Mario Bertini

The electroencephalographic fingerprint of sleep is genetically determined: a twin study.

Humans have an individual profile of the electroencephalographic power spectra at the 8 to 16Hz frequency during non–rapid eye movement sleep that is stable over time and resistant to experimental perturbations. We tested the hypothesis that this electroencephalographic “fingerprint” is genetically determined, by recording 40 monozygotic and dizygotic twins during baseline and recovery sleep after prolonged wakefulness. We show a largely greater similarity within monozygotic than dizygotic pairs, resulting in a heritability estimate of 96%, not influenced by sleep need and intensity. If replicated, these results will establish the electroencephalographic profile during sleep as one of the most heritable traits of humans. Ann Neurol 2008

Is the brain influenced by a phone call? An EEG study of resting wakefulness

We recorded the resting electroencephalogram of 20 healthy subjects in order to investigate the effect of electromagnetic field (EMF) exposure on EEG waking activity and its temporal development. The subjects were randomly assigned to two groups and exposed, in double-blind conditions, to a typical mobile phone signal (902.40 MHz, modulated at 217 Hz, with an average power of 0.25 W) before or during the EEG recording session. The results show that, under real exposure as compared to baseline and sham conditions, EEG spectral power was influenced in some bins of the alpha band. This effect was greater when the EMF was on during the EEG recording session than before it. The present data lend further support to the idea that pulsed high-frequency electromagnetic fields can affect normal brain functioning, also if no conclusions can be drawn about the possible health effects.

Beneficial effects of enriched environment on adolescent rats from stressed pregnancies.

The capacity of an early environmental intervention to normalize the behavioural and immunological dysfunctions produced by a stressed pregnancy was investigated. Pregnant Sprague‐Dawley rats underwent three 45‐min sessions per day of prenatal restraint stress (PS) on gestation days 11–21, and their offspring were assigned to either an enriched‐environment or standard living cages throughout adolescence [postnatal days (pnd) 22–43]. Juvenile rats from stressed pregnancies had a prominent depression of affiliative/playful behaviour and of basal circulating CD4 T lymphocytes, CD8 T lymphocytes and T4/T8 ratio. They also showed increased emotionality and spleen and brain frontal cortex levels of pro‐inflammatory interleoukin‐1β (IL‐1β) cytokine. A more marked response to cyclophosphamide (CPA: two 2 mg/kg IP injections) induced immunosuppression was also found in prenatal stressed rats. Enriched housing increased the amount of time adolescent PS rats spent in positive species‐typical behaviours (i.e. play behaviour), reduced emotionality and reverted most of immunological alterations. In addition to its effects in PS rats, enriched housing increased anti‐inflammatory IL‐2 and reduced pro‐inflammatory IL‐1β production by activated splenocytes, also producing a marked alleviation of CPA‐induced immune depression. In the brain, enriched housing increased IL‐1β values in hypothalamus, while slightly normalizing these values in the frontal cortex from PS rats. This is a first indication that an environmental intervention, such as enriched housing, during adolescence can beneficially affect basal immune parameters and rats response to both early stress and drug‐induced immunosuppression.

Social Conformity and Psychological Differentiation

Abstract This study examined the role of socialization experiences in the development of psychological differentiation. In each of three countries (Holland, Italy, Mexico) two villages were selected as presenting a contrasting picture with regard to degree of emphasis on conformity to family, religious and political authority. It was hypothesized that within the pair of villages in each country children from the village which stressed social conformity would tend to be more field dependent and show other signs of less developed differentiation than children from the village in which social conformity was less emphasized. In each of the six villages approximately 100 children (boys and girls, aged 9–11 and 13–15) were studied. Differentiation was assessed by a battery of tests of field-dependence-independence and the figure-drawing test. In every comparison of mean test scores between pairs of villages, in each of the three countries, children from the village in which social conformity was stressed obtain...

Psychosocial factors and clinical evolution in HIV-1 infection : a longitudinal study

The aim of the study was to assess the relationship between the initial psychosocial situation and the probability of later symptom development in HIV-1 infection. One hundred HIV-1 seropositive subjects, 79 in Stage III (LAS) and 21 in Stage II (asymptomatic), were examined both immunologically (CD4+, Skin Test) and psychologically (test battery). Follow-up at 6 and 12 months involved clinical and immunological reassessment of subjects, who were then classified as fully symptomatic (S, Stage IV) or unchanged (U). The two groups were compared through ANOVA on initial psychosocial measures, while stepwise logistic multiple regression was employed to assess the predictive value of psychosocial measures on clinical and immunological evolution. Psychosocial measures most clearly showing an association with clinical evolution were Denial/Repression attitudes (negatively) and Fighting Spirit (positively), whereas aspects of Hardiness and Social Support showed an effect in interaction with initial CD4+ levels. No stable results were obtained on immunologic evolution. The two groups (U and S) did not show significant differences on other independent variables, with the exception of age.

Sleepiness: evaluating and quantifying methods.

The aim of this literature review is to analyze the methods mainly used for evaluating and quantifying the complex phenomenon of sleepiness. The most common distinction is between subjective measures or self-evaluations, performance decrement measures, measures for evaluating sleep propensity and measures of arousal decrease. Techniques mainly used in specialized literature will be briefly presented and commented upon, evaluating their sensitivity, advantages and limitations. We conclude that: (a) different measures inevitably are differently sensitive to sleepiness fluctuations; (b) the amount of prior sleep is strongly relevant in quantifying sleepiness levels; (c) subjective and behavioral measures show a higher level of vulnerability to external and motivational factors.

The spontaneous K-complex during stage 2 sleep: is it the ‘forerunner’ of delta waves?

The hypothesis that K-complexes (KCs) contribute to the process of synchronization leading to Slow-Wave Sleep (SWS) was evaluated by measuring their dynamic evolution across sleep cycles and before transitions to rapid eye movement (REM) or to SWS. KC density and inter-KC intervals respectively decreased and increased across the sleep cycles, revealing linear trends. Comparisons among transitions from stage 2 to SWS or to REM sleep showed a prevalence of KCs before the shift to SWS as compared to REM. Changes in KC density before the shift to SWS were fitted by a linear regression, at variance with the transition to REM sleep. Intra-night variations of KCs, paralleling the well-known decrease of slow waves across sleep cycles, and intracycle variations before shifting to SWS, both converge to indicate that KCs can be considered as the forerunner of delta waves.

Handedness is mainly associated with an asymmetry of corticospinal excitability and not of transcallosal inhibition

OBJECTIVE The study aims to compare transcallosal inhibition (TI), as assessed by the paired-pulse transcranial magnetic stimulation (TMS) technique, in a sample of right-handed subjects (RH) and left-handed subjects (LH). Motor thresholds (MTs) and motor evoked potential (MEP) amplitudes were also measured in the two groups, as an index of corticospinal activity. METHODS Thirty-two normal subjects (16 RH and 16 LH) were recorded with a paired-pulse TMS paradigm (intensity of both pulses=120% of MT). The inter-stimulus intervals (ISIs) were 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 ms for both motor cortices, and MEP responses were recorded from the abductor digiti minimi muscles. RESULTS Both groups showed a clear TI centred around the 12 ms ISI, but no difference was found as a function of handedness or of hemisphere. On the other hand, the two groups differed in terms of corticospinal activity, since the hand motor dominant hemisphere had lower MTs than the non-dominant one in LH, and larger MEP amplitudes for the right hand were found in RH. CONCLUSIONS Results point to a functional asymmetry of the motor cortex on the hand-dominant versus the non-dominant hemisphere, while handedness does not seem associated with functional differences in callosal inhibition, as measured by the inter-hemispheric paired-pulse TMS technique.

Neurophysiological correlates of sleepiness: A combined TMS and EEG study

Changes of cortical and corticospinal excitability as a function of sleep deprivation have been studied, using EEG power maps and several TMS measures in 33 normal subjects before and after a 40-h sleep deprivation (SD). The effects of SD were independently assessed by subjective and EEG measures of sleepiness, the latter being represented in terms of cortical maps for different frequency bands. Short intracortical facilitation (SICF) and inhibition (SICI) were measured by the paired-pulse TMS technique with different inter-stimulus intervals. Besides standardized motor threshold (MT), lower threshold (LT) and upper threshold (UT) were also determined. Subjective sleepiness severely increased as a consequence of SD, paralleled by a drastic decrease of alertness. EEG topography showed large increases in delta and theta activity, mainly evident at fronto-central areas. Standard MTs, as well as LTs and UTs, all increased as a consequence of SD. SICF also showed a significant increase as compared to pre-deprivation values, but only in females. The increase of theta activity was strongly associated in the left frontal and prefrontal cortex to a smaller decrease of corticospinal excitability, expressed by MTs, and a larger increase of intracortical facilitation, expressed by SICF. TMS and EEG measures converge in indicating that SD has severe effects on both cortical and corticospinal excitability, as shown respectively by the increases of slow-frequency EEG power and MTs. The SICF enhancement in females and the results of the combined topographical analysis of EEG and TMS changes are coherent with the hypothesis that cortical TMS-evoked responses are higher as a consequence of a longer wakefulness. However, the lack of an increase in cortical excitability after prolonged wakefulness in males suggests some caution in the generalization of these effects, that deserve further investigation.

Visual search performance across 40 h of continuous wakefulness: Measures of speed and accuracy and relation with oculomotor performance

The aim of the study was to estimate the sensitivity of a brief self-paced visual search task to increased levels of sleepiness as a consequence of 40 h of sleep deprivation. Time-of-day effects on this task, on subjective sleepiness and on oculomotor performance changes, were also assessed. Eight normal subjects slept for three nights in the laboratory (adaptation, baseline, recovery). Baseline and recovery nights were separated by a period of 40 h of continuous wakefulness, during which subjects were tested every 2 h from 10:00 to 22:00 h on both days preceding and following the sleep deprivation night, as well as from 24:00 to 08:00 h during the deprivation period. At the same time, subjects filled in a visual analogue sleepiness scale and the Stanford Sleepiness Scale (SSS). As regards cognitive performance, significant effects were found on speed measures, while accuracy was not affected. The number of explored rows was higher after the baseline night than after the sleepless night, and showed a consistent time-of-day trend. Omissions ratio (OR), false positives ratio (FPR) and hits ratio (HR) did not show any significant effect. Subjective ratings of sleepiness varied according to speed measures, being affected by sleep deprivation and time of day. Since similar effects were found with an oculomotor task, detrended functions for all variables across the 40 h of continuous wakefulness were calculated. A circadian effect was found, in which speed measures seem to be more affected than accuracy ones in both visual search and oculomotor tasks. It is concluded that 40 h of prolonged wakefulness significantly impairs performance in a brief cognitive visual search task. Such a performance worsening is evident on speed, but not on accuracy indices, and is strictly related to the deterioration of oculomotor performance, indicating a clear circadian effect.