Shifting ear differences in melody recognition through strategy inducement

Ear Advantage for Musical Location and Relative Pitch: Effects of Musical Training and Attention

Trained musicians have been found to exhibit a right-ear advantage for high tones and a left-ear advantage for low tones. We investigated whether this right/high, left/low pattern of musical processing advantage exists in listeners who had varying levels of musical experience, and whether such a pattern might be modulated by attentional strategy. A dichotic listening paradigm was used in which different melodic sequences were presented to each ear, and listeners attended to (a) the left ear or the right ear or (b) the higher pitched tones or the lower pitched tones. Listeners judged whether tone-to-tone transitions within each melodic sequence moved upward or downward in pitch. Only musically experienced listeners could adequately judge the direction of successive pitch transitions when attending to a specific ear; however, all listeners could judge the direction of successive pitch transitions within a high-tone stream or a low-tone stream. Overall, listeners exhibited greater accuracy when attending to relatively higher pitches, but there was no evidence to support a right/high, left/low bias. Results were consistent with effects of attentional strategy rather than an ear advantage for high or low tones. Implications for a potential performer/audience paradox in listening space are considered.

The influence of musical experience on lateralisation of auditory processing

The influence of musical experience on free-recall dichotic listening to environmental sounds, two-tone sequences, and consonant-vowel (CV) syllables was investigated. A total of 60 healthy right-handed participants were divided into two groups according to their active musical competence ("musicians" and "non-musicians"). In both groups, we found a left ear advantage (LEA) for nonverbal stimuli (environmental sounds and two-tone sequences) and a right ear advantage (REA) for CV syllables. Dichotic listening to environmental sounds was uninfluenced by musical experience. The total accuracy of recall for two-tone sequences was higher in musicians than in non-musicians but the lateralisation was similar in both groups. For CV syllables a lower REA was found in male but not female musicians in comparison to non-musicians. The results indicate a specific sex-dependent effect of musical experience on lateralisation of phonological auditory processing.

Interval and Contour Processing in Autism

High functioning children with autism and age and intelligence matched controls participated in experiments testing perception of pitch intervals and musical contours. The finding from the interval study showed superior detection of pitch direction over small pitch distances in the autism group. On the test of contour discrimination no group differences emerged. These findings confirm earlier studies showing facilitated pitch processing and a preserved ability to represent small-scale musical structures in autism.

Serial processing in melody identification and the organization of musical semantic memory

Unlike the visual stimuli used in most object identification experiments, melodies are organized temporally rather than spatially. Therefore, they may be particularly sensitive to manipulations of the order in which information is revealed. Two experiments examined whether the initial elements of a melody are differentially important for identification. Initial exposures to impoverished versions of a melody significantly decreased subsequent identification, especially when the early exposures did not include the initial notes of the melody. Analyses of the initial notes indicated that they are differentially important for melody identification because they help the listener detect the overall structure of the melody. Confusion errors tended to be songs that either were drawn from the same genre or shared similar phrasing. These data indicate that conceptual processing influences melody identification, that phrase-level information is used to organize melodies in semantic memory, and that phrase-level information is required to effectively search semantic memory.

Musical Training Enhances Automatic Encoding of Melodic Contour and Interval Structure

In music, melodic information is thought to be encoded in two forms, a contour code (up/down pattern of pitch changes) and an interval code (pitch distances between successive notes). A recent study recording the mismatch negativity (MMN) evoked by pitch contour and interval deviations in simple melodies demonstrated that people with no formal music education process both contour and interval information in the auditory cortex automatically. However, it is still unclear whether musical experience enhances both strategies of melodic encoding. We designed stimuli to examine contour and interval information separately. In the contour condition there were eight different standard melodies (presented on 80% of trials), each consisting of five notes all ascending in pitch, and the corresponding deviant melodies (20%) were altered to descending on their final note. The interval condition used one five-note standard melody transposed to eight keys from trial to trial, and on deviant trials the last note was raised by one whole tone without changing the pitch contour. There was also a control condition, in which a standard tone (990.7 Hz) and a deviant tone (1111.0 Hz) were presented. The magnetic counterpart of the MMN (MMNm) from musicians and nonmusicians was obtained as the difference between the dipole moment in response to the standard and deviant trials recorded by magnetoencephalography. Significantly larger MMNm was present in musicians in both contour and interval conditions than in nonmusicians, whereas MMNm in the control condition was similar for both groups. The interval MMNm was larger than the contour MMNm in musicians. No hemispheric difference was found in either group. The results suggest that musical training enhances the ability to automatically register abstract changes in the relative pitch structure of melodies.

Automatic and controlled processing of melodic contour and interval information measured by electrical brain activity

Most work on how pitch is encoded in the auditory cortex has focused on tonotopic (absolute) pitch maps. However, melodic information is thought to be encoded in the brain in two different "relative pitch" forms, a domain-general contour code (up/down pattern of pitch changes) and a music-specific interval code (exact pitch distances between notes). Event-related potentials were analyzed in nonmusicians from both passive and active oddball tasks where either the contour or the interval of melody-final notes was occasionally altered. The occasional deviant notes generated a right frontal positivity peaking around 350 msec and a central parietal P3b peaking around 580 msec that were present only when participants focused their attention on the auditory stimuli. Both types of melodic information were encoded automatically in the absence of absolute pitch cues, as indexed by a mismatch negativity wave recorded during the passive conditions. The results indicate that even in the absence of musical training, the brain is set up to automatically encode music-specific melodic information, even when absolute pitch information is not available.

Music and cerebral hemodynamics

Previous studies performed by positron emission tomography and Transcranial Doppler (TCD) found a different cerebral activation during musical stimuli in musicians compared to non-musicians. The aim of our study is to evaluate by means of TCD, possible different pattern of cerebral activation during the performance of different musical tasks in musicians, non-musicians and lyrical singers. Our findings show a left hemispheric activation in musicians and a right one in non-musicians. Preliminary data on lyrical singers' activation patterns need further confirmation with a larger population. These data could be related to a different approach to music listening in musicians (analytical) and non-musicians who are supposed to have an emotional approach to music.

Global and local processing of musical sequences: an event-related brain potential study

Musical processing can be decomposed into the appreciation of global/holistic and local elements. Here, we investigated the pattern of neural activity associated with the processing of contour-violated (CV) and contour-preserved (CP) melodies. The CV and CP musical sequences were obtained by altering the pitch value of one note within the musical phrase, while keeping both the scale and the key constant. In the unadulterated melody, there was a sustained negativity that was larger over the right than left fronto-central regions. Participants were equally accurate in detecting CV and CP trials, but were slower in detecting CP than CV trials. Globally altered melodies (i.e. CV) generated an early, negative waveform (N2) and a P3b deflection, whereas the CP target only generated a P3b wave. This suggests that global precedence may occur at an early perceptual stage and argues in favor of fractionating musical processing into global and local components.

Is there a sex difference in human laterality? I. An exhaustive survey of auditory laterality studies from six neuropsychology journals

The entire contents of six neuropsychology journals (98 volumes, 368 issues) were screened to identify auditory laterality experiments. Of the 352 dichotic and monaural listening experiments identified, 40% provided information about sex differences. Among the 49 experiments that yielded at least one significant effect or interaction involving the sex factor, 11 outcomes met stringent criteria for sex differences in laterality. Of those 11 positive outcomes, 9 supported the hypothesis of greater hemispheric specialization in males than in females. The 9 confirmatory outcomes represent 6.4% of the informative experiments. When less stringent criteria were invoked, 21 outcomes (14.9% of the informative experiments) were found to be consistent with the differential lateralization hypothesis. The overall pattern of results is compatible with a weak population-level sex difference in hemispheric specialization.

Hemisphericity and information processing in North American Native (Ojibwa) and non-native adolescents

Thirty-two male and female adolescents of native ancestry (Ojibwa) and 32 controls were tested using (1) four WISC-R subtests and (2) two dichotic listening tasks which employed a focused-attention paradigm for processing consonant-vowel combinations (CVs) and musical melodies. On the WISC-R, natives scored higher than controls on Block Design and Picture Completion subtests but lower on Vocabulary and Similarities subtests. On laterality measures more native males showed a left ear advantage on the CV task and the melody task. For CVs the left ear advantage was due to native males' lower right ear (i.e., left hemisphere) involvement. For melodies, the laterality index pointed to less left hemisphere involvement for native males, however, the raw scores showed that natives were performing lower overall. The findings are consistent with culturally-based strategy differences, possibly linked to "hemisphericity," but additional clarifying research regarding the cause and extent of such differences is warranted. Thus, implications for education are premature but a focus on teaching "left hemisphere type" strategies to all individuals not utilizing such skills, including many native males, may prove beneficial.

The role of contour and intervals in the recognition of melody parts: evidence from cerebral asymmetries in musicians

The left hemisphere (LH) has been shown to be involved in tasks requiring interval-based procedures, and the right hemisphere (RH) in task allowing a contour-based approach in melody recognition. Support for this distinction was obtained by studying contour properties at the level of whole melodies and interval characteristics at the level of individual tones. The purpose of the present study was to extend the validity of this two-component model at the level of melody parts. It was predicted that both the LH interval-based procedure and the RH contour-based approach contribute to melody part recognition, but that their respective efficiency will depend on the structure of the parts used as recognition probes. To address this question along the lines of prior work Bever and Chiarello, Science 185, 537-539, 1974), a probe recognition task was presented monaurally to right-handed musicians. The recognition probes that corresponded to one of the melody parts were found to be far more accurately and quickly recognized than the probes that bridged across the contour-defined boundary. On the latter, subjects performed initially at about chance level. They improved, however, after some exposure to the task, that is on the second half of the test material in Experiment 1 and on the second half of Experiment 2, and displayed the predicted interaction between laterality and probe type. Subjects recognized the probes that coincided with a part delineated by contour boundaries in the left ear (or the RH) more easily; whereas they recognized more easily the probes which crossed contour boundaries in the right ear (or the LH). These findings justify the consideration of contour as an important grouping factor in pitch sequences and emphasize the usefulness of laterality effects.

Cerebral lateralization of familiar and unfamiliar music perception in nonmusicians: a dual task approach

In a dual task procedure that controls for attentional trade-off effects, asymmetrical interference effects were observed in dual task conditions of finger tapping and concurrent processing of familiar and unfamiliar music. Laterality effects suggested that perception of orchestral presentations is largely lateralized to the left hemisphere in both males and females. In a second dual task condition of vocalization and music processing, both males and females displayed interference in speech production during concurrent music processing. Males showed greater left hemispheric interference effects during simultaneous vocalization and music processing.

Hemisphere priming through practice in a musical chords task

In a study of selective hemisphere activation, the performance of 30 subjects given either a "local" or "global" priming activity before and after a monoaurally presented chord analysis task was compared with an unprimed control group. The hypothesis was that ear advantage scores on the chords task would show increased left hemisphere involvement following local priming and increased right hemisphere involvement following global priming. The results failed to support this hypothesis. All subjects, however, regardless of priming condition, showed a very strong practice effect represented by a shift from a weak initial left ear (right hemisphere) advantage towards a significant right ear (left hemisphere) advantage (P less than 0.00006). The findings suggest that although the local/global priming activity did not lead to selective hemisphere activation, repeated exposure to the chords task resulted in increased use of analytic left hemisphere processing strategies as subjects became familiar with its processing requirements.

Hemispheric asymmetry in the matching of melodies to rhythm sequences tapped in the right and left palms

Two experiments were conducted to investigate the ability of the cerebral hemispheres to match rhythm sequences tapped in the palms of the hands to tape-recorded melodies. Reaction time (RT) for same/different judgments and accuracy of responses served as the (LP/RH) advantage was found in the ability to match tapped rhythms to tape-recorded melodies, but only on Different trials. On Same trials (which were found to be somewhat easier), both hemispheres were equally efficient at making such comparisons. In Experiment 2, there was no reliable difference between the LP/RH and the RP/LH in the ability to match tapped rhythms to tape-recorded rhythm sequences which were devoid of melodic intonation (i.e., the sound of two blocks of wood struck together in a specified rhythm). The results of these experiments taken in composite lend support to the contention that the right hemisphere advantage typically reported for the processing of musical stimuli is primarily related to pitch and/or intonation rather than rhythm.

Analytic processing in the classification of melodies as same or different

Two groups of non-musicians were required to classify pairs of melodies as "same" or "different". The experimental group was instructed to respond as fast as possible, while the control group did not receive such a speed requirement. Contrary to the control subjects, the experimental subjects exhibited a right-ear advantage in accuracy for "different" responses. Thus, time pressure was instrumental in inducing subjects to rely mainly on left-hemisphere processing. The fact that "different" responses were both faster than "same" ones and quicker than melody offset indicates the use of a self-terminating search process. The features searched for were, in all likelihood, local. Indeed, contrary to control subjects, experimental subjects performed equally well with (1) melodies differing in both contour and local pitches and with (2) melodies differing in local pitches only.