Florian Ph.S. Fischmeister

Altered reward processing in the nucleus accumbens and mesial prefrontal cortex of patients with posttraumatic stress disorder.

Posttraumatic stress disorder (PTSD) is known to be associated with altered medial prefrontal activation in response to threatening stimuli and with behavioural deficits in prefrontal functions such as working memory and attention. Given the importance of these areas and processes for decision-making, this functional magnetic resonance imaging study investigated whether decision-making is altered in patients with PTSD. In particular, the neural response to gain and loss feedback was evaluated in a decision-making task in which subjects could maximise their number of points total by learning a particular response pattern. Behaviourally, controls learned the correct response pattern faster than patients. Functionally, patients and controls differed in their neural response to gains, but not in their response to losses. During the processing of gains in the late phase of learning, PTSD patients as compared to controls showed lower activation in the nucleus accumbens and the mesial PFC, critical structures in the reward pathway. This reduced activation was not due to different rates of learning, since it was similarly present in patients with unimpaired learning performance. These findings suggest that positive outcome information lost its salience for patients with PTSD. This may reflect decreasing motivation as the task progressed.

Fully exploratory network ICA (FENICA) on resting-state fMRI data.

Independent component analysis (ICA) is one of the most valuable explorative methods for analyzing resting-state networks (RSNs) in fMRI, representing a data-driven approach that enables decomposition of high-dimensional data into discrete components. Extensions to a group-level suffer from the drawback of evaluating single-subject resting-state components of interest either using a predefined spatial template or via visual inspection. FENICA introduced in the context of group ICA methods is based solely on spatially consistency across subjects directly reflecting similar networks. Therefore, group data can be processed without further visual inspection of the single-subject components or the definition of a template (Schöpf et al., 2009). In this study FENICA was applied to fMRI resting-state data from 28 healthy subjects resulting in eight group RSNs. These RSNs resemble the spatial patterns of the following previously described networks: (1) visual network, (2) default mode network, (3) sensorimotor network, (4) dorsolateral prefrontal network, (5) temporal prefrontal network, (6) basal ganglia network, (7) auditory processing network, and (8) working memory network. This novel analysis approach for identifying spatially consistent networks across a group of subjects does not require manual or template-based selection of single-subject components and, therefore, offers a truly explorative procedure of assessing RSNs.

Effects of learning on feedback-related brain potentials in a decision-making task

This study investigated the neural mechanisms of feedback processing during learning. While their event-related potentials were recorded, subjects learned to make a sequence of correct choices in a decision-making task. Each choice was followed by gain or loss feedback. In subjects who learned the task, both the feedback-related negativity (FRN), the P3 and the late positivity decreased in the course of the experiment. In subjects who did not learn the task, only the FRN decreased. Moreover, from all ERPs investigated, only changes in P3 amplitude were able to predict performance. These results suggest that the motivational significance of the feedback decreased in all the subjects, but attentive processing of the feedback only decreased in subjects who learned the task. These findings support the view that learning leads to economy of effort and more efficient processing. Moreover, they show that the P3 with its close relationship to learning should be included in future studies investigating the effects of learning on ERPs.

Imaging the changing role of feedback during learning in decision-making

Learning from the outcome of decisions can be expected not only to change future decisions, but also our reaction to future outcomes. Using functional magnetic resonance imaging we investigated the neural responses of healthy subjects to feedback about choice outcomes before and after learning a response strategy which led to correct choices only. The task was designed so that losses were unavoidable even when all the choices made were correct. Subjects showed a distinct pattern of learning starting with an initial exploratory phase in which hypotheses about the correct strategy were generated and tested, followed by a phase of rapid strategy acquisition before reaching a final phase of proficiency. Neural activation was more pronounced during feedback processing in the exploratory phase than in the proficiency phase in a distributed network encompassing prefrontal and parietal areas as well as the striatum. These areas are involved in working memory processes, the management of uncertainty and the establishment of stimulus-outcome contingencies. Reduced activation during feedback processing following learning was not only observed within subjects across learning phases, but also between subjects with different learning speeds. Thus, controlled and automatic processing are characterised by differing amounts of activation in identical task-relevant areas. Furthermore, whereas the same brain regions coded for gains and losses, the activation following gains changed to a larger extent with learning than following losses. This suggests that positive prediction errors are more sensitive to increased reward predictability than are negative prediction errors.

New Type of Cortical Neuroplasticity After Nerve Repair in Brachial Plexus Lesions

BACKGROUND In brachial plexus avulsion, a recent technique connects the ending of the disrupted musculocutaneous nerve to the side of the intact phrenic nerve to regain elbow flexion. This requires the phrenic nerve to perform a new double function: independent control of breathing and elbow flexion. Neuroplastic changes associated with acquisition of double nerve functions have not yet been investigated. OBJECTIVE To evaluate neuroplastic changes associated with acquisition of double nerve functions in a monofunctional nerve (phrenic nerve). DESIGN Clinical and functional magnetic resonance imaging investigations during arm movements, forced inspiration, and motor control tasks. SETTING Investigations at the Medical University of Vienna, Vienna, Austria. PARTICIPANTS Three healthy control subjects, 2 patients with phrenic nerve end-to-side coaptation, and 1 control patient with C7 end-to-end coaptation (same clinical presentation but phrenic nerve unchanged). RESULTS Clinical documentation showed that both patients with phrenic nerve end-to-side coaptation were able to control the diaphragm and the biceps independently via the same phrenic nerve. In contrast to all controls, both patients with phrenic nerve end-to-side coaptation activated the cortical diaphragm areas with flexion of the diseased arm. CONCLUSION Our functional magnetic resonance imaging data indicate that the patients cortical diaphragm areas reorganize in such a way that independent control of breathing and elbow flexion is possible with the same neuronal population.

Finger dexterity deficits in Parkinson's disease and somatosensory cortical dysfunction

INTRODUCTION The patho-physiological basis for finger dexterity deficits in Parkinsons disease (PD) is controversial. Previously, bradykinesia was regarded as the major mechanism. However, recent research suggested limb-kinetic apraxia as an important component of impaired fine motor skills in PD. In contrast to bradykinesia, limb-kinetic apraxia only marginally responds to dopaminergic treatment. Here we investigate the novel hypothesis that the dexterity deficits are related to an intrinsic dysfunction of primary somatosensory cortex (S1), which is not reversible by dopaminergic medication. METHODS Applying a standard and approved dexterity task (coin rotation), brain activation networks were investigated using functional magnetic resonance imaging in PD patients both ON and OFF medication and matched healthy controls. RESULTS PD patients both ON and OFF medication showed impaired S1 activation relative to controls (p < 0.05; region of interest based analysis). The impaired S1 activation remained unchanged by dopaminergic medication. Despite the considerable clinical deficit, no other brain area showed impaired activation. In contrast, structures of the basal ganglia--motor cortex loop responded to dopaminergic medication. Behaviorally, dexterity performance both ON and OFF was significantly (p < 0.05) reduced relative to controls. CONCLUSIONS Our results provide first evidence that dexterity deficits in PD are related to an S1 dysfunction which is insensitive to dopaminergic treatment.

Variability of Clinical Functional MR Imaging Results: A Multicenter Study

PURPOSE To investigate intersite variability of clinical functional magnetic resonance (MR) imaging, including influence of task standardization on variability and use of various parameters to inform the clinician whether the reliability of a given functional localization is high or low. MATERIALS AND METHODS Local ethics committees approved the study; all participants gave written informed consent. Eight women and seven men (mean age, 40 years) were prospectively investigated at three experienced functional MR sites with 1.5- (two sites) or 3-T (one site) MR. Nonstandardized motor and highly standardized somatosensory versions of a frequently requested clinical task (localization of the primary sensorimotor cortex) were used. Perirolandic functional MR variability was assessed (peak activation variability, center of mass [COM] variability, intraclass correlation values, overlap ratio [OR], activation size ratio). Data quality measures for functional MR images included percentage signal change (PSC), contrast-to-noise ratio (CNR), and head motion parameters. Data were analyzed with analysis of variance and a correlation analysis. RESULTS Localization of perirolandic functional MR activity differed by 8 mm (peak activity) and 6 mm (COM activity) among sites. Peak activation varied up to 16.5 mm (COM range, 0.4-16.5 mm) and 45.5 mm (peak activity range, 1.8-45.5 mm). Signal strength (PSC, CNR) was significantly lower for the somatosensory task (mean PSC, 1.0% ± 0.5 [standard deviation]; mean CNR, 1.2 ± 0.4) than for the motor task (mean PSC, 2.4% ± 0.8; mean CNR, 2.9 ± 0.9) (P < .001, both). Intersite variability was larger with low signal strength (negative correlations between signal strength and peak activation variability) even if the task was highly standardized (mean OR, 22.0% ± 18.9 [somatosensory task] and 50.1% ± 18.8 [motor task]). CONCLUSION Clinical practice and clinical functional MR biomarker studies should consider that the center of task-specific brain activation may vary up to 16.5 mm, with the investigating site, and should maximize functional MR signal strength and evaluate reliability of local results with PSC and CNR.

Agency matters! Social preferences in the three-person ultimatum game.

In the present study EEG was recorded simultaneously while two participants were playing the three-person ultimatum game (UG). Both participants received different offers from changing proposers about how to split up a certain amount of money between the three players. One of the participants had no say, whereas the other, the responder, was able to harm the payoff of all other players. The aim of the study was to investigate how the outcomes of the respective other are evaluated by participants who were treated fairly or unfairly themselves and to what extent agency influences concerns for fairness. Analyses were focused on the medial frontal negativity (MFN) as an early index for subjective value assignment. Recipients with veto-power exhibited enhanced, more negative-going, MFN amplitudes following proposals that comprised a low share for both recipients, suggesting that responders favored offers with a fair amount to at least one of the two players. Though, the powerless players cared about the amount assigned to the responder, MFN amplitudes were larger following fair compared to unfair offers assigned to the responder. Similarly, concerns for fairness which determined the amplitude of the MFN, suggested that the powerless players exhibited negative and conversely the responders, positive social preferences.

Windows on the Human Body - in Vivo High-Field Magnetic Resonance Research and Applications in Medicine and Psychology

Analogous to the evolution of biological sensor-systems, the progress in “medical sensor-systems”, i.e., diagnostic procedures, is paradigmatically described. Outstanding highlights of this progress are magnetic resonance imaging (MRI) and spectroscopy (MRS), which enable non-invasive, in vivo acquisition of morphological, functional, and metabolic information from the human body with unsurpassed quality. Recent achievements in high and ultra-high field MR (at 3 and 7 Tesla) are described, and representative research applications in Medicine and Psychology in Austria are discussed. Finally, an overview of current and prospective research in multi-modal imaging, potential clinical applications, as well as current limitations and challenges is given.

Differential functional benefits of ultra highfield MR systems within the language network

Several investigations have shown limitations of fMRI reliability with the current standard field strengths. Improvement is expected from ultra highfield systems but studies on possible benefits for cognitive networks are lacking. Here we provide an initial investigation on a prominent and clinically highly-relevant cognitive function: language processing in individual brains. 26 patients evaluated for presurgical language localization were investigated with a standardized overt language fMRI paradigm on both 3 T and 7 T MR scanners. During data acquisition and analysis we made particular efforts to minimize effects not related to static magnetic field strength differences. Six measures relevant for functional activation showed a large dissociation between essential language network nodes: although in Wernickes area 5/6 measures indicated a benefit of ultra highfield, in Brocas area no comparison was significant. The most important reason for this discrepancy was identified as being an increase in susceptibility-related artifacts in inferior frontal brain areas at ultra high field. We conclude that functional UHF benefits are evident, however these depend crucially on the brain region investigated and the ability to control local artifacts.