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Abstract: Objective: To design a fast algorithm that evaluates the degree of correlation of recordings among single trials (CoRaST) for mismatch negativity (MMN) activity. Methods: The participants were 114 children, aged 8–16years. MMNs were elicited by two deviants in duration that occurred in an uninterrupted sound within a passive oddball paradigm, and each trial lasted 650ms with 130 samples. CoRaST was derived from the frequency-domain MMN model through Fourier transformation. To validate the effectiveness of the proposed method, the wavelet transformation-based inter-trial coherence (ITC) was taken as a reference. Results: Performances of the proposed CoRaST and ITC were similar in evaluating the correlation of MMN activity among single trials. However, the analysis of electroencephalograph (EEG) recordings comprising approximately 330 trials at one channel took approximately 0.12s with CoRaST, whereas ITC required approximately 45s in our workstation. Conclusions: CoRaST has the potential to evaluate the correlation of MMN activity among single trials in a real-time system. Furthermore, the new method can be facilitated to study other event-related potentials (ERPs) of evoked or induced brain activity. Significance: The correlation of ERP activity among single trials can be immediately inspected during the ERP data collection in a real-time system. [Copyright &y& Elsevier]

Abstract: This study addresses how to validate the rationale of group component analysis (CA) for blind source separation through estimating the number of sources in each individual EEG dataset via model order selection. Control children, typically reading children with risk for reading disability (RD), and children with RD participated in the experiment. Passive oddball paradigm was used for eliciting mismatch negativity during EEG data collection. Data were cleaned by two digital filters with pass bands of 1–30Hz and 1–15Hz and a wavelet filter with the pass band narrower than 1–12Hz. Three model order selection methods were used to estimate the number of sources in each filtered EEG dataset. Under the filter with the pass band of 1–30Hz, the numbers of sources were very similar among different individual EEG datasets and the group ICA would be suggested; regarding the other two filters with much narrower pass bands, the numbers of sources were relatively diverse, and then, applying group ICA would not be appropriate. Hence, before group ICA is performed, its rationale can be logically validated by the estimated number of sources in EEG data through model order selection. [Copyright &y& Elsevier]

Abstract: This study focuses on comparison of procedures for extracting the brain event-related potentials (ERPs) – brain responses to stimuli recorded using electroencephalography (EEG). These responses are used to study how the synchronization of brain electrical responses is associated with cognition such as how the brain detects changes in the auditory world. One such event-related response to auditory change is called mismatch negativity (MMN). It is typically observed by computing a difference wave between ERPs elicited by a frequently repeated sound and ERPs elicited by an infrequently occurring sound which differs from the repeated sounds. Fast and reliable extraction of the ERPs, such as the genuine MMN, is an important focus of studies devoted to basic cognitive brain research. In this study, we compared three procedures for extraction of the MMN elicited by infrequent duration decrements in auditory sound stimulation. These were the conventional difference wave (DW) with average standard sweep, optimal digital filtering (ODF), and recently proposed independent component analysis (ICA) decomposition procedures. The statistical comparison was made in a group of 12 healthy adults aged 23–30 years. The MMN was elicited in a passive oddball protocol presenting an auditory stimulation consisting of frequent tones of 600Hz of 100ms duration each (standard stimuli). Infrequently, one of the tones was shortened to 75, 50, or 30ms (deviant stimuli). The ICA decomposition procedure, similarly to the DW procedure with average standard sweep, extracted a cleaner MMN compared to the ODF procedure. Both procedures extracted the MMN, whose amplitude and latency characteristics concur with substantial number of publications in contrast to the ODF procedure. [Copyright &y& Elsevier]

Abstract: We compared the efficiency of the independent component analysis (ICA) decomposition procedure against the difference wave (DW) and optimal digital filtering (ODF) procedures in the analysis of the mismatch negativity (MMN). The comparison was made in a group of 54 children aged 8–16 years. The MMN was elicited in a passive oddball protocol presenting uninterrupted auditory stimulation consisting of two frequent alternating tones (600 and 800Hz) of 100ms duration each. Infrequently, one of the 600Hz tones was shortened to 50 or 30ms. The event related potentials (ERPs) were decomposed into the MMN-like and non-MMN-like independent components (ICs) through the FastICA algorithm. The ICA decomposition procedure extracted a cleaner MMN compared to the ODF or DW procedures. It extracted the MMN, whose characteristics concurred with the substantial number of publications demonstrating a significantly larger peak amplitude and shorter latency of the MMN in response to the more deviant stimulus (30ms) compared to the less deviant stimulus (50ms). The MMN to these two deviant stimuli did not differ in the peak amplitude or latency when it was extracted through the other two procedures. The ICA decomposition and ODF procedures, similarly, significantly improved the single trial signal-to-noise ratio (SNR) of the MMN compared to the DW procedure. Due to this improvement, the proposed ICA decomposition procedure might allow shortening of the recording session and could be used to study the MMN in paradigms similar to this with small modifications. [Copyright &y& Elsevier]

Abstract: According to several studies auditory discrimination as measured by mismatch negativity (MMN) is compromised in participants with reading disorder. However, studies on duration discrimination have produced conflicting findings [Baldeweg, T., Richardson, A., Watkins, S., Foale, C., & Gruzelier, J., 1999. Impaired auditory frequency discrimination in dyslexia detected with mismatch evoked potentials. Annals of Neurology, 4, 1–9; Corbera, S., Escera, C., & Artigas, J., 2006. Impaired duration mismatch negativity in developmental dyslexia. Neuroreport, 17, 1051–1055]. Auditory sensitivity has not been as actively investigated among children with attention deficit, although attention problems often co-occur with dyslexia. The present study is a reanalysis of MMN data gathered from control children and children with reading disorder (RD) and/or attention deficit (AD). In our previous analysis [Huttunen, T., Halonen, A., Kaartinen, J. & Lyytinen, H., 2007. Does mismatch negativity show differences in reading disabled children as compared to normal children and children with attention deficit? Developmental Neuropsychology, 31, 453–470.], the only significant difference between the groups was in the lateralization of the MMNs in the RD and the control group: the MMNs of the RD group were more pronounced over the left hemisphere, while those of the control group appeared larger over the right hemisphere. A reanalysis was conducted to study whether the group definition criteria and/or overlap of the attention and reading deficits in the AD group might have affected the results. For this purpose participants were divided to four groups: control children, children with RD, children with AD, and children with both RD and AD. MMN was elicited by duration deviations in a continuous sound. Significant differences were observed in the MMN peaks between the control group and all clinical groups: the MMNs were diminished in the right hemisphere in the RD group, in all frontal and central channels in the RD+AD group, and the MMN peaks appeared earlier in frontal channels in the AD group. [Copyright &y& Elsevier]

Changes in the temporal properties of the speech signal provide important cues for phoneme identification. An impairment or inability to detect such changes may adversely affect one’s ability to understand spoken speech. The difference in meaning between the Finnish words tuli (fire) and tuuli (wind), for example, lies in the difference between the duration of the vowel /u/. Detecting changes in the temporal properties of the speech signal, therefore, is critical for distinguishing between phonemes and identifying words. In the current study, we tested whether detection of changes in speech sounds, in native Finnish speakers, would vary as a function of the position within the word that the informational changes occurred (beginning, middle, or end) by evaluating how length contrasts in segments of three-syllable Finnish pseudo-words and their acoustic correlates were discriminated. We recorded a combination of cortical components of event-related brain potentials (MMN, N2b, P3b) along with behavioral measures of the perception of the same sounds. It was found that speech sounds were not processed differently than non-speech sounds in the early stages of auditory processing indexed by MMN. Differences occurred only in later stages associated with controlled processes. The effects of position and attention on speech and non-speech stimuli are discussed. [Copyright &y& Elsevier]