One of the most remarkable aspects of multimodal perception is its coherence. Our conscious perception is unified at any given moment, although we acquire information from diverse channels with... Show moreOne of the most remarkable aspects of multimodal perception is its coherence. Our conscious perception is unified at any given moment, although we acquire information from diverse channels with distinct transduction mechanisms, and process it in different cortical areas not necessarily at the same time and pace. The problem of how the brain integrates the different types of information, which are processed in distinct cortical regions to a unified event, is referred to in literature as the binding problem (Triesman, 1996). The current thesis reflects a gradual inquest in order to reveal different aspects of the binding mechanism across multimodal perception and action. The empirical evidence suggests that feature integration emerges in a graded manner through intra and inter connections within and across modalities and domains, employing general principles (such as temporal overlap of feature activation), which capture the role of attention, salience and dominance among the features and the domains. Also, control processes are important in handling retrieved traces for efficient use. Nevertheless, the binding mechanism does not require a conscious or unified perception and unified perception is not the outcome of feature binding. Show less
One of the most striking features of the brain is that it is modular; it consists of often highly specialized areas. This modular organization requires efficient communication in order to integrate... Show moreOne of the most striking features of the brain is that it is modular; it consists of often highly specialized areas. This modular organization requires efficient communication in order to integrate the information that is represented in distinct brain areas. In my thesis, I studied the neural basis of this communication. With various brain imaging techniques (fMRI, EEG), I found support for the idea that fast communication is omnipresent in the brain and that cognitive control processes can influence this communication. Using a method (neurofeedback) with which subjects were trained to enhance a particular type of brain activity (gamma band activity, or ‘GBA’), I demonstrated that enhanced GBA resulted in an increase of performance on tasks measuring short-term and long-term memory of associated information and fluid intelligence. These findings suggest that GBA underlies the control of associated information, presumably originating from frontal brain regions. 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
After experiencing distraction or temptation, people tend to be better able to cope with future conflict. In cognitive psychology, this is often shown by using sequential conflict tasks, such as... Show moreAfter experiencing distraction or temptation, people tend to be better able to cope with future conflict. In cognitive psychology, this is often shown by using sequential conflict tasks, such as the Stroop task, in which people are required to name the colour of the ink of a word, and ignore the word itself. After presentation of the word “red” in a green colour, for example, people show a smaller conflict effect if later shown the word “green” in a red colour. According to established theory, this is related to the working of executive control: initial conflict triggers increased attention (towards the colour instead of the word) or inhibition (of the word), thus making it easier to cope with repeated conflict. In this dissertation, I argue for a revision of this prominent theory towards a more memory based explanation of executive control. Instead of initial conflict working forward in time to affect the later task, the behavioural and psychophysiological experiments reported here show that the previous task is remembered due to the similarity with the current task, triggering similar modes of behaviour. Show less
