Bell, Davis, Morgan-Fisher, and Ross (1990)
BELL, William L., Diana L. Davis, Anna Morgan-Fisher, and Elliott D. Ross. “Acquired Aprosodia in Children.” Journal of Child Neurology 5 (Jan 1990): 19-26.
Records case histories for two 10-year old girls who suffered from mild acquired right-hemispheric damage, and comparisons to seven age-matched female controls. Patients and controls were assessed for spontaneous and imitative affective prosody in speech, as well as spontaneous requested singing of “Happy Birthday.” Both patients showed initial deficits in spontaneous affective prosody. [1] Case 2 exhibited severe loss of imitative affective prosody as well, whereas the affective repetition deficits for Case 1 were reported as minor. Similarly, relative to controls, singing was impaired for Case 1, whereas it appeared normal for Case 2. This lead the authors to suspect a direct correlation between modulation of pitch in speech and singing. Since the findings of Gordon & Bogen 1974 appeared to contradict this conclusion, the authors confirmed by private communication with Dr. Bogen, that the normality of speech reported therein referred only to propositional and not affective components of speech prosody.
It is interesting to compare this, however, with the findings of Yamadori, et al 1977, which note that text production is normally intact during singing by Broca’s aphasics. Therefore, while pitch may be dominantly encoded in the right hemisphere for both speaking and singing (though I believe the evidence is inconclusive at this point) [2], text appears to have dual encoding in both hemispheres. It may be that right-hemispheric encoding of words is purely phonological, that the sounds of the words may be separately or redundantly encoded from a holistic representation in the opposite hemisphere, which includes sound or articulatory elements. Empirical studies could address this question, with brain scans of singers during production of songs with both familiar (native) and unfamiliar (foreign) words. However, if dual-encoding is found to be the case, it may be that singers switch back and forth between linguistic and phonological processing of text sounds, in the course of song production. Therefore brain imaging techniques that showed good temporal resolution would be essential. [3]
[1] Happily, normal functioning was recovered by both patients within a matter of months.
[2] This is complicated by issues regarding the acquisition of song. Children and inexperienced singers often attend first to linguistic, then rhythmic, and only last to melodic elements of singing. It is possible that processing for melody in song is more variable in the population than other aspects of vocal production, which may account for ambiguous and contradictory evidence in the literature. This compares to findings that early musical training, in particular for pianists and violinists, often causes a shift to left-hemisphere dominance for procedures that are otherwise right-hemispheric in the general population.
Additionally, it must be pointed out that pitch processing for music (and thus assumedly for singing) is more precise than it is for prosody in speech. Non-lexically significant pitch (i.e. non-tone-dependent intonation, in both tone and nontone languages) appears to be processed as a gestalt. Because of this, it seems a reasonablehypothesis to expect intonational pitch processing and musical pitch processing to be encoded differentially in the brain. Such redundancies in the brain may have arisen as a result of separate adaptive pressures converging on auditory processing. And this may explain some of the confusions which arise as a result of trying to define boundaries for musical and linguistic phenomena. It just may be that acoustic signals are processed redundantly, and varyingly, by different members of the population, and under different expectational conditions.
[3] It is commonly acknowledged that fMRI, while giving better spatial data than PET scans, trades this off with lousy temporal data. New techniques combine both MRI and PET technologies, but these may still prove inadequate for the type of study proposed. We can only hope that the technologies will continue to progress, along with the greater complexity of the questions researchers ask.
