Effect of the Temporal Window of Integration of Speech Sound on Mismatch Negativity.

Speech-sound stimuli have a complex structure, and it is unclear how the brain processes them. An event-related potential (ERP), known as mismatch negativity (MMN), is elicited when an individual's brain detects a rare sound. In this study, MMNs were measured in response to an omitted segment of a complex sound consisting of a Japanese vowel. The results indicated that the latency from onset in the right hemisphere was significantly shorter than that in the frontal midline and left hemispheres during left ear stimulation. Additionally, the results of latency from omission showed that the latency of stimuli omitted in the latter part of the temporal window of integration (TWI) was longer than that of stimuli omitted in the first part of the TWI. The mean peak amplitude was found to be higher in the right hemisphere than in the frontal midline and left hemispheres in response to left ear stimulation. In conclusion, the results of this study suggest that would be incorrect to believe that the stimuli have strictly the characteristics of speech-sound. However. the results of the interaction effect in the latencies from omission were insignificant. These results suggest that the detection time for deviance may not be related to the stimulus ear. However, the type of deviant stimuli on latencies was found to be significant. This is because the detection of the deviants was delayed when a deviation occurred in the latter part of the TWI, regardless of the stimulation of the ear.

Effect of oxytocin nasal spray on auditory automatic discrimination measured by mismatch negativity.

RATIONALE: As a treatment for cognitive dysfunction in schizophrenia, oxytocin nasal sprays potentially improve social cognition, facial expression recognition, and sense of smell. Mismatch negativity (MMN) is an event-related potential (ERP) reflecting auditory discrimination while MMN deficits reflect cognitive function decline in schizophrenia. OBJECTIVES: To determine whether oxytocin nasal spray affects auditory MMN METHODS: We measured ERPs in healthy subjects during an auditory oddball task, both before and after oxytocin nasal spray administration. Forty healthy subjects were randomly assigned to either the oxytocin or placebo group. ERPs were recorded during the oddball task for all subjects before and after a 24 international unit (IU) intranasal administration, and MMN was compared between the two groups. RESULTS: Participants who received oxytocin had significantly shorter MMN latencies than those who received a placebo. Oxytocin had no significant effect on the Change in MMN amplitude. CONCLUSIONS: The shortened MMN latencies that were observed after oxytocin nasal spray administration suggest that oxytocin may promote the comparison-decision stage.

Estimation of frequency difference at which stream segregation precedes temporal integration as reflected by omission mismatch negativity.

Both stream segregation and temporal integration are considered important for auditory scene analysis in the brain. Several previous studies have indicated that stream segregation may precede temporal integration when both processes are required. In the present study, we utilized mismatch negativity (MMN)-which reflects automatic change detection-to systematically estimate the threshold of the frequency difference at which stream segregation occurs prior to temporal integration when these functions occur together during a state of inattention. Electroencephalography (EEG) data were recorded from 22 healthy Japanese men presented with six blocks of alternating high pure tones (high tones) and low pure tones (low tones). Only high tones were omitted with 5 % probability in all blocks. Our results indicated that stream segregation should cancel temporal integration of close sounds, as indicated by omission-MMN elicitation, when the frequency difference is 1000 Hz or larger.

Do tone duration changes that elicit the mismatch negativity also affect the preceding middle latency responses?

The human brain can automatically detect sound changes. Previous studies have reported that rare sounds presented within a sequence of repetitive sounds elicit the mismatch negativity (MMN) in the absence of attention in the latency range of 100-250 ms. On the other hand, a previous study discovered that occasional changes in sound location enhance the middle latency response (MLR) elicited in the latency range of 10-50 ms. Several studies have reported an increase in the amplitude of the MLR within the frame of oddball paradigms such as frequency and location changes. However, few studies have been conducted on paradigms employing a duration change. The purpose of the present study was to examine whether the peak amplitudes of the MLR components are enhanced by a change in duration. Twenty healthy Japanese men (age: 23.9 ± 2.9 years) participated in the present study. We used an oddball paradigm that contained standard stimuli with a duration of 10 ms and deviant stimuli with a duration of 5 ms. The peak amplitudes of the MLR for the deviant stimuli were then compared with those for the standard stimuli. No changes were observed in the peak amplitude of the MLR resulting from a duration change, whereas a definite MMN was elicited. The amplitude of the MLR was increased within the frame of oddball paradigms such as frequency and location changes. By contrast, the amplitude of the MLR was not changed within the duration change oddball paradigm that elicited the MMN.

Alteration of Duration Mismatch Negativity Induced by Transcranial Magnetic Stimulation Over the Left Parietal Lobe.

Mismatch negativity (MMN) is generated by a comparison between an incoming sound and the memory trace of preceding sounds stored in sensory memory without any attention to the sound. N100 (N1) is associated with the afferent response to sound onset and reflects early analysis of stimulus characteristics. MMN generators are present in the temporal and frontal lobe, and N1 generators are present in the temporal lobe. The parietal lobe is involved in MMN generation elicited by a change in duration. The anatomical network connecting these areas, lateralization, and the effect of the side of ear stimulation on MMN remain unknown. Thus, we studied the effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) over the left parietal lobe on MMN and N1 in 10 healthy subjects. Low-frequency rTMS over the left parietal lobe decreased the amplitude of MMN following right ear sound stimulation, but the amplitude was unaffected with left ear sound stimulation. We observed no significant changes in the amplitude of N1 or the latency of MMN or N1. These results suggest that low-frequency rTMS over the left parietal lobe modulates the detection of early auditory changes in duration in healthy subjects. Stimulation that is contralateral to the side of the ear experiencing sound may affect the generation of duration MMN more than ipsilateral stimulation.

Temporal integration of segmented-speech sounds probed with mismatch negativity.

Deviant sounds occurring in a sequence of standard sounds, in the absence of attention, elicit an event-related potential known as mismatch negativity (MMN). Standard sounds are encoded in auditory sensory memory trace and processed as a single unit within 160-170 ms, where each unitary event stored is closely related to the temporal window of integration. The temporal window of integration of pure tone sound has already been reported. However, there are no reported correlations between segmented-speech sounds and a temporal unit. It is well known that pure tone sounds are predominantly recognized in the right hemisphere, whereas speech sounds are recognized in the left hemisphere. The aim of this study was to examine whether segmented-speech sounds were processed as a temporal unit like pure tone sounds and whether there were differences between right and left ear stimuli. Twenty-five right-handed healthy Japanese men participated in this study. Stimuli consisted of the vowel /a/ spoken by a Japanese female and the stimuli sequences were randomized from short standard sounds and three types of long deviant sounds. The stimuli were presented to both ears separately. All bilateral stimuli induced definite MMN with similar peak latencies. The MMN amplitude gradually enhanced from the short to the long duration deviant. There were no differences in MMN between the right and the left ear stimuli. These findings perhaps show that bilateral deviant segmented-speech sounds were processed equally as a temporal unit.

Deviance-Related Responses along the Auditory Hierarchy: Combined FFR, MLR and MMN Evidence.

The mismatch negativity (MMN) provides a correlate of automatic auditory discrimination in human auditory cortex that is elicited in response to violation of any acoustic regularity. Recently, deviance-related responses were found at much earlier cortical processing stages as reflected by the middle latency response (MLR) of the auditory evoked potential, and even at the level of the auditory brainstem as reflected by the frequency following response (FFR). However, no study has reported deviance-related responses in the FFR, MLR and long latency response (LLR) concurrently in a single recording protocol. Amplitude-modulated (AM) sounds were presented to healthy human participants in a frequency oddball paradigm to investigate deviance-related responses along the auditory hierarchy in the ranges of FFR, MLR and LLR. AM frequency deviants modulated the FFR, the Na and Nb components of the MLR, and the LLR eliciting the MMN. These findings demonstrate that it is possible to elicit deviance-related responses at three different levels (FFR, MLR and LLR) in one single recording protocol, highlight the involvement of the whole auditory hierarchy in deviance detection and have implications for cognitive and clinical auditory neuroscience. Moreover, the present protocol provides a new research tool into clinical neuroscience so that the functional integrity of the auditory novelty system can now be tested as a whole in a range of clinical populations where the MMN was previously shown to be defective.