By monitoring ongoing actions and performance outcomes, we are able to detect errors or mismatches between our intentions or predictions. Disturbances in such performance-monitoring processes may... Show moreBy monitoring ongoing actions and performance outcomes, we are able to detect errors or mismatches between our intentions or predictions. Disturbances in such performance-monitoring processes may importantly contribute to impaired adaptive behavior in clinical disorders, such as excessively impulsive behavior in externalizing disorders or excessively rigid or careful behavior in anxiety- and obsessive-compulsive disorders. In daily life, performance monitoring often takes place in a social context, where our actions have consequences not only for ourselves, but also for others. The investigation of (alterations in) such (pro)social performance-monitoring processes may help explain functional and social impairments across a wide range of clinical disorders. In this dissertation, we used various neuroimaging paradigms to examine subclinical and neurochemical influences on performance monitoring when errors had consequences for oneself or others. The studies in this dissertation indicate that neural performance-monitoring correlates are modulated by social, subclinical, and neurochemical factors, including social (responsibility) context, obsessive-compulsive symptoms, ovarian hormones, and pharmacological manipulations of dopamine and oxytocin. These findings have implications for the potential and utility of error-related brain activity as a clinical biomarker or endophenotype, our insight into social symptoms and impairments in obsessive-compulsive disorder, and for our understanding of the neurochemical mechanisms underlying performance monitoring. Show less
Without even realizing, human beings perform extraordinary feats on a daily basis. We navigate an increasingly complicated and demanding world by using our sophisticated ability to override... Show moreWithout even realizing, human beings perform extraordinary feats on a daily basis. We navigate an increasingly complicated and demanding world by using our sophisticated ability to override habitual tendencies. Furthermore, we can meticulously plan, carry out and adapt actions in order to achieve goals that we set for ourselves. This capacity for goal-directed behavior—often considered a hallmark of human excellence over other animals—is commonly referred to as ‘cognitive control’ or ‘executive function’. These are rather vague, typically synonymous concepts that serve more as an umbrella term for many different processes rather than referring to a single, unitary function. Decades of neuropsychological research have been devoted to understanding cognitive control and its component processes, the way it is implemented in the brain, and how we can alter—and possibly improve—its efficacy. These issues have driven the work included in this dissertation. In particular, the research presented in this dissertation concerns itself with the overarching questions of how chemical processes in the brain (dopamine, glutamate, and GABA) enable and affect cognitive control, and how we might non-invasively measure and manipulate these biological underpinnings of goal-directed behavior. Show less
The locus coeruleus (LC) is a nucleus in the brainstem, and projects widely to the forebrain where it releases norepinephrine (NE). Catecholamines such as NE do not have a unitary effect on their... Show moreThe locus coeruleus (LC) is a nucleus in the brainstem, and projects widely to the forebrain where it releases norepinephrine (NE). Catecholamines such as NE do not have a unitary effect on their target neurons, but instead influence the function of other neurotransmitters, a process that is known known as neuromodulation. By virtue of the LC’s wide projection profile and the neuromodulatory properties of NE, the LC-NE system profoundly influences neural firing characteristics and associated cognitive processes. The work presented in this thesis addresses the role of the LC-NE system in various aspects of human cognition, and the modulation of brain state. Show less
The research presented in this thesis focused on the effects of cannabis on mental functions and the brain. Specifically, the investigation aimed at exploring how cannabis affects creative... Show moreThe research presented in this thesis focused on the effects of cannabis on mental functions and the brain. Specifically, the investigation aimed at exploring how cannabis affects creative thinking, awareness of errors, and the neurotransmitter dopamine among regular cannabis users. It was discovered that cannabis does not improve creativity and that it can decrease error awareness and impair dopaminergic functioning. Consequently, these findings allow for a better understanding of the nature of subtle mental impairments among chronic cannabis users. Show less
The studies of this thesis provide empirical evidence that creativity is not a homogeneous concept; rather it reflects the interplay of separate, dissociable processes such as convergent and... Show moreThe studies of this thesis provide empirical evidence that creativity is not a homogeneous concept; rather it reflects the interplay of separate, dissociable processes such as convergent and divergent thinking (e.g., Guilford, 1967). The cognitive mechanism of these two processes is different, but not opposite as assumed by Eysenck (1993). The results suggest that divergent and convergent thinking are both related to dopamine, but to different degrees and in different ways. It was observed that eye-blink rate was predicting creative performance, which provides strong support for approaches that relate creativity to dopamine (Ashby et al., 1999). However, the obtained dissociation calls for a more differentiated approach that distinguishes between convergent and divergent processes and allows for tapping different creativity-dopamine functions. The findings of this thesis also suggest that convergent thinking induces a control state that emphasizes the top-down biasing of creative solutions and/or local competition between them, whereas divergent thinking is associated with reduced top-down control and/or local competition. Taken together, results of four studies presented in this thesis show that convergent and divergent thinking are not necessarily opposite but they are not the same either, and optimal performance in different types of creativity tasks requires different conditions. Show less
Top-down guidance of behavior in a complex and dynamically changing world is often based on information held in working memory. Such guidance serves to bias decision-making processes in directions... Show moreTop-down guidance of behavior in a complex and dynamically changing world is often based on information held in working memory. Such guidance serves to bias decision-making processes in directions consistent with externally set rules or internally maintained intentions. Orthogonal to this goal-driven guidance, decisions may be biased also by stimulus-driven factors, such as the automatic reactivation of episodic associations that accompanied the current stimulus in a previous instance. We investigated whether top-down and bottom-up processes account for variation in context based decision making as measured by the AX-CPT in a behavioral [1] and fMRI study [2]. Moreover, several behavioural studies have indicated that transiently induced positive affect modulates control processes in context-based decision making, generally leading to enhanced flexibility. Using ERPs in a classic AX-CPT, we studied the temporal dynamics of a positive affect induction on control processes in context-based decision making [3]. Additionally, we studied learning the associations between a situation, the response to it, and the outcome of that decision and the effect of basal ganglia modulations on this learning process by means of a Parkinson’s patient study. Studies [1] and [2] pointed out that in decisions with rapidly changing environmental demands, goal-driven preparation is often beneficial but may also hamper performance which can be overcome by applying increased control. Moreover, this top-down bias is regulated more efficiently when the specific stimulus is presented in the same context it was previously associated with, compared to when it is presented in a new and unusual context. Additionally, fMRI study shed light on the way these stimulus-driven performance changes may be represented in the brain. Study [3] showed that a positive affect induction influenced reactive and evaluative components of control (indexed by the N2 elicited by the target, and by the Error-Related Negativity elicited after incorrect responses) in an AX-CPT task, whereas cue-induced preparation and maintenance processes remained largely unaffected (as reflected in the P3b and the Contingent Negative Variation components of the ERP). The patient studies suggest that moderate dopaminergic medication and STN stimulation in Parkinson’s patients [chapter 5,6] both improve learning functions relying on caudate and putamen. However, the improvement induced by dopaminergic medication largely depended on individual patient characteristics. Show less
