Category effects: is top-down control alone sufficient to elicit the mismatch negativity (MMN) component?

Influence of Musical Enculturation on Brain Responses to Metric Deviants

The ability to recognize metric accents is fundamental in both music and language perception. It has been suggested that music listeners prefer rhythms that follow simple binary meters, which are common in Western music. This means that listeners expect odd-numbered beats to be strong and even-numbered beats to be weak. In support of this, studies have shown that listeners exposed to Western music show stronger novelty and incongruity related P3 and irregularity detection related mismatch negativity (MMN) brain responses to attenuated odd- than attenuated even-numbered metric positions. Furthermore, behavioral evidence suggests that music listeners' preferences can be changed by long-term exposure to non-Western rhythms and meters, e.g., by listening to African or Balkan music. In our study, we investigated whether it might be possible to measure effects of music enculturation on neural responses to attenuated tones on specific metric positions. We compared the magnetic mismatch negativity (MMNm) to attenuated beats in a “Western group” of listeners (n = 12) mainly exposed to Western music and a “Bicultural group” of listeners (n = 13) exposed for at least 1 year to both Sub-Saharan African music in addition to Western music. We found that in the “Western group” the MMNm was higher in amplitude to deviant tones on odd compared to even metric positions, but not in the “Bicultural group.” In support of this finding, there was also a trend of the “Western group” to rate omitted beats as more surprising on odd than even metric positions, whereas the “Bicultural group” seemed to discriminate less between metric positions in terms of surprise ratings. Also, we observed that the overall latency of the MMNm was significantly shorter in the Bicultural group compared to the Western group. These effects were not biased by possible differences in rhythm perception ability or music training, measured with the Musical Ear Test (MET). Furthermore, source localization analyses suggest that auditory, inferior temporal, sensory-motor, superior frontal, and parahippocampal regions might be involved in eliciting the MMNm to the metric deviants. These findings suggest that effects of music enculturation can be measured on MMNm responses to attenuated tones on specific metric positions.

Effects of Presentation Rate and Attention on Auditory Discrimination: A Comparison of Long-Latency Auditory Evoked Potentials in School-Aged Children and Adults

Decoding human speech requires both perception and integration of brief, successive auditory stimuli that enter the central nervous system as well as the allocation of attention to language-relevant signals. This study assesses the role of attention on processing rapid transient stimuli in adults and children. Cortical responses (EEG/ERPs), specifically mismatch negativity (MMN) responses, to paired tones (standard 100-100 Hz; deviant 100-300 Hz) separated by a 300, 70 or 10 ms silent gap (ISI) were recorded under Ignore and Attend conditions in 21 adults and 23 children (6-11 years old). In adults, an attention-related enhancement was found for all rate conditions and laterality effects (L>R) were observed. In children, 2 auditory discrimination-related peaks were identified from the difference wave (deviant-standard): an early peak (eMMN) at about 100-300 ms indexing sensory processing, and a later peak (LDN), at about 400-600 ms, thought to reflect reorientation to the deviant stimuli or "second-look" processing. Results revealed differing patterns of activation and attention modulation for the eMMN in children as compared to the MMN in adults: The eMMN had a more frontal topography as compared to adults and attention played a significantly greater role in childrens' rate processing. The pattern of findings for the LDN was consistent with hypothesized mechanisms related to further processing of complex stimuli. The differences between eMMN and LDN observed here support the premise that separate cognitive processes and mechanisms underlie these ERP peaks. These findings are the first to show that the eMMN and LDN differ under different temporal and attentional conditions, and that a more complete understanding of children's responses to rapid successive auditory stimulation requires an examination of both peaks.

Auditory pre-experience modulates classification of affect intensity: evidence for the evaluation of call salience by a non-human mammal, the bat Megaderma lyra

INTRODUCTION

Immediate responses towards emotional utterances in humans are determined by the acoustic structure and perceived relevance, i.e. salience, of the stimuli, and are controlled via a central feedback taking into account acoustic pre-experience. The present study explores whether the evaluation of stimulus salience in the acoustic communication of emotions is specifically human or has precursors in mammals. We created different pre-experiences by habituating bats (Megaderma lyra) to stimuli based on aggression, and response, calls from high or low intensity level agonistic interactions, respectively. Then we presented a test stimulus of opposite affect intensity of the same call type. We compared the modulation of response behaviour by affect intensity between the reciprocal experiments.

RESULTS

For aggression call stimuli, the bats responded to the dishabituation stimuli independent of affect intensity, emphasising the attention-grabbing function of this call type. For response call stimuli, the bats responded to a high affect intensity test stimulus after experiencing stimuli of low affect intensity, but transferred habituation to a low affect intensity test stimulus after experiencing stimuli of high affect intensity. This transfer of habituation was not due to over-habituation as the bats responded to a frequency-shifted control stimulus. A direct comparison confirmed the asymmetric response behaviour in the reciprocal experiments.

CONCLUSIONS

Thus, the present study provides not only evidence for a discrimination of affect intensity, but also for an evaluation of stimulus salience, suggesting that basic assessment mechanisms involved in the perception of emotion are an ancestral trait in mammals.

Altered visual information processing systems in bipolar disorder: evidence from visual MMN and P3

Objective: Mismatch negativity (MMN) and P3 are unique ERP components that provide objective indices of human cognitive functions such as short-term memory and prediction. Bipolar disorder (BD) is an endogenous psychiatric disorder characterized by extreme shifts in mood, energy, and ability to function socially. BD patients usually show cognitive dysfunction, and the goal of this study was to access their altered visual information processing via visual MMN (vMMN) and P3 using windmill pattern stimuli.

Methods: Twenty patients with BD and 20 healthy controls matched for age, gender, and handedness participated in this study. Subjects were seated in front of a monitor and listened to a story via earphones. Two types of windmill patterns (standard and deviant) and white circle (target) stimuli were randomly presented on the monitor. All stimuli were presented in random order at 200-ms durations with an 800-ms inter-stimulus interval. Stimuli were presented at 80% (standard), 10% (deviant), and 10% (target) probabilities. The participants were instructed to attend to the story and press a button as soon as possible when the target stimuli were presented. Event-related potentials (ERPs) were recorded throughout the experiment using 128-channel EEG equipment. vMMN was obtained by subtracting standard from deviant stimuli responses, and P3 was evoked from the target stimulus.

Results: Mean reaction times for target stimuli in the BD group were significantly higher than those in the control group. Additionally, mean vMMN-amplitudes and peak P3-amplitudes were significantly lower in the BD group than in controls.

Conclusions: Abnormal vMMN and P3 in patients indicate a deficit of visual information processing in BD, which is consistent with their increased reaction time to visual target stimuli.

Significance: Both bottom-up and top-down visual information processing are likely altered in BD.

Can eye of origin serve as a deviant? Visual mismatch negativity from binocular rivalry

The visual mismatch negativity (vMMN) is a negative deflection in an event-related potential (ERP) between 200 and 400 ms after onset of an infrequent stimulus in a sequence of frequent stimuli. Binocular rivalry occurs when one image is presented to one eye and a different image is presented to the other. Although the images in the two eyes are unchanging, perception alternates unpredictably between the two images for as long as one cares to look. Binocular rivalry, therefore, provides a useful test of whether the vMMN is produced by low levels of the visual system at which the images are processed, or by higher levels at which perception is mediated. To investigate whether a vMMN can be evoked during binocular rivalry, we showed 80% standards comprising a vertical grating to one eye and a horizontal grating to the other and 20% deviants, in which the gratings either swapped between the eyes (eye-swap deviants) or changed their orientations by 45° (oblique deviants). Fourteen participants observed the stimuli in 16, 4-min blocks. In eight consecutive blocks, participants recorded their experiences of rivalry by pressing keys-we call this the attend-to-rivalry condition. In the remaining eight consecutive blocks, participants performed a demanding task at fixation (a 2-back task), also by pressing keys-we call this the reduced-attention condition. We found deviance-related negativity from about 140 ms to about 220 ms after onset of a deviant. There were two noticeable troughs that we call an early vMMN (140-160 ms) and a late vMMN (200-220 ms). These were essentially similar for oblique deviants and eye-swap deviants. They were also essentially similar in the attend-to-rivalry conditions and the reduced-attention conditions. We also found a late, deviance-related negativity from about 270 to about 290 ms in the attend-to-rivalry conditions. We conclude that the vMMN can be evoked during the ever-changing perceptual changes of binocular rivalry and that it is sensitive to the eye of origin of binocular-rivalry stimuli. This is consistent with the vMMN's being produced by low levels of the visual system.