Patricia Moreau

Pitch discrimination without awareness in congenital amusia: Evidence from event-related potentials

Congenital amusia is a lifelong disorder characterized by a difficulty in perceiving and producing music despite normal intelligence and hearing. Behavioral data have indicated that it originates from a deficit in fine-grained pitch discrimination, and is expressed by the absence of a P3b event-related brain response for pitch differences smaller than a semitone and a bigger N2b-P3b brain response for large pitch differences as compared to controls. However, it is still unclear why the amusic brain overreacts to large pitch changes. Furthermore, another electrophysiological study indicates that the amusic brain can respond to changes in melodies as small as a quarter-tone, without awareness, by exhibiting a normal mismatch negativity (MMN) brain response. Here, we re-examine the event-related N2b-P3b components with the aim to clarify the cause of the larger amplitude observed by Peretz, Brattico, and Tervaniemi (2005), by experimentally matching the number of deviants presented to the controls according to the number of deviants detected by amusics. We also re-examine the MMN component as well as the N1 in an acoustical context to investigate further the pitch discrimination deficit underlying congenital amusia. In two separate conditions, namely ignore and attend, we measured the MMN, the N1, the N2b and the P3b to tones that deviated by an eight of a tone (25 cents) or whole tone (200 cents) from a repeated standard tone. The results show a normal MMN, a seemingly normal N1, a normal P3b for the 200 cents pitch deviance, and no P3b for the small 25 cents pitch differences in amusics. These results indicate that the amusic brain responds to small pitch differences at a pre-attentive level of perception, but is unable to detect consciously those same pitch deviances at a later attentive level. The results are consistent with previous MRI and fMRI studies indicating that the auditory cortex of amusic individuals is functioning normally.

Automatic Brain Responses to Pitch Changes in Congenital Amusia

Congenital amusia is a lifelong disorder affecting the processing of pitch. This pitch deficit can be traced down to abnormal brain responses elicited by pitch changes smaller than a semitone in conditions requiring attention. Here, we use the mismatch negativity (MMN) to investigate pre‐attentive pitch change detection in 10 amusics and eight matched controls. Results indicate similar MMN in amusics and controls, even for an eighth of a tone change, revealing that the amusic brain can process small pitch changes at a pre‐attentive level. Thus, the pitch deficit in congenital amusia may be related to a problem of perceptual awareness.

Congenital amusia persists in the developing brain after daily music listening.

Congenital amusia is a neurodevelopmental disorder that affects about 3% of the adult population. Adults experiencing this musical disorder in the absence of macroscopically visible brain injury are described as cases of congenital amusia under the assumption that the musical deficits have been present from birth. Here, we show that this disorder can be expressed in the developing brain. We found that (10–13 year-old) children exhibit a marked deficit in the detection of fine-grained pitch differences in both musical and acoustical context in comparison to their normally developing peers comparable in age and general intelligence. This behavioral deficit could be traced down to their abnormal P300 brain responses to the detection of subtle pitch changes. The altered pattern of electrical activity does not seem to arise from an anomalous functioning of the auditory cortex, because all early components of the brain potentials, the N100, the MMN, and the P200 appear normal. Rather, the brain and behavioral measures point to disrupted information propagation from the auditory cortex to other cortical regions. Furthermore, the behavioral and neural manifestations of the disorder remained unchanged after 4 weeks of daily musical listening. These results show that congenital amusia can be detected in childhood despite regular musical exposure and normal intellectual functioning.

Congenital amusia in childhood: A case study

Here we describe the first documented case of congenital amusia in childhood. AS is a 10-year-old girl who was referred to us by her choir director for persisting difficulties in singing. We tested her with the child version of the Montreal Battery for the Evaluation of Amusia (MBEA) which confirmed ASs severe problems with melodic and rhythmic discrimination and memory for melodies. The disorder appears to be limited to music since her audiometry as well as her intellectual and language skills are normal. Furthermore, the musical disorder is associated to a severe deficit in detecting small pitch changes. The electrical brain responses point to an anomaly in the early stages of auditory processing, such as reflected by an abnormal mismatch negativity (MMN) response to small pitch changes. In singing, AS makes more pitch than time errors. Thus, despite frequent and regular musical practice, ASs profile is similar to the adult form of congenital amusia.

Early integration of vowel and pitch processing: A mismatch negativity study

OBJECTIVE Several studies have explored the processing specificity of music and speech, but only a few have addressed the processing autonomy of their fundamental components: pitch and phonemes. Here, we examined the additivity of the mismatch negativity (MMN) indexing the early interactions between vowels and pitch when sung. METHODS Event-related potentials (ERPs) were recorded while participants heard frequent sung vowels and rare stimuli deviating in pitch only, in vowel only, or in both pitch and vowel. The task was to watch a silent movie while ignoring the sounds. RESULTS All three types of deviants elicited both an MMN and a P3a ERP component. The observed MMNs were of similar amplitude for the three types of deviants and the P3a was larger for double deviants. The MMNs to deviance in vowel and deviance in pitch were not additive. CONCLUSIONS The underadditivity of the MMN responses suggests that vowel and pitch differences are processed by interacting neural networks. SIGNIFICANCE The results indicate that vowel and pitch are processed as integrated units, even at a pre-attentive level. Music-processing specificity thus rests on more complex dimensions of music and speech.

Integrated preattentive processing of vowel and pitch: a mismatch negativity study.

This study examines the additivity of the Mismatch Negativity (MMN) as an index of the early interactions between vowels and pitch when sung. Event‐related potentials (ERPs) were recorded while participants were presented with sung vowels. Sixteen percent of stimuli deviated in pitch only, in vowel only, or in both pitch and vowel. All three kinds of deviants elicited an MMN of similar amplitude. The MMNs to vowel and pitch deviants did not show significant additivity. This suggests that vowel and pitch are processed by shared neural substrates at the preattentive level.

Successful measurement of the mismatch negativity despite a concurrent movie soundtrack: Reduced amplitude but normal component morphology

OBJECTIVE To examine the mechanisms responsible for the reduction of the mismatch negativity (MMN) ERP component observed in response to pitch changes when the soundtrack of a movie is presented while recording the MMN. METHODS In three experiments we measured the MMN to tones that differed in pitch from a repeated standard tone presented with a silent subtitled movie, with the soundtrack played forward or backward, or with soundtracks set at different intensity levels. RESULTS MMN amplitude was reduced when the soundtrack was presented either forward or backward compared to the silent subtitled movie. With the soundtrack, MMN amplitude increased proportionally to the increments in the sound-to-noise intensity ratio. CONCLUSION MMN was reduced in amplitude but had normal morphology with a concurrent soundtrack, most likely because of basic acoustical interference from the soundtrack with MMN-critical tones rather than from attentional effects. SIGNIFICANCE A normal MMN can be recorded with a concurrent movie soundtrack, but signal amplitudes need to be set with caution to ensure a sufficiently high sound-to-noise ratio between MMN stimuli and the soundtrack.

Reliable mismatch negativity event-related potentials for tones presented with a concurrent video soundtrack

Specific language impairment (SLI) is a developmental language impairment of unidentified (presumed hereditary) etiology. The general development of children suffering from SLI is neat and harmonious: They have no hearing problems; their motor, emotional, social and cognitive development is in accordance with their age. Children suffering from SLI present with no neurological impairment, but this does not mean that the cause of their difficulties is not in the central nervous system. Their language development is delayed but it is also different than in their peers. The aim of this study was to analyze the speech of Croatian children suffering from SLI, and compare it with the speech of children with normal language development (NLD). The analysis was based on their ability to repeat 14 sentences differing in length and level of complexity, and the ability of narration (retelling), based on the mean length of utterance and the number of verbs used in the narrated text. Two girls and three boys suffering from SLI and two girls and three boys with NLD were studied. All subjects were five years old. The SLI children were less successful in repeating the sentences than the control group, especially when repeating grammatically more complex sentences. The SLI children were also less successful in retelling the story, which was manifested as considerably shorter length of utterance and a smaller number of verbs used in the narrative text.