Erwin L. Hahn Institute for Magnetic Resonance Imaging

Recent models on the development of behavioral addictions stress the transfer from goal-directed behavior to stimulus-response habits. Administering a Pavlovian-to-instrumental transfer (PIT) paradigm to individuals with risky or non-problematic gaming, we recently reported that shopping-related cues increase instrumental behavior for a shopping-related reward (i.e. shopping voucher) while gaming-related stimuli triggered instrumental behavior for the gaming-reward (i.e. gaming voucher). This was observed even after devaluation of the gaming-reward. We now investigated the predictive value of the 'Shopping-PIT'- and the 'Gaming-PIT'-effects regarding gaming disorder symptoms. Data on symptom severity of gaming disorder six months after the baseline assessment were available for 48 individuals with risky gaming and 46 individuals with non-problematic gaming. Hierarchical regression analyses with stepwise inclusion of control variables, the 'Shopping-PIT'-effect as indicator of responding for a general reward after devaluation of the gaming reward and 'The Gaming-PIT'-effect after devaluation of the gaming reward as indicator of habitual responding as well as their interaction effects with symptom severity was calculated. Higher gaming disorder symptoms at the six-month follow-up assessment were predicted by symptom severity at baseline and the interaction of the 'Shopping-PIT'-effect with symptom severity at baseline. The 'Gaming-PIT'-effect after devaluation did not predict symptom severity. The finding that cue-triggered responding for a general reward contributes to future symptom severity in individuals with higher symptom severity at baseline suggests a cascade model with higher symptom severity leading to stronger cue-triggered reward-related responding which in turn leads to higher symptom severity.

The human hippocampus has been extensively studied at the macroscale using functional magnetic resonance imaging (fMRI) but the underlying microcircuits at the mesoscale (i.e., at the level of layers) are largely uninvestigated in humans. We target two questions fundamental to hippocampal laminar fMRI: How does the venous bias affect the interpretation of hippocampal laminar responses, and is it possible to establish a benchmark laminar fMRI experiment which robustly elicits single-subject hippocampal activation utilizing the most widely applied GRE-BOLD contrast. We comprehensively characterized GRE-BOLD responses as well as T2*, tSNR, and physiological noise as a function of cortical depth in individual subfields of the human hippocampus. Our results show that the vascular architecture differs between subfields leading to subfield-specific laminar biases of GRE-BOLD responses. Using an autobiographical memory paradigm, we robustly acquired depth-specific BOLD responses in hippocampal subfields. In the CA1 and subiculum subregions, our results indicate a more pronounced trisynaptic path input rather than dominant direct inputs from the entorhinal cortex during autobiographical memory retrieval. Our study provides unique insights into the hippocampus at the mesoscale level, will help interpreting hippocampal laminar fMRI responses and allow researchers to test mechanistic hypotheses of hippocampal function.

Abstract: Aim: Empirical evidence suggests that Internet Use Disorders (IUDs) can be considered as disorders due to addictive behaviors that are related to impairment and are of clinical relevance. Currently, no guidelines following a standardised methodology are available. Methods: Based on a narrative review, the evidence supporting guidelines for IUDs is reported. The methodological approach underlying the guideline recommendations is described. Results: In addition to gaming disorder, which has been included in the 11th revision of the International Classification of Diseases (ICD-11), meta-level criteria support that Social Network Use Disorder, Shopping Disorder and Pornography Use Disorder can be considered as specified disorders due to addictive behaviours. Mechanisms based on etiological models of IUDs are comparable to other addictive disorders and warrant classification as such. The development of the recommendations in this guideline followed the method­ology of the S1 guidelines of the German Association of the Scientific Medical Societies (AWMF) and was based primarily on systematic literature reviews. Twelve German professional associations and societies were involved and approved the guideline. Conclusions: The recommendations of this guideline serve as an aid for the diagnosis and treatment of IUDs. Updates are important to keep up with the rapidly evolving field.

Ultrahigh field magnetic resonance imaging (MRI) (≥ 7 T) has the potential to provide superior spatial resolution and unique image contrast. Apart from radiofrequency transmit inhomogeneities in the body at this field strength, imaging of the upper abdomen faces additional challenges associated with motion-induced ghosting artifacts. To address these challenges, the goal of this work was to develop a technique for high-resolution free-breathing upper abdominal MRI at 7 T with a large field of view. Free-breathing 3D gradient-recalled echo (GRE) water-excited radial stack-of-stars data were acquired in seven healthy volunteers (five males/two females, body mass index: 19.6-24.8 kg/m2) at 7 T using an eight-channel transceive array coil. Two volunteers were also examined at 3 T. In each volunteer, the liver and kidney regions were scanned in two separate acquisitions. To homogenize signal excitation, the time-interleaved acquisition of modes (TIAMO) method was used with personalized pairs of B1 shims, based on a 23-s Cartesian fast low angle shot(FLASH) acquisition. Utilizing free-induction decay navigator signals, respiratory-gated images were reconstructed at a spatial resolution of 0.8 × 0.8 × 1.0 mm3. Two experienced radiologists rated the image quality and the impact of B1 inhomogeneity and motion-related artifacts on multipoint scales. The images of all volunteers showcased effective water excitation and were accurately corrected for respiratory motion. The impact of B1 inhomogeneity on image quality was minimal, underscoring the efficacy of the multitransmit TIAMO shim. The high spatial resolution allowed excellent depiction of small structures such as the adrenal glands, the proximal ureter, the diaphragm, and small blood vessels, although some streaking artifacts persisted in liver image data. In direct comparisons with 3 T performed for two volunteers, 7-T acquisitions demonstrated increases in signal-to-noise ratio of 77% and 58%. Overall, this work demonstrates the feasibility of free-breathing MRI in the upper abdomen at submillimeter spatial resolution at a magnetic field strength of 7 T.

Measurements of frequency offset are commonly required in MRI. The standard method measures the signal phase as a function of evolution time. Here we use a single shot turbo-spin-echo acquisition method to measure frequency offset at a single evolution time. After excitation the transverse magnetisation evolves during the evolution time, and is then repeatedly refocused. The phase is conjugated between alternate echoes. Using partial parallel acquisition techniques we obtain separate odd- and even- echo images. An iterative procedure ensures self-consistency between them. The difference in phase between the two images yields frequency offset maps. The technique was implemented at 3 Tesla and tested on a healthy human volunteer for a range of evolution times between 6 and 42ms. A standard method using a similar readout train and multiple evolution times was used as a gold-standard measure. In a statistical comparison with the gold standard no evidence for bias or offset was found. There was no systematic variation in precision or accuracy as a function of evolution time. We conclude that the presented approach represents a viable method for the rapid generation of frequency offset maps with a high image quality and minimal distortion.

BackgroundRepetitive traumatic brain injuries in American football players (AFPs) can lead to the neurodegenerative disease chronic traumatic encephalopathy (CTE). Clinical symptoms of CTE range from mood and behavioral changes to cognitive impairment, depression, and suicidality. So far, CTE cannot be diagnosed in vivo and thus specific diagnostic parameters for CTE need to be found, to observe and treat exposed athletes as early as possible. Promising blood-based biomarkers for CTE include total tau (tTau), hyperphosphorylated tau (pTau), neurofilament light protein (NF-L), glial fibrillary acidic protein (GFAP), amyloid-β40 (Aβ40), amyloid-β42 (Aβ42) and calcium-binding protein B (S100-B). Previous studies have found elevated levels of these biomarkers in subjects exposed to TBIs, whereas cerebrospinal fluid (CSF) levels of Aβ40 and Aβ42 were decreased in CTE subjects. Here, we investigated whether young AFPs already exhibit changes of these biomarker candidates during the course of a single active season.MethodsBlood samples were drawn from n = 18 American Football Players before and after a full season and n = 18 male age-matched control subjects. The plasma titers of tTau, pTau, NF-L, GFAP, Aβ40, Aβ42 and S100-B were determined. Additionally, Apathy, Depression, and Health status as well as the concussion history and medical care were assessed and analyzed for correlations.ResultsHere we show, that the selected biomarker candidates for CTE do not change significantly during the seven-month period of a single active season of American Football in blood samples of AFPs compared to healthy controls. But interestingly, they exhibit generally elevated pTau titers. Furthermore, we found correlations of depression, quality-of-life, career length, training participation and training continuation with headache after concussion with various titers.ConclusionOur data indicates, that changes of CTE marker candidates either occur slowly over several active seasons of American Football or are exclusively found in CSF. Nevertheless, our results underline the importance of a long-term assessment of these biomarker candidates, which might be possible through repeated blood biomarker monitoring in exposed athletes in the future.

Traditional mindfulness interventions have been frequently reported to be effective in improving cognitive functions. In recent years, however, traditional programs are being increasingly replaced by technology-enabled mindfulness training programs. The aim of the present systematic review (PROSPERO ID: CRD42021289480) is to evaluate the research evidence on their effects on cognitive functions. Empirical training studies in the realm of digital mindfulness training that fulfilled the inclusion criteria led to 19 studies and 1654 participants being included in this review from among the papers searched in PubMed, Scopus, and Web of Knowledge. Results support previous assumptions on the potential of digital mindfulness training, with the most robust effect on attention control, followed by executive regulation, memory, cognitive flexibility, and other cognitive functions. However, the number of studies that did not find significant changes at least equaled, if not exceeded, the number of studies that found increases. The heterogeneity of identified studies prompted us to discuss several aspects in order to help the future development of digital applications.

Attenuation correction (AC) is an important methodical step in positron emission tomography/magnetic resonance imaging (PET/MRI) to correct for attenuated and scattered PET photons. The overall quality of magnetic resonance (MR)-based AC in whole-body PET/MRI was evaluated in direct comparison to computed tomography (CT)-based AC serving as reference. The quantitative impact of isolated tissue classes in the MR-AC was systematically investigated to identify potential optimization needs and strategies. Data of n=60 whole-body PET/CT patients with normal lung tissue and without metal implants/prostheses were used to generate six different AC-models based on the CT data for each patient, simulating variations of MR-AC. The original continuous CT-AC (CT-org) is referred to as reference. A pseudo MR-AC (CT-mrac), generated from CT data, with four tissue classes and a bone atlas represents the MR-AC. Relative difference in linear attenuation coefficients (LAC) and standardized uptake values were calculated. From the results two improvements regarding soft tissue AC and lung AC were proposed and evaluated. The overall performance of MR-AC is in good agreement compared to CT-AC. Lungs, heart, and bone tissue were identified as the regions with most deviation to the CT-AC (myocardium -15%, bone tissue -14%, and lungs ±20%). Using single-valued LACs for AC in the lung only provides limited accuracy. For improved soft tissue AC, splitting the combined soft tissue class into muscles and organs each with adapted LAC could reduce the deviations to the CT-AC to <±1%. For improved lung AC, applying a gradient LAC in the lungs could remarkably reduce over- or undercorrections in PET signal compared to CT-AC (±5%). The AC is important to ensure best PET image quality and accurate PET quantification for diagnostics and radiotherapy planning. The optimized segment-based AC proposed in this study, which was evaluated on PET/CT data, inherently reduces quantification bias in normal lung tissue and soft tissue compared to the CT-AC reference.