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Objective : The present studies examined the role of environmental cues in steering people’s dietary decisions in response to food temptations. Based on the notion that people show a tendency to conform to eating standards derived from the eating behavior of others, it was hypothesized that communication of other people’s dietary decisions through environmental cues affect whether and what people eat. Methods : Conformity to environmental cues about food intake was assessed in a local bakery (Study 1, N = 144) and a lab setting (Study 2, N = 65). Participants were unobtrusively presented with a bowl of individually wrapped chocolates. The presence of empty wrappers was manipulated, to indicate whether others who had been in the same situation had or had not eaten. Conformity to environmental cues about food choice was assessed in Study 3 ( N = 90). Participants were required to choose between a healthy and an unhealthy snack. Food wrappers indicated whether previous participants had chosen the healthy or the unhealthy snack. Results : As expected, participants were more likely to take chocolates in the presence of an environmental cue that others did too. Also, participants were more likely to choose a snack that was consistent with the choice of others. Conclusions : Together, these findings support our main hypothesis that environmental cues steer people’s decisions concerning food intake and food choice. Moreover, the results suggest that only small changes in the environment may support healthy eating behavior.

This review discusses neurobiological studies of oppositional defiant disorder and conduct disorder within the conceptual framework of three interrelated mental domains: punishment processing, reward processing, and cognitive control. First, impaired fear conditioning, reduced cortisol reactivity to stress, amygdala hyporeactivity to negative stimuli, and altered serotonin and noradrenaline neurotransmission suggest low punishment sensitivity, which may compromise the ability of children and adolescents to make associations between inappropriate behaviors and forthcoming punishments. Second, sympathetic nervous system hyporeactivity to incentives, low basal heart rate associated with sensation seeking, orbitofrontal cortex hyporeactiviy to reward, and altered dopamine functioning suggest a hyposensitivity to reward. The associated unpleasant emotional state may make children and adolescents prone to sensation-seeking behavior such as rule breaking, delinquency, and substance abuse. Third, impairments in executive functions, especially when motivational factors are involved, as well as structural deficits and impaired functioning of the paralimbic system encompassing the orbitofrontal and cingulate cortex, suggest impaired cognitive control over emotional behavior. In the discussion we argue that more insight into the neurobiology of oppositional defiance disorder and conduct disorder may be obtained by studying these disorders separately and by paying attention to the heterogeneity of symptoms within each disorder.

The ability to work with the symbolic number system, the Arabic numbers, enables humans to perform more complex and accurate calculations than the non-symbolic numerosity system (e.g. arrays of dots). The application of this symbolic system has turned out to be so useful that we have a hard time imagining the world without it. This makes the study of questions about the acquisition and implementation of these processes in the human brain very relevant. In this thesis we therefore investigated the brain processes involved in learning the symbolic number code, and we investigated whether symbolic and non-symbolic numerosities are processed in a similar manner. In addition, we looked at associations between magnitudes and other sensory or cognitive processes in synesthetes. For all these studies we used Stroop-like or priming paradigms, where congruent and incongruent stimuli generally result in different response times, and Event related potentials as a measure for the underlying neural correlates. From the results we can conclude that education plays a major role in the automatisation of symbolic number knowledge. Automatisation means that the child directly and implicitly knows that for instance the number symbol 5 refers to the quantity 5. Children that just learned and automatised the number symbols rely on distinct brain processes than children that have more experience with Arabic numbers. This reliance on different processes is not the result of not yet fully developed cognitive abilities such as attention and working memory instead the brain is presumably not functionally specialized yet. In contrast to the learned symbolic code, humans can already differentiate between non-symbolic numerosities (e.g. groups of dots) at a very young age. Adults rely on the same mechanisms as infants, but are less accurate. This could be due to the larger reliance on the symbolic code with increasing age or to the fact that infants are more prone to numerosity changes (in a task that does not require any responses) than adults are. The non-symbolic numerosity system is suggested to form the basis for the later acquired symbolic system. It has therefore been suggested that these initially distinct numerosities are transcoded into a general magnitude code. Our results underline this notion but also reveal support for an alternative explanation. Similar task related processes such as categorization might also explain this interaction at an early stage of processing. Last, we investigated the interaction between arbitrary associations in grapheme-color synesthetes. Synesthetes experience a color when a grapheme is presented but not the reverse. In our studies we investigated whether colors do activate number processes even though the synesthete is not aware of it (synesthetic number experience). Our results revealed that at the behavioral as well as neuronal level the percept of a color does activate number processes. These processes appeared to be differentially activated for subgroups of synesthetes suggesting that synesthesia is not a heterogeneous phenomenon.

The main question of this thesis was: Can we dissociate multiple body representations in the healthy brain? Patient studies have already shown a dichotomy between the perceptual representation used for localizing a body part (body image) versus the motor representation used for moving a body part (body schema). Here it is shown for the first time that there is also a similar dichotomy in healthy individuals, as revealed by task dependency of bodily illusions. This dissociation between motor and perception tasks relied heavily on the high susceptibility of the body image, versus robustness of the body schema. To investigate whether the impermeability of the motoric body representation was dependent on the type of induction of the bodily illusion, feeling of agency was manipulated. Even active movement during induction could however not affect the body schema. Although motor actions themselves thus seemed robust to illusion, its possible mediating effect on subsequent perceptual body localization judgments was investigated. Results showed a reduction in the strength of the bodily illusion (in this case the rubber hand illusion) that was dependent on the number of movements made with the illuded hand. In other words, the more (new) proprioceptive information was provided about the illuded limb, the smaller the perceived relocation of the illuded hand (as measured by perceptual judgments). However, even though the strength of the illusion on the body image was reduced by preceding motor responses, it did not erase the effect of the illusion completely. Consequently, the main question Can we dissociate multiple body representations in the healthy brain? can be answered affirmatively. However, the main line of reasoning behind the used paradigm - significantly different responses are subserved by dissociable body representations - becomes problematic when significant different responses within the same type of task can be identified. In that case, this line of reasoning runs the risk of dissociating numerous body representations. Therefore a more dynamic angle is suggested, focusing on the question of how these different body representations are created, therefore looking more closely into the weighting of sensory information. Although this approach has its own pitfalls and does not answer the questions of how many body representations there are, it might lead to relevant new insight when combined with other fields of research and paradigms. As an example, a loss of proprioceptive influence on a visual afterimage is for the first time demonstrated, revealing a critical mediating role of feeling of ownership. This shows that studying the integration of proprioceptive and visual information, while keeping in mind the (dynamic) representation of the body and bodily sensations like feeling of ownership, might cast new light on the weighting of multisensory information and consequently on the way the representation of the body is built.

In this review, a conceptualization of oppositional defiant (ODD) and conduct disorder (CD) is presented according to which social learning processes in these disorders are affected by neurocognitive dysfunctions. Neurobiological studies in ODD and CD suggest that the ability to make associations between behaviors and negative and positive consequences is compromised in children and adolescents with these disorders due to reduced sensitivity to punishment and to reward. As a result, both learning of appropriate behavior and learning to refrain from inappropriate behavior may be affected. Likewise, problem solving is impaired due to deficiencies in inhibition, attention, cognitive flexibility, and decision making. Consequently, children and adolescents with ODD and CD may have difficulty learning to optimize their behavior in changeable environments. This conceptualization of ODD and CD is relevant for the improvement of the effect of psychological treatments. Behavioral and cognitive-behavioral interventions that have been shown to be modestly effective in ODD and CD are based on social learning. Limited effectiveness of these interventions may be caused by difficulties in social learning in children and adolescents with ODD and CD. However, although these impairments have been observed at a group level, the deficits in reward processing, punishment processing, and cognitive control mentioned above may not be present to the same extent in each individual with ODD and CD. Therefore, the neurocognitive characteristics in children and adolescents with ODD and CD should be assessed individually. Thus, instead of delivering interventions in a standardized way, these programs may benefit from an individualized approach that depends on the weaknesses and strengths of the neurocognitive characteristics of the child and the adolescent.

It is commonly assumed that the processing of magnitudes occurs independent of modality or notation. Several studies have reported similar behavioural as well as neurophysiological responses to magnitudes presented in distinct modalities as well as notations, but a direct assessment of possible interactions between different modalities and notations, using measures of electro-cortical processing, is lacking. The present study investigates whether the neural activity underlying symbolic and non-symbolic numerosity processing interacts with the neural activity underlying physical size processing before, or proceeds independently until, selective activation of the motor system. We used a symbolic (Arabic numbers) and non-symbolic (arrays of dots) size congruency task and instructed subjects to judge either the numerical or the physical size of the stimuli, while event related potentials were recorded. Longer reaction times as well as a decrease in accuracy were obtained for incongruent compared to congruent trials. For the event related potential data, this congruency effect was also found with respect to the latency of the P3 component reflecting an interaction at the level of stimulus evaluation. Moreover, incongruence delayed the stimulus-locked but not the response-locked lateralized readiness potential. Together these results suggest that, irrespective of notation, the interaction between different magnitudes occurs before selective response activation.

Contains fulltext : 69295.pdf (Publisher’s version ) (Closed access) Although patients with attention-deficit hyperactivity disorder (ADHD) have reported improved driving performance on methylphenidate, limited evidence exists to support an effect of treatment on driving performance and some regions prohibit driving on methylphenidate. A randomized, crossover trial examining the effects of methylphenidate versus placebo on highway driving in 18 adults with ADHD was carried out. After three days of no treatment, patients received either their usual methylphenidate dose (mean: 14.7 mg; range: 10-30 mg) or placebo and then the opposite treatment after a six to seven days washout period. Patients performed a 100 km driving test during normal traffic, 1.5 h after treatment administration. Standard deviation of lateral position (SDLP), the weaving of the car, was the primary outcome measure. Secondary outcome measurements included the standard deviation of speed and patient reports of driving performance. Driving performance was significantly better in the methylphenidate than in the placebo condition, as reflected by the SDLP difference (2.3 cm, 95% CI = 0.8-3.8, P = 0.004). Variation in speed was similar on treatment and on placebo (-0.05 km/h, 95% CI = -0.4 to 0.2, P = 0.70). Among adults with ADHD, with a history of a positive clinical response to methylphenidate, methylphenidate significantly improves driving performance.