Olga Martynova

Speech sounds learned by sleeping newborns.

It is not yet clear whether humans are able to learn while they are sleeping. Here we show that full-term human newborns can be taught to discriminate between similar vowel sounds when they are fast asleep. It is possible that such sleep training soon after birth could find application in clinical or educational situations.

Mismatch Negativity and Late Discriminative Negativity in Investigating Speech Perception and Learning in Children and Infants

For decades, behavioral methods, such as the head-turning or sucking paradigms, have been the primary tools to investigate speech perception and learning of a language in infancy. Recently, however, new methods provided by event-related potentials have emerged. These are called mismatch negativity (MMN) and late discriminative negativity (LDN). MMN, the brain’s automatic change-detection response in audition, has been intensively used in adults in both basic and clinical studies for longer than 20 years. LDN, on the other hand, was only recently discovered. There seem to be many differences between these two responses. MMN is developmentally quite stable and can be obtained even from preterm infants. LDN, however, can be obtained most reliably from young children, and its amplitude decreases as a function of age. New data suggest that both of these responses have a special role in language processing, although both of them can also be elicited by nonspeech stimuli.

Mismatch negativity and late discriminative negativity in sleeping human newborns

Event-related potentials were recorded from sleeping newborns to compare amplitudes and latencies of mismatch negativity (MMN) and late discriminative negativity (LDN) in active and quiet sleep stages. MMN and LDN were obtained in response to changes in semi-synthesized vowels from 20 healthy newborn infants. MMN and LDN responses were significant for both active and quiet sleep. The amplitude and latency of MMN or LDN did not differ between the sleep stages. Thus, in contrast to adult studies that show a significant drop in the MMN amplitude and an increase in the MMN latency as the sleep gets deeper, arousal stages do not seem to effect either MMN or LDN characteristics in newborns. These results suggest functional differences between infant and adult sleep.

Psychobiology: Speech sounds learned by sleeping newborns

It is not yet clear whether humans are able to learn while they are sleeping. Here we show that full-term human newborns can be taught to discriminate between similar vowel sounds when they are fast asleep. It is possible that such sleep training soon after birth could find application in clinical or educational situations.

Correlation of BOLD Signal with Linear and Nonlinear Patterns of EEG in Resting State EEG-Informed fMRI

Concurrent EEG and fMRI acquisitions in resting state showed a correlation between EEG power in various bands and spontaneous BOLD fluctuations. However, there is a lack of data on how changes in the complexity of brain dynamics derived from EEG reflect variations in the BOLD signal. The purpose of our study was to correlate both spectral patterns, as linear features of EEG rhythms, and nonlinear EEG dynamic complexity with neuronal activity obtained by fMRI. We examined the relationships between EEG patterns and brain activation obtained by simultaneous EEG-fMRI during the resting state condition in 25 healthy right-handed adult volunteers. Using EEG-derived regressors, we demonstrated a substantial correlation of BOLD signal changes with linear and nonlinear features of EEG. We found the most significant positive correlation of fMRI signal with delta spectral power. Beta and alpha spectral features had no reliable effect on BOLD fluctuation. However, dynamic changes of alpha peak frequency exhibited a significant association with BOLD signal increase in right-hemisphere areas. Additionally, EEG dynamic complexity as measured by the HFD of the 2–20 Hz EEG frequency range significantly correlated with the activation of cortical and subcortical limbic system areas. Our results indicate that both spectral features of EEG frequency bands and nonlinear dynamic properties of spontaneous EEG are strongly associated with fluctuations of the BOLD signal during the resting state condition.

Commentary: Selective Development of Anticorrelated Networks in the Intrinsic Functional Organization of the Human Brain.

As adults we solve problems by applying our executive know-how and directing our mental-attention to relevant information. When we are not problem solving, our mind is free to wonder to things like lunchtime; this is often referred to as the default-mode. It is established that for adults the relation among executive and default-mode brain areas is negative (Fox et al., 2005; Arsalidou et al., 2013). Parts of the prefrontal cortex are involved in both the executive and default-mode networks. Chai et al. (2014) examined the relation among executive and default-mode areas in children, adolescents and adults, using resting-state fMRI. This is likely the most thorough, methodologically sound paper to date that investigates this relation across typical development. Although it was unclear whether data adhered to assumptions for parametric tests such as homoscedasticity, as Pearsons correlations are sensitive to outlier data, the authors examine different aspects of their data by (a) controlling for movement and artifact, (b) performing group analyses and covarying outliers, and (c) repeating the analyses using global signal regression. Overall, results show that across groups (8–12, 13–17, and 18–24 year-olds), relations among executive and default-mode areas are heterogeneous. In many regions the relation among executive and default-mode areas are positive in children. For adolescents it becomes more anti-correlated (i.e., more adult-like), eventually converting to a negative relation in adults. The authors highlight that functional connectivity reversal cannot be accounted by performance differences per se, because functional images were recorded at rest. Results are fascinating and understandably interpreting such findings is challenging. The authors suggest that lower performance on working memory and cognitive control generally found in younger children may relate to the lack of anti-correlation. Yet they report that Intelligence Quotient (IQ) scores did not correlate with age, suggesting that participants were cognitively comparable. Why is this relation positive in children? We believe what is lacking in Chai et al. (2014) is a developmental theory-based interpretation. Here we highlight that the mechanisms that underlie this change from positive correlation in children to negative correlation in adults may

An fMRI Study of Impairments to Speech Perception in Patients with Vascular Sensory Aphasia

The aim of the present work was to use the noninvasive fMRI method to identify neurophysiological correlates of impairments at the sensory stage of the perception of verbal information, i.e., phonematic hearing, in patients with sensory aphasia after acute impairments to cerebral circulation in the left hemisphere of the brain. This was addressed by recording the fMRI equivalent of mismatch negativity in response to verbal phonemes – the syllables “ba” and “pa” – using the oddball paradigm in 20 healthy subjects and 23 patients with post-stroke sensory aphasia. Calculation of mismatch negativity contrast in healthy subjects identified activation of the superior temporal and inferior frontal gyri in the right and left hemispheres. Patients showed significant activation of the auditory zone of the cortex only in the right hemisphere, activation at this site was less marked in terms of volume and intensity than in healthy subjects, and correlated with the extent of speech preservation. Thus, recording of the fMRI equivalent of mismatch negativity provides a sensitive method for studies of impaired perception of speech sounds.

Age differences of event-related potentials in the perception of successive and spatial components of auditory information

The perception of spatial and successive contexts of auditory information develops during child ontogeny. We compared event-related potentials (ERPs) recorded in 5- to 6-year-old children (N = 15) and adults (N = 15) in response to a digital series with omitted digits to explore age differences in the perception of successive auditory information. In addition, ERPs in response to the sound of a falling drop presented binaurally were obtained to examine the spatial content of auditory information. The ERPs obtained from the omitted digits significantly differed in the amplitude and latency of the N200 and P300 components between adults and children, which supports the hypothesis that the perception of a successive auditory structure is less automatic in children compared to adults. Although no significant differences were found in adults, the sound of a falling drop presented to the left ears of children elicited ERPs with earlier latencies and higher amplitudes of the P300 and N400 components in the right temporal area. Stimulation of the right ear caused an increasing amplitude of the N100 component in children. Thus, the observed differences in the auditory ERPs of children and adults reflect developmental changes in the perception of spatial and successive auditory information.

Changes in some indices of the cardiovascular system in different mental tasks

In order to study the effects of the type of mental activity on the function of the cardiovascular system in humans, the following indices were used: the heart rate (HR), RR interval, variation magnitude (VM), systolic wave amplitude (SWA), and pulse wave transit time (PWTT). These indices were recorded when the subjects solved verbal-logical or spatial mental tasks. The HR was substantially increased during solving of the spatial tasks as compared to solving of the verbal-logical tasks, whereas the SWA showed the opposite changes. The latencies of the performance of the tasks of various types were similar in the subjects; therefore, the changes in the autonomic indices did not depend on the difficulties of the mental tasks. They rather depended on specific features of the mental processes involved in the performance of the tasks of different types. Thus, changes in the HR and the decreased SWA, which was related to elevated blood pressure, represent the effect of the sympathetic nervous system on the heart function during solving verbal-logical tasks. Our data demonstrate that the HR and blood pressure can be used as additional indices for the development of new techniques for assessment of different types of mental processes together with the indices of electrical brain activity.

Lateral Asymmetry in Weekly Reproducibility of Resting State Amygdala Functional Connectivity

Abnormal functional connectivity of the amygdala with several other brain regions has been observed in patients with higher anxiety or post-traumatic stress disorder, both in a resting state and threatening conditions. However, findings on the specific connections of the amygdala might be varied due to temporal and individual fluctuations in the resting state functional connectivity (rsFC) of the amygdala and its lateral asymmetry, as well as possible variability in anxiety among healthy subjects. We studied reproducibility of rsFC data for the right and left amygdala, obtained by functional magnetic resonance imaging twice in a one-week interval in 20 healthy volunteers with low to moderate anxiety. We found resting-state amygdala network, which included not only areas involved in the emotion circuit, but regions of the default mode network (DMN) associated with memory and other brain areas involved in motor inhibition and emotion suppression. The amygdala network was stable in time and within subjects, but between-session reproducibility was asymmetrical for the right and left amygdala rsFC. The right amygdala had more significant connections with DMN regions and the right ventrolateral prefrontal cortex. The rsFC values of the right amygdala were more sustained across the week than the left amygdala rsFC. Our results support a hypothesis of functional lateralization of the amygdala. The left amygdala is more responsible for the conscious processing of threats, which may produce more variable rsFC; the right amygdala rsFC is more stable due to its greater engagement in continuous automatic evaluation of stimuli. Highlights Amygdala resting state network included areas of emotion circuit and motor control During rest amygdala was functionally connected with areas of default mode network Functional connectivity of the right amygdala was more sustained across the week Functional connections of amygdala network were more stable in the right hemisphere