Fren T.Y. Smulders

Impulsivity in obese women

In our obesogenic environment, self-control might be necessary in order to prevent overeating. Impulsivity is supposed to make it more difficult to resist the temptation to eat too much and can thereby contribute to overweight. In the present study, the hypotheses is tested that obese individuals are more impulsive. Thirty-one obese and 28 lean women, sampled from the normal population, are tested on a behavioural measure and three self-report measures of impulsivity. The obese women appeared more impulsive on the last part of the behavioural task, but not on the self-report measures. Implications of the results are discussed.

Cephalic phase responses, craving and food intake in normal subjects

Cephalic phase responses (CPRs) are elicited during exposure to food cues. They gear up the body to optimize digestion or they compensate for unwanted changes during a meal. The cue reactivity model of binge eating predicts that CPRs are experienced as craving for food, thereby increasing food intake and playing a role in abnormal eating behaviour. The present experiment was designed to measure CPRs in normal women and to examine its relationship with craving, food intake and restraint. Results show that normal subjects do react to food exposure with changes in heart rate, heart rate variability (HRV), salivation, blood pressure, skin conductance and gastric activity. These CPRs presumably gear up the body and presumably do not reflect compensatory responses. Significant correlations between restraint and blood pressure, between blood pressure and craving, and between craving and food intake were also found. These results are in line with the cue reactivity model and suggest that research into physiological CPRs and craving in the field of eating disorders is valuable.

Cerebral event-related potentials associated with selective attention to color: Developmental changes from childhood to adulthood

Event-related potentials were recorded from 80 participants ranging in age from 7 to 24 years while they attended selectively to stimuli with a specified color (red or blue) in an attempt to detect the occurrence of target stimuli. Color attention effects were identified as frontal selection positivity (FSP; 140-275 ms), selection negativity (SN; 150-300 ms), and N2b (200-450 ms), whereas target detection was reflected in P3b (300-700 ms). There were age-related decreases in the latencies of FSP, N2b, and P3b that paralleled decreases in reaction time and error rates. Also, the SN amplitude increased with advancing age, whereas both N2b and P3b showed changes in scalp topography. These results represent neurophysiological evidence that the efficiency of visual selective processes increases during childhood and adolescence. Developmental growth may take place at both relatively early and late levels of visual selective information processing.

At first sight: How do restrained eaters evaluate high-fat palatable foods?

Two experiments tested the hypothesis that restrained eaters display a greater liking for high-fat palatable foods, than do unrestrained eaters. This hypothesis was tested in the affective priming paradigm and in the extrinsic affective Simon task . Both paradigms were successful in uncovering food likes and dislikes, and both showed that participants were able to evaluate the palatability of foods relatively automatically. However, contrary to the hypothesis, food likes were not substantially affected by fat content, nor were they affected by restraint-status. Restrained and unrestrained eaters may like high-fat palatable foods to the same extent, but may differ in their craving for these foods.

Exposure to binge food in bulimia nervosa: finger pulse amplitude as a potential measure of urge to eat and predictor of food intake

The conditioning model of binge eating states that cues such as the sight, smell and taste of binge food prepare the bingers body for the intake of large amounts of food. The bodily preparations are supposed to be felt as an almost irresistible urge to binge. In the present study, the validity of the model was tested. Clinical binge eaters (bulimia nervosa patients) and healthy control participants were exposed to their most favourite food and physiological responding was measured. As predicted, the exposure increased physiological responding and led to more intense urge to eat, but no significant differences between the bulimics and the normal controls were found. For both groups, increased urge to eat appeared to be related to finger pulse amplitude (FPA), and both the FPA and the self-reported urge to eat predicted increased caloric intake during a subsequent taste test. It is concluded that changes in FPA might reflect classically conditioned bodily responses that prepare for eating.

The effect of visual sexual content on the event-related potential

In the present study we investigated the effect of emotional valence and arousal value of non-erotic visual stimuli on event-related potentials. We also directly compared the effects of erotic and non-erotic stimuli of comparable valence and arousal levels. Sixteen sexually functional heterosexual males rated 150 computer screen pictures, selected from the International Affective Picture System, representing five stimulus types differing along dimensions of emotional valence and arousal, and erotic vs. non-erotic content. A positive deflection of the ERP between 300 and 500 ms after stimulus onset (P300) was found to be sensitive to stimulus differences, with positive valence and high arousal resulting in larger P300. Furthermore, the positive slow wave (PSW) between 500 and 750 ms revealed additive effects of valence and arousal value. High arousal and positive valence of the stimuli resulted in larger PSW. Importantly, an interaction effect was absent here. In addition, sexual content led to a larger P300 and PSW than expected on the basis of a mere additive contribution of high arousal and positive valence.

Effect of Cue Exposure, Urge to Smoke, and Nicotine Deprivation on Cognitive Performance in Smokers

The primary aim of this investigation was to test the hypothesis that the urge to smoke interferes directly with cognitive performance. Fifty-four smokers were randomly assigned to 1 of 3 groups: (a). ad lib, (b). deprived, or (c). nicotine patch. Participants rated their urge to smoke on continuous visual analogue scales. Cognitive performance was determined by measuring reaction times (RTs) on a Sternberg task. The deprived group reported a higher urge and had longer RTs than the ad lib group when exposed to smoking-related cues. However, the nicotine patch group reported a higher urge in the absence of longer RTs. The results indicated that nicotine deprivation affects cognitive performance and that the urge to smoke only partially mediated RTs.

The functional role of individual-alpha based frontal asymmetry in stress responding

Asymmetry in frontal electrical activity has been suggested to index tendencies in affective responding and thus may be associated with hormonal stress responses. To assess the functional role of frontal asymmetry (FA) in stress, we measured FA at rest and following exposure to acute stress induced with the Maastricht Acute Stress Task (MAST; N=70) in the standard 8-13Hz band as well as based on individual alpha frequency (IAF) band. IAF-based resting FAF4-F3 was associated with the stress-induced neuroendocrine response, such that left individual frontal activity predicted smaller total cortisol increases in response to the MAST. Like previous studies, we found resting left-sided FAF8-F7 to predict trait behavioural activation measured with the BIS/BAS scales. FA remained unaffected by stress-induced cortisol response. These findings suggest that individual FA might reflect a trait-like characteristic that moderates the stress response. Our results underscore the utility of IAF in studying individual differences in stress responding.

Recording of Swallowing Events Using Electromyography as a Non-invasive Measurement of Salivation

The present study examined whether the measurement of swallowing activity by electromyography (EMG) provides a sensitive and valid method for the assessment of the amount of saliva secreted. Thirteen subjects tasted lemon juice and water, and smelled lasagna and hay, while the amount of saliva, measured with the aid of cotton dental rolls, was compared with the number of peaks in the EMG activity of the musculus digastricus. Swallowing indeed differentiated between the stimuli and the correlation between the number of swallows and the amount of saliva was significant. The present data suggest that monitoring the swallowing movement using EMG might be a sensitive, valid and reliable method for the measurement of salivary flow. The use is recommended for the measurement of salivation when a simple and non-invasive method is needed.

Extracting Concealed Information from Groups

Abstract:  Lie detection procedures are typically aimed at determining guilt or innocence of a single suspect. Serious security threats, however, often involve groups, such as terrorist networks or criminal organizations. In this report, we describe a variant of the skin conductance‐based Concealed Information Test (CIT) that allows for the extraction of critical information from such groups. Twelve participants were given information about an upcoming (mock) terrorist attack, with specific instructions not to reveal this information to anyone. Next, each subject was subjected to a CIT, with questions pertaining to the details of the attack. Results showed that for every question, the average skin conductance response to the correct answer option differed significantly (p < 0.05) from those to all other options. These results show that the information about the upcoming attack could be extracted from the group of terror suspects as a whole.