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.

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.

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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.

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Altered functional connectivity of the amygdala has been observed in a resting state immediately after fear learning, even one day after aversive exposure. The persistence of increased resting-state functional connectivity (rsFC) of the amygdala has been a critical finding in patients with stress and anxiety disorders. However, longitudinal changes in amygdala rsFC have rarely been explored in healthy participants. To address this issue, we studied the rsFC of the amygdala in two groups of healthy volunteers. The control group participated in three fMRI scanning sessions of their resting state at the first visit, one day, and one week later. The experimental group participated in three fMRI sessions on the first day: a resting state before fear conditioning, a fear extinction session, and a resting state immediately after fear extinction. Furthermore, this group experienced scanning after one day and week. The fear-conditioning paradigm consisted of visual stimuli with a distinct rate of partial reinforcement by electric shock. During the extinction, we presented the same stimuli in another sequence without aversive pairing. In the control group, rsFC maps were statistically similar between sessions for the left and right amygdala. However, in the experimental group, the increased rsFC mainly of the left amygdala was observed after extinction, one day, and one week. The between-group comparison also demonstrated an increase in the left amygdala rsFC in the experimental group. Our results indicate that functional connections of the left amygdala influenced by fear learning may persist for several hours and days in the human brain.

Lateral asymmetry is one of the fundamental properties of the functional anatomy of the human brain. Amygdala (AMYG) asymmetry was also reported in clinical studies of resting-state functional connectivity (rsFC) but rarely in healthy groups. To explore this issue, we investigated the reproducibility of the data on rsFC of the left and right AMYG using functional MRI twice a week in 20 healthy volunteers with mild-to-moderate anxiety. We found a resting-state network of the AMYG, which included regions involved in emotional processing and several other brain areas associated with memory and motor inhibition. The AMYG network was stable in time and within subjects, but the right AMYG had more significant connections with anatomical brain regions. The rsFC values of the right AMYG were also more sustained across the week than the left AMYG rsFC. Subjective ratings of anxiety did not correlate significantly with the patterns of seed-based AMYG connectivity. Our findings indicate that, for healthy subjects, rsFC may differ for the right and left AMYG. Moreover, the AMYG functional connectivity is variable in short-term observations, which may also influence the results of longitude studies.