Brain Stimulation and Cognition

Visual, Awareness and Consciousness

This research line focusses on the fundamental question on how visual input is transformed in a percept of the world of which we are consciously aware. This research line utilises Brain Stimulation-induced visual masking and behavioural priming paradigms to determine the functional relevance and chronometry of early visual cortex involvement in conscious vision.

Visual Learning and Memory

The brain's ability to flexibly adapt to its environment, while storing relevant information in both the short- and long-run are crucial to human day-to-day performance. In this research line we investigate the mechanisms of visual learning and memory by means of psychophysical studies, non-invasive brain stimulation, and neuroimaging. For example, in our lab we have psychophysically investigated the accuracy (or fidelity) of visual information being remembered in working memory, and the robustness of such information against interference. The lab also uses TMS to identify the contribution of early visual cortex to the different processes that constitute visual memory (e.g., learning, maintenance, consolidation). Lastly, we use fMRI to investigate the role of attentional mechanisms in visual working memory control.

Visual Spatial Attention

This research line combines fMRI and NIBS to study the neural network effects underlying the control of spatial attention. The fronto-parietal networks involved include both the ventral and dorsal attention network and their dynamic interaction during processes of automatic bottom-up and voluntary top-down attentional control. NIBS is used to specifically interfere with various nodes within these networks during endogenous and exogenous spatial cueing, visual detection, and visual search paradigms. A special focus lies on the functional hemispheric asymmetries in spatial attention control and the respective empirical assessment of the opponent processor and hemispheric balance model. The latter has direct relevance for a possible clinical application for the rehabilitation of spatial neglect and extinction after stroke.

Crossmodal Perception

This research line focuses on two different aspects.  Firstly, we investigate cross-modal associations which underlie and influence multisensory perception. Research includes spatial association such as the mental number line and the SNARC effect, but also synesthesia. Secondly, we investigate the role of oscillations, and specifically the mechanisms of cross-modal phase reset, in enhancing perception at relevant moments in time. Besides investigating the fundamental phase reset mechanisms, we also investigate audio-visual speech. Research methods for these projects include psychophysics, TMS, tDCS, tACS, EEG, and fMRI.

Cognitive Control

In this research line we aim to investigate the role of fronto-cortical brain areas in cognitive control and self-regulation, and how functions supported by this part of the brain relate to human decision making and social behavior. Tasks involving inhibition are often used as a tool to study cognitive control, and we use such tasks in combination with functional Magnetic Resonance Imaging (fMRI) to find a link between response inhibition, and impulsivity and/or aggressive behavior. We furthermore focus on the neural correlates of deception, and on possible neural processes underlying decision making in a neuroeconomical context.
We also investigate how self-regulation can be enhanced through brain stimulation and mental training such as mindfulness meditation. With regard to mindfulness meditation we are particularly interested in the neural mechanisms of how the experience of pain can be modulated through meditation. We are particularly interested in understanding how the neural mechanisms of self-regulation through meditation overlap with or differ from other self-regulation strategies.

Clinical NIBS applications

Noninvasive brain stimulation (NIBS) is capable of manipulating neural activity and network excitability during and beyond the stimulation protocol. This gives rise to its clinical application in various psychiatric, neurological and rehabilitation settings. Our first and most direct clinical application is related to neglect rehabilitation after stroke. It is important to realize that the spontaneous functional reorganization in stroke patients is often maladaptive.

We intend to use NIBS (TMS/TDCS) to suppress / activate different parts within the reorganised activation network in order to restore a more healthy balance between hemispheres and thereby promote behavioural recovery. We will systematically exploit our basic brain research findings in order to initiate, guide, and support brain recovery in stroke and neglect patients, developing a new and powerful tool for the rehabilitative armamentarium. Existing fragmentary evidence indicates that our approach of manipulating brain plasticity (block it when it is maladaptive, stimulate it when it is adaptive) will be highly successful, and offers a realistic perspective for extension to other neurological populations, including amputation or Parkinson patients.

Another clinical application of NIBS that we are investigating is related to Alzheimer’s disease. More specifically, we want to examine the potential of rhythmic brain stimulation (rTMS/tACS) in modulating frontoparietal attention networks in prodromal Alzheimer’s diesase to beneficially modify cognitive symptoms and interfere with disease progression. In our investigations, we focus on mechanisms in frontoparietal attention networks that support working memory performance, and we are currently conducting fMRI studies to explore these mechanisms in healthy controls and patients (see also our research line on Visual Learning & Memory).

Furthermore, we combine NIBS with electromyography (EMG) and electroencephalography (EEG) to characterize aberrant cortical brain plasticity in patient groups. Our aim is to advance our understanding of the neurobiological substrate of neurodegenerative brain processes in Alzheimer’s disease and in diabetes mellitus. Transcranial magnetic stimulation-based measures of cortical plasticity can provide an objective assessment of central nervous system malfunctioning. Eventually, our goal is to develop a reliable assay for an early detection and longitudinal assessment of adverse cortical brain consequences, such as impaired cognitive function, an increase in age-related cognitive decline, and an increased risk of dementia. These measures can eventually serve as early biomarkers for cognitive dysfunctions. Moreover, they can inform about the development and effectiveness of therapies and assess treatment responses in clinical trials.

Human Decision Making

This research line focusses on the underlying neural mechanisms of decision making. We aim to understand how humans decide in complex and social contexts in order to generate valuable contributions to academia and society. This research line utilises Brain Stimulation-induced behavioural modulation to determine the functional relevance of different cortical areas and its involvement with decision making in particular contexts.

This research line is part of the Human Decision and Policy Design research line in partnership with the School of Business and Economics in Maastricht University.

Gender and the brain

This research line focusses on transgender individuals, people whose gender identity is incongruent with their sex assigned at birth. We follow a cohort of transgender individuals as they undergo a sex transition through hormone therapy and gender confirming surgery, and aim to answer questions about (changes in) brain structure, function, and connectivity. One of our main objectives is to identify possible neural correlates underpinning core human characteristics such as gender identity and sexual orientation, as well as to investigate the influence of factors such as sex hormones on the human brain.

Neurobiology of Rhythm

My research is motivated by theories in the neurobiology of language and realised in naturalistic experimental designs, so that the results provide insights about our everyday language experience. I am currently working on my MSCA fellowship project “The NEurobiology of RHYthm: effects of MUSical expertise on natural speech comprehension” NERHYMUS. In this blog I am documenting its progress. This project brings together the Brain Stimulation and Cognition group led by professor Alex Sack, and the BAND-LAB, led by professor Sonja Kotz.

Read this article about the Neurobiology of Rhythm