18. Hunter, T. (1998). Anti-phosphatasestake the stage. Nature Genet. 18,303–305.

19. Da Costa, M., Bach, L., Landrieu, I.,Bellec, Y., Catrice, O., Brown, S.,De Veylder, L., Lippens, G.,Inze, D., and Faure, J.-D. (2006).Arabidopsis PASTICCINO2 is anantiphosphatase involved in

regulation of cyclin-dependentkinase A. Plant Cell 18, 1426–1437.

20. Juo, P., and Kaplan, J.M. (2004). Theanaphase-promoting complexregulates the abundance ofGLR-1 glutamate receptorsin the ventral nerve cord ofC. elegans. Curr. Biol.14, 2057–2062.

Department of Genetics, Cell Biologyand Development, University ofMinnesota, Minneapolis, Minnesota55455, USA.E-mail: green959@umn.edu

DOI: 10.1016/j.cub.2007.08.019

Current Biology Vol 17 No 20R892

Music Perception: Sounds Lostin Space

A recent study of spatial processing in amusia makes a controversialclaim that such musical deficits may be understood in terms of a problemin the representation of space. If such a link is demonstrated to be causal,it would challenge the prevailing view that deficits in amusia are specificto the musical or even the auditory domain.

Lauren Stewart1

and Vincent Walsh2

Individuals with amusia reportlife-long difficulties in making senseof music, even though their hearingand other cognitive faculties arenormal. They cannot recognizetunesthatwouldbefamiliar toothersfrom their culture; they fail to sing intune; and, to them, one song soundsvery much like another. For somepeople with this condition, musicis highly aversive. One describedRachmaninov’s second pianoconcerto as sounding like ‘bangingand noise’, while another admittedshe avoided social occasionsinvolving music ‘at all costs’ [1].

While a body of research hasconverged in pinpointingfine-grained pitch perception as thecause of the deficit, a recent study[2] has proposed an associationbetween amusia and spatialdeficits. These researchersidentified a group of amusicindividuals using a subtest from theMontreal Battery for the Evaluationof Amusia (MBEA) [3]. This batteryis a series of tests in whichparticipants indicate whether a pairof tunes is exactly the same orslightly different. In the ‘contour’subtest used by Douglas andBilkey [2], the difference, when itoccurred, involved a change inone of the notes of the secondtune such that the pattern of upsand downs was different for eachtune — a very salient change formost people.

Douglas and Bilkey’s [2] amusicgroup made incorrect responsesfor eight or more trials out of 30,putting their performance in thebottom 2.5% of a normativesample [3]. The amusics werecompared to control subjects ona classic mental rotation task whichrequired them to report whetherpairs of line drawings representedthe same three-dimensional objectfrom a different viewpoint, ora different three-dimensionalobject altogether. Compared withthe control subjects, who scored inthe normal range on the MBEA, theamusics made significantly moreerrors, even when matched formusical training background.Furthermore, within the amusicgroup, there was a positivecorrelation between mentalrotation score and performance onthe MBEA contour subtest.Although the two groups were notbalanced for gender (there weremore females in the amusic group),this relationship between themusical score and the spatial scorestill held when gender waspartialled out.

Two further experiments arepresented to bolster the claim thatamusia is associated with deficitsin spatial processing. Douglas andBilkey [2] used a StimulusResponse Compatibility Task(SRC), in which participantscompared the pitches of two tonesand indicated whether the secondwas higher or lower, usinga response configuration that was

either ‘compatible’ (‘higher’ and‘lower’ responses mapped toresponses that are higher andlower in vertical space) or‘incompatible’ (the reverse). Asimilar task has been previouslyused by Rusconi et al. [4] and Lidjiet al. [5] to demonstrate that pitch ismapped onto a verticalrepresentation, even when the taskdoes not explicitly concern pitch.Control participants made moreerrors for the incompatibleconfiguration, while the amusicsmade equivalent numbers of errorsfor both configurations.

While at first sight this may seemto support the claim that amusicsare failing to implement a spatialrepresentation of pitch, it seemsthat the amusics were worse atdiscriminating pitch directionoverall, with twice as many errorsas controls. Foxton et al. [6] havereported that amusics, as a group,have thresholds for pitch directiondiscrimination that exceed twosemitones (the difference betweenDo and Re in ‘Do-Re-Mi’). The issuehere is that Douglas and Bilkey’s [2]inclusion of such a small intervaldoes not allow for disambiguationof a deficit in simple perception ofpitch direction from a deficit in themapping of pitch onto verticalspace.

These potential limitationsnotwithstanding, the findingsconcerning mental rotationperformance resonate with otherstudies of amusia and pitchrepresentation. Links betweenvisuo-spatial performance andmusical expertise have previouslybeen drawn, variously highlightingsuperior performance of musicianson visuospatial tasks [7,8], theactivation of brain areasassociated with spatial processingsuch as superior parietal cortexduring musical perception [9–11],and changes in the structure ofsuperior parietal cortex and otherregions associated with

DispatchR893

visuo-spatial processing [12].However, such findings havegenerally been attributed tomusicians’ expertise in makingspatial sensori-motortransformations — the rapidconversion from spatiallyorganized symbols on the stave tothe instrument-specific fingeringsthat must occur during musicreading and performance.

The closest suggestion for a linkbetween spatial abilities andmusical listening in musicallyuntrained individuals comes froma paper by Cupchik et al. [13] whodemonstrated a correlationbetween performance on a mentalrotation task and the ability of thelistener to detect when a musicaltune had been played backwards.Similar to the mental rotation task,this musical permutation involvesexplicitly transforming therepresentation of a sensorystimulus from one co-ordinateframe to another. There is a sensein which musical listening, evenwithout such explicit demands,involves keeping track of musicalevents as they are transposed ortransformed — a fusion of thefamiliar and the unexpected [14].The extent to which the co-ordinatesystems involved in making visualtransformations are independentor interact with the co-ordinatesystems involved in auditorytransformations is an importantquestion which remains to beelucidated.

Although Douglas and Bilkey [2]argue that differences in spatialability may affect the extent towhich music can be perceived, thereverse argument can also bemade: that is, the amount of timespent engaged in active musicallistening may contribute to shapingspatial processing in general. Theauthors report that both amusic andcontrol subjects claimed to listen toan equal amount of music, yet thisseems surprising given a recentstudy [1] which found that amusicsreported, on average, listening tomusic of their own choice for threehours a week compared to ninehours in a matched control group. Ittherefore seems possible that theamusic and control groups inDouglas and Bilkey’s [2] study werenot equated for the amount of timespent listening to music of their own

choice, as opposed to music thatthey are incidentally exposed to, forinstance in public places [15]. Theview that the musical listeningprocess is an active one, involvinglisteners consciously anddeliberately using music to achieveor enhance certain, predominantlyaffective states [16], underlines theimportance of making thisdistinction explicit. Of course, it isalso possible that even if theamount of active musical listeningwere similar in amusic and controlparticipants, music perceptualdeficits may limit the capacity forprocessing the higher orderstructure of music.

These two opposing hypothesesconcerning the directionality of theassociation between musical andspatial ability can be tested: if activemusical listening impacts uponspatial ability, the extent of activemusical listening should predictspatial ability but not vice versa. Onthe other hand, if spatial abilityunderlies musical perception,performance on tasks like mentalrotation should predict the score ona test such as the MBEA but not viceversa. Nature’s experiments [1] —neurological injury due to stroke —already provide a test of the latter.Brain injury to the parietal cortexseverely limits visuo-spatialperception, in the form ofvisual-neglect syndrome. To thebest of our knowledge theliterature does not include reportsof musical deficiency in visualneglect syndrome, althoughlesion-based investigations of pitchability in these patients are lacking.

The suggestion of Douglas andBilkey [2] that music perceptionmay depend on the same cognitivemechanisms that are required toprocess space may cause discordwithin the scientific community.Although it encourages us to look atamusia from a differentperspective, there is a clear needfor replication and extension beforesuch a view is accepted. Inparticular it will be important toestablish that differences in spatialrepresentation (as suggested forthe SRC task) are independent ofdifferences in simple pitchperception and to determinewhether the deficits in spatial abilityemerge from or result in the deficitsseen in musical perception.

References1. McDonald, C., and Stewart, L. (2007).

Uses and functions of music in congenitalamusia. Music Perception, in press.

2. Douglas, K.M., and Bilkey, D.K. (2007).Amusia is associated with deficits inspatial processing. Nat. Neurosci. 10,915–921.

3. Peretz, I., Champod, A.-S., and Hyde, K.L.(2003). Varieties of musical disorders.The Montreal Battery of Evaluation ofAmusia. Ann. NY Acad. Sci. 999,58–75.

4. Rusconi, E., Kwan, B., Giordano, B.L.,Umilta, C., and Butterworth, B. (2006).Spatial representation of pitch height:the SMARC effect. Cognition 99,113–129.

5. Lidji, P., Kolinsky, R., Lochy, A., andMorais, J. (2007). Spatial association formusical stimuli: a piano in the head?J. Exp. Psychol. Hum. Percept. Perform.,in press.

6. Foxton, J.M., Dean, J.L., Gee, R.,Peretz, I., and Griffiths, T.D. (2004).Characterization of deficits in pitchperception underlying ‘tone deafness’.Brain 127, 801–810.

7. Brochard, R., Dufour, A., and Despres, O.(2004). Effect of musical expertise onvisuospatial abilities: evidence fromreaction times and mental imagery. BrainCogn. 54, 103–109.

8. Sluming, V., Brooks, J., Howard, M.,Downes, J.J., and Roberts, N. (2007).Broca’s area supports enhancedvisuospatial cognition in orchestralmusicians. J. Neurosci. 27, 3799–3806.

9. Sergent, J., Zuck, E., Terriah, S., andMacDonald, B. (1992). Distributed neuralnetwork underlying musical sight-readingand keyboard performance. Science 257,106–109.

10. Platel, H., Price, C., Baron, J.C., Wise, R.,Lambert, J., Frackowiak, R.S.,Lechevalier, B., and Eustache, F. (1997).The structural components of musicperception. A functional anatomical study.Brain 120, 229–243.

11. Stewart, L., Walsh, V., and Frith, U. (2004).Reading music modifies spatial mappingin pianists. Percept. Psychophys. 66,183–195.

12. Gaser, C., and Schlaug, G. (2003). Brainstructures differ between musicians andnon-musicians. J. Neurosci. 23,9240–9245.

13. Cupchik, G.C., Phillips, K., and Hill, D.S.(2001). Shared processes in spatialrotation and musical permutation. BrainCogn. 46, 373–382.

14. Huron, D. (2006). Sweet Anticipation:Music and the Psychology of Expectation(Cambridge, MA: MIT Press).

15. North, A., and Hargreaves, D.J. (1997).Experimental aesthetics and everydaymusic listening. In The Social Psychologyof Music, D.J. Hargreaves and A. North,eds. (Oxford: Oxford University Press),pp. 84–103.

16. Sloboda, J. (1999). Everyday uses ofmusic listening: a preliminary study. InMusic, Mind and Science, S.W. Yi, ed.(Seoul, Korea: Western Music ResearchInstitute), pp. 354–369.

1Department of Psychology, WhiteheadBuilding, Goldsmiths, University ofLondon, New Cross, London, UK.2Institute of Cognitive Neuroscience andDepartment of Psychology, UniversityCollege London, London, UK.E-mail: l.stewart@gold.ac.uk

DOI: 10.1016/j.cub.2007.08.012