Prolongation of alpha oscillations in auditory oddball paradigm

Although an important component of the P300 target response is the "prolonged alpha response". no relevant analysis is found in the literature. The present study emphasizes the relevance of prolongation of alpha responses in auditory oddball paradigm. Two types of stimuli were applied to twenty subjects. As standard stimuli 80 dB-1500 Hz tones and the target stimuli 80 dB-1600 Hz tones were used. The prolongations of alpha responses were measured in 13 recording sites in the frequency range of 8-13 Hz

Analysis of non-REM sleep staging with electroencephalography bispectral index

The present study provides results in an early sleep period for non-REM stage correlation with bispectral index (BIS) values. The purpose of the study was to assess the applicability of an objective procedure to monitor sleep. Nine healthy subjects (mean age: 25.0 +/- 4.4; 1 female) were recruited for the study without history of any neurological, psychiatric, or sleep-related disorders. Electroencephalography (EEG) signals from 30 electrodes referenced to linked earlobe electrodes, and electrooculography (EOG) and electromyography (EMG) activities were recorded. BIS recording was performed simultaneously with EEG recording. Because that the current study is related to non-REM sleep, corresponding to the first sleep cycle, approximately 90 min of data was processed both for BIS and EEG data pools. The sleep staging was done using traditional Rechtschaffen and Kales scoring (R&K) and BIS scores were acquired online. The BIS values corresponded well to sleep depth, decreasing in accordance with sleep stages. Overall BIS correlation with sleep scores in the non-REM was found to be r = 0.86 (Spearman analysis, n = 9, r(2) = 0.75). Accompanying the traditional scoring, BIS and BIS-like tools can be useful for information processing and for psychophysiological applications in neurology, psychiatry, and further studies on consciousness

Principles of oscillatory brain dynamics and a treatise of recognition of faces and facial expressions

The research of event-related oscillations is one of fast-growing fields in neuroscience. In this study, a theory of the "whole-brain-work," which can be useful for functional interpretation of brain oscillations, is presented together with its application to recognition of faces and facial expressions. Following results are summarized: (1) Mechanisms leading to the perception of the grandmother picture are manifested with parallel activations of neural assemblies in different cortical locations and as superposition of delta, theta, alpha, beta, and gamma oscillations. Known and anonymous faces can be differentiated by means of oscillatory brain dynamics. Percepts cannot be localized in a given specific region. The differentiation of facial expression induces significant change in alpha and theta oscillation. (2) While the importance of fMRI in object recognition is clear, this method has low temporal resolution. Our results shows that multiple brain oscillations clearly differentiate the known and unknown faces with varied degrees of selective-responsiveness in a short time window between 0 and 800 ins, thus completing and implementing the analysis of percepts in the dynamic window and indicating a broader distribution at the cortex. (3) The presented evidence of selectively distributed multiple oscillations for differentiation of facial percepts is in conceptual accordance with the "selectively distributed processing" in neurocognitive networks of Goldman-Rakic, Fuster, and of Mesulam. The large-scale approach of several investigators is also confirmed with the new results. On facial stimuli, a given location can show a considerable selected activation, but the formation of percepts is manifested by multiple oscillations with differentiated weight in large neural populations. (4) The most important feature of the comparison of percepts of grandmother and anonymous faces is the existence of a variety of significant differences in delta, theta, alpha, beta, and gamma responses between the anonymous and grandmother faces in frontal, central, parietal, temporal, and occipital sites. (5) The brain response is a construct in a multi-dimensional state manifested by amplitudes of oscillatory responses, topological coordinates, and changes in the time axis following presentation of the percepts including delays and prolongations, coherence between locations. Only a new metrics embracing all these parameters can be representative for dynamics of functionality in the brain. The conceptual aspects of this new scope are explained in the presented theory