Biomedical subjects

Y Shtyrov

Publications and source records attributed to Y Shtyrov.

8 recordsLinked to original sources

PubMed2006

The sound of actions as reflected by mismatch negativity: rapid activation of cortical sensory-motor networks by sounds associated with finger and tongue movements.

In order to explore the activation dynamics of the human action recognition system, we investigated electrophysiological distinctions between the brain responses to sounds produced by human finger and tongue movements. Of special interest were the questions of how early these differences may occur, and whether the neural activation at the early stages of processing involves cortical motor representations related to the generation of these sounds. For this purpose we employed a high-density EEG set-up and recorded mismatch negativity (MMN) using a recently developed novel multideviant paradigm which allows acquisition of a high number of trials within a given time period. Deviant stimuli were naturally recorded finger and tongue clicks, as well as control stimuli with similar physical features but without the clear action associations (this was tested in a separate behavioural experiment). Both natural stimuli produced larger MMNs than their respective control stimuli at approximately 100 ms, indicating activation of memory traces for familiar action-related sounds. Furthermore, MMN topography at this latency differed between the brain responses to the natural finger and natural tongue sounds. Source estimation revealed the strongest sources for finger sounds in centrolateral areas of the left hemisphere, suggesting that hearing a sound related to finger actions evokes activity in motor areas associated with the dominant hand. Furthermore, tongue sounds produced activation in more inferior brain areas. Our data suggest that motor areas in the human brain are part of neural systems subserving the early automatic recognition of action-related sounds.

Acoustic Stimulation↗

PubMed2005

The effect of different noise types on the speech and non-speech elicited mismatch negativity.

The effect of different types of real-life noise on the central auditory processing of speech and non-speech sounds was evaluated by the means of mismatch negativity and behavioral responses. Subjects (19-34 years old; 6 males, 4 females) were presented, in separate conditions, with either speech or non-speech stimuli of approximately equal complexity in five background conditions: babble noise, industrial noise, traffic noise, wide band noise, and silent condition. Whereas there were no effects of stimuli or noise on the behavioral responses, the MMN results revealed that speech and non-speech sounds are processed differently both in silent and noisy conditions. Speech processing was more affected than non-speech processing in all noise conditions. Moreover, different noise types had a differential effect on the pre-attentive discrimination, as reflected in MMN, on speech and non-speech sounds. Babble and industrial noises dramatically reduced the MMN amplitudes for both stimulus types, while traffic noise affected only speech stimuli.

Acoustic Stimulation↗

PubMed2001

Memory traces for words as revealed by the mismatch negativity.

Brain responses to the same spoken syllable completing a Finnish word or a pseudo-word were studied. Native Finnish-speaking subjects were instructed to ignore the sound stimuli and watch a silent movie while the mismatch negativity (MMN), an automatic index of experience-dependent auditory memory traces, was recorded. The MMN to each syllable was larger when it completed a word than when it completed a pseudo-word. This enhancement, reaching its maximum amplitude at about 150 ms after the word's recognition point, did not occur in foreign subjects who did not know any Finnish. These results provide the first demonstration of the presence of memory traces for individual spoken words in the human brain. Using whole-head magnetoencephalography, the major intracranial source of this word-related MMN was found in the left superior temporal lobe.

Adult↗

PubMed2000

Auditory cortex evoked magnetic fields and lateralization of speech processing.

Potential use of different auditory evoked brain responses for determining cerebral lateralization of speech function was evaluated. Cortical magnetic fields elicited by plosive syllables or complex non-speech sounds analogous to them were recorded with 122-channel magnetometer. We estimated parameters of magnetic P1, N1 and P2 responses to both stimuli in the two hemispheres and found no hemispheric asymmetry for any of the responses. No correlation between the right-ear advantage, determined with dichotic listening test, and any of asymmetry indexes, calculated for the speech-elicited responses, was observed. These results suggest that P1, N1 and P2 responses to speech signals do not indicate lateralization of speech function in the brain. The results are discussed in relation to previous studies suggesting that the mismatch negativity (MMN) seems to be the only early auditory cortex response sensitive to the lateralization of speech function.

Adolescent↗

PubMed2000

Discrimination of speech and of complex nonspeech sounds of different temporal structure in the left and right cerebral hemispheres.

The key question in understanding the nature of speech perception is whether the human brain has unique speech-specific mechanisms or treats all sounds equally. We assessed possible differences between the processing of speech and complex nonspeech sounds in the two cerebral hemispheres by measuring the magnetic equivalent of the mismatch negativity, the brain's automatic change-detection response, which was elicited by speech sounds and by similarly complex nonspeech sounds with either fast or slow acoustic transitions. Our results suggest that the right hemisphere is predominant in the perception of slow acoustic transitions, whereas neither hemisphere clearly dominates the discrimination of nonspeech sounds with fast acoustic transitions. In contrast, the perception of speech stimuli with similarly rapid acoustic transitions was dominated by the left hemisphere, which may be explained by the presence of acoustic templates (long-term memory traces) for speech sounds formed in this hemisphere.

Adolescent↗

PubMed1999

Noise affects speech-signal processing differently in the cerebral hemispheres.

This study explored the effects of acoustic noise on the cerebral asymmetry of speech perception. We measured magnetic fields of the brain elicited by consonant-vowel syllables in silence and white noise. Background noise affected brain responses to these stimuli differently in the left and right auditory cortices. Its depressive effect on cortical responses was found mainly in the left hemisphere, whereas the right hemisphere was unaffected or exhibited increased activity in noise. Locations of the P1, N1, and P2 activity sources in noise were different from those in silence in the right but not in the left hemisphere. These results suggest an increased right hemisphere role in speech sound processing in noisy conditions, involving the recruitment of additional right auditory cortex structures.

Adult↗

PubMed1998

Background acoustic noise and the hemispheric lateralization of speech processing in the human brain: magnetic mismatch negativity study.

The present study explored effects of background noise on the cerebral functional asymmetry of speech perception. The magnetic equivalent (MMNm) of mismatch negativity (MMN) elicited by consonant-vowel syllable change presented in silence and during background white noise was measured with a whole-head magnetometer. It was found that in silence MMNm to speech stimuli, registered from the auditory cortex, was stronger in the left than in the right hemisphere. However, when speech signals were presented in white noise background, MMNm in the left hemisphere diminished while that in the right hemisphere increased in amplitude and dipole moment. These results confirm that in silence, speech signals are mainly discriminated in the left hemisphere's auditory cortex. However, in noisy conditions the involvement of the left hemisphere's auditory cortex in speech discrimination is considerably decreased, while that of the right hemisphere increases.

Brain↗

PubMedDate not supplied

Lateralization of speech processing in the brain as indicated by mismatch negativity and dichotic listening.

The goal of the present study was to evaluate the differences between dichotic listening and mismatch negativity as measures of speech lateralization in the human brain. For this purpose, we recorded the magnetic equivalent of the mismatch negativity, elicited by consonant-vowel syllable change, and tested the same subjects in the dichotic listening procedure. The results showed that both methods indicated left-hemisphere dominance in speech processing. However, the mismatch negativity, as compared to the right-ear advantage, suggested slightly stronger left-hemisphere dominance in speech processing. No clear correlation was found between the laterality indexes of mismatch negativity and right-ear advantage calculated from dichotic listening results. The possible explanation for this finding would be that these two measures reflect different stages of speech processing in the human brain.

Adult↗