Neuroimaging Correlates of Substantia Nigra Hyperechogenicity in Parkinson's Disease.

BACKGROUND: Degeneration of dopaminergic neurons within the brainstem substantia nigra (SN) is both a pathological hallmark of Parkinson's disease (PD) and a major contributor to symptom expression. Therefore, non-invasive evaluation of the SN is critical for diagnosis and evaluation of disease progression. Hyperechogenicity (HE+) on midbrain transcranial sonography (TCS) supports the clinically established diagnosis of PD. Further, postmortem studies suggest involvement of neuromelanin (NM) loss and iron deposition in nigral neurodegeneration and HE+ emergence. However, the associations between HE+ and signs of nigral NM loss and iron deposition revealed by magnetic resonance imaging (MRI) have not been examined. OBJECTIVE: To elucidate the magnetic resonance- (MR-) morphological representation of the HE+ by NM-weighted (NMI) and susceptibility-weighted MRI (SWI). METHODS: Thirty-four PD patients and 29 healthy controls (HCs) received TCS followed by NMI and SWI. From MR images, two independent raters manually identified the SN, placed seeds in non-SN midbrain areas, and performed semi-automated SN segmentation with different thresholds based on seed mean values and standard deviations. Masks of the SN were then used to extract mean area, mean signal intensity, maximal signal area, maximum signal (for NMI), and minimum signal (for SWI). RESULTS: There were no significant differences in NMI- and SWI-based parameters between patients and HCs, and no significant associations between HE+ extent and NMI- or SWI-based parameters. CONCLUSION: HE+ on TCS appears unrelated to PD pathology revealed by NMI and SWI. Thus, TCS and MRI parameters should be considered complementary, and the pathophysiological correlates of the HE+ require further study.

Modulation of visual processing of food by transcutaneous vagus nerve stimulation (tVNS).

Present project is concerned with the possibility to modulate the neural regulation of food intake by non-invasive stimulation of the vagus nerve. This nerve carries viscero-afferent information from the gut and other internal organs and therefore serves an important role in ingestive behavior. The electrical stimulation of the vagus nerve (VNS) is a qualified procedure in the treatment of drug-resistant epilepsy and depression. Since weight loss is a known common side effect of VNS treatment in patients with implanted devices, VNS is evaluated as a treatment of obesity. To investigate potential VNS-related changes in the cognitive processing of food-related items, 21 healthy participants were recorded in a 3-Tesla scanner in two counterbalanced sessions. Participants were presented with 72 food pictures and asked to rate how much they liked that food. Before entering the scanner subjects received a 1-h sham or verum stimulation, which was implemented transcutanously with a Cerbomed NEMOS® device. We found significant activations in core areas of the vagal afferent pathway, including left brainstem, thalamus, temporal pole, amygdala, insula, hippocampus, and supplementary motor area for the interaction between ratings (high vs low) and session (verum vs sham stimulation). Significant activations were also found for the main effect of verum compared to sham stimulation in the left inferior and superior parietal cortex. These results demonstrate an effect of tVNS on food image processing even with a preceding short stimulation period. This is a necessary prerequisite for a therapeutic application of tVNS which has to be evaluated in longer-term studies.

Effects of a Rhodiola rosea extract on mental resource allocation and attention: An event-related potential dual task study.

Rhodiola rosea extract is widely used to alleviate stress and improve cognition and mental resources. A total of 50 adult participants were treated with 2 × 200 mg R. rosea extract (Rosalin®, WS® 1,375) for 12 weeks and were subjected to a neuropsychological test battery as well as an event-related brain potential measurement in a dual task paradigm prior to administration, after 6 weeks and after 12 weeks. The study followed a single-arm open-label design. Reaction times improved for the attention network task (ANT), the Go/Nogo task, and the divided attention task. Moreover, the orienting effect and the executive effect in the ANT showed an improvement. The P3 component in a dual task paradigm was increased in amplitude. The results of this pilot study show an improvement of mental speed and moreover, suggest improved mental resources. As the current study is single-armed these findings need to be replicated in a double-blind placebo controlled study.

Effects of hunger, satiety and oral glucose on effective connectivity between hypothalamus and insular cortex.

The hypothalamus and insular cortex play an essential role in the integration of endocrine and homeostatic signals and their impact on food intake. Resting-state functional connectivity alterations of the hypothalamus, posterior insula (PINS) and anterior insula (AINS) are modulated by metabolic states and caloric intake. Nevertheless, a deeper understanding of how these factors affect the strength of connectivity between hypothalamus, PINS and AINS is missing. This study investigated whether effective (directed) connectivity within this network varies as a function of prandial states (hunger vs. satiety) and energy availability (glucose levels and/or hormonal modulation). To address this question, we measured twenty healthy male participants of normal weight twice: once after 36 â€‹h of fasting (except water consumption) and once under satiated conditions. During each session, resting-state functional MRI (rs-fMRI) and hormone concentrations were recorded before and after glucose administration. Spectral dynamic causal modeling (spDCM) was used to assess the effective connectivity between the hypothalamus and anterior and posterior insula. Using Bayesian model selection, we observed that the same model was identified as the most likely model for each rs-fMRI recording. Compared to satiety, the hunger condition enhanced the strength of the forward connections from PINS to AINS and reduced the strength of backward connections from AINS to PINS. Furthermore, the strength of connectivity from PINS to AINS was positively related to plasma cortisol levels in the hunger condition, mainly before glucose administration. However, there was no direct relationship between glucose treatment and effective connectivity. Our findings suggest that prandial states modulate connectivity between PINS and AINS and relate to theories of interoception and homeostatic regulation that invoke hierarchical relations between posterior and anterior insula.

Structural brain changes in young males addicted to video-gaming.

Excessive video gaming has a number of psychological and social consequences. In this study, we looked at possible changes in gray and white matter and asked whether these changes are correlated to psychological measures. Twentynine players of violent videogames (mean daily playing time 4.7 h) and age matched controls were subjected to a battery of questionnaires assessing aggression, empathy, hostility, internet addiction and psychological well-being. Diffusion tensor and 3D T1-weighted MR images were obtained to examine gray (via voxel-based morphometry) and white (via tract-based spatial statistics) matter changes. Widespread regions of decreased gray matter in the players were found but no region showed increased intensity of gray matter. Density of gray matter showed a negative correlation with the total length of playing in years in the right posterior cingulate gyrus, left pre- and postcentral gyrus, right thalamus, among others. Furthermore, fractional anisotropy, a marker for white matter structure, was decreased in the left and right cingulum in the players. Both, gray and white matter changes correlated with measures of aggression, hostility, self esteem, and the degree of internet addiction. This study thus shows profound changes of brain structure as a function of excessive playing of violent video games.

Processing of Local and Global Auditory Deviants in Parkinson Disease: Electrophysiological Evidence for Enhanced Attention Capture.

OBJECTIVE: To investigate automatic auditory-change detection in patients with Parkinson disease (pwPD). BACKGROUND: Previous results regarding changes in preattentive processing in pwPD have been inconclusive. METHODS: We employed a paradigm assessing the preattentive processing of sequences of auditory tones containing deviants at either the local or global level, or at both levels. Twenty pwPD and 20 age-matched healthy controls were exposed to the tone series while they performed a visual task and had their event-related potentials recorded by electroencephalogram. RESULTS: Event-related potentials showed a mismatch negativity, which was largest for the double-deviant stimuli, of intermediate amplitude for the local deviant stimuli, and smallest for the global deviant stimuli. The mismatch negativity was of similar size in the patients and controls, with the exception of the double-deviant condition (larger in controls). By contrast, the subsequent positive component was more pronounced for the Parkinson disease group than controls, particularly for the double-deviant condition. CONCLUSIONS: The larger positivity suggests that pwPD are more prone to distraction than healthy controls, probably because dopaminergic medication shifts the stability-flexibility balance toward cognitive flexibility with increased distractibility.

Human subthalamic nucleus - Automatic auditory change detection as a basis for action selection.

The subthalamic nucleus (STN) shapes motor behavior and is important for the initiation and termination of movements. Here we ask whether the STN takes aggregated sensory information into account, in order to exert this function. To this end, local field potentials (LFP) were recorded in eight patients suffering from Parkinson's disease and receiving deep-brain stimulation of the STN bilaterally. Bipolar recordings were obtained postoperatively from the externalized electrode leads. Patients were passively exposed to trains of auditory stimuli containing global deviants, local deviants or combined global/local deviants. The surface event-related potentials of the Parkinson's patients as well as those of 19 age-matched healthy controls were characterized by a mismatch negativity (MMN) that was most pronounced for the global/local double deviants and less prominent for the other deviant conditions. The left and right STN LFPs similarly were modulated by stimulus deviance starting at about 100ms post-stimulus onset. The MMN has been viewed as an index of an automatic auditory change detection system, more recently phrased in terms of predictive coding theory, which prepares the organism for attention shifts and for action. The LFP-data from the STN clearly demonstrate that the STN receives information on stimulus deviance, possibly as a means to bias the system to interrupt ongoing and to allow alternative actions.

Winning is not enough: ventral striatum connectivity during physical aggression.

Social neuroscience studies have shown that the ventral striatum (VS), a highly reward-sensitive brain area, is activated when participants win competitive tasks. However, in these settings winning often entails both avoiding punishment and punishing the opponent. It is thus unclear whether the rewarding properties of winning are mainly associated to punishment avoidance, or if punishing the opponent can be additionally gratifying. In the present paper we explored the neurophysiological correlates of each outcome, aiming to better understand the development of aggression episodes. We previously introduced a competitive reaction time task that separates both effects: in half of the won trials, participants can physically punish their opponent (active trials), whereas in the other half they can only avoid a punishment (passive trials). We performed functional connectivity analysis seeded in the VS to test for differential network interactions in active compared to passive trials. The VS showed greater connectivity with areas involved in reward valuation (orbitofrontal cortex), arousal (dorsal thalamus and posterior insula), attention (inferior occipital gyrus), and motor control (supplementary motor area) in active compared to passive trials, whereas connectivity between the VS and the inferior frontal gyrus decreased. Interindividual variability in connectivity strength between VS and posterior insula was related to aggressive behavior, whereas connectivity between VS and supplementary motor area was related to faster reaction times in active trials. Our results suggest that punishing a provoking opponent when winning might adaptively favor a "competitive state" in the course of an aggressive interaction.

Syllable congruency and word frequency effects on brain activation.

This article investigates the neural representation of the processes involved in recognizing multisyllabic words in Spanish asking whether lexical and sublexical processes are reflected in a different neuronal activation pattern. High and low frequency words were presented for lexical decision in two different colors. In the congruent condition the color boundaries matched the limit of the first syllable, whereas in the incongruent condition color boundaries and syllable boundaries did not match. The results revealed robust and dissociable brain activations for lexical frequency and syllable-color congruency, but no interaction between the two. We interpreted the greater activation for low relative to high frequency words in the left pre/SMA region, and in the insula/inferior frontal cortex bilaterally to reflect a differential recruitment of lexico-phonological and/or semantic processes. In contrast, we considered two interpretations for the greater deactivation in the precuneus for both lexical frequency and syllable-color congruency words, and in the thalami and a frontal area for syllable-color congruency words only. The deactivations may reflect the differential engagement of semantic processing or may result from the differential allocation of attentional resources. Importantly, while a differential deactivation pattern was observed in the precuneus region for lexicality and syllable-color congruency, BOLD deconvolution revealed a remarkable difference in timing of the two effects with a much earlier deactivation peak for the syllable-color congruency factor. Thus, effects of lexical frequency and syllable-color congruency on brain activation show an important dissociation between lexical and sublexical processes during visual word recognition of multisyllabic words.