Unnoticed regularity violation elicits change-related brain activity

Event-related brain electric activity (ERP) was investigated to unnoticed visual changes. The orientation of grid elements (vertical or horizontal) changed after the presentation of 10–15 identical stimuli. The grid patterns were task irrelevant, and were presented in the background of a shape discrimination task. During the first half of the session, participants were unaware of the stimulus change. However, in comparison to the ERPs to the fifth identical stimuli, stimulus change elicited posterior negativities in the 270–375 ms range (visual mismatch negativity, vMMN). With participants instructed on the stimulus change, negativities emerged with earlier onset and with wider distribution. When stimulus change was preceded by only two identical stimuli, there were no such ERP effects. As the results show, a longer sequence of identical unattended stimuli may establish the memory representation of stimulus regularity, and violation of regularity is indicated by posterior negative ERP components (vMMN).     

Memory-based detection of task-irrelevant visual changes

Colored grating patterns were presented to 8 participants in a passive oddball condition (standard, 87.5% and deviant, 12.5%, differing in their color). In the corresponding multicolor condition, grating patterns of eight different colors were presented, their probabilities set equal both to each other and to that of the deviant in the oddball task. Compared with the ERP response elicited by the standard stimulus, the deviant response was negatively displaced over posterior areas, the difference wave peaking at 136 ms. A similar negative wave was obtained when the ERP response to the deviant was compared with the ERP elicited by the same stimulus in the multicolor condition. This result rules out stimulus- (color-) specific refractoriness as a major factor in the generation of the deviance-related posterior negativity. The observed posterior negativity can therefore be regarded as a visual analog of the mismatch negativity (vMMN).     

Deviance detection in congruent audiovisual speech: Evidence for implicit integrated audiovisual memory representations

Detection of deviant speech syllables embedded in continuous noise was investigated in an oddball paradigm. Behavioral results showed improvement of detecting and identifying the syllables when congruent visual speech accompanied the utterances. A centrally maximal negative ERP difference wave peaking at approximately 290 ms post-stimulus was elicited by audiovisual but not by auditory- or visual-only task-irrelevant deviant syllables. Whereas the circumstances of the elicitation of this ERP response are similar to those of the mismatch negativity component (MMN and its visual counterpart, vMMN), its scalp distribution differs from that of both unimodal MMNs. Elicitation of an MMN-like ERP response (termed here as the audiovisual MMN: avMMN) suggests that detection of the audiovisual deviants involved integrated audiovisual memory representations. The pattern of behavioral and ERP results suggest that the formation of such cross-modal memory representation does not require voluntary operations and may even proceed for stimuli outside the focus of attention.     

Brain activity from stimuli that are not perceived: Visual mismatch negativity during binocular rivalry suppression

Predictive coding explains visual perception as the result of an interaction between bottom‐up sensory input and top‐down generative models at each level of the visual hierarchy. Evidence for this comes from the visual mismatch negativity (vMMN): a more negative ERP for rare, unpredictable visual stimuli—deviants, than for frequent, predictable visual stimuli—standards. Here, we show that the vMMN does not require conscious experience. We measured the vMMN from monocular luminance‐decrement deviants that were either perceived or not during binocular rivalry dominance or suppression, respectively. We found that both sorts of deviants elicited the vMMN at about 250 ms after stimulus onset, with perceived deviants eliciting a bigger vMMN than not‐perceived deviants. These results show that vMMN occurs in the absence of consciousness, and that consciousness enhances the processing underlying vMMN. We conclude that generative models of visual perception are tested, even when sensory input for those models is not perceived.     

Loudness summation and the mismatch negativity event-related brain potential in humans

Abstract Infrequently omitting a sound from a repetitive sequence elicits the mismatch negativity (MMN) ERP response when the stimulus onset asynchrony (SOA) is less than 200 ms. We contrasted two alternative explanations of omission MMN. (1) Each sound starts a separate temporal integration process. Omissions violate the constancy of the temporal structure within the integration window. (2) Sounds preceding an omission are perceived to be louder than those followed by a sound within the integration period, because omissions allow the full stimulus aftereffect to be included in perceived loudness. We varied the SOA between 117 and 217 ms. For this case, the temporal structure explanation predicts that no MMN will be elicited, whereas the loudness summation explanation predicts that MMN will be elicited. MMN was elicited by tone omissions with random SOA, suggesting that loudness summation plays an important role in the elicitation of omission MMN.     

The quest for the genuine visual mismatch negativity (vMMN): Event-related potential indications of deviance detection for low-level visual features

Research shows that the visual system monitors the environment for changes. For example, a left-tilted bar, a deviant, that appears after several presentations of a right-tilted bar, standards, elicits a classic visual mismatch negativity (vMMN): greater negativity for deviants than standards in event-related potentials (ERPs) between 100 and 300 ms after onset of the deviant. The classic vMMN is contributed to by adaptation; it can be distinguished from the genuine vMMN that, through use of control conditions, compares standards and deviants that are equally adapted and physically identical. To determine whether the vMMN follows similar principles to the auditory mismatch negativity (MMN), in two experiments we searched for a genuine vMMN from simple, physiologically plausible stimuli that change in fundamental dimensions: orientation, contrast, phase, and spatial frequency. We carefully controlled for attention and eye movements. We found no evidence for the genuine vMMN, despite adequate statistical power. We conclude that either the genuine vMMN is a rather unstable phenomenon that depends on still-to-be-identified experimental parameters, or it is confined to visual stimuli for which monitoring across time is more natural than monitoring over space, such as for high-level features. We also observed an early deviant-related positivity that we propose might reflect earlier predictive processing.     

How the human auditory system treats repetition amongst change

Occasional repetitions embedded in a sequence of ever-changing sounds elicit a frontally negative event-related potential peaking between 100 and 200 ms from the onset of sound repetition (repetition negativity, RN). Three interpretations have been suggested for the emergence of RN: (1) RN is a mismatch negativity (MMN) response elicited because the auditory system detected sound change as a regular feature of the stimulus sequence, which is violated by repetitions. (2) RN reflects short-term sensitization of the auditory system to the specific acoustic parameters of each sound, a process subserving the formation of durable memory traces. (3) The difference between responses elicited by repetition and change reflects differential refractoriness of the P2 component. In order to distinguish between the MMN-based and the other two explanations of RN, we varied the global sequential probability of tone-repetitions (at 5, 20, and 50%) in sequences composed of tones of five different frequencies. Whereas all three explanations of the RN predict a local repetition-probability effect on the RN amplitude, MMN should also be affected by the global repetition-probability, because MMN is sensitive to the global deviant-probability, independently of local deviant-probability. To eliminate differences in local repetition-probabilities, we compared the responses elicited by tones that followed the same micro-sequence (change-change-repetition) across the three different global-probability conditions. Global repetition probability had a significant effect on RN: it was only elicited with 5%, but not with the two higher repetition-probabilities. This result supports the MMN interpretation of the RN.     

Nicotinic modulation of human auditory sensory memory: Evidence from mismatch negativity potentials.

Impairment in mismatch negativity (MMN) generation is a robust biological marker of schizophrenia. Understanding the physiological and pharmacological processes involved in its generation may therefore advance our understanding of this complex disorder. The present study tested if acute administration of nicotine modulates human auditory sensory memory as measured with MMN. ERP responses to tone duration deviants were recorded using a stimulation protocol with continuously changing (roving) standard stimuli in order to measure the effect of stimulus repetitions on encoding of new stimuli (MMN memory trace effect). Twenty healthy adult volunteers were randomly assigned to receive either a nicotine gum or placebo after a baseline ERP recording. Nicotine administration augmented MMN amplitude in the treatment group compared to the baseline recording, while no MMN change was found in the placebo group. The drug effect was due to a selective enhancement of a frontal positive potential to standard stimuli (from 80-200 ms post-stimulus), while the negativity to deviants remained unaffected. Furthermore, under nicotine stimulation this repetition positivity showed a more marked increase with stimulus repetition compared to baseline and placebo. These results have potential implications for schizophrenia by suggesting that nicotinic agonists could ameliorate patients' MMN deficits by improving stimulus encoding and sensory memory trace formation.     

ERPs for infrequent omissions and inclusions of stimulus elements

A negative event-related potential (ERP) wave called mismatch negativity (MMN) is elicited by an infrequent deviant stimulus in a sequence of frequent standard stimuli. Omission of a stimulus in a sequence of stimuli, however, has been considered to elicit a negativity different from MMN. The present study addressed this issue by examining ERPs for infrequent omissions and inclusions of compound stimuli or their elements. Three kinds of stimuli were presented: a 1000-Hz sine wave tone (Sine), white noise with the 1000-Hz frequency sharply filtered out (Noise), and a composite of the pure tone and the filtered white noise (SiNoise). All stimuli had 50 ms duration and were presented with a regular interstimulus interval of 650 ms. Intensities were 75 dB SPL for the tone and noise stimuli and slightly higher for the composite stimulus. The three kinds of stimuli were presented on separate runs, either as the frequent stimulus or one of two infrequent stimuli, each with 10% probability. Infrequent omission of the large stimulus element (Sine deviant to SiNoise) tended to elicit later MMN than inclusion of the same element (SiNoise deviant to Sine). Omission of the small stimulus element (Noise deviant to SiNoise) elicited a smaller and later MMN than did inclusion of the same element (SiNoise deviant to Noise). These data suggest that MMNs are also elicited by partial stimulus omissions, although they seem to be more sensitive to other kinds of stimulus deviances.     

Magnetic Source Localization of Early Visual Mismatch Response

Previous studies have reported a visual analogue of the auditory mismatch negativity (MMN) response that is based on sensory memory. The neural generators and attention dependence of the visual MMN (vMMN) still remain unclear. We used magnetoencephalography (MEG) and spatio-temporal source localization to determine the generators of the sensory-memory-based vMMN response to non-attended deviants. Ten participants were asked to discriminate between odd and even digits presented at the center of the visual field while grating patterns with different spatial frequencies were presented outside the focus of attention. vMMN was calculated as the difference between MEG responses to infrequent gratings in oddball blocks and the same gratings in equiprobable blocks. The peak latency of the vMMN response was between 100 and 160 ms. The neuromagnetic sources of the vMMN localized in the occipital cortex differed from the sources evoked by the equiprobable gratings and were stimulus-dependent. Our results suggest the existence of separate neural systems for pre-attentive memory-based detection of visual change and provide new evidence that the vMMN is feature-specific.     

Backward masking and visual mismatch negativity: electrophysiological evidence for memory-based detection of deviant stimuli

Sequences composed of two different colored checkerboard patterns (standard and deviant) were presented to adults. Each pattern was followed by a mask with stimulus onset asynchronies (SOAs) varying between 14 and 174 ms. ERPs were recorded to the deviant and standard stimuli while the participants detected changes of a cross, which was continuously present at the center of the screen. In further experiments, the participants performed a Go-NoGo task detecting the deviant checkerboards. Deviant stimuli elicited an occipital negative component with 124-132 ms mean latency (the visual mismatch negativity, vMMN) at test (standard or deviant)-to-mask SOAs longer than 27 ms. No vMMN amplitude increase was observed beyond 40 ms test-to-mask intervals, whereas detection of deviant checkerboard patterns improved up to 174-ms SOA. Therefore the processes underlying vMMN elicitation cannot fully explain the overt detection of visual deviance.     

Impairment in processing visual information at the pre-attentive stage in patients with a major depressive disorder: A visual mismatch negativity study

We compared the pre-attentive processing in patients with a major depressive disorder (MDD) and matched healthy controls as indexed by the visual mismatch negativity (vMMN) elicited by exposure duration of visual stimuli randomly presented on both peripheral visual fields. To obtain the memory-comparison-based visual MMN, the role of standard and deviant stimuli was reversed in separate blocks. Compared with healthy participants, MDD patients exhibited decreased MMN amplitudes of long duration deviant only and this deficit was not correlated with the depression severity. These data suggests functional impairment of pre-attentive basic visual information processing in MDD patients.     

Mismatch Negativity Outside Strong Attentional Focus: A Commentary on Woldorff et al. (1991)

Several previous papers have suggested that the mismatch negativity (MMN), an event-related potential (ERP) component specific to stimulus change after repetition, is fully automatic, that is, not affected by attention. Woldorff, Hackley, and Hillyard (1991), however, report that the MMN elicited by an intensity decrement of a repeating stimulus is considerably attenuated when attention is strongly focused on other stimuli. The present commentary attributes most of this effect to attention effects on ERP components other than the MMN but also admits that some attentional reduction of the MMN component indeed occurred. This attenuation was interpreted by Woldorff et al. as indicating suppression of early sensory processing in unattended channels, but this is contraindicated by some very recent data from the present author's laboratory and elsewhere showing that the MMN to frequency change is not attenuated outside a strong attentional focus. Consequently, an alternative explanation is proposed for Woldorff et al.'s important finding.     

Visual change detection: event-related potentials are dependent on stimulus location in humans

Infrequent colored patterns within sequences of patterns of frequent color elicited a posterior negative event-related potential component only in case of lower half-field stimulation. This negativity in the 140-200 ms latency range is considered as a correlate of automatic visual change detection (visual mismatch negativity, vMMN). Retinotopic prestriate visual areas are suggested to be the generating loci of vMMN.     

Differential changes in frontal and sub-temporal components of mismatch negativity.

Novel evidence is reported showing changes in the mismatch negativity (MMN) event-related potential (ERP) that followed a different time course in frontal and sub-temporal (mastoid) electrodes. MMN recorded in frontal electrode sites, assumed to originate predominantly in the superior temporal gyrus, showed amplitude enhancement from the first to the second recording block. In contrast, the amplitude of the sub-temporal, mastoid component (termed mismatch positivity, MMP) diminished. In addition to these changes in the MMN elicited by tone duration deviants, there were also significant changes in the ERP to the standard stimulus. The positivity in the standard ERP between 50 and 150 ms increased in bilateral mastoid electrodes but showed no reliable change in frontal electrodes. This suggests that more than one generator underpins the two mismatch components, and that the sub-temporal mismatch component does not only represent a polarity reversal of the main MMN component in the superior temporal gyrus.     

Probability-independent and -dependent ERPs reflecting visual change detection

In ERP studies, two posterior components with different polarities have been identified as ERP correlates of visual change detection. To compare these components in terms of sensitivity to the preceding stimulus sequence, two peripheral stimuli of different colors (red and blue) were presented with equal (50:50) or different probabilities (20:80 or 80:20), while 12 participants performed shape discrimination at a central location. A posterior positivity at around 90-140 ms was observed with similar amplitude to all stimuli immediately preceded by a different stimulus. In contrast, a posterior negativity at around 140-180 ms was observed to increase in amplitude with increasing number of preceding different stimuli. These results suggest the existence of probability-independent and -dependent change processing in the human visual system. The functional significance is discussed in terms of memory-based comparison and stimulus-specific refractoriness.     

Distinct neural mechanisms for repetition effects of visual objects

Repetition of visually common objects was examined in relation to prior intentional learning and memory status using a delayed match-to-sample task in humans. Both response time and two temporally separate event-related potential (ERP) components indexed repetition. The early repetition effect ( approximately 200-550 ms) evoked more ERP responses for repeated visual objects, and was diminished by prior intentional learning (old/new) or being maintained in working memory (targets/distracters). In contrast, the late repetition effect (after approximately 550 ms) evoked reduced ERP activation for repeated items, and was not affected by prior learning or working memory status. Our source localization results indicate that the late and posterior repetition effect in visual cortex is consistent with repetition suppression results reported in monkey physiology and human fMRI studies. Meanwhile, the early and anterior repetition effect, in temporal pole and frontal cortices, is modulated by explicit memory mechanisms.     

Dysfunction of processing task-irrelevant emotional faces in major depressive disorder patients revealed by expression-related visual MMN

We compared the pre-attentive processing of emotional faces in major depressive disorder (MDD) patients and matched healthy controls as indexed by the visual mismatch negativity (vMMN) elicited by emotional faces presented in upright and inverted orientations. Compared with standard neutral faces, infrequent emotional faces elicited posterior negativities between 100 ms and 350 ms. Early vMMN was smaller, while late vMMN was absent in the MDD group, as compared with the normal group. Face inversion decreased the vMMN in the normal group but had no effect on MDD patients. These data suggest the functional dysfunction of pre-attentive expressional information processing in MDD patients, coupled with the disorder of high-level perceptual strategy of processing emotional faces.     

The visual mismatch negativity (vMMN): Toward the optimal paradigm

In the present article, we tested an optimal vMMN paradigm allowing one to obtain vMMNs for several visual attributes in a short time. vMMN responses to changes in color, duration, orientation, shape, and size were compared between the traditional ‘oddball’ paradigm (a single type of visual change in each sequence) and the optimal paradigm in which all the 5 types of changes appeared within the same sequence. The vMMNs obtained in the optimal paradigm were equal or larger in amplitude to those in the traditional vMMN paradigm. The optimal paradigm can provide 5 different vMMNs in the same time in which usually only one MMN is obtained. This short objective measure could putatively be used as an index for visual cognition function especially in clinical research.     

An electrophysiological correlate of human visual awareness

In order to shed more light on the neural correlates of human visual awareness, event-related potentials (ERPs) were recorded in a perceptual threshold experiment. The masked stimuli (line-drawings of coherent, familiar objects and scrambled, meaningless non-objects) were presented below, near, and above the subjective perceptual threshold. A prominent negative ERP deflection, peaking around 260-270 ms from stimulus onset, was observed only for the stimuli reaching subjective visual awareness. The results indicate a direct relationship between the crossing of the subjective threshold and this negative ERP deflection. A similar ERP response called 'visual awareness negativity' (VAN) has been observed in recent studies, using completely different stimulus manipulations (change blindness, reduced contrast stimuli). Hence, VAN appears to be a general electrophysiological correlate of visual awareness, observed in any experimental design that contrasts consciously perceived vs. unperceived visual stimuli.