Some individuals with difficulties understanding language also have problems perceiving music (Anvari, 2002
). These problems may be related because musical pitch perception and speech perception share many of the same processing requirements. Both rely on the elements of sound (notes in music and phonemes in speech) organized into acoustic sequences comprised of small perceptual units and highly structured sequences (Patel and Daniele, 2002). These sequences are formed by rule-based permutations of a limited number of these discrete elements (phonemes in speech or tones in music) to yield meaningful structures (words or musical phrases). These are subject to further hierarchical organization resulting in more complex entities, such as sentences or melodies (Foxton et al., 2004
; Zatorre et al., 2002
Music and speech are common to all human societies (Peretz et al, 2002
). Both develop over time, and require continuous sustained attention, memory, exposure, and training. (Foxton et al., 2004
). Furthermore, music perception and speech perception are the result of sound processing by the listener (Ayotte, 2002
; de Cheveigne, 2004
; Shamma, 2004
; Zatorre et al., 2002
), and pitch information is an important component of both melodies and speech sounds.
In view of these concepts, it was surprising when studies of individuals with focal brain lesions demonstrated instances in which perception of these two sound classes could be separated, and isolated deficits in the perception of either one or the other class of sounds were clearly documented (Peretz, 2002
). The separation of these functions was also supported by brain imaging studies. PET and fMRI scans showed that while areas of the left temporal lobe, in particular Broca’s and Wernicke’s areas, are most highly activated in speech, musical listening activates other more caudal regions of the brain, such as the superior temporal sulcus, Hechl’s gyrus, and the plana polare and temporale. (Levitin & Menon, 2003
However, more recent brain activity and functional imaging studies have supported the view that auditory processing of speech and music are localized in similar regions of the brain. Koelsch (2002)
noted that there is considerable overlap of cortical networks, in the inferior fronto-lateral, anterior, and posterior temporal lobe structures in both hemispheres that are involved in the processing of speech and music. These structures have been assumed to be specific to language and auditory processing (Koelsch, 2000
; Levitin & Menon, 2003
; Patterson, 2002
). Recent studies by Wong et al. (2007)
have supported similar localization, and suggest that in addition to cortical processes, the brainstem functions to encode both musical and linguistic pitch perception.
In a study of music and speech, Anvari et al. (2002)
investigated language and musical skills in children 4 to 5 years of age. They theorized that some of the auditory skills used in the processing of speech, such as blending and segmenting sounds, are similar to the skills necessary for music perception, such as rhythmic, melodic, and harmonic discrimination. Their results indicated that music perception appears to make use of auditory mechanisms that partially overlap with those related to phonological awareness (Anvari et al., 2002
In another study, Overy (2003)
investigated musical timing skills in children with deficits in phonological awareness. Their results indicated that children with phonological awareness deficits also demonstrated deficits in some areas of musical processing, including those required for rapid timing, rhythm, and tempo. However, these children demonstrated strong pitch discrimination skills. Thus, despite a large amount of data from studies using a number of different experimental approaches, the degree of overlap in the structures and mechanisms required to process speech sounds versus musical sounds has remained uncertain.
Another way to examine pitch and speech sound perception is to study naturally occurring disorders of these functions. Although deficits in musical pitch perception and speech perception are well documented in individual adults (Peretz et al., 2002
), we focused on a large group of tune deaf individuals to obtain a broader view of this population. Several previous studies of music and speech perception focused on young children in whom rapid brain development occurs. We limited our study to adults to reduce the impact of developmental factors on the results.
Deficits in musical pitch perception have also been referred to as congenital amusia, note-deafness, dysmelodia, tune deafness, or music agnosia (Allen, 1878
; Ayotte et al., 2002
; Hyde & Peretz, 2004; Kalmus and Fry, 1980
; Drayna et al., 2001
; Foxton et al., 2004
). We have operationally defined tune deaf individuals as those with reproducibly low scores on the Distorted Tunes Test (DTT), a widely used test of musical pitch recognition (Kalmus & Fry, 1980
; Drayna et al, 2001
). To understand the relationship between musical pitch perception and speech sound perception, we evaluated a number of phonologic and phonemic functions in tune deaf individuals.
We used the Comprehensive Test of Phonological Processing (CTOPP) to assess phonological awareness, which is the ability to manipulate and discriminate sounds in syllables and words, and phonemic awareness, which is the ability to segment and blend phonemes, which are the sounds in words. The CTOPP is a well-validated instrument that measures a number of aspects of phonological processing and memory (Lennon & Slesinski, 2001
). We hypothesized that tune deafness, initially ascertained as deficits in musical pitch recognition, may be related to specific components of auditory processing used in speech, including phonological and phonemic awareness.