Comparing TMS perturbations to occipital and parietal cortices in concurrent TMS-fMRI studies-Methodological considerations

Neglect and hemianopia are two neuropsychological syndromes that are associated with reduced awareness for visual signals in patients' contralesional hemifield. They offer the unique possibility to dissociate the contributions of retino-geniculate and retino-colliculo circuitries in visual perception. Yet, insights from patient fMRI studies are limited by heterogeneity in lesion location and extent, long-term functional reorganization and behavioural compensation after stroke. Transcranial magnetic stimulation (TMS) has therefore been proposed as a complementary method to investigate the effect of transient perturbations on functional brain organization. This concurrent TMS-fMRI study applied TMS perturbation to occipital and parietal cortices with the aim to 'mimick' neglect and hemianopia. Based on the challenges and interpretational limitations of our own study we aim to provide tutorial guidance on how future studies should compare TMS to primary sensory and association areas that are governed by distinct computational principles, neural dynamics and functional architecture

Insights into the Interconnected Brain during (Multi-)sensory Processing - A concurrent TMS-fMRI Approach

The ability to appropriately respond to sensory information from our surroundings relies on the dynamic interplay between different and distributed brain regions, which is flexibly adapted according to current contexts and demands. By allowing direct monitoring of local and distal effects of transcranial magnetic stimulation (TMS), the concurrent application of TMS and functional magnetic resonance imaging (fMRI) provides a causal interventional approach to investigate this interconnected nature of the brain. In this dissertation, we used this methodology to investigate the neural mechanisms underlying (audio-)visual processing under different cognitive and experimental settings. In particular, given the functional heterogeneity of the intraparietal sulcus (IPS) in a number of different cognitive functions, a special focus was given to the functional role of this region during such processes. As a first step, we evaluated the causal involvement of the IPS during crossmodal deactivations by applying continuous repetitive TMS at different intensity levels to the right IPS and at the Vertex during three different sensory contexts (visual, auditory and fixation). Second, by engaging the attentional network in a demanding visual detection task we investigated how TMS at the right IPS influenced task-related activations, by applying bursts of TMS pulses over the right IPS and during a Sham condition. Moreover, given that additional sensory information might influence task performance in a beneficial or in a detrimental way, we further manipulated the bottom-up sensory context by introducing two different auditory contexts (present vs. absent). Third, to evaluate the differential effects of stimulating low-level sensory areas and higher-order association cortices, we compared the consequences of parietal and occipital stimulation on task-related activations during an identical experimental setting. Lastly, keeping the same visual detection task, we assessed the role of the IPS during perceptual decisions by categorizing participants’ responses into hits, misses, false alarms and correct rejections and comparing conditions with matched visual input but different behavioural response categories and vice versa. Overall, our results provide causal evidence for the involvement of the right IPS in different stages of sensory processing. Moreover, they also reflect the ability of the concurrent TMS-fMRI approach to divide a global task-related network into those elements that are specifically associated to the targeted area

Preliminary exploratory impact assessment of short-lived pollutants over the Danube Basin

This report is presented as deliverable D2.3 of work package 2 of the Danube Air Nexus. It presents the results of an exploratory impact assessment of short-lived air pollutant emissions on human health, crop production and near-term climate with a focus on the Danube basin. We use a global reduced-form source receptor air quality model TM5-FASST and a recent global pollutant emission inventory (HTAP V2, 2014) to make an attribution by sector of the various impacts and to explore the challenges and opportunities for possible. Preliminary results show that trans-boundary pollution is significantly contributing to population exposure to PM2.5 in the Danube area. Dominating polluting sectors are residential sector and agriculture. We estimate that annually 170000 premature mortalities can be attributed to PM2.5 pollution in the Danube area, and annual crop losses add up to an economic value of nearly 1 billion US$. This analysis is a first step in a more detailed, country-wise analysis that will be carried out as a follow-up of this report, with an improved version of the model and specifically designed scenarios for the Danube Basin.JRC.H.2-Air and Climat

Amygdala in action: functional connectivity during approach and avoidance behaviors

Motivation is an important feature of emotion. By driving approach to positive events and promoting avoidance of negative stimuli, motivation drives adaptive actions and goal pursuit. The amygdala has been associated with a variety of affective processes, particularly the appraisal of stimulus valence that is assumed to play a crucial role in the generation of approach and avoidance behaviors. Here, we measured amygdala functional connectivity patterns while participants played a video game manipulating goal conduciveness through the presence of good, neutral, or bad monsters. As expected, good versus bad monsters elicited opposing motivated behaviors, whereby good monsters induced more approach and bad monsters triggered more avoidance. These opposing directional behaviors were paralleled by increased connectivity between the amygdala and medial brain areas, such as the OFC and posterior cingulate, for good relative to bad, and between amygdala and caudate for bad relative to good monsters. Moreover, in both conditions, individual connectivity strength between the amygdala and medial prefrontal regions was positively correlated with brain scores from a latent component representing efficient goal pursuit, which was identified by a partial least squares analysis determining the multivariate association between amygdala connectivity and behavioral motivation indices during gameplay. At the brain level, this latent component highlighted a widespread pattern of amygdala connectivity, including a dorsal frontoparietal network and motor areas. These results suggest that amygdala-medial prefrontal interactions captured the overall subjective relevance of ongoing events, which could consecutively drive the engagement of attentional, executive, and motor circuits necessary for implementing successful goal-pursuit, irrespective of approach or avoidance directions

Concurrent TMS-fMRI Reveals Interactions between Dorsal and Ventral Attentional Systems

Adaptive behavior relies on combining bottom-up sensory inputs with top-down control signals to guide responses in line with current goals and task demands. Over the past decade, accumulating evidence has suggested that the dorsal and ventral frontoparietal attentional systems are recruited interactively in this process. This fMRI study used concurrent transcranial magnetic stimulation (TMS) as a causal perturbation approach to investigate the interactions between dorsal and ventral attentional systems and sensory processing areas. In a sustained spatial attention paradigm, human participants detected weak visual targets that were presented in the lower-left visual field on 50 of the trials. Further, we manipulated the presence/absence of task-irrelevant auditory signals. Critically, on each trial we applied 10 Hz bursts of four TMS (or Sham) pulses to the intraparietal sulcus (IPS). IPS-TMS relative to Sham-TMS increased activation in the parietal cortex regardless of sensory stimulation, confirming the neural effectiveness of TMS stimulation. Visual targets increased activations in the anterior insula, a component of the ventral attentional system responsible for salience detection. Conversely, they decreased activations in the ventral visual areas. Importantly, IPS-TMS abolished target-evoked activation increases in the right temporoparietal junction (TPJ) of the ventral attentional system, whereas it eliminated target-evoked activation decreases in the right fusiform. Our results demonstrate that IPS-TMS exerts profound directional causal influences not only on visual areas but also on the TPJ as a critical component of the ventral attentional system. They reveal a complex interplay between dorsal and ventral attentional systems during target detection under sustained spatial attention

Computational imaging during video game playing shows dynamic synchronization of cortical and subcortical networks of emotions

Emotions are multifaceted phenomena affecting mind, body, and behavior. Previous studies sought to link particular emotion categories (e.g., fear) or dimensions (e.g., valence) to specific brain substrates but generally found distributed and overlapping activation patterns across various emotions. In contrast, distributed patterns accord with multi-componential theories whereby emotions emerge from appraisal processes triggered by current events, combined with motivational, expressive, and physiological mechanisms orchestrating behavioral responses. According to this framework, components are recruited in parallel and dynamically synchronized during emotion episodes. Here, we use functional MRI (fMRI) to investigate brain-wide systems engaged by theoretically defined components and measure their synchronization during an interactive emotion-eliciting video game. We show that each emotion component recruits large-scale cortico-subcortical networks, and that moments of dynamic synchronization between components selectively engage basal ganglia, sensory-motor structures, and midline brain areas. These neural results support theoretical accounts grounding emotions onto embodied and action-oriented functions triggered by synchronized component processe

Transcranial magnetic stimulation of right inferior parietal cortex causally influences prefrontal activation for visual detection

For effective interactions with the environment, the brain needs to form perceptual decisions based on noisy sensory evidence. Accumulating evidence suggests that perceptual decisions are formed by widespread interactions amongst sensory areas representing the noisy sensory evidence and fronto-parietal areas integrating the evidence into a decision variable that is compared to a decisional threshold. This concurrent transcranial magnetic stimulation (TMS)-fMRI study applied 10 Hz bursts of four TMS (or Sham) pulses to the intraparietal sulcus (IPS) to investigate the causal influence of IPS on the neural systems involved in perceptual decision-making. Participants had to detect visual signals at threshold intensity that were presented in their left lower visual field on 50% of the trials. Critically, we adjusted the signal strength such that participants failed to detect the visual stimulus on approximately 30% of the trials allowing us to categorise trials into hits, misses and correct rejections (CR). Our results show that IPS-relative to Sham-TMS attenuated activation increases for misses relative to CR in the left middle and superior frontal gyri. Critically, while IPS-TMS did not significantly affect participants' performance accuracy, it affected how observers adjusted their response times after making an error. We therefore suggest that activation increases in superior frontal gyri for misses relative to correct responses may not be critical for signal detection performance, but rather reflect post-decisional processing such as metacognitive monitoring of choice accuracy or decisional confidenc