Coincident frequencies and relative phases among brain activity and hormonal signals

Abstract

Background: Fourier transform is a basic tool for analyzing biological signals and is computed for a finite sequence of data sample. The electroencephalographic (EEG) signals analyzed with this method provide only information based on the frequency range, for short periods. In some cases, for long periods it can be useful to know whether EEG signals coincide or have a relative phase between them or with other biological signals. Some studies have evidenced that sex hormones and EEG signals show oscillations in their frequencies across a period of 28 days; so it seems of relevance to seek after possible patterns relating EEG signals and endogenous sex hormones, assumed as long time-periodic functions to determine their typical periods, frequencies and relative phases.

The Method to Obtain the Rise and Fall of Anxiety, Estrogen, Progesterone and EEG Signals and Their Coincident Frequencies

“…The previously described outcome (Solís-Ortiz, Campos, Felix, & Obregón, 2009) indicated that the estrogen levels of participants displayed significantly change over the menstrual cycle (X 2 (9) = 74.08, p = 0.001). Comparisons post hoc demonstrated that estrogen levels were higher during the days 14 of the menstrual cycle (t = −34.29, p = 0.001) compared with the day 1of menstruation, when the estrogen levels are lower.…”

“…The current study also employed a dataset of estrogen and progesterone levels in serum obtained before starting the sessions of EEG across of the menstrual cycle previously reported (Solís-Ortiz, Campos, Felix, & Obregón, 2009;Solís-Ortiz & Corsi-Cabrera, 2002). The serum hormone levels were employed to confirm the hormone levels during the menstrual cycle and to establish relations with EEG frequencies and anxiety frequencies.…”

“…Next, we review briefly how to use the XFT. The interested reader can consult a more detailed description elsewhere (Solís-Ortiz, Campos, Felix, & Obregón, 2009;Campos, Rico-Melgoza, & Chavez, 2012;Campos & Figueroa, 2011). Let us denote by V n the vector formed with the N samples of the signal v(t) evaluated at the equidis-…”

“…In a previous study, we reported the application of a new method of analysis of the EEG signals in a long-time period, namely the entire menstrual cycle, we were able to determine coincident frequencies, and relative phases among brain activity and hormonal signals during the menstrual cycle (Solís-Ortiz, Campos, Felix, & Obregón, 2009). Since this method is based on an ordinary Fourier Transform of one variable, it cannot be used to determine when the signals be-gin and end.…”

Efecto del alcohol en la organización eléctrica cerebral durante una tarea de memoria de trabajo visuoespacial y su relación con el ciclo menstrual

“…En reposo, durante la fase periovulatoria, existe un incremento de la correlación interfrontal y un decremento de la PA. En contraste, en la fase menstrual, se incrementa la PA de las frecuencias rápidas, mientras que la PR de theta decrece [24]. Además, en las mujeres existe una correlación positiva entre los niveles de progesterona y la PA de las bandas theta, alfa1, alfa2 y beta1, así como una correlación negativa con las bandas delta y beta2 [25].…”