Mari Tervaniemi

The mismatch negativity in cognitive and clinical neuroscience: Theoretical and methodological considerations

Mismatch negativity (MMN) component of the event-related brain potentials has become popular in cognitive and clinical brain research during the recent years. It is an early response to a violation of an auditory rule such as an infrequent change in the physical feature of a repetitive sound. There is a lot of evidence on the association of the MMN parameters and behavioral discrimination ability, although this relationship is not always straight-forward. Since the MMN reflects sound discrimination accuracy, it can be used for probing how well different groups of individuals perceive sound differences, and how training or remediation affects this ability. In the present review, we first introduce some of the essential MMN findings in probing sound discrimination, memory, and their deficits. Thereafter, issues which need to be taken into account in MMN investigations as well as new improved recording paradigms are discussed.

Superior pre-attentive auditory processing in musicians

The present study focuses on influences of long-term experience on auditory processing, providing the first evidence for pre-attentively superior auditory processing in musicians. This was revealed by the brains automatic change-detection response, which is reflected electrically as the mismatch negativity (MMN) and generated by the operation of sensoric (echoic) memory, the earliest cognitive memory system. Major chords and single tones were presented to both professional violinists and non-musicians under ignore and attend conditions. Slightly impure chords, presented among perfect major chords elicited a distinct MMN in professional musicians, but not in non-musicians. This demonstrates that compared to non-musicians, musicians are superior in pre-attentively extracting more information out of musically relevant stimuli. Since effects of long-term experience on pre-attentive auditory processing have so far been reported for language-specific phonemes only, results indicate that sensory memory mechanisms can be modulated by training on a more general level.

Temporal window of integration revealed by MMN to sound omission

THE central auditory system for event perception involves the integrating mechanism of sequential information addressed by the present study. The mismatch negativity (MMN) component of the event-related potentials (ERP) reflects the automatic detection of sound change. ERPs to occasionally omitted stimuli were measured when sequences with constant stimulus onset asynchronies (SOAs) were presented. In separate blocks, the SOA was from 100 to 350 ms. A clear MMN was elicited by a stimulus omission in a sequence of regularly spaced tone pips only when the SOA was shorter than 150 ms, yielding an estimate for the duration of the temporal window of integration used the perceptual segregation of auditory events.

Pitch discrimination accuracy in musicians vs nonmusicians: an event-related potential and behavioral study.

Previously, professional violin players were found to automatically discriminate tiny pitch changes, not discriminable by nonmusicians. The present study addressed the pitch processing accuracy in musicians with expertise in playing a wide selection of instruments (e.g., piano; wind and string instruments). Of specific interest was whether also musicians with such divergent backgrounds have facilitated accuracy in automatic and/or attentive levels of auditory processing. Thirteen professional musicians and 13 nonmusicians were presented with frequent standard sounds and rare deviant sounds (0.8, 2, or 4% higher in frequency). Auditory event-related potentials evoked by these sounds were recorded while first the subjects read a self-chosen book and second they indicated behaviorally the detection of sounds with deviant frequency. Musicians detected the pitch changes faster and more accurately than nonmusicians. The N2b and P3 responses recorded during attentive listening had larger amplitude in musicians than in nonmusicians. Interestingly, the superiority in pitch discrimination accuracy in musicians over nonmusicians was observed not only with the 0.8% but also with the 2% frequency changes. Moreover, also nonmusicians detected quite reliably the smallest pitch changes of 0.8%. However, the mismatch negativity (MMN) and P3a recorded during a reading condition did not differentiate musicians and nonmusicians. These results suggest that musical expertise may exert its effects merely at attentive levels of processing and not necessarily already at the preattentive levels.

Lateralized Automatic Auditory Processing of Phonetic Versus Musical Information: A PET Study

Previous positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies show that during attentive listening, processing of phonetic information is associated with higher activity in the left auditory cortex than in the right auditory cortex while the opposite is true for musical information. The present PET study determined whether automatically activated neural mechanisms for phonetic and musical information are lateralized. To this end, subjects engaged in a visual word classification task were presented with phonetic sound sequences consisting of frequent (P = 0.8) and infrequent (P = 0.2) phonemes and with musical sound sequences consisting of frequent (P = 0.8) and infrequent (P = 0.2) chords. The phonemes and chords were matched in spectral complexity as well as in the magnitude of frequency difference between the frequent and infrequent sounds (/e/ vs. /o/; A major vs. A minor). In addition, control sequences, consisting of either frequent (/e/; A major) or infrequent sounds (/o/; A minor) were employed in separate blocks. When sound sequences consisted of intermixed frequent and infrequent sounds, automatic phonetic processing was lateralized to the left hemisphere and musical to the right hemisphere. This lateralization, however, did not occur in control blocks with one type of sound (frequent or infrequent). The data thus indicate that automatic activation of lateralized neuronal circuits requires sound comparison based on short‐term sound representations. Hum. Brain Mapping 10:74–79, 2000.

Representation of abstract attributes of auditory stimuli in the human brain

Representations of abstract attributes of auditory stimuli in the human brain were demonstrated using the mismatch negativity (MMN), an event-related potential component elicited by a change in a repetitive sound. Stimuli were pairs of sinusoidal tones. There were two types of tone pairs in each block, standard (p = 85%) and deviant pairs (p = 15%), delivered in a random order. Standard and deviant tone pairs differed only in the direction of within-pair frequency change. In addition, the frequency levels of both the standard and deviant pairs varied randomly within a wide range in a block; thus the standard pairs shared the direction of the within-pair frequency change but not the absolute frequency level. Correspondingly, the deviant pairs only shared the opposite direction of the within-pair change. Nevertheless, the deviant tone pairs elicited MMN, implying that even the direction of the within-pair frequency change of the standard stimuli, and not just their absolute frequencies, developed a neural representation.

Temporal window of integration of auditory information in the human brain

A deviation in the acoustic environment activates an automatic change-detection system based on a memory mechanism that builds a neural trace representing the preceding sounds. The present study revealed that the auditory-cortex mechanisms underlying this sensory memory integrate acoustic events over time, producing a perception of a unitary auditory event. We recorded magnetic responses (MMNm) to occasional stimulus omissions in trains of stimuli presented at a constant stimulus-onset asynchrony (SOA) that was, in different blocks, either shorter or longer in duration than the assumed length of the temporal window of integration. A definite MMNm was elicited by stimulus omission only with the three shortest SOAs used: 100, 125, and 150 ms, but not with 175 ms. Thus, 160-170 ms was estimated as the length of the temporal window used by the central auditory system in integrating successive auditory input into auditory event percepts.

Individual music therapy for depression: randomised controlled trial

BACKGROUND Music therapy has previously been found to be effective in the treatment of depression but the studies have been methodologically insufficient and lacking in clarity about the clinical model employed. Aims To determine the efficacy of music therapy added to standard care compared with standard care only in the treatment of depression among working-age people. METHOD Participants (n = 79) with an ICD-10 diagnosis of depression were randomised to receive individual music therapy plus standard care (20 bi-weekly sessions) or standard care only, and followed up at baseline, at 3 months (after intervention) and at 6 months. Clinical measures included depression, anxiety, general functioning, quality of life and alexithymia. TRIAL REGISTRATION ISRCTN84185937. RESULTS Participants receiving music therapy plus standard care showed greater improvement than those receiving standard care only in depression symptoms (mean difference 4.65, 95% CI 0.59 to 8.70), anxiety symptoms (1.82, 95% CI 0.09 to 3.55) and general functioning (-4.58, 95% CI -8.93 to -0.24) at 3-month follow-up. The response rate was significantly higher for the music therapy plus standard care group than for the standard care only group (odds ratio 2.96, 95% CI 1.01 to 9.02). CONCLUSIONS Individual music therapy combined with standard care is effective for depression among working-age people with depression. The results of this study along with the previous research indicate that music therapy with its specific qualities is a valuable enhancement to established treatment practices.

Neural representations of abstract stimulus features in the human brain as reflected by the mismatch negativity

Neural sensory-memory representations that encode physical properties of incoming stimuli can be probed by recording the change-specific mismatch negativity of the event-related potential (ERP). The present study was aimed at determining whether invariant stimulus features, abstracted from the continuously changing acoustic environment, are encoded in these sensory-memory representations. Regularly descending tone sequences with an occasional ascending tone or tone repetition were presented to reading subjects. A significant MMN was elicited by the ascending tones. When instead of simple tones, Shepard tones creating an illusion of a continuous pitch decrement were used in the same paradigm, the MMN was elicited by both ascending and repeating tones. It was concluded that besides physical stimulus properties, abstract stimulus features are also encoded in the neural representations of sensory memory.

The amusic brain: in tune, out of key, and unaware

Like language, music engagement is universal, complex and present early in life. However, approximately 4% of the general population experiences a lifelong deficit in music perception that cannot be explained by hearing loss, brain damage, intellectual deficiencies or lack of exposure. This musical disorder, commonly known as tone-deafness and now termed congenital amusia, affects mostly the melodic pitch dimension. Congenital amusia is hereditary and is associated with abnormal grey and white matter in the auditory cortex and the inferior frontal cortex. In order to relate these anatomical anomalies to the behavioural expression of the disorder, we measured the electrical brain activity of amusic subjects and matched controls while they monitored melodies for the presence of pitch anomalies. Contrary to current reports, we show that the amusic brain can track quarter-tone pitch differences, exhibiting an early right-lateralized negative brain response. This suggests near-normal neural processing of musical pitch incongruities in congenital amusia. It is important because it reveals that the amusic brain is equipped with the essential neural circuitry to perceive fine-grained pitch differences. What distinguishes the amusic from the normal brain is the limited awareness of this ability and the lack of responsiveness to the semitone changes that violate musical keys. These findings suggest that, in the amusic brain, the neural pitch representation cannot make contact with musical pitch knowledge along the auditory-frontal neural pathway.