Peter Dechent

YNIMG Journal 2025 Journal Article

Atrial fibrillation reduces CSF flow dynamics. A multimodal MRI study

• Sabine Hofer
• Marlena Schnieder
• Leonie Polster
• Peter Dechent
• Mathias Bähr

BACKGROUND: Atrial fibrillation (AF), the most common cardiac arrhythmia, is linked to cognitive impairment and dementia but the mechanisms behind are not understood. In the brain, the glymphatic system (GS) is crucial for clearing waste from the brain through rhythmic flow of CSF. In order to ensure optimal GS function a synchrony between the dynamics of blood flow and cerebrospinal fluid (CSF) flow is necessary. Thus, our aim was to examine GS function in AF using a fast multimodal imaging protocol in a single MRI session. METHODS: We measured 13 healthy volunteers and 13 patients with AF, using a 3T MRI system. To capture CSF and blood flow, real-time phase-contrast flow MRI was employed in the aqueduct, internal carotid artery, and jugular vein. T1-weighted imaging segmented brain tissue and ventricular size, while fast T1Flash examined tissue anatomy. EPI diffusion assessed fluid motion along the perivascular space, and artefact-free STEAM diffusion described whole-brain CSF dynamics. RESULTS: The results showed that AF patients had reduced and aperiodic CSF flow compared to healthy controls, with lower flow volume and less periodic flow patterns. Anatomical parameters such as brain volume, ventricular size, white matter integrity, and perivascular fluid flow showed no significant differences between the groups. CONCLUSIONS: These findings suggest that AF changes CSF dynamics and disrupts its rhythmicity, likely impairing GS function.

YNIMG Journal 2024 Journal Article

Neural correlates of sensorimotor adaptation: Thalamic contributions to learning from sensory prediction error

• Shirin Mahdavi
• Axel Lindner
• Carsten Schmidt-Samoa
• Anna-Lena Müsch
• Peter Dechent
• Melanie Wilke

Understanding the neural mechanism of sensorimotor adaptation is essential to reveal how the brain learns from errors, a process driven by sensory prediction errors. While the previous literature has focused on cortical and cerebellar changes, the involvement of the thalamus has received less attention. This functional magnetic resonance imaging study aims to explore the neural substrates of learning from sensory prediction errors with an additional focus on the thalamus. Thirty participants adapted their goal-directed reaches to visual feedback rotations introduced in a step-wise manner, while reporting their predicted visual consequences of their movements intermittently. We found that adaptation initially engaged the cerebellum and fronto-parietal cortical regions, which persisted as adaptation progressed. By the end of adaptation, additional regions within the fronto-parietal cortex and medial pulvinar of the thalamus were recruited. Another finding was the involvement of bilateral medial dorsal nuclei, which showed a positive correlation with the level of motor adaptation. Notably, the gradual shift in the predicted hand movement consequences was associated with activity in the cerebellum, motor cortex and thalamus (ventral lateral, medial dorsal, and medial pulvinar). Our study presents clear evidence for an involvement of the thalamus, both classical 'motor' and higher-order nuclei, in error-based motor learning.

YNICL Journal 2023 Journal Article

Multi-spectral diffusion MRI mega-analysis in genetic generalized epilepsy: Relation to outcomes

• Barbara A.K. Kreilkamp
• Christina Stier
• Erik H. Rauf
• Pascal Martin
• Silke Ethofer
• Holger Lerche
• Raviteja Kotikalapudi
• Justus Marquetand

BACKGROUND AND OBJECTIVES: Genetic generalized epilepsy (GGE) is the most common form of generalized epilepsy. Although individual patients with GGE typically present without structural alterations, group differences have been demonstrated in GGE and some GGE subtypes like juvenile myoclonic epilepsy (GGE-JME). Previous studies usually involved only small cohorts from single centers and therefore could not assess imaging markers of multiple GGE subtypes. METHODS: We performed a diffusion MRI mega-analysis in 192 participants consisting of 126 controls and 66 patients with GGE from four different cohorts and two different epilepsy centers. We applied whole-brain multi-site harmonization and analyzed fractional anisotropy (FA), as well as mean, radial and axial diffusivity (MD/RD/AD) to assess differences between controls, patients with GGE and the common GGE subtypes, i.e. GGE with generalized tonic-clonic seizures only (GGE-GTCS), GGE-JME and absence epilepsy (GGE-AE). We also analyzed relationships with patients' response to anti-seizure-medication (ASM). RESULTS: Relative to controls, we identified decreased anisotropy and increased RD in patients with GGE. We found no significant effects of disease duration, age of onset or seizure frequency on diffusion metrics. Patients with JME had increased MD and RD when compared to controls, while patients with GGE-GTCS showed decreased MD/AD when compared to controls. Compared to patients with GGE-AE, patients with GGE-GTCS had lower AD/MD. Compared to patients with GGE-GTCS, patients with GGE-JME had higher MD/RD and AD. Moreover, we found lower FA in patients with refractory when compared to patients with non-refractory GGE in the right cortico-spinal tract, but no significant differences in patients with active versus controlled epilepsy. DISCUSSION: We provide evidence that clinically defined GGE as a whole and GGE-subtypes harbor marked microstructural differences detectable with diffusion MRI. Moreover, we found an association between microstructural changes and treatment resistance. Our findings have important implications for future full-resolution multi-site studies when assessing GGE, its subtypes and ASM refractoriness.

YNICL Journal 2021 Journal Article

Association between composite scores of domain-specific cognitive functions and regional patterns of atrophy and functional connectivity in the Alzheimer’s disease spectrum

• Chimezie O. Amaefule
• Martin Dyrba
• Steffen Wolfsgruber
• Alexandra Polcher
• Anja Schneider
• Klaus Fliessbach
• Annika Spottke
• Dix Meiberth

BACKGROUND: Cognitive decline has been found to be associated with gray matter atrophy and disruption of functional neural networks in Alzheimer's disease (AD) in structural and functional imaging (fMRI) studies. Most previous studies have used single test scores of cognitive performance among monocentric cohorts. However, cognitive domain composite scores could be more reliable than single test scores due to the reduction of measurement error. Adopting a multicentric resting state fMRI (rs-fMRI) and cognitive domain approach, we provide a comprehensive description of the structural and functional correlates of the key cognitive domains of AD. METHOD: We analyzed MRI, rs-fMRI and cognitive domain score data of 490 participants from an interim baseline release of the multicenter DELCODE study cohort, including 54 people with AD, 86 with Mild Cognitive Impairment (MCI), 175 with Subjective Cognitive Decline (SCD), and 175 Healthy Controls (HC) in the AD-spectrum. Resulting cognitive domain composite scores (executive, visuo-spatial, memory, working memory and language) from the DELCODE neuropsychological battery (DELCODE-NP), were previously derived using confirmatory factor analysis. Statistical analyses examined the differences between diagnostic groups, and the association of composite scores with regional atrophy and network-specific functional connectivity among the patient subgroup of SCD, MCI and AD. RESULT: Cognitive performance, atrophy patterns and functional connectivity significantly differed between diagnostic groups in the AD-spectrum. Regional gray matter atrophy was positively associated with visuospatial and other cognitive impairments among the patient subgroup in the AD-spectrum. Except for the visual network, patterns of network-specific resting-state functional connectivity were positively associated with distinct cognitive impairments among the patient subgroup in the AD-spectrum. CONCLUSION: Consistent associations between cognitive domain scores and both regional atrophy and network-specific functional connectivity (except for the visual network), support the utility of a multicentric and cognitive domain approach towards explicating the relationship between imaging markers and cognition in the AD-spectrum.

YNIMG Journal 2021 Journal Article

Fluency shaping increases integration of the command-to-execution and the auditory-to-motor pathways in persistent developmental stuttering

• Alexandra Korzeczek
• Annika Primaßin
• Alexander Wolff von Gudenberg
• Peter Dechent
• Walter Paulus
• Martin Sommer
• Nicole E. Neef

Fluency-shaping enhances the speech fluency of persons who stutter, yet underlying conditions and neuroplasticity-related mechanisms are largely unknown. While speech production-related brain activity in stuttering is well studied, it is unclear whether therapy repairs networks of altered sensorimotor integration, imprecise neural timing and sequencing, faulty error monitoring, or insufficient speech planning. Here, we tested the impact of one-year fluency-shaping therapy on resting-state fMRI connectivity within sets of brain regions subserving these speech functions. We analyzed resting-state data of 22 patients who participated in a fluency-shaping program, 18 patients not participating in therapy, and 28 fluent control participants, measured one year apart. Improved fluency was accompanied by an increased connectivity within the sensorimotor integration network. Specifically, two connections were strengthened; the left inferior frontal gyrus showed increased connectivity with the precentral gyrus at the representation of the left laryngeal motor cortex, and the left inferior frontal gyrus showed increased connectivity with the right superior temporal gyrus. Thus, therapy-associated neural remediation was based on a strengthened integration of the command-to-execution pathway together with an increased auditory-to-motor coupling. Since we investigated task-free brain activity, we assume that our findings are not biased to network activity involved in compensation but represent long-term focal neuroplasticity effects.

YNICL Journal 2020 Journal Article

Multimodal MRI analysis of basal forebrain structure and function across the Alzheimer’s disease spectrum

• Meret Herdick
• Martin Dyrba
• Hans-Christian J. Fritz
• Slawek Altenstein
• Tommaso Ballarini
• Frederic Brosseron
• Katharina Buerger
• Arda Can Cetindag

BACKGROUND: Dysfunction of the cholinergic basal forebrain (cBF) is associated with cognitive decline in Alzheimer's disease (AD). Multimodal MRI allows for the investigation of cBF changes in-vivo. In this study we assessed alterations in cBF functional connectivity (FC), mean diffusivity (MD), and volume across the spectrum of AD. We further assessed effects of amyloid pathology on these changes. METHODS: Participants included healthy controls, and subjects with subjective cognitive decline (SCD), mild cognitive impairment (MCI), or AD dementia (ADD) from the multicenter DELCODE study. Resting-state functional MRI (rs-fMRI) and structural MRI data was available for 477 subjects, and a subset of 243 subjects also had DTI data available. Differences between diagnostic groups were investigated using seed-based FC, volumetric, and MD analyses of functionally defined anterior (a-cBF) and posterior (p-cBF) subdivisions of a cytoarchitectonic cBF region-of-interest. In complementary analyses groups were stratified according to amyloid status based on CSF Aβ42/40 biomarker data, which was available in a subset of participants. RESULTS: a-cBF and p-cBF subdivisions showed regional FC profiles that were highly consistent with previously reported patterns, but there were only minimal differences between diagnostic groups. Compared to controls, cBF volumes and MD were significantly different in MCI and ADD but not in SCD. The Aβ42/40 stratified analyses largely matched these results. CONCLUSIONS: We reproduced subregion-specific FC profiles of the cBF in a clinical sample spanning the AD spectrum. At least in this multicentric cohort study, cBF-FC did not show marked changes along the AD spectrum, and multimodal MRI did not provide more sensitive measures of AD-related cBF changes compared to volumetry.

YNIMG Journal 2016 Journal Article

Transcranial alternating current stimulation modulates spontaneous low frequency fluctuations as measured with fMRI

• Yuranny Cabral-Calderin
• Kathleen A. Williams
• Alexander Opitz
• Peter Dechent
• Melanie Wilke

Transcranial alternating current stimulation (tACS) is a promising tool for modulating brain oscillations. Combining tACS with functional magnetic resonance imaging (fMRI), we recently showed that tACS applied over the occipital cortex did not exert its strongest effect on regions below the electrodes, but mainly on more distant fronto-parietal regions. Theoretically, this effect could be explained by tACS-induced modulation of functional connectivity between directly stimulated areas and more distant but anatomically and functionally connected regions. In the present study, we aimed to characterize the effect of tACS on low frequency fMRI signal fluctuations. We employed simultaneous fMRI-tACS in 20 subjects during resting state (eyes open with central fixation for ~8min). Subjects received tACS at different frequencies (10, 16, 40Hz) and with different electrode montages (Cz-Oz, P5–P6) previously used in behavioral studies. Electric field simulations showed that tACS over Cz-Oz directly stimulates occipital cortex, while tACS over P5–P6 primarily targets parietal cortices. Group-level simulation-based functional connectivity maps for Cz-Oz and P5–P6 resembled the visual and fronto-parietal control resting-state networks, respectively. The effects of tACS were frequency and partly electrode montage dependent. In regions where frequency-dependent effects of tACS were observed, 10 and 40Hz tACS generally induced opposite effects. Most tACS effects on functional connectivity were observed between, as opposed to within, resting-state networks. The left fronto-parietal control network showed the most extensive frequency-dependent modulation in functional connectivity, mainly with occipito-parietal regions, where 10Hz tACS increased and 40Hz tACS decreased correlation values. Taken together, our results show that tACS modulates local spontaneous low frequency fluctuations and their correlations with more distant regions, which should be taken into account when interpreting tACS effects on brain function.

YNIMG Journal 2014 Journal Article

Imaging artifacts induced by electrical stimulation during conventional fMRI of the brain

• Andrea Antal
• Marom Bikson
• Abhishek Datta
• Belen Lafon
• Peter Dechent
• Lucas C. Parra
• Walter Paulus

Functional magnetic resonance imaging (fMRI) of brain activation during transcranial electrical stimulation is used to provide insight into the mechanisms of neuromodulation and targeting of particular brain structures. However, the passage of current through the body may interfere with the concurrent detection of blood oxygen level-dependent (BOLD) signal, which is sensitive to local magnetic fields. To test whether these currents can affect concurrent fMRI recordings we performed conventional gradient echo-planar imaging (EPI) during transcranial direct current (tDCS) and alternating current stimulation (tACS) on two post-mortem subjects. tDCS induced signals in both superficial and deep structures. The signal was specific to the electrode montage, with the strongest signal near cerebrospinal fluid (CSF) and scalp. The direction of change relative to non-stimulation reversed with tDCS stimulation polarity. For tACS there was no net effect of the MRI signal. High-resolution individualized modeling of current flow and induced static magnetic fields suggested a strong coincidence of the change EPI signal with regions of large current density and magnetic fields. These initial results indicate that (1) fMRI studies of tDCS must consider this potentially confounding interference from current flow and (2) conventional MRI imaging protocols can be potentially used to measure current flow during transcranial electrical stimulation. The optimization of current measurement and artifact correction techniques, including consideration of the underlying physics, remains to be addressed.

YNIMG Journal 2013 Journal Article

Effects of age on negative BOLD signal changes in the primary somatosensory cortex

• Sonja Gröschel
• Jan Martin Sohns
• Carsten Schmidt-Samoa
• Jürgen Baudewig
• Lars Becker
• Peter Dechent
• Andreas Kastrup

In addition to a contralateral activation of the primary and secondary somatosensory cortices, peripheral sensory stimulation has been shown to elicit responses in the ipsilateral primary somatosensory cortex (SI). In particular, evidence is accumulating that processes of interhemispheric inhibition as depicted by negative blood oxygenation level dependent (BOLD) signal changes are part of somatosensory processes. The aim of the study was to analyze age-related differences in patterns of cerebral activation in the somatosensory system in general and processes of interhemispheric inhibition in particular. For this, a functional magnetic resonance imaging (fMRI) study was performed including 14 younger (mean age 23. 3±0. 9years) and 13 healthy older participants (mean age 73. 2±8. 3years). All subjects were scanned during peripheral electrical median nerve stimulation (40Hz) to obtain BOLD responses in the somatosensory system. Moreover, the individual current perception threshold (CPT) as a quantitative measure of sensory function was determined in a separate psychophysical testing. Significant increases in BOLD signal across the entire group could be measured within the contralateral SI, in the bilateral secondary somatosensory cortex (SII), the contralateral supplementary motor area and the insula. Negative BOLD signal changes were delineated in ipsilateral SI/MI as well as in the ipsilateral thalamus and basal ganglia. After comparing the two groups, only the cortical deactivation in ipsilateral SI in the early stimulation phase as well as the activation in contralateral SI and SII in the late stimulation block remained as statistically significant differences between the two groups. The psychophysical experiments yielded a significant age-dependent effect of CPT change with less difference in the older group which is in line with the significantly smaller alterations in maximal BOLD signal change in the contra- and ipsilateral SI found between the two groups. Healthy aging seems to be associated with a decrease in intracerebral inhibition as reflected by smaller negative BOLD signal changes during fMRI tasks. This finding could constitute an important link between age-related neurophysiological changes and behavioral alterations in humans.

YNICL Journal 2012 Journal Article

Egocentric spatial learning in schizophrenia investigated with functional magnetic resonance imaging

• Jakob Siemerkus
• Eva Irle
• Carsten Schmidt-Samoa
• Peter Dechent
• Godehard Weniger

Psychotic symptoms in schizophrenia are related to disturbed self-recognition and to disturbed experience of agency. Possibly, these impairments contribute to first-person large-scale egocentric learning deficits. Sixteen inpatients with schizophrenia and 16 matched healthy comparison subjects underwent functional magnetic resonance imaging (fMRI) while finding their way in a virtual maze. The virtual maze presented a first-person view, lacked any topographical landmarks and afforded egocentric navigation strategies. The participants with schizophrenia showed impaired performance in the virtual maze when compared with controls, and showed a similar but weaker pattern of activity changes during egocentric learning when compared with controls. Especially the activity of task-relevant brain regions (precuneus and posterior cingulate and retrosplenial cortex) differed from that of controls across all trials of the task. Activity increase within the right-sided precuneus was related to worse virtual maze performance and to stronger positive symptoms in participants with schizophrenia. We suggest that psychotic symptoms in schizophrenia are related to aberrant neural activity within the precuneus. Possibly, first-person large-scale egocentric navigation and learning designs may be a feasible tool for the assessment and treatment of cognitive deficits related to self-recognition in patients with schizophrenia.

YNIMG Journal 2011 Journal Article

A gateway system in rostral PFC? Evidence from biasing attention to perceptual information and internal representations

• Ilona Henseler
• Sebastian Krüger
• Peter Dechent
• Oliver Gruber

Some situations require us to be highly sensitive to information in the environment, whereas in other situations, our attention is mainly focused on internally represented information. It has been hypothesized that a control system located in the rostral prefrontal cortex (PFC) acts as gateway between these two forms of attention. Here, we examined the neural underpinnings of this ‘gateway system’ using fMRI and functional connectivity analysis. We designed different tasks, in which the demands for attending to external or internal information were manipulated, and tested 1) whether there is a functional specialization within the rostral PFC along a medial–lateral dimension, and 2) whether these subregions can influence attentional weighting processes by specifically interacting with other parts of the brain. Our results show that lateral aspects of the rostral PFC are preferentially activated when attention is directed to internal representations, whereas anterior medial aspects are activated when attention is directed to sensory events. Furthermore, the rostrolateral subregion was preferentially connected to regions in the prefrontal and parietal cortex during internal attending, whereas the rostromedial subregion was connected to the basal ganglia, thalamus, and sensory association cortices during external attending. Finally, both subregions interacted with another important prefrontal region involved in cognitive control, the inferior frontal junction, in a task-specific manner, depending on the current attentional demands. These findings suggest that the rostrolateral and rostromedial part of the anterior PFC have dissociable roles in attentional control, and that they might, as part of larger networks, be involved in dynamically adjusting the contribution of internal and external information to current cognition.

YNIMG Journal 2011 Journal Article

The power of imagination — How anticipatory mental imagery alters perceptual processing of fearful facial expressions

• Esther K. Diekhof
• Hanne E. Kipshagen
• Peter Falkai
• Peter Dechent
• Jürgen Baudewig
• Oliver Gruber

Expectancies strongly shape our perception of the world and preconceptions about stimulus characteristics can even bias the sensory system for illusory percepts. Here we assessed with functional magnetic resonance imaging how anticipatory mental imagery of a mildly fearful face created a predictive bias that proactively altered perception of highly fearful faces and generated the “illusion” of reduced fearfulness. We found that anticipatory activation of the fusiform gyrus (FG) was modulated by the fearfulness of the imagined face. Further during anticipatory imagery, regulatory influences from the lateral and ventromedial prefrontal cortex on the FG primed the perceptual system for a subsequent misperception. This was achieved by increasing perceptual activation in higher-order brain regions for the evaluation of affective valence and contextual framing, while at the same time restricting bottom-up arousal and attention to fearful expressions. Anticipatory mental imagery may thus represent an effective antecedent strategy through which emotional perception can be significantly altered.

YNIMG Journal 2011 Journal Article

Transcranial direct current stimulation over the primary motor cortex during fMRI

• Andrea Antal
• Rafael Polania
• Carsten Schmidt-Samoa
• Peter Dechent
• Walter Paulus

Measurements of motor evoked potentials (MEPs) have shown that anodal and cathodal transcranial direct current stimulations (tDCS) have facilitatory or inhibitory effects on corticospinal excitability in the stimulated area of the primary motor cortex (M1). Here, we investigated the online effects of short periods of anodal and cathodal tDCS on human brain activity of healthy subjects and associated hemodynamics by concurrent blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T. Using a block design, 20s periods of tDCS at 1mA intensity over the left M1 altered with 20s periods without tDCS. In different fMRI runs, the effect of anodal or cathodal tDCS was assessed at rest or during finger tapping. A control experiment was also performed, in which the electrodes were placed over the left and right occipito-temporo-parietal junction. Neither anodal nor cathodal tDCS over the M1 for 20s stimulation duration induced a detectable BOLD signal change. However, in comparison to a voluntary finger tapping task without stimulation, anodal tDCS during finger tapping resulted in a decrease in the BOLD response in the supplementary motor area (SMA). Cathodal stimulation did not result in significant change in BOLD response in the SMA, however, a tendency toward decreased activity could be seen. In the control experiment neither cathodal nor anodal stimulation resulted in a significant change of BOLD signal during finger tapping in any brain area including SMA, PM, and M1. These findings demonstrate that the well-known polarity-dependent shifts in corticospinal excitability that have previously been demonstrated using measurements of MEPs after M1 stimulation are not paralleled by analogous changes in regional BOLD signal. This difference implies that the BOLD signal and measurements of MEPs probe diverse physiological mechanisms. The MEP amplitude reflects changes in transsynaptic excitability of large pyramidal neurons while the BOLD signal is a measure of net synaptic activity of all cortical neurons.

YNIMG Journal 2008 Journal Article

Behavioral correlates of negative BOLD signal changes in the primary somatosensory cortex

• Andreas Kastrup
• Jürgen Baudewig
• Sonja Schnaudigel
• Ralph Huonker
• Lars Becker
• Jan Martin Sohns
• Peter Dechent
• Carsten Klingner

Functional magnetic resonance imaging (fMRI) hypothesis testing based on the blood oxygenation level dependent (BOLD) contrast mechanism typically involves a search for a positive effect during a specific task relative to a control state. However, aside from positive BOLD signal changes there is converging evidence that neuronal responses within various cortical areas also induce negative BOLD signals. Although it is commonly believed that these negative BOLD signal changes reflect suppression of neuronal activity direct evidence for this assumption is sparse. Since the somatosensory system offers the opportunity to quantitatively test sensory function during concomitant activation and has been well-characterized with fMRI in the past, the aim of this study was to determine the functional significance of ipsilateral negative BOLD signal changes during unilateral sensory stimulation. For this, we measured BOLD responses in the somatosensory system during unilateral electric stimulation of the right median nerve and additionally determined the current perception threshold of the left index finger during right-sided electrical median nerve stimulation as a quantitative measure of sensory function. As expected, positive BOLD signal changes were observed in the contralateral primary and bilateral secondary somatosensory areas, whereas a decreased BOLD signal was observed in the ipsilateral primary somatosensory cortex (SI). The negative BOLD signal changes were much more spatially extensive than the representation of the hand area within the ipsilateral SI. The negative BOLD signal changes in the area of the index finger highly correlated with an increase in current perception thresholds of the contralateral, unstimulated finger, thus supporting the notion that the ipsilateral negative BOLD response reflects a functionally effective inhibition in the somatosensory system.

YNIMG Journal 2008 Journal Article

The post-stimulation undershoot in BOLD fMRI of human brain is not caused by elevated cerebral blood volume

• Jens Frahm
• Jürgen Baudewig
• Kai Kallenberg
• Andreas Kastrup
• K. Dietmar Merboldt
• Peter Dechent

Functional magnetic resonance imaging (fMRI) based on blood oxygenation level dependent (BOLD) contrast is the most widely used technique for imaging human brain function. However, the dynamic interplay of altered cerebral blood flow (CBF), cerebral blood volume (CBV), and oxidative metabolism (CMRO2) is not yet fully understood. One of the characteristics of the BOLD response is the post-stimulation undershoot, that is increased deoxyhemoglobin, which has been suggested to originate from a delayed recovery of elevated CBV or CMRO2 to baseline. To investigate the CBV contribution to the post-stimulation BOLD undershoot, we performed bolus-tracking experiments using a paramagnetic contrast agent in eight healthy subjects at 3 T. In an initial BOLD experiment without contrast agent, we determined the individual hemodynamic responsiveness. In two separate experiments, we then evaluated the relative CBV (rCBV) during visual stimulation and the post-stimulation undershoot, respectively. The results confirm a pronounced rCBV increase during stimulation (31. 4±8. 6%), but reveal no change in rCBV relative to baseline in the post-stimulation phase (0. 7±7. 2%). This finding renders a CBV contribution to the BOLD MRI undershoot unlikely and – in conjunction with a rapid post-stimulation return of CBF to baseline – supports the idea of a prolonged elevation of oxidative metabolism.

YNIMG Journal 2001 Journal Article

Fine-scale finger somatotopy in the human primary motor cortex as revealed by high-resolution functional MRI

• Peter Dechent
• Jens Frahm

YNIMG Journal 2001 Journal Article

Separate mapping of left and right eye activation reveals ocular dominance columns in human primary visual cortex

• Peter Dechent
• Jens Frahn