J.L. Kenemans

Utrecht University, Utrecht, Utrecht, Netherlands

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Publications (256)662.78 Total impact

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    Full-text · Article · Oct 2015 · Toxicology Letters
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    Christian Janssen · J. Leon Kenemans
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    ABSTRACT: Autonomous cars can take over tasks from the driver and thereby have the potential to free cognitive resources that humans normally allocate to vehicle control. Theoretically, this can create opportunities for the driver to spend time on other tasks such as reading email or making a phone call. However, what happens in situations where the car makes a fatal error? How well does the driver notice this? And how quickly do they respond? In this paper we take the position that a better understanding is needed of the consequences of autonomous vehicles for the human operator.
    Full-text · Conference Paper · Sep 2015
  • J Leon Kenemans
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    ABSTRACT: Inhibition concerns the capacity to suppress on-going response tendencies. Patient data and results from neuro-imaging and magnetic-stimulation studies point to a proactive mechanism involving top-down control signals that potentiate inhibitory sensory-motor connections, depending on whether possibly necessary inhibition is anticipated or not. The proactive mechanism is manifest in stronger sensory-cortex responses to stop signals yielding successful inhibition, observed as a modulation of short-latency human evoked potentials (N1) which may overlap with generic mechanisms for infrequent-event detection. A second, reactive, mechanism would be much more independent of the specific inhibition context, and generalize to situations in which behavioral interrupt is not dictated by task demands but invoked by the salience of task-irrelevant but potentially distracting events. The reactive mechanism is visible in a longer-latency human event-related potential termed frontal P3 (fP3) which is elicited by (successful) stop stimuli and most likely originates from dorsal-medial prefrontal cortex (preSMA), and is dissociated from the reactive mechanism pharmacologically and by individual differences. Implications may arise for more personalized treatments of disorders such as ADHD. Copyright © 2015. Published by Elsevier Ltd.
    No preview · Article · Jun 2015 · Neuroscience & Biobehavioral Reviews
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    ABSTRACT: Preparation for an action, such as grasping an object, is accompanied by an enhanced perception of the object's action-relevant features, such as orientation and size. Cortical feedback from motor planning areas to early visual areas may drive this enhanced perception. To examine whether action preparation modulates activity in early human visual cortex, subjects grasped or pointed to oriented objects while high-resolution fMRI data were acquired. Using multivoxel pattern analysis techniques, we could decode with >70% accuracy whether a grasping or pointing action was prepared from signals in visual cortex as early as V1. These signals in early visual cortex were observed even when actions were only prepared but not executed. Anterior parietal cortex, on the other hand, showed clearest modulation for actual movements. This demonstrates that preparation of actions, even without execution, modulates relevant neuronal populations in early visual areas. Copyright © 2015 the authors 0270-6474/15/356472-09$15.00/0.
    No preview · Article · Apr 2015 · The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
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    Martijn Arns · Ilse Feddema · J Leon Kenemans
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    ABSTRACT: Recent studies suggest a role for sleep and sleep problems in the etiology of attention deficit hyperactivity disorder (ADHD) and a recent model about the working mechanism of sensori-motor rhythm (SMR) neurofeedback, proposed that this intervention normalizes sleep and thus improves ADHD symptoms such as inattention and hyperactivity/impulsivity. In this study we compared adult ADHD patients (N = 19) to a control group (N = 28) and investigated if differences existed in sleep parameters such as Sleep Onset Latency (SOL), Sleep Duration (DUR) and overall reported sleep problems (PSQI) and if there is an association between sleep-parameters and ADHD symptoms. Secondly, in 37 ADHD patients we investigated the effects of SMR and Theta/Beta (TBR) neurofeedback on ADHD symptoms and sleep parameters and if these sleep parameters may mediate treatment outcome to SMR and TBR neurofeedback. In this study we found a clear continuous relationship between self-reported sleep problems (PSQI) and inattention in adults with- and without-ADHD. TBR neurofeedback resulted in a small reduction of SOL, this change in SOL did not correlate with the change in ADHD symptoms and the reduction in SOL only happened in the last half of treatment, suggesting this is an effect of symptom improvement not specifically related to TBR neurofeedback. SMR neurofeedback specifically reduced the SOL and PSQI score, and the change in SOL and change in PSQI correlated strongly with the change in inattention, and the reduction in SOL was achieved in the first half of treatment, suggesting the reduction in SOL mediated treatment response to SMR neurofeedback. Clinically, TBR and SMR neurofeedback had similar effects on symptom reduction in ADHD (inattention and hyperactivity/impulsivity). These results suggest differential effects and different working mechanisms for TBR and SMR neurofeedback in the treatment of ADHD.
    Full-text · Article · Dec 2014 · Frontiers in Human Neuroscience
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    I Heitland · J L Kenemans · K B E Böcker · J M P Baas
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    ABSTRACT: It has long been postulated that exogenous cannabinoids have a profound effect on human cognitive functioning. These cannabinoid effects are thought to depend, at least in parts, on alterations of phase-locking of local field potential neuronal firing. The latter can be measured as activity in the theta frequency band (4Hz-7Hz) by electroencephalogram. Theta oscillations are supposed to serve as a mechanism in neural representations of behaviorally relevant information. However, it remains unknown whether variability in endogenous cannabinoid activity is involved in theta rhythms and therefore, may serve as an individual differences index of human cognitive functioning. To clarify this issue, we recorded resting state EEG activity in 164 healthy human subjects and extracted EEG power across frequency bands (δ, θ, α, β). To assess variability in the endocannabinoid system, two genetic polymorphisms (rs1049353, rs2180619) within the cannabinoid receptor 1 (CB1) were determined in all participants. As expected, we observed significant effects of rs1049353 on EEG power in the theta band at frontal, central and parietal electrode regions. Crucially, these effects were specific for the theta band, with no effects on activity in the other frequency bands. Rs2180619 showed no significant associations with theta power after Bonferroni correction. Taken together, we provide novel evidence in humans showing that genetic variability in the cannabinoid receptor 1 is associated with resting state EEG power in the theta frequency band. This extends prior findings of exogenous cannabinoid effects on theta power to the endogenous cannabinoid system.
    Full-text · Article · Aug 2014 · Behavioural Brain Research
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    ABSTRACT: Background Excessive anticipatory reactions to potential future adversity are observed across a range of anxiety disorders but the neurogenetic mechanisms driving inter-individual differences are largely unknown. We aimed to discover and validate a gene-brain-behaviour pathway by linking presumed genetic risk for anxiety-related psychopathology, key neural activity involved in anxious anticipation and resulting aversive emotional states. Methods The functional neuroanatomy of aversive anticipation was probed through functional magnetic resonance imaging (fMRI) in two independent samples of healthy subjects (N=99 & N=69) and we studied the influence of genetic variance in the serotonin transporter linked polymorphic region (5-HTTLPR). Skin conductance and startle data served as objective psychophysiological indices of the intensity of individuals’ anticipatory responses to potential threat. Results Threat cues signalling risk of future electrical shock activated the dorsomedial prefrontal cortex (dmPFC), anterior insula, bed nucleus of the stria terminalis, thalamus, and midbrain consistently across both samples. Threat-related dmPFC activation was enhanced in 5-HTTLPR short (S) allele carriers in sample 1 and this effect was validated in sample 2. Critically, we show that this region mediates the increase in anticipatory psychophysiological reactions in S-carriers indexed by skin conductance (experiment 1) and startle reactions (experiment 2). Conclusions The converging results from these experiments demonstrate that innate 5-HTTLPR linked variation in dmPFC activity predicts psychophysiological responsivity to pending threats. Our results reveal a neurogenetic pathway mediating inter-individual variability in anticipatory responses to threat and yield a novel mechanistic account for previously reported associations between genetic variability in serotonin transporter function and stress-related psychopathology.
    Full-text · Article · Aug 2014 · Biological Psychiatry
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    ABSTRACT: The cholinergic system is implicated in visuospatial attention and inhibition, however the exact role is still unclear. Two key mechanisms in visuospatial attention are bias and disengagement. Bias refers to neuronal signals that enhance the sensitivity of sensory cortex, disengagement is the decoupling of attention. Previous studies suggest that nicotine affects disengagement and (related) inhibition. However the exact relation is still unknown. Furthermore, nicotine-abstinence in 'healthy' smokers may resemble some anomalies of visuospatial attention and inhibition as seen in Attention Deficit / Hyperactivity Disorder. Smokers and non-smokers (32 male students) performed in a visuospatial cueing (VSC) task, to assess bias and disengagement, and in a stop signal task (SST) to assess inhibition. It was expected that nicotine abstinent smokers compared to non-smokers, would show poor disengagement (indicated by an enhanced validity effect) and poor inhibitory control (indicated by an enhanced SSRT). It was expected that nicotine would positively affect disengagement and inhibition: hypothesis 1 stated that this effect would be larger in smokers as opposed to non-smokers, in terms of smoking related deficient inhibitory control. Hypothesis 2 stated the exact opposite, in terms of drug-tolerance. Results indicated no baseline differences. Nicotine enhanced inhibition more in non-smokers relative to smokers. Integrating the results, nicotine-abstinent smokers do not seem to resemble ADHD patients, and do not seem to smoke in order to self-medicate a pre-existing deficit pertaining to mechanisms of visuospatial attention and inhibition. Nicotine may affect inhibition more in non-smokers relative to smokers, consistent with a drug-tolerance account.
    No preview · Article · Jul 2014 · Neuroscience
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    ABSTRACT: Rationale An increase in the potency of the cannabis cigarettes has been observed over the past three decades. Objectives In this study, we aimed to establish the impact of Δ9-tetrahydrocannabinol (THC) on the rating of subjective effects (intensity and duration of the effects), up to 23 % THC potency (69 mg THC) among recreational users. Methods Recreational users (N = 24) smoked cannabis cigarettes with four doses of THC (placebo 29, 49 and 69 mg of THC) on four separate test days in a randomized, double-blind, placebo-controlled, crossover study. The participants filled in three different questionnaires measuring subjective effects during the exposure up to 8 h post-smoking. The ‘high’ feeling, heart rate, blood pressure and THC serum concentrations were also regularly recorded during these 8 h. Results THC significantly increased the high feeling, dizziness, dry-mouthed feeling, palpitations, impaired memory and concentration, and ‘down’, ‘sedated’ and ‘anxious’ feelings. In addition, THC significantly decreased alertness, contentment and calmness. A cubic relationship was observed between ‘feeling the drug’ and ‘wanting more’. The THC-induced decrease in ‘feeling stimulated’ and increase in anxiety lasted up to 8 h post-smoking. Sedation at 8 h post-smoking was increased by a factor of 5.7 with the highest THC dose, compared to the placebo. Conclusions This study shows a strong effect of cannabis containing high percentages of THC on the rating of subjective effects. Regular users and forensic toxicologists should be aware that the THC-induced increase in ‘feeling sedated’ continues longer with a 69 mg THC dose than with a 29 mg THC dose.
    Full-text · Article · May 2014 · Psychopharmacology
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    ABSTRACT: The role of the cholinergic system in inhibition remains to be elucidated. Nicotine is a potent tool to augment this system, but most studies investigated its effects solely on behaviour. Reference to brain activity is important to specifically identify inhibition-related mechanisms. In the current study the objective was to elucidate the role of the cholinergic system in inhibition. 16 healthy non-smokers performed in a stop task while EEG was recorded. A pre- versus post-treatment, within subjects, placebo controlled, single-blind design was used. It was hypothesized that nicotine would decrease stop-signal reaction time (SSRT) and increase the amplitude of inhibition-related event related potentials, the stop N2 and stop P3. Behavioral measures show nicotine shortened SSRT, but only when pretreatment values were not taken into account. On EEG measures, an enhanced stop P3 under nicotine was found, but only in a subsample sensitive to nicotine based on diastolic blood pressure. The results are indicative of enhanced inhibitory activity possibly reflecting enhanced activation in the superior frontal gyrus.
    No preview · Article · Mar 2014 · Pharmacology Biochemistry and Behavior
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    ABSTRACT: Empathy has been associated with decreased antisocial and increased prosocial behavior. This study examined empathy and prosocial behavior in response to sadness and distress in disruptive behavior disorder (DBD) and attention-deficit hyperactivity disorder (ADHD). Six- and 7-year-old children with DBD (with and without ADHD) (n = 67) and with ADHD only (n = 27) were compared to typically developing children (TD) (n = 37). Parents and teachers rated affective empathy in response to sadness and distress on the Griffith Empathy Measure. Children reported affective empathic ability in response to sad story vignettes. Empathy-induced prosocial behavior in response to sadness and distress was assessed with a computer task, the Interpersonal Response Task (IRT). Compared to TD, children with DBD (with and without ADHD) and those with ADHD only were rated as less empathic by their teachers, but not by their parents. No differences between groups were observed in children who reported affect correspondence. Children with DBD (with and without ADHD) showed less prosocial behavior in response to sadness and distress compared to TD. Children with ADHD only did not differ from TD. An additional analysis comparing all children with a diagnosis to the TD group revealed that the difference in prosocial behavior remained after controlling for ADHD symptoms, but not after controlling for DBD symptoms. These findings of impaired empathy-induced prosocial behavior in response to sadness and distress in young children with DBD suggest that interventions to ameliorate peer relationships may benefit from targeting on increasing prosocial behavior in these children.
    No preview · Article · Mar 2014 · European Child & Adolescent Psychiatry
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    ABSTRACT: In the current study, we investigated the role of noradrenaline in directing (bias) and disengagement of visuospatial attention. We assessed the effect of clonidine on event-related brain potential (ERP) reflections of bias and disengagement in a double-blind placebo-controlled crossover design. An initial dose of 200-µg clonidine was replaced by 100 µg because of marked side effects. Twenty-one healthy male participants performed the visual-spatial cueing task while an electroencephalogram (EEG) was recorded. The behavioral output is the validity effect (benefit of cueing in terms of reaction time to targets). ERP indices for bias were the cue-related early directing attention negativity and late directing attention positivity, and the target-elicited P1 and N1 modulations by validity ('validity-effect'). The ERP index for disengagement was the target-elicited 'late positive deflection' modulation by validity. Behavioral analyses were performed on 16 participants, electrophysiological analyses on a subset (n = 9). Clonidine attenuated the N1 effect, albeit in a subsample. Neither cue-elicited ERPs nor the behavioral validity effect were affected. Clonidine-induced blood pressure reduction was correlated with the reduction of the late positive deflection effect under clonidine. Clonidine attenuated the result of bias in a subsample and may have a modulating effect on disengagement. Copyright © 2013 John Wiley & Sons, Ltd.
    No preview · Article · Feb 2014 · Human Psychopharmacology Clinical and Experimental
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    ABSTRACT: The cholinergic system has been implicated in visuospatial attention but the exact role remains unclear. In visuospatial attention, bias refers to neuronal signals that modulate the sensitivity of sensory cortex, while disengagement refers to the decoupling of attention making reorienting possible. In the current study we investigated the effect of facilitating cholinergic neurotransmission by nicotine (Nicorette Freshmint 2mg, polacrilex chewing gum) on behavioural and electrophysiological indices of bias and disengagement. Sixteen non-smoking participants performed in a Visual Spatial Cueing (VSC) task while EEG was recorded. A randomized, single-blind, crossover design was implemented. Based on the scarce literature, it was expected that nicotine would specifically augment disengagement related processing, especially manifest as an increase of the modulation of the Late Positive Deflection (LPD) by validity of cueing. No effect was expected on bias related components (cue-locked: EDAN, LDAP; target-locked: P1 and N1 modulations). Results show weak indications for a reduction of the reaction time validity effect by nicotine, but only for half of the sample in which the validity effect on the pretest was largest. Nicotine reduced the result of bias as indexed by a reduced P1 modulation by validity, especially in subjects with strong peripheral responses to nicotine. Nicotine did not affect ERP manifestations of the directing of bias (EDAN, LDAP) or disengagement (LPD).
    No preview · Article · Dec 2013 · Behavioural brain research
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    ABSTRACT: Increased theta (4-7Hz)-beta (13-30Hz) power ratio in resting state electroencephalography (EEG) has been associated with risky disadvantageous decision making and with impaired reinforcement learning. However, the specific contributions of theta and beta power in risky decision making remain unclear. The first aim of the present study was to replicate the earlier found relationship and examine the specific contributions of theta and beta power in risky decision making using the Iowa gambling task. The second aim of the study was to examine whether the relation were associated with differences in reward or punishment sensitivity. We replicated the earlier found relationship by showing a positive association between theta/beta ratio and risky decision making. This correlation was mainly driven by theta oscillations. Furthermore, theta power correlated with reward motivated learning, but not with punishment learning. The present findings replicated and extend earlier findings by providing novel insights into the relation between theta-beta ratios and risky decision making. Specifically, findings show that resting-state theta activity is correlated with reinforcement learning, and that this association may be explained by differences in reward sensitivity.
    No preview · Article · Oct 2013 · International journal of psychophysiology: official journal of the International Organization of Psychophysiology
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    Full-text · Article · Oct 2013 · Biological psychiatry
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    ABSTRACT: This study aimed to examine facial mimicry in 6-7 year old children with autism spectrum disorder (ASD) and to explore whether facial mimicry was related to the severity of impairment in social responsiveness. Facial electromyographic activity in response to angry, fearful, sad and happy facial expressions was recorded in twenty 6-7 year old children with ASD and twenty-seven typically developing children. Even though results did not show differences in facial mimicry between children with ASD and typically developing children, impairment in social responsiveness was significantly associated with reduced fear mimicry in children with ASD. These findings demonstrate normal mimicry in children with ASD as compared to healthy controls, but that in children with ASD the degree of impairments in social responsiveness may be associated with reduced sensitivity to distress signals.
    No preview · Article · Jul 2013 · Journal of Autism and Developmental Disorders
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    Full-text · Article · Jul 2013 · Biological psychiatry
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    ABSTRACT: Understanding the neuropharmacology of inhibition is of importance to fuel optimal treatment for disorders such as Attention Deficit / Hyperactivity Disorder. The aim of the present study was to assess the effect of noradrenergic antagonism by clonidine on behavioral-performance and brain-activity indices of inhibition. A placebo-controlled, double-blind, randomized, crossover design was implemented. Male (N=21) participants performed in a visual Stop Signal Task while EEG was recorded under clonidine in one session and under placebo in another. We expected that 100μg clonidine would have a negative effect on EEG indices of inhibition, the stop N2 and stop P3. Furthermore, we expected that clonidine would negatively affect the behavioural measure of inhibition, the Stop Signal Reaction Time (SSRT). Behavioural analyses were performed on data of 17 participants, EEG analyses on a subset (N=13). Performance data suggested that clonidine negatively affected attention (response variability, omissions) without affecting inhibition as indexed by SSRT. Electrophysiological data show that clonidine reduced the stop P3, but not the stop N2, indicating a partial negative effect on inhibition. Results show that it is unlikely that the stop P3 reduction was related to the effect of clonidine on lapses of attention and on peripheral cardiovascular functioning. In conclusion, the current dose of clonidine had a negative effect on attention and a partial effect on inhibitory control. This inhibitory effect was restricted to the dorsal region of the prefrontal cortex (presumably the superior frontal gyrus) as opposed to the ventral region of the prefrontal cortex (right inferior frontal gyrus).
    No preview · Article · Jun 2013 · Pharmacology Biochemistry and Behavior
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    ABSTRACT: : Major depressive disorder has a large impact on patients and society and is projected to be the second greatest global burden of disease by 2020. The brain-derived neurotrophic factor (BDNF) gene is considered to be one of the important factors in the etiology of major depressive disorder. In a recent study, alpha power was found to mediate between BDNF Met and subclinical depressed mood. The current study looked at a population of patients with major depressive disorder (N = 107) to examine the association between the BDNF Val66Met polymorphism, resting state EEG alpha power, and depression severity. For this purpose, repeated-measures analysis of variance, partial correlation, and multiple linear models were used. Results indicated a negative association between parietal-occipital alpha power in the eyes open resting state and depression severity. In addition, Met/Met patients showed lower global absolute alpha power in the eyes closed condition compared with Val-carriers. These findings are in accordance with the previously uncovered pathway between BDNF Val66Met, resting state EEG alpha power, and depression severity. Additional research is needed for the clarification of this tentative pathway and its implication in personalized treatment of major depressive disorder.
    Full-text · Article · Jun 2013 · Journal of clinical neurophysiology: official publication of the American Electroencephalographic Society
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    ABSTRACT: Background / Purpose: Attention-deficit/hyperactivity disorder (ADHD) is the most common psychiatric disorder of childhood with an average worldwide prevalence of 5.3%. Main conclusion: In three datasets (across 49 US States for 2003 and 2007 and across 9 non-US countries) a clear relationship between solar intensity (SI) and the prevalence of ADHD was found, explaining 34-57% of the variance in ADHD prevalence, with high SI having an apparent preventative effect. Controlling for low birth weight, infant mortality, average income (SES), latitude, and other relevant factors did not change these findings. Furthermore, these findings were specific to ADHD, not found for the prevalence of autism spectrum disorders nor major depressive disorder.In this study we found a lower prevalence of ADHD in areas with high SI for both US and non-US data. This association has not been reported before in the literature. The preventative effect of high SI may be related to an improvement of circadian clock disturbances, which have recently been associated with ADHD.
    Full-text · Conference Paper · May 2013

Publication Stats

5k Citations
662.78 Total Impact Points


  • 1988-2015
    • Utrecht University
      • • Division of Experimental Psychology
      • • Division of Psychofarmacology
      • • Division of Pharmacology and Pathofysiology
      Utrecht, Utrecht, Netherlands
  • 2009
    • Netherlands Institute for Neuroscience
      Amsterdamo, North Holland, Netherlands
  • 2004
    • Tilburg University
      Tilburg, North Brabant, Netherlands
  • 2003
    • VU University Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 2002
    • Duke University
      Durham, North Carolina, United States
  • 1991-1995
    • University of Amsterdam
      • Department of Psychonomics
      Amsterdam, North Holland, Netherlands