3D statistical parametric mapping of quiet sleep EEG in the first year of life.

This paper extends previously developed 3D SPM for Electrophysiological Source Imaging (Bosch et al., 2001) for neonate EEG. It builds on a prior paper by our group that established age dependent means and standard deviations for the scalp EEG Broad Band Spectral Parameters of children in the first year of life. We now present developmental equations for the narrow band log spectral power of EEG sources, obtained from a sample of 93 normal neonates from age 1 to 10 months in quiet sleep. The main finding from these regressions is that EEG power from 0.78 to 7.5 Hz decreases with age and also for 45-50 Hz. By contrast, there is an increase with age in the frequency band of 19-32 Hz localized to parietal, temporal and occipital areas. Deviations from the norm were analyzed for normal neonates and 17 with brain damage. The diagnostic accuracy (measured by the area under the ROC curve) of EEG source SPM is 0.80, 0.69 for average reference scalp EEG SPM, and 0.48 for Laplacian EEG SPM. This superior performance of 3D SPM over scalp qEEG suggests that it might be a promising approach for the evaluation of brain damage in the first year of life.

Mother and stranger: an electrophysiological study of voice processing in newborns.

In the mature adult brain, there are voice selective regions that are especially tuned to familiar voices. Yet, little is known about how the infant's brain treats such information. Here, we investigated, using electrophysiology and source analyses, how newborns process their mother's voice compared with that of a stranger. Results suggest that, shortly after birth, newborns distinctly process their mother's voice at an early preattentional level and at a later presumably cognitive level. Activation sources revealed that exposure to the maternal voice elicited early language-relevant processing, whereas the stranger's voice elicited more voice-specific responses. A central probably motor response was also observed at a later time, which may reflect an innate auditory-articulatory loop. The singularity of left-dominant brain activation pattern together with its ensuing sustained greater central activation in response to the mother's voice may provide the first neurophysiologic index of the preferential mother's role in language acquisition.

Time-frequency-topographic analysis of induced power and synchrony of EEG signals during a Go/No-Go task.

Induced changes in electroencephalographic power and synchrony between pairs of electrodes were assessed during the Go/No-Go task in 15 young adults. Processes common to both conditions, such as attention, activation of working memory, letter identification, and discrimination processes were characterized by increased power and synchrony in the following frequency ranges: delta band (inhibition of the non-relevant stimuli), theta band (activation of working memory), and low alpha band in occipital regions immediately after the stimulus (withhold or control of the execution of a response), and decreased power in the high alpha band from 300 to 700 ms. However, the most important findings were those specific for each condition. Changes in power in frontal areas were observed immediately after the stimulus in delta and high alpha bands for the Go condition and in the theta band for the No-Go condition. Increased synchrony and power at 1 Hz from 350-500 ms and increased power at 1, 5 and 6 Hz after 300 ms in the No-Go condition may be related to inhibition. Other important difference between conditions was observed in the synchronization increases of the gamma band between 33 and 36 Hz in the Go condition, whereas synchrony decreased at these frequencies in the No-Go condition; these differences may be due to the preparation and execution of the motor response during the Go condition and its inhibition in the No-Go condition.

Exploration of event-induced EEG phase synchronization patterns in cognitive tasks using a time-frequency-topography visualization system.

In this paper, we present a method for the study of synchronization patterns measured from EEG scalp potentials in psychophysiological experiments. This method is based on various techniques: a time-frequency decomposition using sinusoidal filters which improve phase accuracy for low frequencies, a Bayesian approach for the estimation of significant synchrony changes, and a time-frequency-topography visualization technique which allows for easy exploration and provides detailed insights of a particular experiment. Particularly, we focus on in-phase synchrony using an instantaneous phase-lock measure. We also discuss some of the most common methods in the literature, focusing on their relevance to long-range synchrony analysis; this discussion includes a comparison among various synchrony measures. Finally, we present the analysis of a figure categorization experiment to illustrate our method.

Distinct hemispheric specializations for native and non-native languages in one-day-old newborns identified by fNIRS.

This study assessed whether the neonatal brain recruits different neural networks for native and non-native languages at birth. Twenty-seven one-day-old full-term infants underwent functional near-infrared spectroscopy (fNIRS) recording during linguistic and non-linguistic stimulation. Fourteen newborns listened to linguistic stimuli (native and non-native language stories) and 13 newborns were exposed to non-linguistic conditions (native and non-native stimuli played in reverse). Comparisons between left and right hemisphere oxyhemoglobin (HbO2) concentration changes over the temporal areas revealed clear left hemisphere dominance for native language, whereas non-native stimuli were associated with right hemisphere lateralization. In addition, bilateral cerebral activation was found for non-linguistic stimulus processing. Overall, our findings indicate that from the first day after birth, native language and prosodic features are processed in parallel by distinct neural networks.

Developmental patterns of expressive language hemispheric lateralization in children, adolescents and adults using functional near-infrared spectroscopy.

The development of language hemispheric specialization is not well understood in young children, especially regarding expressive language functions. In this study, we investigated age-related changes in expressive language lateralization patterns in a population of children (3-6 and 7-10 years old), adolescents (11-16 years old), and young adults (19-30 years old). During functional near-infrared spectroscopy recordings, all participants performed a verbal fluency task, which consisted in naming as many words as possible belonging to a given semantic category. Hemoglobin concentration changes were measured in bilateral frontal and temporal cortical areas. During the language task, results showed a strong left hemisphere response along with weaker right hemisphere activation in all groups. Age-related increases in hemodynamic responses were found bilaterally, with younger children showing smaller hemodynamic responses than adolescents and adults in both hemispheres. Overall, these findings confirm that a left hemisphere specialization is already established in young children and persists through adulthood. Early left hemisphere specialization for expressive language suggests that language development hinges on structural and functional properties of the human brain with little reorganization occurring with development.

Habituation of visual evoked potentials in healthy infants and in infants with periventricular leukomalacia.

OBJECTIVE: To investigate whether habituation of flash visual evoked potentials is already present during the first 3 months of life, and to explore differences between healthy infants, term infants with periventricular leukomalacia (PVL), and preterm infants with PVL. METHODS: Referential recordings to stimuli consisting of photic stimulation presented in blocks were obtained. A total of 25 blocks, 15-stimuli each, were presented. Intrablock and interblock habituation effects were analyzed. RESULTS: In healthy infants of 42-50 and 51-58 weeks of post-conceptional age (PCA), a negative central component (NCC) showed a significant decrease in amplitude due to stimulus repetition. NCC habituation was also observed in term infants with PVL at 51-58 weeks of PCA, but not in term infants with PVL at 42-50 weeks of PCA. NCC habituation was not apparent in preterm infants with PVL. CONCLUSIONS: These results suggest that the neural mechanisms of visual habituation are normally present during the first month of life, but the presence of PVL delays the emergence of these mechanisms, particularly in preterm infants. SIGNIFICANCE: The habituation of flash visual evoked potentials may be developed into a reliable tool to examine normal and abnormal development of early neural processes.