Identification of Changes along a Continuum of Speech Intonation is Impaired in Congenital Amusia

Abstract

A small number of individuals have severe musical problems that have neuro-genetic underpinnings. This musical disorder is termed “congenital amusia,” an umbrella term for lifelong musical disabilities that cannot be attributed to deafness, lack of exposure, or brain damage after birth. Amusics seem to lack the ability to detect fine pitch differences in tone sequences. However, differences between statements and questions, which vary in final pitch, are well perceived by most congenital amusic individuals. We hypothesized that the origin of this apparent domain-specificity of the disorder lies in the range of pitch variations, which are very coarse in speech as compared to music. Here, we tested this hypothesis by using a continuum of gradually increasing final pitch in both speech and tone sequences. To this aim, nine amusic cases and nine matched controls were presented with statements and questions that varied on a pitch continuum from falling to rising in 11 steps. The sentences were either naturally spoken or were tone sequence versions of these. The task was to categorize the sentences as statements or questions and the tone sequences as falling or rising. In each case, the observation of an S-shaped identification function indicates that amusics can accurately identify unambiguous examples of statements and questions but have problems with fine variations between these endpoints. Thus, the results indicate that a deficient pitch perception might compromise music, not because it is specialized for that domain but because music requirements are more fine-grained.

Fine-grained pitch processing of music and speech in congenital amusia

“…This outcome differs from the first reports on congenital amusia indicating unimpaired pitch processing in language material Patel et al, 2005), but is in agreement with more recent reports revealing pitch deficits also for language materials (Patel et al, 2008;Nguyen et al, 2009;Hutchins et al, 2010;Liu et al, 2010;Nan et al, 2010;Tillmann et al, 2011). The affected pitch processing in language material suggests a domain-general pitch deficit that is causing amusia.…”

Reduced sensitivity to emotional prosody in congenital amusia rekindles the musical protolanguage hypothesis

“…Other investigations have reported that amusic individuals have elevated thresholds for pitch-change detection and pitch-direction discrimination (34) along with impaired sensitivity to subtle pitch changes derived from speech stimuli (39,(42)(43)(44)(45)49). For example, individuals with amusia who speak a tone language have reduced ability to discriminate individual words that differ only in tone, and reduced sensitivity to pitch sequences derived from questions and statements (34).…”

“…As such, the impairment underlying congenital amusia may be highly relevant to music because of the reliance of music on finegrained pitch movements. Supporting this hypothesis, a recent investigation revealed that amusic individuals can correctly identify unambiguous examples of questions and statements, but exhibit deficits with subtle exemplars (49).…”

Meta-analytic evidence for the non-modularity of pitch processing in congenital amusia

“…In other words, the amusic deficit has been proposed to lie in the acoustic analysis of sounds, and since music processing lies downstream from acoustic processing and makes high demands on fine-grained pitch resolution, amusics manifest a musical impairment. The literature has since been converging towards the finding that amusics display significantly worse pitch discrimination performance as compared to controls (e.g., Hutchins, Gosselin, & Peretz, 2010;Jiang, Hamm, Lim, Kirk, & Yang, 2010;Liu, Patel, Fourcin, & Stewart, 2010;Jiang et al, 2012;Liu et al, 2013;Nan, Sun, & Peretz, 2010;Omigie & Stewart, 2011;Patel, Wong, Foxton, Lochy, & Peretz, 2008;Tillmann, Burnham, et al, 2011;Tillmann, Rusconi, et al, 2011), bearing out Peretz et al's (2002) hypothesis. Indeed, in addition to poor performance on the MBEA, a pitch discrimination deficit has become a diagnostic benchmark for the identification of new amusic cases.…”

“…For instance, amusics seem to perceive speech normally, and they can recognize and sing songs through lyrics but not the tune (Ayotte, Peretz, & Hyde, 2002;Dalla Bella, Gigu ere, & Peretz, 2009; TremblayChampoux, Dalla Bella, Phillips-Silver, Lebrun, & Peretz, 2010). However, amusics do show an impairment of pitch perception in speech (Hutchins, Gosselin, et al, 2010;Hutchins, Zarate, Zatorre, & Peretz, 2010;Liu et al, 2010;Patel et al, 2008;Tillmann, Rusconi, et al, 2011), but as Peretz (2013) notes, this deficit is mild relative to their impairment with musical materials. Assuming modular Fig.…”