Maastricht Brain Imaging Center

Maastricht, Netherlands

Maastricht Brain Imaging Center

Maastricht, Netherlands
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Verschuere B.,University of Amsterdam | Verschuere B.,Ghent University | Verschuere B.,Maastricht University | Schuhmann T.,Maastricht University | And 3 more authors.
Frontiers in Human Neuroscience | Year: 2012

Background. By definition, lying involves withholding the truth. Response inhibition may therefore be the cognitive function at the heart of deception. Neuroimaging research has shown that the same brain region that is activated during response inhibition tasks, namely the inferior frontal region, is also activated during deception paradigms. This led to the hypothesis that the inferior frontal region is the neural substrate critically involved in withholding the truth. Objective. We critically examine the functional necessity of the inferior frontal region in withholding the truth during deception. Method. We experimentally manipulated the neural activity level in right inferior frontal sulcus (IFS) by means of neuronavigated continuous theta burst stimulation (cTBS). Individual structural magnetic resonance brain images (MRI) were used to allow precise stimulation in each participant. Twenty-six participants answered autobiographical questions truthfully or deceptively before and after sham and real cTBS. Results. Deception was reliably associated with more errors, longer and more variable response times than truth telling. Despite the potential role of IFS in deception as suggested by neuroimaging data, the cTBS-induced disruption of right IFS did not affect response times or error rates, when compared to sham stimulation. Conclusions. The present findings do not support the hypothesis that the right inferior frontal sulcus is critically involved in deception. © 2012 Verschuere, Schuhmann and Sack.

de Graaf T.A.,Maastricht University | de Graaf T.A.,Maastricht Brain Imaging Center | Koivisto M.,University of Turku | Jacobs C.,Maastricht University | And 4 more authors.
Neuroscience and Biobehavioral Reviews | Year: 2014

Transcranial magnetic stimulation (TMS) continues to deliver on its promise as a research tool. In this review article we focus on the application of TMS to early visual cortex (V1, V2, V3) in studies of visual perception and visual awareness. Depending on the asynchrony between visual stimulus onset and TMS pulse (SOA), TMS can suppress visual perception, allowing one to track the time course of functional relevance (chronometry) of early visual cortex for vision. This procedure has revealed multiple masking effects ('dips'), some consistently (~+100. ms SOA) but others less so (~-50. ms, ~-20. ms, ~+30. ms, ~+200. ms SOA). We review the state of TMS masking research, focusing on the evidence for these multiple dips, the relevance of several experimental parameters to the obtained 'masking curve', and the use of multiple measures of visual processing (subjective measures of awareness, objective discrimination tasks, priming effects). Lastly, we consider possible future directions for this field. We conclude that while TMS masking has yielded many fundamental insights into the chronometry of visual perception already, much remains unknown. Not only are there several temporal windows when TMS pulses can induce visual suppression, even the well-established 'classical' masking effect (~+100. ms) may reflect more than one functional visual process. © 2014 Elsevier Ltd.

Valente G.,Maastricht University | Valente G.,Maastricht Brain Imaging Center | Castellanos A.L.,Cuban Neuroscience Center | Vanacore G.,University of Rome La Sapienza | And 2 more authors.
Human Brain Mapping | Year: 2014

Multivariate regression is increasingly used to study the relation between fMRI spatial activation patterns and experimental stimuli or behavioral ratings. With linear models, informative brain locations are identified by mapping the model coefficients. This is a central aspect in neuroimaging, as it provides the sought-after link between the activity of neuronal populations and subject's perception, cognition or behavior. Here, we show that mapping of informative brain locations using multivariate linear regression (MLR) may lead to incorrect conclusions and interpretations. MLR algorithms for high dimensional data are designed to deal with targets (stimuli or behavioral ratings, in fMRI) separately, and the predictive map of a model integrates information deriving from both neural activity patterns and experimental design. Not accounting explicitly for the presence of other targets whose associated activity spatially overlaps with the one of interest may lead to predictive maps of troublesome interpretation. We propose a new model that can correctly identify the spatial patterns associated with a target while achieving good generalization. For each target, the training is based on an augmented dataset, which includes all remaining targets. The estimation on such datasets produces both maps and interaction coefficients, which are then used to generalize. The proposed formulation is independent of the regression algorithm employed. We validate this model on simulated fMRI data and on a publicly available dataset. Results indicate that our method achieves high spatial sensitivity and good generalization and that it helps disentangle specific neural effects from interaction with predictive maps associated with other targets. © 2013 Wiley Periodicals, Inc.

Luckmann H.C.,Maastricht University | Jacobs H.I.L.,Jülich Research Center | Sack A.T.,Maastricht University | Sack A.T.,Maastricht Brain Imaging Center
Progress in Neurobiology | Year: 2014

Neuroimaging studies have repeatedly reported findings of activation in frontoparietal regions that largely overlap across various cognitive functions. Part of this frontoparietal activation has been interpreted as reflecting attentional mechanisms that can adaptively be directed towards external stimulation as well as internal representations (internal attention), thereby generating the experience of distinct cognitive functions. Nevertheless, findings of material- and task-specific activation in frontal and parietal regions challenge this internal attention hypothesis and have been used to support more modular hypotheses of cognitive function. The aim of this review is twofold: First, it discusses evidence in support of the concept of internal attention and the so-called dorsal attention network (DAN) as its neural source with respect to three cognitive functions (working memory, episodic retrieval, and mental imagery). While DAN activation in all three functions has been separately linked to internal attention, a comprehensive and integrative review has so far been lacking. Second, the review examines findings of material- and process-specific activation within frontoparietal regions, arguing that these results are well compatible with the internal attention account of frontoparietal activation. A new model of cognition is presented, proposing that supposedly different cognitive concepts actually rely on similar attentional network dynamics to maintain, reactivate and newly create internal representations of stimuli in various modalities. Attentional as well as representational mechanisms are assigned to frontal and parietal regions, positing that some regions are implicated in the allocation of attentional resources to perceptual or internal representations, but others are involved in the representational processes themselves. © 2014 Elsevier Ltd.

Sack A.T.,Maastricht University | Sack A.T.,Maastricht Brain Imaging Center
Restorative Neurology and Neuroscience | Year: 2010

Visuospatial processing refers to the spatial perception, recognition and analysis of visual input. Human functional brain imaging studies have consistently revealed the involvement of fronto-parietal brain areas during the execution of visuospatial tasks. Just as the execution of these tasks activates fronto-parietal regions in the healthy brain, lesions to those structures, e.g. after stroke or brain injury, cause specific spatial deficits. The most prominent of these is known as spatial neglect. There are several competing theories on the neural mechanisms underlying spatial neglect. Although each of these theories postulates different underlying physiological mechanisms, they all account in their own way for the fact that the prevalence of neglect is much higher following right hemisphere lesions. This makes it difficult to distinguish between the different models at a behavioural level. Until today, it was impossible to empirically address these matters and to provide direct and conclusive empirical evidence in favour of one of the competing theories of spatial neglect. This review article describes the neural correlates of intact visuospatial processing as revealed by non-invasive functional brain imaging studies. It subsequently focuses on the approach of using the non-invasive brain inference technique of transcranial magnetic brain stimulation (TMS) to transiently and reversibly disrupt neural activity in these visuospatial processing-related brain regions. Using this approach, we can now imitate specific spatial deficits and neglect-like symptoms in healthy volunteers. Mimicking and manipulating the spatial deficits following unilateral brain lesions, under controlled experimental conditions, may allow for the development of new therapeutic interventions for parietal stroke patients suffering from real spatial neglect. The perspective is to use non-invasive brain interference to guide and promote functional recovery on a brain-system level in stroke and neglect patients, based on knowledge directly derived from fundamental brain research in healthy volunteers. © 2010 IOS Press and the authors. All rights reserved.

de Graaf T.A.,Maastricht University | de Graaf T.A.,Maastricht Brain Imaging Center | Gross J.,University of Glasgow | Paterson G.,University of Glasgow | And 5 more authors.
PLoS ONE | Year: 2013

Oscillations are an important aspect of neuronal activity. Interestingly, oscillatory patterns are also observed in behaviour, such as in visual performance measures after the presentation of a brief sensory event in the visual or another modality. These oscillations in visual performance cycle at the typical frequencies of brain rhythms, suggesting that perception may be closely linked to brain oscillations. We here investigated this link for a prominent rhythm of the visual system (the alpha-rhythm, 8-12 Hz) by applying rhythmic visual stimulation at alpha-frequency (10.6 Hz), known to lead to a resonance response in visual areas, and testing its effects on subsequent visual target discrimination. Our data show that rhythmic visual stimulation at 10.6 Hz: 1) has specific behavioral consequences, relative to stimulation at control frequencies (3.9 Hz, 7.1 Hz, 14.2 Hz), and 2) leads to alpha-band oscillations in visual performance measures, that 3) correlate in precise frequency across individuals with resting alpha-rhythms recorded over parieto-occipital areas. The most parsimonious explanation for these three findings is entrainment (phase-locking) of ongoing perceptually relevant alpha-band brain oscillations by rhythmic sensory events. These findings are in line with occipital alpha-oscillations underlying periodicity in visual performance, and suggest that rhythmic stimulation at frequencies of intrinsic brain-rhythms can be used to reveal influences of these rhythms on task performance to study their functional roles. © 2013 de Graaf et al.

Jacobs C.,Maastricht University | Jacobs C.,Maastricht Brain Imaging Center | de Graaf T.A.,Maastricht University | de Graaf T.A.,Maastricht Brain Imaging Center | And 4 more authors.
PLoS ONE | Year: 2012

Transcranial magnetic stimulation (TMS) allows for non-invasive interference with ongoing neural processing. Applied in a chronometric design over early visual cortex (EVC), TMS has proved valuable in indicating at which particular time point EVC must remain unperturbed for (conscious) vision to be established. In the current study, we set out to examine the effect of EVC TMS across a broad range of time points, both before (pre-stimulus) and after (post-stimulus) the onset of symbolic visual stimuli. Behavioral priming studies have shown that the behavioral impact of a visual stimulus can be independent from its conscious perception, suggesting two independent neural signatures. To assess whether TMS-induced suppression of visual awareness can be dissociated from behavioral priming in the temporal domain, we thus implemented three different measures of visual processing, namely performance on a standard visual discrimination task, a subjective rating of stimulus visibility, and a visual priming task. To control for non-neural TMS effects, we performed electrooculographical recordings, placebo TMS (sham), and control site TMS (vertex). Our results suggest that, when considering the appropriate control data, the temporal pattern of EVC TMS disruption on visual discrimination, subjective awareness and behavioral priming are not dissociable. Instead, TMS to EVC disrupts visual perception holistically, both when applied before and after the onset of a visual stimulus. The current findings are discussed in light of their implications on models of visual awareness and (subliminal) priming. © 2012 Jacobs et al.

Sorger B.,Maastricht University | Sorger B.,Maastricht Brain Imaging Center | Reithler J.,Maastricht University | Reithler J.,Maastricht Brain Imaging Center | And 5 more authors.
Current Biology | Year: 2012

Human communication entirely depends on the functional integrity of the neuromuscular system. This is devastatingly illustrated in clinical conditions such as the so-called locked-in syndrome (LIS) [1], in which severely motor-disabled patients become incapable to communicate naturally - while being fully conscious and awake. For the last 20 years, research on motor-independent communication has focused on developing brain-computer interfaces (BCIs) implementing neuroelectric signals for communication (e.g., [2-7]), and BCIs based on electroencephalography (EEG) have already been applied successfully to concerned patients [8-11]. However, not all patients achieve proficiency in EEG-based BCI control [12]. Thus, more recently, hemodynamic brain signals have also been explored for BCI purposes [13-16]. Here, we introduce the first spelling device based on fMRI. By exploiting spatiotemporal characteristics of hemodynamic responses, evoked by performing differently timed mental imagery tasks, our novel letter encoding technique allows translating any freely chosen answer (letter-by-letter) into reliable and differentiable single-trial fMRI signals. Most importantly, automated letter decoding in real time enables back-and-forth communication within a single scanning session. Because the suggested spelling device requires only little effort and pretraining, it is immediately operational and possesses high potential for clinical applications, both in terms of diagnostics and establishing short-term communication with nonresponsive and severely motor-impaired patients. © 2012 Elsevier Ltd.

Jacobs C.,University of Westminster | Jacobs C.,Maastricht University | Jacobs C.,Maastricht Brain Imaging Center | de Graaf T.A.,Maastricht University | And 3 more authors.
Cortex | Year: 2014

Neuroscience research has conventionally focused on how the brain processes sensory information, after the information has been received. Recently, increased interest focuses on how the state of the brain upon receiving inputs determines and biases their subsequent processing and interpretation. Here, we investigated such 'pre-stimulus' brain mechanisms and their relevance for objective and subjective visual processing. Using non-invasive focal brain stimulation [transcranial magnetic stimulation(TMS)] we disrupted spontaneous brain state activity within early visual cortex (EVC) before onset of visual stimulation, at two different pre-stimulus-onset-asynchronies (pSOAs). We found that TMS pulses applied to EVC at either 20msec or 50msec before onset of a simple orientation stimulus both prevented this stimulus from reaching visual awareness. Interestingly, only the TMS-induced visual suppression following TMS at a pSOA of -20msec was retinotopically specific, while TMS at a pSOA of -50msec was not. In a second experiment, we used more complex symbolic arrow stimuli, and found TMS-induced suppression only when disrupting EVC at a pSOA of~-60msec, which, in line with Experiment 1, was not retinotopically specific. Despite this topographic unspecificity of the -50msec effect, the additional control measurements as well as tracking and removal of eye blinks, suggested that also this effect was not the result of an unspecific artifact, and thus neural in origin. We therefore obtained evidence of two distinct neural mechanisms taking place in EVC, both determining whether or not subsequent visual inputs are successfully processed by the human visual system. © 2014 Elsevier Ltd.

Schiltz C.,University of Luxembourg | Dricot L.,Catholic University of Leuven | Goebel R.,Maastricht Brain Imaging Center | Goebel R.,Fc Donders Center For Cognitive Neuroimaging | Rossion B.,Catholic University of Leuven
Journal of Vision | Year: 2010

The perception of a facial feature (e.g., the eyes) is influenced by the position and identity of other features (e.g., the mouth) supporting an integrated, or holistic, representation of individual faces in the human brain. Here we used an event-related adaptation paradigm in functional magnetic resonance imaging (fMRI) to clarify the regions representing faces holistically across the whole brain. In each trial, observers performed the same/different task on top halves (aligned or misaligned) of two faces presented sequentially. For each face pair, the identity of top and bottom parts could be both identical, both different, or different only for the bottom half. The latter manipulation resulted in a composite face illusion, i.e., the erroneous perception of identical top parts as being different, only for aligned faces. Release from adaptation in this condition was found in two sub-areas of the right middle fusiform gyrus responding preferentially to faces, including the "fusiform face area" ("FFA"). There were no significant effects in homologous regions of the left hemisphere or in the inferior occipital cortex. Altogether, these observations indicate that face-sensitive populations of neurons in the right middle fusiform gyrus are optimally tuned to represent individual exemplars of faces holistically. © ARVO.

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