RESUMEN
INTRODUCTION: Learning by habituation implies a gradual diminution of the organism's responses to non-relevant stimuli. These responses, resulting from electrical oscillations of the brain, can be analyzed through quantitative electroencephalography (qEEG). OBJECTIVE: To characterize the absolute power (AP) in the range of delta (δ), theta (θ), alpha (α), beta (ß) in cortical parasagittal regions during habituation to photostimulation (RPh). MATERIAL AND METHODS: We studied 81 undergraduate students. The EEG was recorded in a Nicolet; awake subjects with closed eyes were photostimulated (5 Hz for 2 s, 20 times, RPh). The UAMI/Yáñez program identifies the RPh signal, chooses and collects 2-sec samples before (Pre) and during RPh, and instruments the Welch periodogram, which integrates the absolute power (AP) of δ, θ, α, and ß. We calculated the average AP (AAP) in Pre and RPh per frequency and lead. AAP differences were assessed with non-parametric tests. Linear regression was used to plot the AAPs of each Pre and each RPh sample, representing the resulting slope with its statistical significance. RESULTS: RPh increased the AAP of δ in frontal and frontocentral leads of both hemispheres, and its slopes were ascendant. AAP of θ increased in fronto-frontal and diminished in the other three leads, its slopes were ascendant in right central parietal and parieto-occipital leads. AAP of α increased in fronto-frontal leads, did not change in fronto-central, and diminished in the other leads; its slopes were descendent in Pre and ascendant in RPh in both hemispheres. AAP of ß increased in the four leads; in Pre, ß slopes were descendent in parieto-occipital leads of both hemispheres. During RPh, δ slopes were ascendant in right parieto-central and in both parieto-occipital leads. CONCLUSION: The progressive diminution of alpha's desynchronization, which ends in synchronization, is probably due to hyperpolarization of neuronal membranes and represents habituation. This is complemented with synchronization of the delta rhythm in anterior cortical areas and of theta and beta in areas of the right hemisphere.
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Sincronización Cortical/fisiología , Electroencefalografía , Habituación Psicofisiológica/fisiología , Estimulación Luminosa , Adulto , Corteza Cerebral/fisiología , Humanos , Modelos LinealesRESUMEN
INTRODUCTION: The EEG records neuronal membrane potential oscillations that depend on the morpho-functional characteristics of the membrane and of modifications by postsynaptic excitatory (PSEP) and inhibitory (PSIP) potentials. The quantitative EEG (qEEG) measures the absolute power (AP) of oscillations separated in frequencies, resulting from the interaction among subcortical-cortical-subcortical ensembles. The hypothesis is that neuronal networks function at a given frequency and that their APs are codes that, by becoming synchronized in diverse ensembles, generate behavior. OBJECTIVE: To establish the spectral power of cortical oscillations under diverse study paradigms and in different populations. In particular, to identify the AP and topographical distribution of four cerebral frequency bands under resting wakefulness and activation, and to integrate results into a database to establish comparison standards. MATERIAL AND METHODS: Undergraduate students, average age of 20.6 +/- 2.6 years, who participated voluntarily in the study. Recordings were made with a Nicolet EEG. We chose, in the first stage, closed eyes (CE) three samples of 12 s each. In the second stage, we chose pairs of 6 s samples, first with CE and then with OE. For their analysis, we applied the Welch periodogram and we plotted the average AP (AAP) and standard deviation (SD) of delta, theta, alpha, and beta per lead. Differences were compared through non-parametric tests (Wilcoxon and Dunnett T3); setting statistical significance at a = 0.05. RESULTS: Average APs of each frequency band differ significantly in intensity and topographic distribution generating a profile of each rhythm. When opening the eyes, rhythms desynchronized significantly at different intensities in the diverse leads, except for beta in the left fronto-frontal lead. DISCUSSION: Results indicate the existence of cortical ensembles that synchronize at a determined frequency and are modified by visual stimulation, indicating the effects of the subcortico-cortical circuits. The integrated database provides comparison standards to support diagnoses and treatments.
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Atención/fisiología , Ondas Encefálicas/fisiología , Corteza Cerebral/fisiología , Red Nerviosa/fisiología , Vigilia/fisiología , Adolescente , Sincronización Cortical/fisiología , Estudios Transversales , Dominancia Cerebral/fisiología , Electroencefalografía , Potenciales Postsinápticos Excitadores/fisiología , Femenino , Humanos , Masculino , Potenciales de la Membrana/fisiología , Estimulación Luminosa , Adulto JovenRESUMEN
BACKGROUND: Berger related the EEG with cognition; we are attempting to identify which rhythms and circuits participate in habituation, a learning that decreases responses to meaningless stimuli which, changed the absolute power (AP) of EEG oscillations. OBJECTIVE: To characterize habituation, analyzing the AP of four rhythms in lateral regions of both hemispheres (BH), proposing that their diminution, desynchronization (D), means activation whereas their increase, synchronization (S), means inhibition. MATERIAL AND METHODS: qEEG analysis in 83 college students, in waking state with closed eyes, and photostimulated (RPh). The used UAMI/Yáñez software identifies RPh signals and takes 2-s samples before (Pre) and during RPh; the Welch periodogram integrates the AP of the four rhythms. We calculated the average AP (AAP) in Pre and RPh per frequency in bipolar lateral leads per hemisphere. AAP differences were evaluated with the Wilcoxon tests correcting with Bonferroni for repeated samples. Applying the linear regression model, we plotted the AAP distribution slopes during Pre and RPh. RESULTS: We established the differences of the AP of the four rhythms within each hemisphere and between both hemispheres (BH). During PRE, AAP of δ and θ increased whereas α and ß decreased. RPh increased the AAP (p = 0.01) of the four rhythms in fronto-frontal (FF) leads; the increase in δ persisted in fronto-temporal (FT) and temporo-occipital (TO), whereas ß's increase persisted in all leads. The AAP of α decreased with the first RPh (D) increasing with the following ones; its slope starts with desynchronization and ends with synchronization. Theta followed a D/S pattern in temporal leads. Beta followed and ascending (S) slope in all leads. CONCLUSIONS: Habituation results from the D/S of a in all cortical regions, of θ in temporal, of δ in frontal regions and ß in all regions. Synchronization reflects hyperpolarization of neuronal membranes, decreasing their activity.