evi- ϭ dence for alterations in sensory and part of auditory cortex; RT rostral-temporal part of auditory cortex. higher-order brain regions. Regarding the former, there is evidence for enhanced perception (Zatorre, 2003). In light of the 2013). Since AP can be understood as a neural responses in AP in Heschl’s gyrus findings of McKetton et al. (2019), to- particular form of auditory object recog- and the planum temporale during acous- gether with previous evidence of brain al- nition where sounds are perceived as tic stimulation (Wengenroth et al., 2014; terations in AP musicians, a question that discrete pitch categories (pitch categoriza- Leipold et al., 2019) and altered connec- arises is as follows: How does the broader tion) and are mapped onto meaningful la- tivity patterns in Heschl’s gyrus during frequency tuning in auditory core areas bels (pitch labeling), it is conceivable that rest (Brauchli et al., 2019). In addition, the translate to stronger responses in second- the ventral stream plays a major role in AP planum polare, which is part of the audi- ary auditory regions and finally to the (compare Kim and Kno¨sche, 2017). This tory association cortex and located imme- defining feature of AP, the labeling of notion is compatible with human and diately anterior to Heschl’s gyrus, has pitches, which is presumably mediated by animal studies demonstrating that audi- recently been implicated in AP (Kim and higher-order regions supporting cogni- tory object recognition, including speech Kno¨sche, 2017). On the other hand, there tive functions? sounds, animal vocalizations, and envi- is also evidence for functional alterations In this context, the widely acknowl- ronmental sounds, strongly depends in hierarchically higher-order regions, for edged dual-stream models of auditory upon the functional integrity of the ven- instance, the superior temporal sulcus processing might provide an interesting tral stream (Rauschecker and Scott, 2009). (Schulze et al., 2009), the inferior frontal framework for future investigations (Fig. Indeed, the superior temporal sulcus, gyrus (Zatorre et al., 1998; Wengenroth et 1). Broadly speaking, these models differ- which is part of the ventral stream and al., 2014), and the DLPFC (Zatorre et al., entiate a ventral stream, projecting from crucial in sound categorization and recog- 1998; but see Leipold et al., 2019). primary auditory areas along anterior nition, has previously been linked to pitch Functional alterations in higher-order (e.g., the planum polare) and middle tem- categorization in AP musicians (Schulze regions are consistent with an influential poral regions to the inferior frontal gyrus, et al., 2009). On the other hand, the dorsal theory proposing that AP relies on two and a dorsal stream, projecting from pri- stream might facilitate the access to verbal cognitive processes, namely, long-term mary areas via the planum temporale to codes necessary for pitch labeling in AP memory representations of pitches and the DLPFC (Rauschecker and Scott, musicians. Furthermore, AP-specific pro- their association with meaningful labels 2009). Currently, there is little doubt that cessing in the dorsal stream might also (e.g., C# or A)(Levitin, 1994; Levitin and the ventral stream is involved in process- vary as a function of task demands, for Rogers, 2005). Findings of alterations in ing spectrally complex sounds and facili- instance, whether subjects are instructed sensory brain regions, as in the study of tates auditory object recognition. The to verbally or nonverbally respond, or not McKetton et al. (2019), might point to a dorsal stream supports sensory-motor respond at all, during acoustic stimula- differential categorization of pitches into integration, articulation, and verbal me- tion. Although these thoughts on the role narrower categories at an earlier stage of mory functions (Lo´pez-Barroso et al., of the two auditory streams in AP are Leipold et al. • Journal Club J. Neurosci., July 24, 2019 • 39(30):5839–5841 • 5841 largely speculative, integrating accounts receptive field estimates in human visual cor- human auditory cortical areas. Front Neuro- of sensory and higher-order alterations tex. Neuroimage 39:647–660. sci 8:225. will be crucial for future investigations Keenan JP, Thangaraj V, Halpern AR, Schlaug G Rauschecker JP, Scott SK (2009) Maps and (2001) Absolute pitch and planum tempo- streams in the auditory cortex: nonhuman into the neural substrates of perception rale. Neuroimage 14:1402–1408. primates illuminate human speech process- and cognition in AP. Kim SG, Kno¨sche TR (2017) Resting state func- ing. Nat Neurosci 12:718–724. In conclusion, the study of McKetton tional connectivity of the ventral auditory Schlaug G, Ja¨ncke L, Huang Y, Steinmetz H (1995) et al. (2019) advances our understanding pathway in musicians with absolute pitch. In vivo evidence of structural brain asymmetry of AP-specific functional and structural Hum Brain Mapp 38:3899–3916. in musicians. Science 267:699–701. alterations in sensory brain regions asso- Leipold S, Brauchli C, Greber M, Ja¨ncke L (2019) Schneider P, Scherg M, Dosch HG, Specht HJ, Absolute and relative pitch processing in the Gutschalk A, Rupp A (2002) Morphology of ciated with early stages of auditory per- human brain: neural and behavioral evidence. Heschl’s gyrus reflects enhanced activation in ception. Future directions for AP research Brain Struct Funct. Advance online publica- the auditory cortex of musicians. Nat Neuro- are the integration of findings concerning tion. Retrieved April 9, 2019. doi:10.1007/ sci 5:688–694. sensory regions with the frequently re- s00429-019-01872-2. Schulze K, Gaab N, Schlaug G (2009) Perceiving ported alterations in higher-order regions Levitin DJ (1994) Absolute memory for musical pitch absolutely: comparing absolute and rel- associated with cognition. The role of the pitch: evidence from the production of learned ative pitch possessors in a pitch memory task. melodies. Percept Psychophys 56:414–423. BMC Neurosci 10:106. two auditory streams in AP could provide Levitin DJ, Rogers SE (2005) Absolute pitch: Wengenroth M, Blatow M, Heinecke A, Rein- a sensible framework for future investiga- perception, coding, and controversies. Trends hardt J, Stippich C, Hofmann E, Schneider P tions into this fascinating phenomenon. Cogn Sci 9:26–33. (2014) Increased volume and function of Lo´pez-Barroso D, Catani M, Ripolle´s P, Dell’Acqua F, right auditory cortex as a marker for absolute Rodríguez-Fornells A, de Diego-Balaguer R pitch. Cereb Cortex 24:1127–1137. 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