Neuroscientific results of experimental studies on the control of acute pain with hypnosis and suggested analgesia

This narrative review summarizes a representative collection of electrophysiological and imaging studies on the neural processes and brain sources underlying hypnotic trance and the effects of hypnotic suggestions on the processing of experimentally induced painful events. It complements several reviews on the effect of hypnosis on brain processes and structures of chronic pain processing. Based on a summary of previous findings on the neuronal processing of experimentally applied pain stimuli and their effects on neuronal brain structures in healthy subjects, three neurophysiological methods are then presented that examine which of these neuronal processes and structures get demonstrably altered by hypnosis and can thus be interpreted as neuronal signatures of the effect of analgesic suggestions: (A) On a more global neuronal level, these are electrical processes of the brain that can be recorded from the cranial surface of the brain with magnetoencephalography (MEG) and electroencephalography (EEG). (B) On a second level, so-called evoked (EPs) or event-related potentials (ERPs) are discussed, which represent a subset of the brain electrical parameters of the EEG. (C) Thirdly, imaging procedures are summarized that focus on brain structures involved in the processing of pain states and belong to the main imaging procedures of magnetic resonance imaging (MRI/fMRI) and positron emission tomography (PET). Finally, these different approaches are summarized in a discussion, and some research and methodological suggestions are made as to how this research could be improved in the future.

The Malnutrition Awareness Scale for community-dwelling older adults: Development and psychometric properties

BACKGROUND & AIMS

Qualitative studies suggest that malnutrition awareness is poor in older adults. The aim of this study was to develop a questionnaire to quantitatively assess malnutrition awareness in community-dwelling older adults aged 60+ years.

METHODS

The Malnutrition Awareness Scale (MAS) was developed based on the awareness phase of the Integrated-Change model, and included four domains: knowledge, perceived cues, risk perceptions, and cognizance. Twenty-six scale items were developed using results from mainly qualitative research and the expertise of the authors. Items were piloted in 10 Dutch older adults using the Thinking Aloud method to optimize wording. In a feasibility study, annoyance, difficulty and time to complete the MAS and its comprehensibility were tested. After final revisions, the MAS was applied to a large sample to test its psychometric properties (i.e., inter-item correlations, Cronbach's alpha, score distribution) and relevance of the items was rated on a 5-point scale by 12 experts to determine content validity.

RESULTS

The feasibility study (n = 42, 55 % women, 19 % 80+ y) showed that the MAS took 12 ± 6 min to complete. Most participants found it not (at all) annoying (81 %) and not (at all) difficult (79 %) to complete the MAS, and found it (very) comprehensible (83 %). Psychometric analyses (n = 216, 63 % women, 28 % 80+ y) showed no redundant items, but two items correlated negatively with other items, and one correlated very low. After removal, the final MAS consists of 23 items with a min-max scoring range from 0 to 22 (with higher scores indicating higher awareness) and an overall Cronbach's alpha of 0.67. The mean MAS score in our sample (n = 216) was 14.8 ± 3.2. The lowest obtained score was 6 (n = 3) and the highest 22 (n = 1), indicating no floor or ceiling effects. Based on the relevance rating, the overall median across all 22 items was 4.0 with IQR 4.0-5.0.

CONCLUSION

The Malnutrition Awareness Scale is a novel, feasible and reliable tool with good content validity to quantitively assess malnutrition awareness in community-dwelling older adults. The scale is now ready to identify groups with poor malnutrition awareness, as a basis to start interventions to increase malnutrition knowledge and awareness.

Low micronutrient intake in nursing home residents, a cross-sectional study

Low intake of micronutrients is associated with health-related problems in nursing home residents. As their food intake is generally low, it is expected that their micronutrient intake will be low as well. The nutrient intake of 189 residents (mean age 85.0 years (SD: 7.4)) in five different Dutch nursing homes was measured based on 3-day direct observations of intake. Micronutrient intake, without supplementation, was calculated using the Dutch food composition table, and SPADE software was used to model habitual intake. Intake was compared to the estimated average requirement (EAR) or adequate intake (AI) as described in the Dutch dietary reference values. A low intake was defined as >10% not meeting the EAR or when the P50 (median) intake was below the AI. Vitamin A, thiamin, riboflavin, niacin, B6, folate, B12, C, D, E, copper, iron, zinc, calcium, iodine, magnesium, phosphorus, potassium, and selenium were investigated. Our data showed that vitamin and mineral intake was low for most assessed nutrients. An AI was only seen for vitamin B12 (men only), iodine (men only), and phosphorus. A total of 50% of the population had an intake below the EAR for riboflavin, vit B6, folate, and vitamin D. For reference values expressed in AI, P50 intake of vitamin E, calcium, iodine, magnesium, potassium, and selenium was below the AI. To conclude: micronutrient intake in nursing home residents is far too low in most of the nursing home population. A "food-first" approach could increase dietary intake, but supplements could be considered if the "food-first" approach is not successful.

Behavioral and Cognitive Problems as Determinants of Malnutrition in Long-Term Care Facilities, a Cross-Sectional and Prospective Study

OBJECTIVES

To investigate the cross-sectional and prospective associations between behavior and cognitive problems and malnutrition in long-term care facilities (LTCF).

DESIGN

Cross-sectional and prospective routine care cohort study.

SETTING

6874 Residents in Dutch LTCFs (period 2005-2020).

PARTICIPANTS

Data were obtained from the InterRAI-LTCF instrument. Cross-sectional analyses on prevalence of malnutrition at admission included 3722 residents. Prospective analyses studied incident malnutrition during stay (total follow-up time 7104 years) and included data of 1826 residents with first measurement on admission ('newly-admitted') and n=3152 with first measurement on average ~1 year after admission ('existing').

MEASUREMENTS

InterRAI scales for communication problems (CS), aggressive behavior (ABS), social engagement (RISE), depressive symptoms (DRS), cognitive performance (CPS) and the total number of behavior and cognitive problems were investigated as independent variables and malnutrition (ESPEN 2015 definition) as dependent variable in regression analyses. Results were stratified for gender and group 'newly-admitted' vs. 'existing'.

RESULTS

On admission, 9.5% of residents was malnourished. In men, low social engagement was associated with prevalence of malnutrition. In women, all behavior and cognitive problems except depression were associated with malnutrition in the unadjusted analyses, but this attenuated in the full model taking all problems into account. The incidence of malnutrition during stay amounted to 8.9%. No significant associations of behavior and cognitive problems with malnutrition incidence were seen in 'newly-admitted' male residents while in 'existing' male residents all determinants were significantly associated. In 'newly-admitted' female residents CS, ABS and CPS, and in 'existing' female residents CS, RISE, ABS and CPS were significantly associated with incident malnutrition. All associations slightly attenuated after adjustment. Malnutrition incidence increased with increasing number of combined behavior and cognitive problems.

CONCLUSION

Residents with behavior and cognitive problems are at an increased risk of being malnourished at admission, or becoming malnourished during stay in a LTCF, especially residents with multiple behavior and cognitive problems.

Suggested visual blockade during hypnosis: Top-down modulation of stimulus processing in a visual oddball task

Several theories of hypnosis assume that responses to hypnotic suggestions are implemented through top-down modulations via a frontoparietal network that is involved in monitoring and cognitive control. The current study addressed this issue re-analyzing previously published event-related-potentials (ERP) (N1, P2, and P3b amplitudes) and combined it with source reconstruction and connectivity analysis methods. ERP data were obtained from participants engaged in a visual oddball paradigm composed of target, standard, and distractor stimuli during a hypnosis (HYP) and a control (CON) condition. In both conditions, participants were asked to count the rare targets presented on a video screen. During HYP participants received suggestions that a wooden board in front of their eyes would obstruct their view of the screen. The results showed that participants’ counting accuracy was significantly impaired during HYP compared to CON. ERP components in the N1 and P2 window revealed no amplitude differences between CON and HYP at sensor-level. In contrast, P3b amplitudes in response to target stimuli were significantly reduced during HYP compared to CON. Source analysis of the P3b amplitudes in response to targets indicated that HYP was associated with reduced source activities in occipital and parietal brain areas related to stimulus categorization and attention. We further explored how these brain sources interacted by computing time-frequency effective connectivity between electrodes that best represented frontal, parietal, and occipital sources. This analysis revealed reduced directed information flow from parietal attentional to frontal executive sources during processing of target stimuli. These results provide preliminary evidence that hypnotic suggestions of a visual blockade are associated with a disruption of the coupling within the frontoparietal network implicated in top-down control.

Suggested deafness during hypnosis and simulation of hypnosis compared to a distraction and control condition: A study on subjective experience and cortical brain responses

Hypnosis is a powerful tool to affect the processing and perception of stimuli. Here, we investigated the effects of hypnosis on the processing of auditory stimuli, the time course of event-related-potentials (ERP; N1 and P3b amplitudes) and the activity of cortical sources of the P3b component. Forty-eight participants completed an auditory oddball paradigm composed of standard, distractor, and target stimuli during a hypnosis (HYP), a simulation of hypnosis (SIM), a distraction (DIS), and a control (CON) condition. During HYP, participants were suggested that an earplug would obstruct the perception of tones and during SIM they should pretend being hypnotized and obstructed to hear the tones. During DIS, participants' attention was withdrawn from the tones by focusing participants' attention onto a film. In each condition, subjects were asked to press a key whenever a target stimulus was presented. Behavioral data show that target hit rates and response time became significantly reduced during HYP and SIM and loudness ratings of tones were only reduced during HYP. Distraction from stimuli by the film was less effective in reducing target hit rate and tone loudness. Although, the N1 amplitude was not affected by the experimental conditions, the P3b amplitude was significantly reduced in HYP and SIM compared to CON and DIS. In addition, source localization results indicate that only a small number of neural sources organize the differences of tone processing between the control condition and the distraction, hypnosis, and simulation of hypnosis conditions. These sources belong to brain areas that control the focus of attention, the discrimination of auditory stimuli, and the organization of behavioral responses to targets. Our data confirm that deafness suggestions significantly change auditory processing and perception but complete deafness is hard to achieve during HYP. Therefore, the term 'deafness' may be misleading and should better be replaced by 'hypoacusis'.

Cardiac cycle phases affect auditory-evoked potentials, startle eye blink and pre-motor reaction times in response to acoustic startle stimuli

Startle stimuli evoke lower responses when presented during the early as compared to the late cardiac cycle phase, an effect that has been called 'cardiac modulation of startle' (CMS). The CMS effect may be associated with visceral-afferent neural traffic, as it is reduced in individuals with degeneration of afferent autonomic nerves. The aim of this study was to investigate whether the CMS effect is due a modulation of only early, automatic stages of stimulus processing by baro-afferent neural traffic, or if late stages are also affected. We, therefore, investigated early and late components of auditory-evoked potentials (AEPs) to acoustic startle stimuli (105, 100, 95 dB), which were presented during the early (R-wave +230 ms) or the late cardiac cycle phase (R +530 ms) in two studies. In Study 1, participants were requested to ignore (n = 25) or to respond to the stimuli with button-presses (n = 24). In Study 2 (n = 23), participants were asked to rate the intensity of the stimuli. We found lower EMG startle response magnitudes (both studies) and slower pre-motor reaction times in the early as compared to the late cardiac cycle phase (Study 1). We also observed lower N1 negativity (both studies), but higher P2 (Study 1) and P3 positivity (both studies) in response to stimuli presented in the early cardiac cycle phase. This AEP modulation pattern appears to be specific to the CMS effect, suggesting that early stages of startle stimulus processing are attenuated, whereas late stages are enhanced by baro-afferent neural traffic.

Potential effective elements in combined lifestyle interventions for overweight children

Background

Combined Lifestyle Interventions (CLIs), offered in primary care, aim to prevent childhood overweight/obesity. Combined means the intervention focuses on optimalising nutrition behaviour, physical activity and mental health, provided by a multidisciplinary team. Although the effectiveness of CLIs is still not clear, CLIs are already implemented in daily practice in the Netherlands. These CLIs are not uniformly designed and have variations in protocols to suit the needs of their community. Due to the many different CLIs it is difficult to investigate their effectiveness. To be able to investigate effectiveness of GLIs, we first need to unravel the ’black boxes’ of CLIs and identify their (potential) effective elements.

Methods

First, we carried out a literature study on elements that may contribute to the effectiveness of a GLI (the so called potential elements). Next, we organized an online brainstorm session, where experts such as researchers and paramedics could add or specify potential elements. We made all elements measurable, with help of experts. These elements were incorporated into a tool to check presence of potential elements in CLIs. This tool was tested on reliability by comparing the results of four researchers who assessed protocols of six CLIs.

Results

42 experts participated in the brainstorm session. The literature study and brainstorm session together resulted in 54 potential elements for CLIs for overweight/obese children, categorized in four themes: organization, content, role of parents and role of experts. For all six protocols, a minimum of 85% of the potential elements in the tool have been scored the same by the four assessors.

Conclusions

We developed a reliable tool to determine potential effective elements in a CLI. In future studies, this tool can be used to identify specific elements that are effective in CLIs for overweight/obese children by comparing the tool with health effects of CLIs.

Key messages

We were able to develop a reliable instrument to better analyze the factors that contribute to positive health effects of combined lifestyle interventions for children with overweight or obesity. the developed tool with potential effective elements must be filled in for more CLIs, where after we can find corresponding elements in the most effective CLIs.

Quantification of Phase-Amplitude Coupling in Neuronal Oscillations: Comparison of Phase-Locking Value, Mean Vector Length, Modulation Index, and Generalized-Linear-Modeling-Cross-Frequency-Coupling

Phase-amplitude coupling is a promising construct to study cognitive processes in electroencephalography (EEG) and magnetencephalography (MEG). Due to the novelty of the concept, various measures are used in the literature to calculate phase-amplitude coupling. Here, performance of the three most widely used phase-amplitude coupling measures – phase-locking value (PLV), mean vector length (MVL), and modulation index (MI) – and of the generalized linear modeling cross-frequency coupling (GLM-CFC) method is thoroughly compared with the help of simulated data. We combine advantages of previous reviews and use a realistic data simulation, examine moderators and provide inferential statistics for the comparison of all four indices of phase-amplitude coupling. Our analyses show that all four indices successfully differentiate coupling strength and coupling width when monophasic coupling is present. While the MVL was most sensitive to modulations in coupling strengths and width, only the MI and GLM-CFC can detect biphasic coupling. Coupling values of all four indices were influenced by moderators including data length, signal-to-noise-ratio, and sampling rate when approaching Nyquist frequencies. The MI was most robust against confounding influences of these moderators. Based on our analyses, we recommend the MI for noisy and short data epochs with unknown forms of coupling. For high quality and long data epochs with monophasic coupling and a high signal-to-noise ratio, the use of the MVL is recommended. Ideally, both indices are reported simultaneously for one data set.

Effects of basal and acute cortisol on cognitive flexibility in an emotional task switching paradigm in men

The stress hormone cortisol is assumed to influence cognitive functions. While cortisol-induced alterations of declarative memory in particular are well-investigated, considerably less is known about its influence on executive functions. Moreover, most research has been focused on slow effects, and rapid non-genomic effects have not been studied. The present study sought to investigate the impact of acute cortisol administration as well as basal cortisol levels on cognitive flexibility, a core executive function, within the non-genomic time frame. Thirty-eight healthy male participants were randomly assigned to intravenously receive either cortisol or a placebo before performing a task switching paradigm with happy and angry faces as stimuli. Cortisol levels were measured at six points during the experiment. Additionally, before the experiment, basal cortisol measures for the cortisol awakening response were collected on three consecutive weekdays immediately following awakening and 30, 45, and 60min after. First and foremost, results showed a pronounced impact of acute and basal cortisol on reaction time switch costs, particularly for angry faces. In the placebo group, low basal cortisol was associated with minimal switch costs, whereas high basal cortisol was related to maximal switch costs. In contrast, after cortisol injection, basal cortisol levels showed no impact. These results show that cognitive flexibility-enhancing effects of acute cortisol administration are only seen in men with high basal cortisol levels. This result supports the context dependency of cortisol administration and shows the relevance of taking basal cortisol levels into account.

Distractor inhibition: Evidence from lateralized readiness potentials

The present study investigated distractor inhibition on the level of stimulus representation. In a sequential distractor-to-distractor priming task participants had to respond to target letters flanked by distractor digits. Reaction time and stimulus-locked lateralized readiness potentials (S-LRPs) of probe responses were measured. Distractor-target onset asynchrony was varied. For RTs responses to probe targets were faster in the case of prime-distractor repetition compared to distractor changes indicating distractor inhibition. Benefits in RTs and the latency of S-LRP onsets for distractor repetition were also modulated by distractor-target onset asynchrony. For S-LRPs distractor inhibition was only present with a simultaneous onset of distractors and target. The results confirm previous results indicating inhibitory mechanisms of object-based selective attention on the level of distractor representations.

Effects of the daily consumption of protein enriched bread and protein enriched drinking yoghurt on the total protein intake in older adults in a rehabilitation centre: a single blind randomised controlled trial

OBJECTIVES

To investigate the effects of protein enriched bread and drinking yoghurt, substituting regular products, on the total protein intake and the distribution of protein intake over the day in older adults.

DESIGN

A single blind randomised controlled trial.

SETTING

Rehabilitation centre.

PARTICIPANTS

Older adults (≥ 55 years) admitted to a rehabilitation centre after hospital discharge (n=34).

INTERVENTION

Participants received a high protein diet (protein enriched bread and protein enriched drinking yoghurt; n=17) or a regular diet (regular bread and regular drinking yoghurt; n=17) for three consecutive weeks.

MEASUREMENTS

Total protein intake and protein intake per meal, measured twice weekly over a three weeks period (six measurements per participant).

RESULTS

Compared with controls, patients who received the protein enriched products had a significantly higher protein intake (115.3 g/d vs 72.5 g/d, P<0.001; 1.6 g/kg/d vs 1.1 g/kg/d, P<0.001). The intervention group consumed quantities over the recommended level (25-30 g/meal) during each of the three meals (32.5 g, 30.0 g, 34.8 g/meal), where the control group consumed quantities below the recommended level during breakfast (17.7 g) and lunch (18.4 g).

CONCLUSIONS

The use of protein enriched products, replacing regular products, results in a significant increased daily protein intake in older adults. In addition, the daily consumption of protein enriched products improves protein distribution over the day.

Intranasal insulin increases regional cerebral blood flow in the insular cortex in men independently of cortisol manipulation

Insulin and cortisol play a key role in the regulation of energy homeostasis, appetite, and satiety. Little is known about the action and interaction of both hormones in brain structures controlling food intake and the processing of neurovisceral signals from the gastrointestinal tract. In this study, we assessed the impact of single and combined application of insulin and cortisol on resting regional cerebral blood flow (rCBF) in the insular cortex. After standardized periods of food restriction, 48 male volunteers were randomly assigned to receive either 40 IU intranasal insulin, 30 mg oral cortisol, both, or neither (placebo). Continuous arterial spin labeling (CASL) sequences were acquired before and after pharmacological treatment. We observed a bilateral, locally distinct rCBF increase after insulin administration in the insular cortex and the putamen. Insulin effects on rCBF were present regardless of whether participants had received cortisol or not. Our results indicate that insulin, but not cortisol, affects blood flow in human brain structures involved in the regulation of eating behavior.

The impact of an implicit manipulation of self-esteem on body dissatisfaction

BACKGROUND AND OBJECTIVES

Given the theoretically postulated causal pathway from low self-esteem on body dissatisfaction, the aim of the present study was to experimentally test this linkage before and after a mirror exposure in body dissatisfied females.

METHOD

Thirty-six women with high body dissatisfaction (HBD) and 39 women with low body dissatisfaction (LBD) received either a positive or a negative implicit manipulation of self-esteem and participants' actual body dissatisfaction and negative emotions were assessed (T1). Following that, they underwent a one minute mirror exposure and actual body dissatisfaction and emotions were assessed once more (T2).

RESULTS

In the HBD group no effects of the self-esteem manipulation were found prior to the mirror exposure. However, the negative manipulation of self-esteem led to a significant increase of body dissatisfaction over the course of the mirror exposure. The positive manipulation of self-esteem did not decrease body dissatisfaction over the course of the mirror exposure. No effects of self-esteem on body dissatisfaction were found in the LBD group.

LIMITATIONS

Formal eating disorder diagnosis in study participants was not established. Therefore, the extension of the results to an eating disordered population is recommended.

CONCLUSIONS

The results yield evidence of a close linkage between negative self-esteem and body dissatisfaction in individuals high on body dissatisfaction. Consistent with cognitive theories, this link is only apparent when shape and weight schemas are activated, e.g. by the confrontation with one's own body.

Exogenous cortisol facilitates responses to social threat under high provocation

Stress is one of the most important promoters of aggression. Human and animal studies have found associations between basal and acute levels of the stress hormone cortisol and (abnormal) aggression. Irrespective of the direction of these changes--i.e., increased or decreased aggressive behavior--the results of these studies suggest dramatic alterations in the processing of threat-related social information. Therefore, the effects of cortisol and provocation on social information processing were addressed by the present study. After a placebo-controlled pharmacological manipulation of acute cortisol levels, we exposed healthy individuals to high or low levels of provocation in a competitive aggression paradigm. Influences of cortisol and provocation on emotional face processing were then investigated with reaction times and event-related potentials (ERPs) in an emotional Stroop task. In line with previous results, enhanced early and later positive, posterior ERP components indicated a provocation-induced enhanced relevance for all kinds of social information. Cortisol, however, reduced an early frontocentral bias for angry faces and--despite the provocation-enhancing relevance--led to faster reactions for all facial expressions in highly provoked participants. The results thus support the moderating role of social information processing in the 'vicious circle of stress and aggression'.

Exogenous cortisol enhances aggressive behavior in females, but not in males

The hypothalamic-pituitary-adrenal (HPA) axis plays a major role in the development, elicitation, and enhancement of aggressive behavior in animals. Increasing evidence suggests that this is also true for humans. Here, we report on a study of the role of basal and acute HPA axis activity in a sample of 48 healthy male and female adults. We pharmacologically enhanced cortisol levels and used the Taylor Aggression Paradigm (TAP) to induce and measure aggression (divided into three blocks). Participants either received an oral dose of 20 mg hydrocortisone (cortisol group) or a placebo (placebo group). Half of each group received high or low levels of provocation with the TAP, respectively. Before, we assessed the cortisol awakening response as a trait measure of basal HPA axis activity. Participants in the cortisol group reacted more aggressively in the third block of the TAP compared to the placebo group. Furthermore, gender interacted with treatment: only females, but not males showed enhanced aggressive behavior after cortisol administration. There was no significant difference in males between the placebo and cortisol group. Basal HPA axis activity was negatively related to aggressive behavior, but again only in females and most strongly within the placebo group. This study provides the first evidence for a causal involvement of acute HPA axis activation in aggressive behavior in humans.

Betaine: New Oxidant in the Stickland Reaction and Methanogenesis from Betaine and l-Alanine by a Clostridium sporogenes-Methanosarcina barkeri Coculture

Growing and nongrowing cells of Clostridium sporogenes fermented betaine with l-alanine, l-valine, l-leucine, and l-isoleucine as electron donors in a coupled oxidation-reduction reaction (Stickland reaction). For the substrate combinations betaine and l-alanine and betaine and l-valine balance studies were performed; the results were in agreement with the following fermentation equation: 1 R- CH(NH(2))-COOH + 2 betaine + 2 H(2)O --> 1 R-COOH + 1 CO(2) + 1 NH(3) + 2 trimethylamine + 2 acetate. Growth and production of trimethylamine were strictly dependent on the presence of selenite in the medium. With cell suspensions it was shown that C. sporogenes was unable to catabolize betaine as a single substrate. Betaine, however, was reduced to trimethylamine and acetate under an atmosphere of molecular hydrogen. For the reduction of betaine by cell extracts of C. sporogenes, dimercaptans such as 1,4-dithiothreitol could serve as electron donors. No betaine reductase activity was detected in cells grown in a complex medium without betaine. The pH optimum of betaine reductase was at pH 7.3. When C. sporogenes was cocultured with Methanosarcina barkeri strain Fusaro on betaine together with l-alanine, an almost complete conversion of the two substrates to CH(4), NH(3), and presumably CO(2) was observed.

Influence of aggression on information processing in the emotional stroop task--an event-related potential study

Aggression is a common behavior which has frequently been explained as involving changes in higher level information processing patterns. Although researchers have started only recently to investigate information processing in healthy individuals while engaged in aggressive behavior, the impact of aggression on information processing beyond an aggressive encounter remains unclear. In an event-related potential study, we investigated the processing of facial expressions (happy, angry, fearful, and neutral) in an emotional Stroop task after experimentally provoking aggressive behavior in healthy participants. Compared to a non-provoked group, these individuals showed increased early (P2) and late (P3) positive amplitudes for all facial expressions. For the P2 amplitude, the effect of provocation was greatest for threat-related expressions. Beyond this, a bias for emotional expressions, i.e., slower reaction times to all emotional expressions, was found in provoked participants with a high level of trait anger. These results indicate significant effects of aggression on information processing, which last beyond the aggressive encounter even in healthy participants.

States vs. Traits

Hans-Jürgen Eysenck suggested that introverts are characterized by greater cortical arousal or arousability than extraverts. This prediction was tested in several studies that used the electroencephalogram (EEG) to index cortical activity, but the relations between the EEG measures and Extraversion are typically small. Possibly, situational factors that are external to the laboratory may act as nuisance variables and affect cortical activity, thus, mitigating the relation between arousal or arousability and Extraversion. To test this hypothesis, resting EEG was acquired on four occasions of measurement and Extraversion was assessed by questionnaire. A structural equation model (SEM) represented cortical arousal, arousability, and external factors. This analysis suggested that (1) arousal and arousability are independent factors, (2) external factors only marginally contribute to the variance of the EEG measures, and (3) the relations between the EEG measures and Extraversion were insignificant even if external factors were statistically controlled.

Latent state-trait structure of cerebral blood flow in a resting state

Cerebral blood flow (CBF) is an important parameter for the study of brain function. The present paper examines to what extent CBF in a resting state reflects a stable latent trait and to what extent it reflects phasic situational effects. In 38 healthy subjects resting CBF was measured with continuous arterial spin labeling. Data analyses were performed within the methodological framework of latent state-trait theory, which allows the decomposition of the measured variables into temporally stable differences, occasion-specific fluctuations, and measurement errors. For most of the regions of interest, about 70% of the observed variance in resting CBF was determined by individual differences on a latent physiological trait whereas about 20% of the variance was due to occasion-specific influences. Thus, an aggregation across measurement occasions is not necessary in order to yield a stable physiological trait.

Skull thickness and magnitude of EEG alpha activity

OBJECTIVE

Electroencephalographic (EEG) research on the physiological basis of individual differences in personality or intelligence commonly presumes that between-subjects differences of EEG alpha activity reflect individual differences in brain functions. However, non-functional sources of variance such as individual differences in skull thickness may significantly contribute to individual differences in the magnitude of EEG amplitudes. Aim of the present study was to assess the association between skull thickness and the magnitude of EEG alpha activity.

METHODS

A 58-channel EEG was recorded from 49 subjects in resting states at three occasions of measurement each 5 weeks apart. Skull thickness was assessed with proton-weighted images of the head that were acquired with a 1.5 T magnetic resonance imaging (MRI) scanner.

RESULTS

There was only a mediocre association between EEG alpha power at frontal, temporal, and parietal sites and the thickness of the underlying skull, with correlations ranging between r = -.36 and r = .10.

CONCLUSIONS

This finding suggests that intracranial sources contribute much more variance to the surface EEG than do variations in skull thickness.

SIGNIFICANCE

Skull thickness may be neglected as a potent source of error when individual differences in brain activity are indexed by the magnitude of EEG alpha activity.

Event-Related Brain Potentials of Spider Phobics to Disorder- Relevant, Generally Disgust- and Fear-Inducing Pictures

This investigation covered the disgust and fear reactivity of patients suffering from spider phobia. We analyzed event-related brain potentials and affective responses to pictures depicting spiders, as well as generally fear-inducing, disgust-inducing, and neutral content, and compared them between 18 phobic and 18 nonphobic female participants. The patients rated the spider scenes as more fear- and disgust-inducing than the controls. This was accompanied by enhanced amplitudes of the P300 and the late positive potential (LPP). The other picture types elicited comparable electrocortical and affective responses in both groups. Separate group analyses showed that the patients were characterized by larger ERP positivity (P300, LPP) for phobic than for nonphobic material. Control subjects’ P300s were equally enhanced for spider, disgust and fear pictures relative to neutral scenes. Their LPPs were smaller for spiders compared to disgust and fear. Taken altogether, motivated attention in emotional picture processing is reflected by P300 and LPP modulation.

Associations of the cortisol awakening response (CAR) with cortical activation asymmetry during the course of an exam stress period

The cortisol awakening response (CAR) is a cortisol rise which is distinct from the circadian rise in hypothalamus-pituitary-adrenal (HPA) axis activity before awakening. The CAR has been shown to be related to experiences of stress and negative affect, and activation of neocortical networks has been suggested as a mechanism. Right-sided cortical activation has been shown to be correlated with negative affect, and an association of electroencephalogram (EEG) asymmetry measures with cortisol secretion has been demonstrated. Therefore, we investigated for associations of the CAR with lateralised trait-like cortical activation and with changes in EEG asymmetry during a putative stressful period. We examined 37 undergraduate students before, during, and after an academic exam period. CARs were measured five times and EEG was measured both about 6 weeks before the beginning of the exams and 1 day before an exam. Trait-like interindividual differences in posterior cortical asymmetry were differentially associated with CARs at different measurement occasions. Participants with greater right centroparietal cortical trait activation showed an increased CAR in anticipation of the exams, whereas all other participants showed an increased CAR in response to the exams. Furthermore, EEG measures taken directly before the exam revealed that greater right frontal cortical activation was related to higher cortisol levels after awakening. The results suggest that lateralised cortical activation moderates CAR changes during the course of a stressful period. Lateralised cortical activation may be an important link between the CAR and health-related variables like experiences of stress and negative affect.

Reproducibility of continuous arterial spin labeling perfusion MRI after 7 weeks

BACKGROUND

Continuous arterial spin labeling (CASL) is a non-invasive technique for the measurement of cerebral blood flow (CBF). The aim of the present study was to examine the reproducibility of CASL measurements and its suitability to consistently detect differences between groups, regions, and resting states.

MATERIALS AND METHODS

Thirty-eight healthy subjects (19 female) were examined at 1.5 T on two measurement occasions that were seven weeks apart. Resting CBF was measured with eyes open and eyes closed.

RESULTS

In different regions of interest (ROIs) the repeatability estimates varied between 9 and 19 ml/100 g/min. There were no significant mean differences between occasions in all ROIs (P > 0.05). Greater CBF in the eyes-open than in the eyes-closed state was consistently present in the primary and secondary visual areas. Furthermore, CBF was consistently greater in the right than in the left hemisphere (P < 0.05) and differed between lobes and between arterial territories (P < 0.001). Finally, we consistently observed greater CBF in women than in men (P < 0.001).

CONCLUSION

This study demonstrates the suitability of CASL to consistently detect differences between groups, regions, and resting states even after seven weeks. This emphasizes its usefulness for longitudinal designs.

Attentional set mixing: Effects on target selection and selective response activation

Performance is impaired under set mixing conditions that require frequent readjustments of attentional focus over an extended time period. We compared set repetitions within pure blocks (constant focus of attention) to physically identical repetitions within mixed blocks (changing focus of attention). The aim was to investigate how set mixing affects target selection, indexed by the N2pc component, and selective response activation, indexed by the lateralized readiness potential (LRP). We found that set mixing prolonged the evolution of the N2pc while leaving its onset unaffected. Impaired target selection indicated by the N2pc mixing effect also delayed the start of response planning indexed by an onset delay of the stimulus-locked LRP, explaining one part of the behavioral mixing cost. A larger part of mixing cost could be attributed to a prolonged response planning phase, indexed by an earlier onset of the response-locked LRP.

The latent state-trait structure of resting EEG asymmetry: replication and extension

Recent research on brain asymmetry suggested that resting electroencephalographic (EEG) asymmetry represents a superimposition of a trait-like asymmetry with state-dependent fluctuations. The present study tested this hypothesis and additionally examined individual differences in state changes. A 61-channel EEG was collected from 59 participants in a resting state on three occasions of measurement. An analysis of latent state-trait models suggested that between 40% and 50% of the variance of anterior asymmetry measures was due to individual differences on a latent trait and approximately the same portion of the variance was due to occasion-specific fluctuations. A further analysis of true intraindividual change models indicated that there were large individual differences in intraindividual change over time. These data replicate previous findings and substantiate that resting asymmetry has trait and state properties.

Brain-Electrical Correlates of Negative Location Priming Under Sustained and Transient Attentional Context Conditions

In the present study event-related potentials (ERPs) and event-related lateralizations (ERLs) were analyzed to investigate mechanisms of attentional inhibition engaged when a target stimulus has to be located within a simultaneous target-distractor display. The putative after-effects of inhibition were examined with a prime-probe technique by comparing a “DT” condition (the prime Distractor location becomes the probe Target location) with a control condition (the probe target appears at a previously empty position). The specific aim was to dissociate more “automatic” aspects from more “controlled” aspects associated with the inhibition of distractor locations. To do so, we compared physically identical prime-probe pairs in a sustained-attention context (same target throughout a block) and a transient-attention context (trial-by-trial target specification). Three early ERP/ERL components showed differential effects for DT compared to control: (1) the posterior N1 with a diminished amplitude contralateral to the visual half-field side of target presentation, (2) the N2pc with an enhanced amplitude contralateral to the visual half-field side of target presentation, and (3) the posteriorly distributed N2 with a nonlateralized enhancement for DT compared to control. These effects were differently affected by the context manipulation. While the N2pc effect was observed exclusively under sustained attention, the N1 lateralization effect and the N2 effect were not differentially modulated. The N1 lateralization effect seems consistent with an inhibition-of-return explanation. The N2pc and N2 effects are supposed to be reflecting different aspects of a biased-competition model of distractor inhibition.

The relation of cortical activity and BIS/BAS on the trait level

The behavioral activation system (BAS) and the behavioral inhibition system (BIS) have been proposed to be related to anterior asymmetry in the BIS/BAS model of anterior asymmetry. As an alternative, it may be suggested that behavioral activation comprises approach and withdrawal motivation and that the BAS is related to bilateral frontal trait activity. The aim of the present study was an empirical investigation on the relation between cortical trait activity, BIS and BAS. Data of 59 subjects on four occasions were analyzed. On each occasion, cortical activity was evaluated with resting EEG, and the BIS and BAS strength was assessed with questionnaires. Subjects with greater bilateral frontal cortical activity showed higher BAS scores. The latter result may suggest that behavioral activation comprises approach and withdrawal motivation.

Alteration of cerebral perfusion in patients with idiopathic normal pressure hydrocephalus measured by 3D perfusion weighted magnetic resonance imaging

OBJECTIVE

It is controversial whether alteration of cerebral perfusion plays an important role in the pathophysiology of patients with idiopathic normal pressure hydrocephalus (NPH) and can help to predict the outcome after shunt surgery.

MATERIALS AND METHODS

28 patients with suspected NPH were examined clinically (Homburg Hydrocephalus Scale, walking test, incontinence protocol) and by 3D dynamic susceptibility based perfusion weighted magnetic resonance imaging (PWI-MRI) before and after cerebrospinal fluid release (spinal tap test, STT). The perfusion parameters (negative integral (NI), time of arrival (T0), time to peak (TTP), mean transit time, and the difference TTP-T0 were analysed.

RESULTS

Three different groups of patients were identified preoperatively: In group 1 seven patients showed an increase in the cerebral perfusion and a clinical improvement after STT. The second group (9 patients) also revealed an increase of the cerebral perfusion, but no significant alteration of the clinical assessment could be found. In the third group neither the cerebral perfusion nor the clinical assessment changed. 14 of the 16 patients (group 1 and 2) were examined three months after shunt placement. 11 patients showed a good or excellent result, 2 patients revealed a fair assessment, and only 1 patient had transiently improved. No patient was downgraded after shunting. In the patient group 1 and 2 the NI increased significantly (effect size: 34%), whereas in group 3 no significant alteration of NI was observed.

CONCLUSION

PWI-MRI improves the prediction of outcome after shunt placement in patients with NPH and can offer new insights into the pathophysiology.

Resting Brain Asymmetry and Affective Reactivity

Abstract. Neuropsychological evidence has given rise to alternative models on brain asymmetry in emotion, each with different implications concerning the biological basis of individual differences in affective responses. The present study tested these implications. Resting EEG and self-reported emotions after the presentation of film clips were collected on four occasions of measurement. Subjects with greater right-sided and smaller left-sided cortical activity reported greater intensities of felt emotions after the presentation of films irrespective of valence. This finding is in line with a recent formulation of the right-hemisphere hypothesis, which proposes that the right hemisphere may play an important role in the automatic generation of emotional responses, whereas the left hemisphere may be involved in the control and modulation of emotional reactions.

Motivated executive attention--incentives and the noise-compatibility effect

The motivational context is an important variable in experimental research. The present study investigates the effects of reward and punishment on performance in a noise-compatibility-task [Eriksen, B.A., Eriksen, C.W., 1974. Effects of noise letters upon the identification of a target letter in a nonsearch task. Perception and Psychophysics 16 (1), 143-149]. Flanking distractors indicated a response, which was identical, undefined, or opposite to the appropriate response indicated by the central target. At the beginning of each trial a cue specified positive, negative or no reinforcement in order to elicit three different motivational states: approach, avoidance and a non-reinforced neutral state. Fifty-three subjects (aged 20-27 years) participated. Incompatibility effects on reaction times and percentage errors were analysed as a function of motivational state, as were the effects on two ERPs, the lateralised readines potential (LRP) and the N2. Error and LRP data showed effects of reinforcement only when incompatible distractors were present, which indicates that controlled processing depends on the motivational context. In contrast to previous findings, the N2 was not found to depend on response conflict.

On the selective relation of frontal cortical asymmetry and anger-out versus anger-control

The model of anterior asymmetry and emotion proposes an asymmetric representation of approach and withdrawal systems in the left and right anterior brain regions. Within this framework, 3 different concepts have been related to anterior asymmetry: affective valence, motivational direction, and behavioral activation. The aim of the present study was an empirical investigation into the relation between anterior cortical activity and questionnaire measures related to the 3 dimensions positive versus negative affect, approach versus withdrawal motivation, and behavioral activation versus inhibition. Subjects with relative greater left than right frontal cortical activity showed higher anger-out scores and lower anger-control scores. These results support the hypothesis that motivational direction is related to frontal asymmetry (approach-left and withdrawal-right). Furthermore, subjects with greater bilateral (left and right) frontal cortical activity showed higher behavioral activation scores. This finding might suggest that behavioral activation is related to approach and withdrawal motivation.

The Relationship of Cortical Activity and Personality in a Reinforced Go-Nogo Paradigm

Abstract. The reinforcement sensitivity theory proposes two biological systems for the regulation of emotion, motivation, and personality: the behavioral activation system (BAS), which responds to stimuli related to positive and negative reinforcement, and the behavioral inhibition system (BIS), which responds to conditioned stimuli of punishment and nonreward. Recent findings provided evidence for increased bilateral frontal cortical trait activity in high BAS subjects. We hypothesized that increased bilateral frontal cortical state activity might be found in high BAS subjects in response to stimuli related to positive and negative reinforcement. The cortical reaction of 38 subjects to a reinforced Go-Nogo task was analyzed. A trial consisted of three subsequent stimuli: a cue stimulus (indicating positive, negative, or no reinforcement), an imperative stimulus (Go or Nogo/Inhibition), and a feedback stimulus (success/failure). Alpha power was extracted as a measure of cortical activity. In addition, BAS and BIS were measured using questionnaires. There was an increased cortical activity in response to the cues for reinforcement. High BAS subjects showed an even higher bilateral frontal cortical activity in response to the cues for positive and negative reinforcement as compared to neutral trials. This finding further corroborates a relation of bilateral frontal cortical activity and the BAS, which has now been demonstrated for cortical trait and state activity.