An investigation of the genetic aspects of the alpha attenuation response

A Critical Analysis on Characterizing the Meditation Experience Through the Electroencephalogram

Meditation practices, originated from ancient traditions, have increasingly received attention due to their potential benefits to mental and physical health. The scientific community invests efforts into scrutinizing and quantifying the effects of these practices, especially on the brain. There are methodological challenges in describing the neural correlates of the subjective experience of meditation. We noticed, however, that technical considerations on signal processing also don't follow standardized approaches, which may hinder generalizations. Therefore, in this article, we discuss the usage of the electroencephalogram (EEG) as a tool to study meditation experiences in healthy individuals. We describe the main EEG signal processing techniques and how they have been translated to the meditation field until April 2020. Moreover, we examine in detail the limitations/assumptions of these techniques and highlight some good practices, further discussing how technical specifications may impact the interpretation of the outcomes. By shedding light on technical features, this article contributes to more rigorous approaches to evaluate the construct of meditation.

The genetics of personality disorder

Most measurable aspects of normal personality appear to be at least moderately heritable, with direct evidence coming from family, twin and adoption studies and indirect support deriving from psychophysiological research and breeding experiments on animals. Interestingly, genetic studies also shed light on the environmental sources of variation in personality and suggest that shared family environment rarely, if ever, has any positive effect on similarity between relatives. Despite problems of classification, and variations in the use of terms, a survey of the literature provides reasonably consistent evidence of a genetic contribution to several categories of abnormal personality, which we here divide into three groups, antisocial, anxious/avoidant, and schizoid-schizotypal personalities. However, personality disorders are complex traits that do not show simple mendelian patterns of inheritance and so far molecular genetics has been of no help in understanding their aetiology. Fortunately, techniques are now becoming available that enable the detection and potential localisation of genes of small effect and which may help elucidate the molecular basis even of (probably) polygenic traits such as abnormal personality.

EEG responses to photic stimulation in persons experienced at meditation

The EEG responses to intermittent photic stimulation were examined in a group of subjects experienced in meditation, and compared with those of a control group. The meditators exhibited a significantly smaller decrement in alpha activity and alpha blocking over the course of the experiment than did the control group, and alpha induction occurred earlier and more frequently in the meditators. These findings support the hypothesis that experienced meditators spontaneously enter the meditative state on closing the eyes, and also the view that physiologically the meditative state is one of prolonged drowsiness. An alternative interpretation, that meditation is a state of sustained attention, is discussed.

The relationship of extraversion and neuroticism to the EEG

In a recent series of investigations significant but conflicting relationships have been claimed between the two personality dimensions extraversion (E) and neuroticism (N) and certain spontaneous and induced features of the normal EEG. Savage (1964), using alpha abundance data from automatic frequency analysis, demonstrated a significant positive correlation between extraversion and high alpha amplitude. Extraversion has been similarly related to the amplitude of the averaged evoked potential waveform (Shagass and Schwartz, 1965). However, in an investigation by Broadhurst and Glass (1969) both alpha amplitude and prevalence bore an inverse relationship to E scores; extraversion was significantly associated with the rate of change of potential of the EEG, as was neuroticism with the alpha frequency. More recently, Winteret al. (1971) could find no direct relationship between extraversion and EEG amplitude, though there was a tendency for low amplitude activity to be associated with high neuroticism scores. The findings were interpreted as showing a significant interaction between the variables measured, the relationship of extraversion and amplitude varying according to the neuroticism score.