Correlation between EEG and cognitive abilities: sex differences

Theta and gamma oscillatory dynamics in mouse models of Alzheimer's disease: A path to prospective therapeutic intervention

Understanding the neural basis of cognitive deficits, a key feature of Alzheimer's disease (AD), is imperative for achieving the therapy of the disease. Rhythmic oscillatory activities in neural systems are a fundamental mechanism for diverse brain functions, including cognition. In several neurological conditions like AD, aberrant neural oscillations have been shown to play a central role. Furthermore, manipulation of brain oscillations in animals has confirmed their impact on cognition and disease. In this article, we review the evidence from mouse models that shows how synchronized oscillatory activity is intricately linked to AD machinery. We primarily focus on recent reports showing abnormal oscillatory activities at theta and gamma frequencies in AD condition and their influence on cellular disturbances and cognitive impairments. A thorough comprehension of the role that neuronal oscillations play in AD pathology should pave the way to therapeutic interventions that can curb the disease.

Sex differences in neuronal systems function and behaviour: beyond a single diagnosis in autism spectrum disorders

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that is associated with functional brain alterations that underlie the expression of behaviour. Males are diagnosed up to four times more than females, and sex differences have been identified in memory, cognitive flexibility, verbal fluency, and social communication. Unfortunately, there exists a lack of information on the sex-dependent mechanisms of ASD, as well as biological markers to distinguish sex-specific symptoms in ASD. This can often result in a standardized diagnosis for individuals across the spectrum, despite significant differences in the various ASD subtypes. Alterations in neuronal connectivity and oscillatory activity, such as is observed in ASD, are highly coupled to behavioural states. Yet, despite the well-identified sexual dimorphisms that exist in ASD, these functional patterns have rarely been analyzed in the context of sex differences or symptomology. This review summarizes alterations in neuronal oscillatory function in ASD, discusses the age, region, symptom and sex-specific differences that are currently observed across the spectrum, and potential targets for regulating neuronal oscillatory activity in ASD. The need to identify sex-specific biomarkers, in order to facilitate specific diagnostic criteria and allow for more targeted therapeutic approaches for ASD will also be discussed.

Hormonal regulation of circuit function: sex, systems and depression

Major depressive disorder (MDD) is a debilitating chronic illness that is two times more prevalent in women than in men. The mechanisms associated with the increased female susceptibility to depression remain poorly characterized. Aberrant neuronal oscillatory activity within the putative depression network is an emerging mechanism underlying MDD. However, innate sex differences in network activity and its contribution to depression vulnerability have not been well described. In this review, current evidence of sex differences in neuronal oscillatory activity, including the influence of sex hormones and female cycling, will first be described followed by evidence of disrupted neuronal circuit function in MDD and the effects of antidepressant treatment. Lastly, current knowledge of sex differences in MDD-associated aberrant circuit function and oscillatory activity will be highlighted, with an emphasis on the role of sex steroids and female cycling. Collectively, it is clear that there are significant gaps in the literature regarding innate and pathologically associated sex differences in network activity and that the elucidation of these differences is invaluable to our understanding of sex-specific vulnerabilities and therapies for MDD.

Sex differences and the neurobiology of affective disorders

Observations of the disproportionate incidence of depression in women compared with men have long preceded the recent explosion of interest in sex differences. Nonetheless, the source and implications of this epidemiologic sex difference remain unclear, as does the practical significance of the multitude of sex differences that have been reported in brain structure and function. In this article, we attempt to provide a framework for thinking about how sex and reproductive hormones (particularly estradiol as an example) might contribute to affective illness. After briefly reviewing some observed sex differences in depression, we discuss how sex might alter brain function through hormonal effects (both organizational (programmed) and activational (acute)), sex chromosome effects, and the interaction of sex with the environment. We next review sex differences in the brain at the structural, cellular, and network levels. We then focus on how sex and reproductive hormones regulate systems implicated in the pathophysiology of depression, including neuroplasticity, genetic and neural networks, the stress axis, and immune function. Finally, we suggest several models that might explain a sex-dependent differential regulation of affect and susceptibility to affective illness. As a disclaimer, the studies cited in this review are not intended to be comprehensive but rather serve as examples of the multitude of levels at which sex and reproductive hormones regulate brain structure and function. As such and despite our current ignorance regarding both the ontogeny of affective illness and the impact of sex on that ontogeny, sex differences may provide a lens through which we may better view the mechanisms underlying affective regulation and dysfunction.

The Sensed Presence as Right Hemispheric Intrusions into the Left Hemispheric Awareness of Self: An Illustrative Case Study

The hypothesis of vectorial hemisphericity predicts that left hemispheric intrusions of the right hemispheric equivalent of the sense of self should be associated with the experience of a “presence” of someone else. The neurophenomenological profile of a woman whose medical history satisfied these theoretical criteria (verified electrical anomalies that could encourage phasic discharges within the right temporal lobe and atrophy within the left temporoparietal region) is presented. In addition to interactions between electrical seizures and thinking, she reported a long history of sensed presences, ego-alien intrusions, and “sudden knowing of the subsequent sequences of seizures” before they occurred clinically. The existence of these neurocognitive processes demands a reevaluation of the psychiatric default explanations of “hysteria” and questions the belief that “awareness during seizures” or “premonition of subsequent somatosensory experience” contraindicates an epileptic process.

EEG-guided meditation: A personalized approach

The therapeutic potential of meditation for physical and mental well-being is well documented, however the possibility of adverse effects warrants further discussion of the suitability of any particular meditation practice for every given participant. This concern highlights the need for a personalized approach in the meditation practice adjusted for a concrete individual. This can be done by using an objective screening procedure that detects the weak and strong cognitive skills in brain function, thus helping design a tailored meditation training protocol. Quantitative electroencephalogram (qEEG) is a suitable tool that allows identification of individual neurophysiological types. Using qEEG screening can aid developing a meditation training program that maximizes results and minimizes risk of potential negative effects. This brief theoretical-conceptual review provides a discussion of the problem and presents some illustrative results on the usage of qEEG screening for the guidance of mediation personalization.

Morphology and dynamic repertoire of EEG short-term spectral patterns in rest: explorative study

In the present explorative experimental study, we examined the diversity of electroencephalographic (EEG) short-term spectral patterns (SPs) within a broad frequency band (1.5-30Hz) for healthy adult subjects during closed eyes and open eyes resting conditions. The types of EEG SPs were assessed by counting all identical SPs with peaks in the same frequency bins from the pools of SPs, which were built from all the SPs of the entire EEG signal (all locations) for all subjects separately for closed and open eyes conditions. This study demonstrated that independently of the resting functional state of the brain (closed eyes vs. open eyes) (a) the diversity of short-term EEG SP types was limited, (b) the percent distribution of SP types among different categories of SPs (based on morphology of SPs) was constant and (c) the most preferred frequencies were restricted to delta-theta and alpha bands. At the same time, closed eyes and open eyes conditions differed from each other by the percent distribution of different types of SPs. The probabilities for the occurrence of particular SP types were typical for each of the examined conditions with domination of alpha-rhythmical SPs during closed eyes condition and domination of delta-theta-rhythmical SPs during open eyes condition. The findings suggest that the diversity of SPs varies as a function of functional state of the brain during resting conditions. Understanding of the diversity of short-term EEG SP types is important theoretically and practically, and is significant for advancing the interpretation of the EEG signal.

Patterns of covariant power and coherent EEG activity during rest in young adults

Functional cortical organization is not dependent on cognition only, but also reflects basic intrinsic individual characteristics stable over time and across physiological conditions that suggest the existence of self-organization patterns operating even during rest. The aim of the present study was to investigate the pattern of functional organization of EEG broad bands and coherent activity during rest by means of Principal Component Analysis (PCA) with closed and open eyes of 28 men and women. PCA revealed patterns of covariant oscillatory activity and functionally related regions with covariant coherent activity present during resting conditions, different for open and closed eyes. Different patterns of covariant oscillations within alpha frequencies were identified consistent with current notions on overlapping frequencies with different origin and behavioral context. Covariant coherent cortical networks were revealed congruent with functional systems described during cognitive processes; one, linking regions involved in visuo-motor coordination, another in language, and a third one in visuo-spatial processes suggesting that strong functional links are present during rest.

Within-subject reliability and inter-session stability of EEG power and coherent activity in women evaluated monthly over nine months

OBJECTIVE

Quantitative EEG parameters during resting conditions are used as baseline in research on cognition and in serial-EEG recordings. Despite its increasing use in cognitive research and the numerous evidences of the existence of sex differences in EEG, EEG stability has been mainly investigated in men. Particularly, studies on stability of coherent activity are scarce. The aim of this study was to investigate within-subject reliability and inter-session stability of resting EEG over a nine-month period in women.

METHODS

Within-subject reliability and inter-session stability were analyzed for absolute power and inter- and intrahemispheric coherent activity at central and posterior regions, once a month, in resting conditions, with eyes open and closed.

RESULTS

Within-subject reliability was very high (r>0.89) for all subjects and EEG parameters. Inter-session stability was higher with eyes closed and for interhemispheric coherent activity, and poorer with eyes open especially in the alpha band.

CONCLUSIONS

Present results indicate high reliability of the pattern of power and coherent activity of each individual woman during rest, and group stability of EEG activity with eyes closed at least over a nine-month period.

SIGNIFICANCE

These results provide information on EEG stability in women over a long period.

The sensed presence within experimental settings: implications for the male and female concept of self

The sense of "a presence" or of a sentient being during partial sensory deprivation and exposure to very weak, complex magnetic fields across the cerebral hemispheres may be a normal neurocognitive experience that is associated with the brief intrusion of the right hemispheric homologue of the left hemispheric (and strongly linguistic) sense of self into awareness. Within an optimal experimental setting, women reported more frequent experiences of a sensed presence than did men, and men were more likely than women to consider these experiences as "intrusions" from extrapersonal or ego-alien sources. Both effects were predicted by the vectorial hemisphericity hypothesis and the known neurocognitive differences between right-handed men and right-handed women. Sociobiological implications for gender differences in the probability of intercalation between distinctive processes within the left and right temporoparietal lobes are discussed.

Effect of diazepam on EEG power and coherent activity: sex differences

Benzodiazepine-steroid interactions and sex differences in brain and circulating levels of gonadal steroids, lead to hypothesized differential effects of DZ on EEG in women and men. Coherent activity has been shown to be relevant for binding information into global percepts therefore diazepam effects on EEG correlation and sex differences were assessed in a double-blind crossover study. Healthy males (9) and females (9) received a single-dose (5 mg) of diazepam or placebo. EEG was recorded with eyes open (FP1, FP2, F3, F4, C3, C4, P3, P4, O1, O2) before and 2 h after drug administration in two counterbalanced sessions. DZ selectively increased delta and theta EEG correlation among frontal regions and decreased it between right parieto-occipital (theta) and fronto-central regions (alpha2) in addition to an increase in beta2 interhemispheric correlation in men and women. Men showed increased beta1 interhemispheric correlation, decreased alpha1 and increased beta power; women showed in addition, decreased theta and alpha2 power. theta rhythm was more sensitive to DZ in women, whereas interhemispheric correlation was more affected in men. DZ had a sexually dimorphic effect on waking EEG and a disrupting effect on coherent activity, increasing balance among frontal regions and decreasing temporal coupling between anterior-posterior regions. These sex differences might be related to differences in brain organization and activational effects of female gonadal steroids which are higher in women than in men.

Geophysical variables and behavior: XCVIII. Ambient geomagnetic activity and experiences of "memories": interactions with sex and implications for receptive psi experiences

During 96 nonsequential days over a 3-yr. period, a total of 53 men and 86 women were exposed only once for 30 min. to transcerebral, weak complex magnetic fields while they sat alone within a quiet chamber. They were asked to record the frequency of specific experiences after the exposure was completed. There was a significant interaction between sex and global geomagnetic activity for the incidence of experiences attributed to memories. Women reported more experiences attributed to "childhood memories" when geomagnetic activity was less than 20 nT, while men reported more of these experiences when the activity was more than 20 nT. Re-analyses of a database of "paranormal experiences" reported by 395 separate individuals over a 100-yr. period indicated that more men than women reported "precognitive experiences" on days the geomagnetic activity was above 20 nT while women reported such experiences if the geomagnetic activity was below 20 nT. These results suggest that these experiences, be they veridical or illusory, may be influenced by global geomagnetic activity that affect the neuroelectrical or neurochemical processes associated with memory consolidation or the attribution of the serial order of experiences during retrieval.

Geophysical variables and behavior: XCVI. "Experiences" attributed to Christ and Mary at Marmora, Ontario, Canada may have been consequences of environmental electromagnetic stimulation: implications for religious movements

Since the year 1992 individuals and groups of people have reported religious experiences near Marmora, Ontario, Canada. The experiences, attributed to Christ or Mary, have occurred near the top of a hill adjacent to an open pit magnetite mine that has been accumulating about 15 million gallons of water per month for more than a decade. During the period between 1992 and 1997 epicentres for local seismic events moved significantly closer to this site. Most of the messages attributed to spiritual beings by "sensitive" individuals occurred one or two days after increased global geomagnetic activity. We suggest that conditions produced by local geophysical and geological properties created the odd lights and induced physiological changes within the thousands of people who visited the area. Direct measurements indicated that weak (0.1 microTesla to 1 microTesla) complex magnetic fields, the temporal patterns of which were similar to the experimental fields we have employed to evoke the sensed presence and altered states within the laboratory, may have been generated within the area.

Accordance between EEG alpha power and dual task performance for different visual cognitive tasks

Evidence from clinical and experimental studies suggests that the left hemisphere is preferentially engaged in language processing and mathematical-analytic tasks while the right is involved with spatial relations and synthetic tasks. The purpose of the present study was to investigate accordance between dual task paradigm (effects of concurrent cognitive tasks on right- and left-hand finger tapping frequency) and EEG alpha power changes, which are used to conduct research in lateralization of cognitive function. Subjects performed reading, face recognition and line orientation tasks. First, the EEG was recorded during the tasks and, after six months, the dual task was carried out using the same cognitive tasks. Statistical analysis yielded no significant main effect for the hemispheres, performing hand and three cognitive tasks separately for the dual task and the EEG alpha power changes. However, significant correlation between the two methods was found, indicating the left parietal activation for the reading task, the right temporal activation for the line orientation task, and both hemispheric activation for the face recognition task. Results first suggest a significant accordance between dual task performance and EEG alpha asymmetry studies.

Topography of evoked brain activity during mental arithmetic and language tasks: sex differences

We studied visual information processing using two different tasks in a group of 10 female and 10 male healthy, right-handed adults. Subjects solved arithmetic tasks shown sequentially on a computer monitor, and they also compared words presented as anagrams. The experimental design allowed us to compare the effects of reading or actively processing a given stimulus. Task difficulty was varied in three steps ('easy', 'medium', 'hard') after an independent group of 81 young adults had judged the stimulus material according to difficulty by answering questionnaires. Brain activity was recorded from an array of 30 electrodes extending from the inion to 5% anterior of F2. For each subject mean potentials were averaged off-line after screening the EEG for artifacts. Components were determined quantitatively as epochs of stable topography resulting in 10 independent components occurring within 1200 ms after stimulus onset. Significant effects were seen with field strength and scalp topography: simply reading the stimuli yielded significantly smaller amplitudes than when the subjects actively processed the same stimuli. Females had consistently larger global field power than males, and they also displayed different scalp field topography of various components. In addition, processing anagrams was accompanied by larger field strength than mental arithmetic. The scalp field distributions were also affected by sex, task type and difficulty indicating the activation of different neuronal assemblies during visual information processing of males and females. Many effects were seen at short latencies in the order of 70-120 ms indicating very early selective processing of visual stimuli where specific differences were introduced by sex and task parameters.

A follow-up study of EEG coherences in children with different pedagogical evaluations

A follow-up study on EEG coherence values was carried out with 46 school-age children divided into three pedagogical groups considering their reading and writing abilities (normal subject and children with mild and with serious reading-writing problems). EEGs were recorded at rest, with eyes closed in 15 referential derivations that gave 105 possible coherence values. Coherence was calculated after the elimination of the average reference. Repeated Measure ANOVAs were calculated to evaluate the effects of time, sex, reading-writing problems and their interactions. The second EEG recordings were taken 2-3 years after the first. The results revealed significant increase of coherence values during the time lapse studied, consisting of an increase of frontal coherences in all bands, with the exception of the theta band. The most numerous changes occurred in the alpha band. Very few differences in coherence values were observed between the two EEG recordings by pedagogical groups and by sex suggesting a similar but not igual maturation of coherences of boys and girls and of the three pedagogical groups, in this age range studied. These findings suggests an abnormal coherence development for the reading disabled group, as well as different coherence maturation for boys and girls in this time lapse studied.

Effect of spatial ability and sex on inter- and intrahemispheric correlation of EEG activity

Inter- and intrahemispheric correlation of the EEG activity at rest was computed in two groups of men and women, between 17 and 21 years old, with extreme degrees of spatial ability (SA) evaluated by the Spatial Relations Subtest of the Differential Aptitudes Test (DAT). Interhemispheric (INTERr) and intrahemispheric (INTRAr) EEG correlations were computed by means of Pearson product-moment coefficients for 5 EEG bands after digitally filtering with an FFT. Women showed significantly higher INTERr of alpha 1 between left and right centrals, lower INTRAr between right frontal and right central regions and lower INTRAr within the left than in the right hemisphere. High SA subjects showed lower INTERr between left and right frontal derivations and higher INTRAr between frontal and parietal and between central and parietal regions of both hemispheres. Sex interacted with SA in INTRAr of alpha between right frontal and right temporal regions with high SA women showing lower INTRAr than low SA women and than men. The present results indicate a different inter- and intrahemispheric functional organization in men and women and in subjects with high and low spatial ability.

Effects of prenatal testosterone treatment on sex differences in the EEG activity of the rat

Pregnant rats were injected either with 2 mg of testosterone propionate or with vehicle on days 14 to 19 of gestation. Ano-genital distance (AGD) and body weight (b.wt.) of the offspring were measured at 10, 20, 30, 45, 60, 75 and 90 days of age. Between 98 and 104 days of age the EEG activity was monopollarly recorded with electrodes implanted in the left and right parietal cortex. Males showed higher interhemispheric correlation than females in delta, theta, alpha] and the total band. Delta relative power (RP) was lower and theta RP was higher in males than in females. These sex differences were eliminated with the prenatal testosterone treatment (PTT), which exerted a masculinizing effect on females. Absolute power (AP) did not show sex differences, but PTT produced an increase in the AP of all bands, except for beta2, regardless of sex. PTT increased the AGD at all ages, except 90 days. This increase was significant only in females at 10, 30, 45, 60 and 75 days of age. PTT increased the b.wt. at all ages, regardless of sex. These data indicate that the organizational action of sex hormones during the prenatal period plays an important role in the establishment of EEG sex differences in the rat.

Effect of spatial ability and sex on EEG power in high school students

Performance at eight cognitive tests and EEG spectral power at rest was computed in 2 groups of men and women, between 17 and 21 years of age, with extreme degrees of spatial ability (SA) evaluated by the spatial relations subtest of the DAT: a low spatial ability group (10 men, 10 women) with scores below percentile 30 and a high spatial ability group (10 men, 10 women) with scores above percentile 80. Ten EEG artifact free samples, 4.096 sec each, were analyzed and absolute (AP) and relative power (RP) were obtained for 5 frequency bands using an FFT. EEG was submitted to principal component analysis and two way ANOVAs. High SA showed lower AP in the entire spectrum with eyes open and closed, and lower alpha 1 RP with eyes open than low SA group regardless of sex. The difference between low and high SA was better explained by high alpha AP at all derivations and high theta AP at right derivations and at left central and occipital regions. Women showed higher beta 1 and beta 2 AP at all derivations except at temporal regions than men regardless of SA scores.

Women reconstruct more details than men for a complex five-minute narrative: implications for right-hemispheric factors in the serial memory effect

A total of 20 men and 20 women listened to a 5-min. ambiguous narrative (the "Billy" story). When the subjects were asked (unexpectedly) to reconstruct the details of the story as a written narrative 30 min. later, women employed about 50% more words and comparably more accurate detail than the men. Covariance for pre-experimental experiences suggested that the women's proficiency could be related to the greater representation of linguistic processes within the right (non-dominant) hemisphere. The hypothesis that the classic deficit of reconstructional accuracy for events during the middle of a story is related to right-hemispheric inhibition was also supported. Subjects who recalled the fewest details reported more vivid dreaming during the subsequent two days.

Sex differences in interhemispheric correlation and spectral power of EEG activity

EEG activity was recorded from left and right parietal cortex in adult male and female rats on a daily basis during 3 days. Absolute and relative power and interhemispheric correlation of the EEG activity were calculated and compared between males and females. Interhemispheric correlation of the theta rhythm was higher in males than in females. Interhemispheric asymmetry in absolute power was larger in males, who showed higher power in the right than in the left parietal for all bands except for delta. Beta2 relative power was significantly higher in females. These results indicate greater functional asymmetry and higher interhemispheric coupling of the parietal cortex in male than in female rats as assessed by cortical EEG activity.

Elevated incidence of a sensed presence and sexual arousal during partial sensory deprivation and sensitivity to hypnosis: implications for hemisphericity and gender differences

As predicted by the vectorial cerebral hemisphericity hypothesis, 24 normal young women reported significantly more experiences of a "presence" than did 24 normal young men within a setting that emphasized hypnosis and partial sensory deprivation. The incidence of these experiences was positively correlated with scores on Spiegel's Hypnosis Induction Profile, while the attribution of the chamber experiences to ego-alien sources was correlated with the magnitude of (Vingiano's) right hemisphericity for the women only. Both sexes exhibited a significant association between the experience of a presence and sexual arousal.

EEG oscillations during menstrual cycle

12 sessions of EEG activity, one every second day, were recorded at F3, F4, C3, C4, P3, P4, O1 and O2 in 9 women with regular menstrual cycles. The following significant oscillations were observed: 1) absolute power was lower during periovulatory period; 2) absolute power of delta theta and alpha 1 was higher during premenstrual period whereas absolute power of alpha 2, beta 1 and beta 2 was higher during menstruation; 3) relative power of low alpha frequencies was lower and that of high frequencies was higher during premenstrual period; 4) interhemispheric correlation between frontals was higher during ovulation and between occipitals was higher during premenstrual phase; 5) no significant power asymmetries were observed. The present findings suggest higher activation of centro-parietal regions during menstruation and lower activation of frontal regions during premenstrual phase.

Women but not men exhibit a positive correlation between complex partial epileptic-like signs and tactile-visual cross-modal matching: implications for hemispheric intercalation

16 right-handed men and 19 women were asked to feel various sized wooden cubes with the dominant hand for 2 sec. (without visual feedback) and then to select this cube from a random visual arrangement of cubes (tactile-visual matching) after a brief delay. The accuracy for men and women for this task did not differ significantly; however, the accuracy was significantly correlated (rho = 0.61) with a history of complex partial epileptic-like signs for the women but not for the men. The results support the hypothesis that elevated scores for complex partial epileptic-like signs in right-handed women enhance their capacity to associate different perceptual domains of the same stimuli because there is elevated activity within the (multimodal) hippocampal-amygdaloid system (sensory-limbic hyperconnectionism) and the correlative enhanced intercalation between the right and left temporoparietal lobes.

The sensed presence as right hemispheric intrusions into the left hemispheric awareness of self: an illustrative case study

The hypothesis of vectorial hemisphericity predicts that left hemispheric intrusions of the right hemispheric equivalent of the sense of self should be associated with the experience of a "presence" of someone else. The neurophenomenological profile of a woman whose medical history satisfied these theoretical criteria (verified electrical anomalies that could encourage phasic discharges within the right temporal lobe and atrophy within the left temporoparietal region) is presented. In addition to interactions between electrical seizures and thinking, she reported a long history of sensed presences, ego-alien intrusions, and "sudden knowing of the subsequent sequences of seizures" before they occurred clinically. The existence of these neurocognitive processes demands a reevaluation of the psychiatric default explanations of "hysteria" and questions the belief that "awareness during seizures" or "premonition of subsequent somatosensory experience" contraindicates an epileptic process.

Gender differences in the EEG during cognitive activity

EEG activity of 16 adult volunteers. 8 male and 8 females was monopolarly recorded at P3 and P4 at rest and during solution of three series of tasks: one analytic, one spatial and one mixed demanding both kinds of processing. The following main effects were observed: Men showed significantly higher beta relative power than women, while women showed significantly higher alpha relative power than men during all conditions. Alpha relative power decreased, while theta relative power increased during tasks solution in both sexes. Beta relative power was significantly higher at the left parietal only in men. Interparietal correlation was significantly higher in women than in men during all conditions and bands. For the theta band it increased from baseline values during tasks solution in men, while in women it decreased during the analytic task.

Vectorial cerebral hemisphericity as differential sources for the sensed presence, mystical experiences and religious conversions

Multiple variants of the sensed presence often precede mystical and religious experiences that are frequently followed by sudden, permanent changes in self-concept. The model of vectorial hemisphericity assumes that the relative metabolic activity of synaptic patterns between the cerebral hemispheres at the time of transient interhemispheric intercalation determines the affect, content, and type of experience. Depending upon the relative activity of the two hemispheres, intrusions of the right hemispheric equivalent of the left hemispheric (and linguistic) sense of self generate experimental phenomena that include "evil entities," gods, out-of-body experiences, and alterations in space-time. Conditions that facilitate interhemispheric intercalation and the generation of these experiences are discussed.

EEG activity during cognitive performance in women

EEG activity of 20 female volunteers was monopolarly recorded at P3, P4, C3 and C4 during four resting periods and three series of cognitive tasks: one analytic, one spatial and one demanding analytical and spatial processing or mixed task. Relative power and inter and intrahemispheric correlations were analysed. Beta relative power was significantly higher during the resting periods at the right parietal and the same pattern of asymmetry was maintained during the three series of tasks. Alpha relative power decreased and theta increased during the three series of tasks regardless of their cognitive nature as compared to baseline. Interhemispheric correlation for theta frequencies, and intrahemispheric correlation for the full band were significantly different during task solution. There were no significant differences between left and right intrahemispheric correlations.

Relative right temporal-lobe theta activity correlates with Vingiano's hemispheric quotient and the "sensed presence"

Measures of monopolar alpha and theta rhythm activity over the left and right temporal lobes were correlated with the subjects' hemisphericity (Vingiano) scores, temporal lobe signs, and concurrent subjective experiences during partial sensory deprivation. There was a positive association (rho = .49) between the scores for right hemisphericity and the relative amount of right/left theta rhythm but not right/left alpha rhythm activity. Significant intercorrelations between right hemisphericity, an history of ego-alien intrusions and experiences of a sensed presence, "detachment from the body," and fear during the recordings were noted. These results support the hypothesis that this class of mystical experiences is encouraged by hemispheric mismatch in temporal-lobe theta activity.

Enhanced incidence of "the sensed presence" in people who have learned to meditate: support for the right hemispheric intrusion hypothesis

If the "sensed presence" is the transient intrusion of the right hemispheric equivalent of the left hemispheric (and highly linguistic) sense of self, then any process that facilitates interhemispheric electrical coherence should enhance these experiences. As predicted, the "ego-alien intrusion" (sensed presence) factor was specifically and significantly elevated in 221 people who had learned to meditate (65 to 70% were involved in Transcendental Meditation) compared to 860 nonmeditators. Variants of a sensed presence were more frequent in female than in male meditators and were particularly evident in left-handers who had learned to mediate. The effect size suggests that learning a meditation technique is counterindicated for subpopulations, such as borderline, schizotypal, or dissociative personalities, who display very fragile self-concepts.

Testosterone and estradiol in right-handed men but only estradiol in right-handed women is inversely correlated with the degree of right-hand preference

Relations of sex hormones to the degree of right-hand preference was studied in right-handed male and female adult subjects. Hand preference was assessed by the Edinburgh and Waterloo Handedness Questionnaires. Males consisted of weakly, moderately, and strongly right-handed subjects. Females comprised only moderately and strongly right-handed subjects. In females, only serum estradiol was found to be negatively linearly and significantly correlated with the degree of right-hand preference. In males, testosterone, as well as estradiol, showed a significant negative linear correlation with the degree of right-hand preference. Sex hormone binding globulin also showed a similar relation to hand preference in males. Thus, nearly all sex hormones caused a decrease in the degree of right-hand preference in males, whereas only estradiol had the same effect on hand preference in females. This would be the cause of stronger right-hand preference in females than males and vice versa.

Greater right hemisphericity is associated with lower self-esteem in adults

28 men and 32 women were given Vingiano's Hemisphericity Questionnaire and the Coopersmith Self-esteem Inventory. People who reported the greatest numbers of right hemispheric indicators displayed the lowest self-esteem; the correlations were moderately strong (r greater than 50) for both men and women. These results support the hypothesis that the sense of self is primarily a linguistic, left-hemispheric phenomenon and that a developmental history of frequent intrusion from right-hemispheric processes can infuse the self-concept with negative affect.

Tobacyk's sex differences in the experiences of ego-alien intrusions

Tobacyk's Revised Paranormal Belief Scale and an inventory that infers temporal lobe signs were administered to 44 men and 54 women who were enrolled in first-year university courses. Women believed more in psi phenomena, witchcraft, and spiritualism than did men, who believed more in extraterrestrial life forms. Although complex partial epileptic-like signs were moderately (0.40) correlated with total beliefs for both sexes, these signs were dominated by experiences of ego-alien intrusions for women only. The results support the concept of greater interhemispheric coherence in women compared to men and emphasize the importance of limbic processes in the formation and maintenance of religious and paranormal beliefs.

Canonical correlation of a temporal lobe signs scale with schizoid and hypomania scales in a normal population: men and women are similar but for different reasons

The relationships between four relevant Minnesota Multiphasic Personality Inventory variables and temporal lobe signs and symptoms were determined separately for 70 university men and 86 women. Canonical correlations were similar in magnitude (0.55 to 0.60) but indicated sex-specific construction of the roots. For men the significant variables were the schizoid and complex partial epileptic-like signs; for women the significant variables were hypomania and all three temporal lobe clusters: complex partial seizure experiences, interictal-like signs, and religious/psi phenomenology.

Gender differences in source location for the N100 auditory evoked magnetic field

Auditory evoked magnetic fields were recorded in response to contralateral stimulation over the right hemisphere in 6 adult males and 6 adult females. The data were fit to a model of a current-dipole source in a homogeneous sphere and 5 parameters of the dipole were computed--3 spatial coordinates, orientation, and strength. When average values for the dipole parameters were compared between sexes, it was found that the current source for the N100m is located more than 1 cm posterior in females and is oriented pointing more downward. These findings were replicated in separate measurement sessions. Viewing of individual magnetic resonance images did not reveal a corresponding anatomical disparity in the location of the primary auditory cortex which is assumed to produce the N100m. Therefore, functional organization of the auditory cortex may be different for the sexes.