Neuropsychology of Musical Perception: New Perspectives

Editorial Neuropsychology of musical perception: new perspectives

For now well over a century, neuropsychologists have competence, such as the `absolute pitch' capability, is a investigated the various components of auditory perception. idea which continues to provoke debate (Zatorre et al., 1998). The central disorders of this perception have been a topic of In a number of experimental conditions, it was clearly shown considerable interest, mainly through observations of audi- that non-musician subjects can present musical capabilities as tory agnosia or amusia (selective loss of musical abilities). In adequately as musicians in their ability to judge modi®cations a remarkable way, it was shown that the disorders of music of musical parameters (Bigand and Pineau, 1997). On the and language perception could be dissociated. Although it is contrary, do we have examples of `naturally' incompetent usual to assert that the perception of music is subserved by the individuals for music? The research team of I. Peretz right hemisphere, observations of brain-damaged patients provided a new and remarkable insight to these questions reveal the involvement of both hemispheres. The idea, that by the thorough study of a cognitively neurologically healthy amusia follows generally right hemispherical lesions, corres- population of subjects, presenting what can be termed as a ponds in particular to the fact that, in rare cases where `congenital amusia'. The work of Ayotte, Peretz and Hyde, musicians have had a left sylvian infarction (e.g. Wernicke's published in this volume, is truly a turning point in the aphasia), they have been able to continue their musical career research carried out on musical perception in that the authors and follow a quasi normal artistic activity. However, the highlighted a new population of interest. Indeed, clinical clinical association of linguistic and musical disorders is also research relating to the observation of selective de®cits of often noted, and the observations of `pure' amusia are musical perception is confronted by the great scarcity of extremely rare in the literature. Thus, it remains dif®cult to neurological syndromes producing such disorders. For a long establish precisely the functional neuroanatomy of musical time, patients having undergone cortectomy of temporal perception from such clinical studies (Lechevalier et al., lobes for intractable epilepsy constituted a privileged popu- 1985). lation of study for central auditory disorders. However, The development of experimental psychology methods numerous studies involving these patients have shown applied to healthy subjects and brain damaged patients during frequently a weak deleterious effect of temporal cortectomies the 1960s made it possible to separate, on a functional level, on musical abilities (LieÂgeois-Chauvel et al., 1998). As such, the involvement of each cerebral hemisphere, and contributed clinical research has had to readdress this question and take to support the distinction between music and language by into account the description of this new and fascinating locating each one of these functions in a different hemisphere. `pathological' population. This concept, however, is not Over the last 20 years, experimental studies have contributed based primarily on the revelation of the existence of the to a more modular conception of musical perception, which is congenital amusia, which was already described in the not satis®ed by one simple opposition between music and literature by the end of the 19th century, but more so on the language, but proposes to approach the perception of music in precise characterization performed by the authors of the all its complexity. For example, one may consider the observed musical de®cits. multiple components of music (pitch, timbre, rhythm), each Ayotte, Peretz and Hyde are the ®rst to describe precisely one of which may be differentially lateralized (Peretz, 1993). the very selective nature of such disturbances. Their selected Thus, the complexity of musical cognition could be revealed subjects (chosen using a rigorous methodological approach) in a number of ways as follows: to perceive a melody, to presented only disorders of musical perception (in particular discriminate between the pitch of two notes, to differentiate the pitch perception), in the absence of linguistic disorders the timbre of musical instruments, to beat the tempo or to (no dif®culty on prosody) and signi®cant dif®culties with perceive a rhythmic pattern. Such are the many high level perception of environmental sounds. Moreover, these de®cits cognitive activities, which are based on perceptive skills, and did not affect only the perceptive level, but the subjects were for whom the musicians remain the experts. also extremely de®cient in their ability to memorize and Beyond the question of independence between music and recall musical information. The main hypothesis, which was language, the innate or acquired character of musical proposed to explain these selective musical disorders, is that ã Oxford University Press 2002 224 Editorial the whole of the de®cits observed are the consequence of an References initial failure of the system of pitch perception. This Ayotte J, Peretz I, Hyde K. Congenital amusia: a group study of assumption, although plausible, will require to be supported adults af¯icted with a music-speci®c disorder. Brain 2002; 125: by other work. On the other hand, no neuro-functional 238±51. explanation can be advanced to support a defect of activation Besson M, Faita F, Peretz I, Bonnel AM, Requin J. Singing in the of a neural network dedicated solely to a musical process. In brain: independence of lyrics and tunes. Psychol Sci 1998; 9: 494±8. addition, the initiation of musical disorders in the history of Bigand E, Pineau M. Global context effects on musical expectancy. the subjects must be considered in relation to possible effects Percept Psychophys 1997; 59: 1098±107. of compensation. For these reasons, one may consider that the prolongation of such studies with this population and with Engelien A, Silbersweig D, Stern E, Huber W, DoÈring W, Frith C, functional neuroimaging techniques presents considerable et al. The functional anatomy of recovery from auditory agnosia. A interest. PET study of sound categorization in a neurological patient and Indeed, the different functional cerebral imaging tech- normal controls. Brain 1995; 118: 1395±409. niques (metabolic or electrophysiological) have allowed, over Lechevalier B, Eustache F, Rossa Y. Les troubles de la perception the last 15 years, to specify the role of primary and secondary de la musique d`origine neurologique. Paris: Masson; 1985. auditory cortex areas. The tonotopic representation of sounds, LieÂgeois-Chauvel C, Peretz I, Babai M, Laguitton V, Chauvel P. already described in animal studies, was also found in man Contribution of different cortical areas in the temporal lobes to (Pantev et al., 1989). However, very few functional music processing. Brain 1998; 121: 1853±67. neuroimaging studies were directly interested in the investi- gation of musical processes (Zatorre et al., 1994; Besson Pantev C, Hoke M, LuÈtkenhoÈner B, Lehnertz K. Tonotopic organization of the human auditory cortex: pitch versus frequency et al., 1998). These studies con®rm, however, the complex representation. Science 1989; 246: 486±8. and composite characteristics of music perception (Platel et al., 1997). Lately, the study of the speci®city of musical Peretz I. Auditory agnosia: a functional analysis. In: Adams SMC, memory was addressed, and now constitutes a new ®eld of Bigand E, editors. Thinking in sound: cognitive aspects of human investigation (Platel et al., 2001). Most of this research work audition. Oxford: Oxford University Press; 1993. p. 199±230. was carried out with normal subjects (musicians or non- Platel H., Price C, Baron JC, Wise R, Lambert J, Frackowiak RS, musicians), but very few studies of functional neuroimaging et al. The structural components of music perception: a functional could be carried out on patients presenting central auditory anatomical study. Brain 1997; 120: 229±43. disorders (Engelien et al., 1995). In fact, the opportunity to Platel H, Baron JC, Desgranges B, Bernard F, Eustache F. Semantic study this new population, having the double characteristic to and episodic memory of music: a positron emission tomography present selective disturbances of musical functions in the study. Neuroimage 2001; 13: S727. absence of an established neurological pathology, represents an opening towards new research and makes it possible to re- Zatorre RJ, Evans AC, Meyer E. Neural mechanisms underlying address the questions about functional independence between melodic perception and memory for pitch. J Neurosci 1994; 14: language and music, and about the innate or acquired nature 1908±19. of the various levels of expression of these typically human Zatorre RJ, Perry DW, Beckett CA, Westbury CF, Evans AC. competences. Functional anatomy of musical processing in listeners with absolute pitch and relative pitch. Proc Natl Acad Sci USA 1998; 95: 3172±7. Herve Platel INSERM U.320, University of Caen, France