Attentional modulation of the mismatch negativity elicited by frequency differences between binaurally presented tone bursts

We examined the attentional sensitivity of the frequency-change mismatch negativity (MMN). Subjects listened to a binaural mixture of a narrative and a series of tone bursts that included 1200-Hz standards and two deviants (1000 and 1400 Hz). In the attend-tones condition, subjects responded to one deviant and ignored the narrative. In the attend-words condition, subjects responded to target words in the narrative and ignored the tones. Event-related potentials (ERPs) were recorded for the tones, and differences waves (deviant ERPs minus standard ERPs) were computed. Two negative peaks in the difference waves, DNI (100–180 ms) and DN2 (200–300 ms), overlapped the known scalp distribution and latency of the MMN. Mean DN1 and DN2 amplitudes were greater in the attend-tones condition than in the attend-words condition. These data suggest that the frequency-change MMN is modulated by nonspatial shifts of auditory attention.     

Processing of auditory deviants with changes in one versus two stimulus dimensions

Auditory event-related potentials (ERPs) in response to 50-ms tones were recorded from the human scalp. A standard stimulus ( p = .88) and three different deviants were randomly presented via earphones. There were two one-dimensional deviants (one frequency and one location deviant) and one two-dimensional deviant, with changes in both frequency and location. In one condition, subjects read a book and ignored the auditory stimuli, whereas in another condition they tried to discriminate deviants from standards. In the ignore condition, the two-dimensional deviant elicited an enhanced mismatch negativity (MMN) as compared with the MMNs elicited by the one-dimensional deviants. The temporal and the topographic distributions of the two-dimensional MMNs could be modeled by adding the one-dimensional MMNs. This additivity of the MMNs probably results from the independent activity of separate neural populations generating the frequency and the location MMN. In the attend condition, the deviance-related ERP effects were not additive in the N2b and P3 range, implicating that the neural processes involved in the conscious detection of changes in location and frequency were not independent.     

Mismatch negativity reflects numbers of tones of specific frequencies in humans

The human brain can automatically quantify objects and events. The mismatch negativity (MMN) of the event-related potential (ERP) was recently found to reflect one such ability in the auditory modality. The present study aimed to further validate the finding. ERPs were recorded in adult humans who passively listened to a series of 300-ms sequences of tones. The sequences occurred at 300-ms silent intervals. They comprised a total of six tones that each was either 440 or 660 Hz in frequency. MMN was found for a rare 4:2 ratio interspersed with a frequent 3:3 ratio between the tones of the different frequencies in a sequence, suggesting the ability of the human brain to preattentively discriminate numbers of sounds of specific frequencies at least at a 3:2 ratio.     

The human brain processes visual changes that are not cued by attended auditory stimulation

Event-related potentials (ERPs) to visual stimuli were recorded from the scalp of eight adult humans performing a task in which they counted vowels from a heard story. In the oddball condition, a repeated (standard) light bar of 50 ms in duration was rarely (P = 0.1) replaced by a (deviant) one differing in orientation from the standard. In the control condition, standards were simply omitted from the series and only (alone-) deviants retained. In both conditions, visual stimuli were asynchronous with auditory-task-relevant stimuli. ERPs to deviants significantly differed in amplitude from those to standards in the midline electrodes centrally, parietally and occipitally at 160-200 ms from stimulus onset. Occipitally, such a difference was absent between ERPs to alone-deviants and those to standards. The occipital differential ERPs to deviants, which thus could be found only when standards were present in the series, are discussed in the context of the mismatch negativity (MMN).     

Temporal grouping affects the automatic processing of deviant sounds

The present study investigates the influence of auditory temporal grouping on automatic sound processing. We compared the mismatch negativity (MMN) event-related potential elicited by successive deviant tones in a condition in which sounds were organized in tone pairs with respective MMN obtained in a non-paired sequence. When successive deviants belonged to different tone pairs the second deviant elicited a higher MMN amplitude than the corresponding deviant in the non-paired condition. Moreover, this temporal grouping had immediate effects on the extraction of rules as revealed by the finding that first and single deviants at the second position of a tone pair elicited larger MMNs than corresponding deviants in the non-paired condition or first and single deviants at the first position of a tone pair. Results demonstrate that auditory objects generated by temporal proximity are treated as relatively encapsulated units and that automatic deviance-detection may rely on multiple hierarchically organized representations of sound sequences.     

N1 and the mismatch negativity are spatiotemporally distinct ERP components: disruption of immediate memory by auditory distraction can be related to N1

Event-related potentials (ERPs) were recorded for ignored tones presented during the retention interval of a delayed serial recall task. The mismatch negativity (MMN) and N1 ERP components were measured to discern spatiotemporal and functional properties of their generation. A nine-token sequence with nine different tone pitches was more disruptive than an oddball (two-token) sequence, yet this oddball sequence was no more disruptive than a single repeating tone (one-token). Tones of the nine-token sequence elicited augmented N1 amplitudes compared to identical tones delivered in the one-token sequence, yet deviants elicited an additional component (MMN) with distinct temporal properties and topography. These results suggested that MMN and N1 are separate, functionally distinct components. Implications are discussed for the N1 hypothesis and the changing-state hypothesis of the disruption of serial recall performance by auditory distraction.     

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.     

Cortical Activity Elicited by Changes in Auditory Stimuli: Different Sources for the Magnetic N1OOm and Mismatch Responses

Magnetic responses to frequent and infrequent auditory stimuli, all presented in the same stimulus block in randomized order, were recorded. The standard stimuli, comprising 90% of all the stimuli, were 100-ms, 1000 Hz, 90dB sinusoidal tone bursts. There were three deviant tones, each presented at a probability of 3.3%, which differed from the standard tone on one dimension only: frequency deviant (1500 Hz), intensity deviant (67dB SPL), or duration deviant (50 ms). All mismatch fields, i.e., responses elicited by different deviants, as well as N100m to the standards and deviants, could be explained by neural activity in the supratemporal auditory cortex. The source of N100m to standards and deviants was significantly posterior to the sources for the three different mismatch fields. The mean locations of the equivalent dipoles for the different mismatch fields did not differ significantly from each other, but some differences were found for individual subjects.     

Preattentive processing of spectral, temporal, and structural characteristics of acoustic regularities: a mismatch negativity study

In the present study we investigated the relationship between detecting violations of structural regularities of tone sequences and detecting deviations from temporal regularities or repetitive spectral auditory stimulus features. Twelve subjects were presented with randomized sequences of two tones (differing both in frequency and intensity) delivered alternately to the left and right ears at a constant stimulus onset asynchrony (SOA). In separate blocks, occasional deviant stimuli broke one, two, or three of the following regularities: spatial alternation, the constancy of SOA, or the dominant frequency-intensity conjunctions. Unlike the mismatch negativity (MMN) elicited by alternation-plus-SOA deviants, the MMN elicited by alternation-plus-conjunction deviants was approximately equal to the sum of the two corresponding single-deviant MMNs. These results suggest that the preattentive change-detection system processes infrequent violations of the structural regularities of sound sequences together with changes in temporal regularities, but separately from changes in repetitive spectral sound features. The MMN elicited by the triple-deviant stimuli corroborated these conclusions.     

Preattentively grouped tones do not elicit MMN with respect to each other

To promote preattenive grouping of two sets of tones, one set of tones with a combination of frequency and ear of delivery was intermixed with another set of tones with a different combination of frequency and ear of delivery. The ERPs elicited by tones delivered to one ear that were preceded by three or four tones delivered in a row to the other ear were associated with an enhanced N1, due to the changes in frequency and ear of delivery with respect to the immediately preceding tones. However, no mismatch negativity (MMN) was obtained, even though these tones differed from the previious tones on the two dimensions of frequency and ear of delivery. The data were interpreted to signify that preattentively grouped sets of tones do not elicit MMN with respect to one another. This implies that once acoustic input has been preattentively grouped, the MMN system is dedicated to detecting changes that occur within but not between preattentively grouped stimuli.     

Representation of harmonic frequencies in auditory memory: a mismatch negativity study

Most natural sounds are composed of a mixture of frequencies, which activate separate neurons in the tonotopic auditory cortex. Nevertheless, we perceive this mixture as an integrated sound with unique acoustic properties. We used the Mismatch Negativity (MMN), a marker of auditory change detection, to determine whether individual harmonics are represented in sensory memory. The MMN elicited by duration and pitch deviations were compared for harmonic and pure tones. Controlled for acoustic differences between standards and deviants and their relative probabilities, the MMN was larger for harmonic than pure tones for duration but not for pitch deviance. Because the magnitude of the MMN reflects the number of concurrent changes in the acoustic input relative to a preexistent acoustic representation, these results suggest that duration is represented and compared separately for individual frequencies, whereas pitch comparison occurs after integration.     

Categorical perception of lexical tones in Chinese revealed by mismatch negativity

The present study investigated the neurophysiological correlates of categorical perception of Chinese lexical tones in Mandarin Chinese. Relative to standard stimuli, both within- and across-category deviants elicited mismatch negativity (MMN) in bilateral frontal-central recording sites. The MMN elicited in the right sites was marginally larger than in the left sites, which reflects the role of the right hemisphere in acoustic processing. At the same time, relative to within-category deviants, the across-category deviants elicited larger MMN in the left recording sites, reflecting the long-term phonemic traces of lexical tones. These results provide strong neurophysiological evidence in support of categorical perception of lexical tones in Chinese. More important, they demonstrate that acoustic and phonological information is processed in parallel within the MMN time window for the perception of lexical tones. Finally, homologous nonspeech stimuli elicited similar MMN patterns, indicating that lexical tone knowledge influences the perception of nonspeech signals.     

ERP correlates of pre-attentive processing of Cantonese lexical tones: The effects of pitch contour and pitch height

The pre-attentive processing of Cantonese tones was studied with an auditory passive oddball paradigm. Event-related potentials to standard and deviant auditory stimuli were recorded as participants watched a silent movie attentively. The standards and deviants differed in either pitch level or pitch contour. Mismatch negativity (MMN) and P3a were elicited by all types of deviant tones, suggesting that lexical tone was processed pre-attentively. In addition, the size and latency of MMN were sensitive to the size of pitch level change, while the latency of P3a captured the presence of pitch contour change. These results indicate that pitch contour and pitch height are two important dimensions in sensory processing of lexical tones.     

Mismatch negativity to frequency changes: no evidence from human event-related brain potentials for categorical speech processing of complex tones resembling vowel formant structure

Based on a memory-comparison process, changes in the pitch of repetitive sounds are pre-attentively detected, reflected by the mismatch negativity (MMN) event-related brain potential. In the present investigation of categorical speech perception, complex tones were used that consisted of vowel-defining F1 and F2 formant information while not being perceived as speech. MMN was obtained in oddball blocks. The auditory system tracks two simultaneous changes in formant frequencies of 50 Hz while also abstracting from three levels of intensity variation. Lower frequency deviants elicited larger MMN. No effects of language-categorical processing were observed.     

Deviance-repetition effects as a function of stimulus feature, feature value variation, and timing: a mismatch negativity study

The human auditory pre-attentive change detection system, indicated by the mismatch negativity component (MMN) of the event-related brain potential is known to be sensitive for the successive presentation of tones deviating in frequency. The present study investigated deviance-repetition effects as a function of stimulus feature, feature value variation, and stimulus-onset asynchrony (SOA). For succession of frequency and location deviants carrying the same feature value, MMN elicited by the second deviant was reduced significantly. The reduction of MMN amplitude was markedly smaller, if the second of two successive deviants carries a different feature value, as compared with same feature value deviants. The variation of SOA across the temporal window of integration did not influence the deviance-repetition effects. We suggest that the pre-attentive change-detection system evaluates the informational content of the succession of deviants enabling an effective scanning of the auditory environment for potentially relevant events.     

Two cognitive systems simultaneously prepared for opposite events.

Event-related potentials (ERPs) were recorded during a go/no-go reaction time (RT) task in which subjects responded to rare target tones and withheld response to frequent tones. In a predictable condition, a rare visual stimulus signalled the impending occurrence of a rare tone, whereas a frequent visual stimulus signalled that a frequent tone would be presented. The rare visual stimuli elicited P3, associated with violations of expectations, whereas the rare tones, being predictable, did not. The rare tones elicited the mismatch negativity (MMN), a component associated with preattentive deviance detection, despite the fact that they were expected. RT was faster in the predictable condition than in another condition in which the tones were not predictable. The P3 and RT data indicate, respectively, that subjects anticipated and were ready to respond to the target tones. The MMN result indicates that immediately before target tones, the preattentive system underlying the MMN was set for frequent tones, being unaffected by the information available to the higher order system. Thus, the higher order cognitive system associated with P3 and the lower order cognitive system associated with the MMN were prepared simultaneously for opposite events.     

Magnetoencephalographic recordings demonstrate attentional modulation of mismatch-related neural activity in human auditory cortex

It is widely agreed that the negative brain potential elicited at 150–200 ms by a deviant, less intense sound in a repetitive series can be modulated by attention. To investigate whether this modulation represents a genuine attention effect on the mismatch negativity (MMN) arising from auditory cortex or attention-related activity from another brain region, we recorded both the MMN and the mismatch magnetic field (MMF) elicited by such deviants in a dichotic listening task. Deviant tones in the attended ear elicited a sizable MMF that was well modeled as a dipolar source in auditory cortex. Both the MMN and MMF to unattended-ear deviants were highly attenuated. These findings support the view that the MMN/MMF elicited in auditory cortex by intensity deviants, and thus the underlying feature-analysis and mismatch-detection processes, are not strongly automatic but rather can be gated or suppressed if attention is strongly focused elsewhere.     

Tonotopic auditory cortex and the magnetoencephalographic (MEG) equivalent of the mismatch negativity

Two tone stimuli, one frequent (standard) and the other infrequent (a slightly higher, deviant tone), were presented in random order and at short intervals to subjects reading texts they had selected. In different blocks, standards were either 250, 1,000, or 4,000 Hz, with the deviants always being 10% higher in frequency than the standards of the same blocks. Magnetic responses elicited by the standard and deviant tones included N1m, the magnetoencephalographic equivalent of the electrical N1 (its supratemporal component). In addition, deviant stimuli elicited MMNm, the magnetic equivalent of the electrical mismatch negativity, MMN. The equivalent dipole sources of the two responses were located in supratemporal auditory cortex, with the MMNm source being anterior to that of N1m. The dipole orientations of both sources in the sagittal plane depended on stimulus frequency, suggesting that the responses are generated by tonotopically organized neuronal populations. The tonotopy reflected by the frequency dependence of the MMNm source might be that of the neural trace system underlying frequency representation of auditory stimuli in sensory memory.     

ERP and EOG responses elicited by deviant tones when presented with and without standard tones to reading subjects.

Event-related potentials (ERPs) and horizontal electro-oculograms (HEOGs) were recorded in 11 subjects to infrequently presented spatially deviant tones (oddball-deviants) embedded in a series of frequently presented standard tones and also to these deviant tones when presented without the standard tones (alone-deviants). Subjects were instructed to read a self-selected book during the stimulus presentation. The mismatch negativity (MMN), a component of the ERP, was elicited by the oddball-deviants, whereas ERPs to the alone-deviants were characterized by a prominent N1. In an additional counting condition (subjects counting the oddball-deviants), the MMN to the oddball-deviants was followed by the P3b. Although the effects of pre-attentive and attentive processing of the oddball-deviants were evident in the ERPs, HEOGs were affected by these stimuli in neither reading nor counting condition. In contrast, robust HEOG responses were elicited by the alone-deviants in the reading condition. The results suggest that reading is a sufficiently demanding task to enable the subject to effectively ignore the oddball-deviants but not the alone-deviants.     

The human brain processes repeated auditory feature conjunctions of low sequential probability

The human brain is known to preattentively trace repeated sounds as holistic entities. It is not clear, however, whether the same holds true if these sounds are rare among other repeated sounds. Adult humans passively listened to a repeated tone with frequent (standard) and rare (deviant) conjunctions of its three features. Six equiprobable variants per conjunction type were assigned from a space built from these features so that the standard variants (P=0.15 each) were not inseparably traceable by means of their linear alignment in this space. Differential scalp-recorded event-related potentials to deviants indicate that the standard variants were traced as repeated wholes despite their preperceptual distinctiveness and resulting rarity among one another.