Differentiating ERAN and MMN: An ERP-study
Stefan Koelsch1, Thomas C. Gunter1, Erich Schröger2, Mari Tervaniemi3, Daniela Sammler1,2 & Angela D. Friederici1
1Max Planck Institute of Cognitive Neuroscience, Leipzig
2Institute of General Psychology, Leipzig
3Cognitive Brain Research Unit, Helsinki
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In the present study, the early right-anterior negativity (ERAN) elicited by harmonically inappropriate chords during listening to music was compared to the frequency mismatch negativity (MMN) and the abstract-feature MMN. Results revealed that the amplitude of the ERAN, in contrast to the MMN, is specifically dependent on the degree of harmonic appropriateness. Thus, the ERAN is correlated with the cognitive processing of complex rule-based information, i.e. with the application of "music-syntactic" rules. Moreover, results showed that the ERAN, compared to the abstract-feature MMN, had both a longer latency, and a larger amplitude. The combined findings indicate that ERAN and MMN reflect different mechanisms of pre-attentive irregularity detection, and that, although both components have several features in common, the ERAN does not easily fit into the classical MMN framework. The present ERPs thus provide evidence for a differentiation of cognitive processes underlying the fast and pre-attentive processing of auditory information.
Figure 1. Examples of stimuli. In all blocks, stimuli were presented with the same time-course, loudness, and probability of deviant events (deviant events are indicated by the arrows).
Figure 2. ERPs elicited at frontal electrode sites by stimuli at the third (top row) and fifth (second row) position, separately for the abstract-feature MMN block, the block with chord sequences, and the frequency MMN block. Vertical line indicates the onset of the deviant stimulus (in the abstract-feature MMN block: second tone of a tone-pair). Bottom row: Potential maps of abstract-feature MMN (standard subtracted from deviant), ERAN (harmonic appropriate chords subtracted from Neapolitan chords), and frequency MMN (standard subtracted from deviant), separately for third and fifth position. Maps were calculated using the data from all 41 electrodes and interpolated over time-windows from 125-185 ms (abstract feature MMN), 170-230 ms (ERAN), and 90-150 ms (frequency MMN), polarity inversions are bordered by thick lines. In contrast to the ERAN, the MMNs did not differ in amplitude between position 3 and 5, indicating that the ERAN reflects context-dependent musical processing. Moreover, the ERAN elicited at the fifth position had a later latency, but larger amplitude compared to the abstract-feature MMN.
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Full color maps from Figure 2.
Figure 3. Amplitudes of abstract-feature MMN (left), ERAN (middle), and MMN (right), separately for positions 3 (white bars) and 5 (gray bars). Latency of the abstract-feature MMN was 160 ms, of the ERAN: 200 ms, and of the frequency-MMN: 100 ms.
The present results demonstrate that the ERAN reflects cognitive operations connected to the processing of complex rule-based musical information, in contrast to the MMN, which is known to reflect mainly sensory memory operations. This finding is important for several reasons: First, it indicates that partly different neuronal processes underlie the generation of ERAN and MMN (although both components share several features). Since both MMN and ERAN can be elicited pre-attentively, the present data provide evidence for a differentiation of fast and pre-attentive neural mechanisms underlying auditory deviancy-detection in the human brain. Second, though the ERAN does not easily fit into the classical MMN framework, both components fit into one concept if one considers that both MMN and ERAN belong to a family of peri-sylvian negativites that mediate the processing of irregularities of auditory input. With this respect, the present results support the hypothesis of a strong adaptabiliy and flexibility of fast and automatic cognitive processes in the human brain, probably indicating that the classical MMN-framework might be expanded (at least with respect to the processing of major-minor tonal music) to the processing of complex, or syntactic, rules. Third, results support the hypothesis that processing of "musical syntax" as reflected in the ERAN is processed pre-attentively5.
