Neural bases of unconscious orienting of attention in hemianopic patients: Hemispheric differences

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Neural bases of visual processing of moving and stationary stimuli presented to the blind hemifield of hemianopic patients

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Functional interactions in patients with hemianopia: A graph theory-based connectivity study of resting fMRI signal

Podeu consultar les dades primàries associades a l'article a: http://hdl.handle.net/2445/136617The assessment of task-independent functional connectivity (FC) after a lesion causing hemianopia remains an uncovered topic and represents a crucial point to better understand the neural basis of blindsight (i.e. unconscious visually triggered behavior) and visual awareness. In this light, we evaluated functional connectivity (FC) in 10 hemianopic patients and 10 healthy controls in a resting state paradigm. The main aim of this study is twofold: first of all we focused on the description and assessment of density and intensity of functional connectivity and network topology with and without a lesion affecting the visual pathway, and then we extracted and statistically compared network metrics, focusing on functional segregation, integration and specialization. Moreover, a study of 3-cycle triangles with prominent connectivity was conducted to analyze functional segregation calculated as the area of each triangle created connecting three neighboring nodes. To achieve these purposes we applied a graph theory-based approach, starting from Pearson correlation coefficients extracted from pairs of regions of interest. In these analyses we focused on the FC extracted by the whole brain as well as by four resting state networks: The Visual (VN), Salience (SN), Attention (AN) and Default Mode Network (DMN), to assess brain functional reorganization following the injury. The results showed a general decrease in density and intensity of functional connections, that leads to a less compact structure characterized by decrease in functional integration, segregation and in the number of interconnected hubs in both the Visual Network and the whole brain, despite an increase in long-range inter-modules connections (occipito-frontal connections). Indeed, the VN was the most affected network, characterized by a decrease in intra- and inter-network connections and by a less compact topology, with less interconnected nodes. Surprisingly, we observed a higher functional integration in the DMN and in the AN regardless of the lesion extent, that may indicate a functional reorganization of the brain following the injury, trying to compensate for the general reduced connectivity. Finally we observed an increase in functional specialization (lower between-network connectivity) and in inter-networks functional segregation, which is reflected in a less compact network topology, highly organized in functional clusters. These descriptive findings provide new insight on the spontaneous brain activity in hemianopic patients by showing an alteration in the intrinsic architecture of a large-scale brain system that goes beyond the impairment of a single RSN

Post-traumatic taste disorders: presentation of three meaningful cases

Since the late 1800s there are reports of post-traumatic anosmia [1], but few studies investigated post-traumatic gustatory deficit and adopted validated evaluation tests [2,3,4,5,6,7]. Post-traumatic ageusia is rare, occurring in ~ 0.5% of head traumas, while a gustatory deficit is more frequently referred (5-7%) when olfaction is impaired [2,4]. Unlike olfaction, gustatory sensation is mediated by several cranial nerves (VII, IX, X) and taste receptors are widely spread in the oral cavity, so that taste is considered a “robust” sense. Peripheral and/or central mechanisms may be involved in the genesis of post-traumatic gustatory dysfunction. Beyond a reduction/loss of gustatory function following a trauma, taste changes (dysgeusia) may occur, even if they are reported to be rare [7,8,9]. Gustatory disorders might not be immediately reported because patient often pays attention to other post-traumatic sequelae. Especially when persistent, taste deficits might be particularly relevant for patients’ quality of life. Physicians are often not well-informed on the possible implications or treatment strategies. Fifty-three consecutive patients with previous head trauma and chemosensory disorders were recruited by the olfactory and taste research group of the University of Verona. Every patient underwent a careful clinical examination, olfactory and gustatory testing by Sniffin’Sticks Extended test, Whole Mouth taste test and Taste Strips Test respectively (Burghart, Germany). Among them, we found 10 cases with hyposmia, 43 with functional anosmia, while 10 cases showed taste deficits (dysgeusia: n = 3, dysgeusia with hypogeusia: n = 1, hypogeusia: n = 5, ageusia: n = 1). Here we report anatomical, clinical correlations and detailed description of three cases representing central and peripheral injury patterns

Neural Correlates of Visuospatial Attention to Unseen Stimuli in Hemianopic Patients. A Steady-State Visual Evoked Potential Study

The relationship between attention and awareness is a topic of great interest in cognitive neuroscience. Some studies in healthy participants and hemianopic patients have shown dissociation between these two processes. In contrast, others confirmed the classic notion that the two processes are mutually exclusive. To try and cast further light on this fascinating dilemma, in the present study we have investigated the neural mechanisms of visual spatial attention when perceptual awareness is totally lacking. To do that, we monitored with steady-state visual evoked potentials (SSVEPs) the neurophysiological correlates of endogenous spatial attention to unseen stimuli presented to the blind field of hemianopic patients. Behaviourally, stimulus detection (a brief change in the orientation of a gabor grating) was absent in the blind hemifield while in the sighted field there was a lower, but non-significant, performance in hit rate with respect to a healthy control group. Importantly, however, in both blind and sighted hemifield of hemianopics (as well as in healthy participants) SSVEP recordings showed an attentional effect with higher frequency power in the attended than unattended condition. The scalp distribution of this effect was broadly in keeping with the location of the dorsal system of endogenous spatial attention. In conclusion, the present results provide evidence that the neural correlates of spatial attention are present regardless of visual awareness and this is in accord with the general hypothesis of a possible dissociation between attention and awareness

Comparison Between CT Texture Data, Resection Margin Status And Clinical Outcomes In Pancreatic Adenocarcinoma Resected After Induction Chemotherapy And Neoadjuvant Stereotactic Body Radiation Therapy

The aim of this study is to compare CT texture analysis parameters with the resection margin status, the recurrence-free survival (RFS) and the overall survival (OS) in patients with pancreatic ductal adenocarcinoma (PDAC) resected after induction chemotherapy and neoadjuvant stereotactic body radiotherapy (SBRT)

Resting-state functional connectivity in multiple sclerosis patients receiving nabiximols for spasticity

Abstract Background Nabiximols (Sativex®) is a cannabinoid approved for multiple sclerosis (MS)-related spasticity. Its mechanism of action is partially understood, and efficacy is variable. Objective To conduct an exploratory analysis of brain networks connectivity changes on resting state (RS) functional MRI (fMRI) of MS patients treated with nabiximols. Methods We identified a group of MS patients treated with Sativex® at Verona University Hospital, who underwent RS brain fMRI in the 4 weeks before (T0) and 4–8 weeks after (T1) treatment start. Sativex® response was defined as ≥ 20% spasticity Numerical Rating Scale score reduction at T1 vs. T0. Connectivity changes on fMRI were compared between T0 and T1 in the whole group and according to response status. ROI-to-ROI and seed-to-voxel connectivity were evaluated. Results Twelve MS patients (7 males) were eligible for the study. Seven patients (58.3%) resulted Sativex® responders at T1. On fMRI analysis, Sativex® exposure was associated with global brain connectivity increase (particularly in responders), decreased connectivity of motor areas, and bidirectional connectivity changes of the left cerebellum with a number of cortical areas. Conclusions Nabiximols administration is associated with brain connectivity increase of MS patients with spasticity. Modulation of sensorimotor cortical areas and cerebellum connectivity could play a role in nabiximols effect

Path Tracing vs. Volume Rendering Technique in Post-Surgical Assessment of Bone Flap in Oncologic Head and Neck Reconstructive Surgery: A Preliminary Study

: This study aims to compare a relatively novel three-dimensional rendering called Path Tracing (PT) to the Volume Rendering technique (VR) in the post-surgical assessment of head and neck oncologic surgery followed by bone flap reconstruction. This retrospective study included 39 oncologic patients who underwent head and neck surgery with free bone flap reconstructions. All exams were acquired using a 64 Multi-Detector CT (MDCT). PT and VR images were created on a dedicated workstation. Five readers, with different expertise in bone flap reconstructive surgery, independently reviewed the images (two radiologists, one head and neck surgeon and two otorhinolaryngologists, respectively). Every observer evaluated the images according to a 5-point Likert scale. The parameters assessed were image quality, anatomical accuracy, bone flap evaluation, and metal artefact. Mean and median values for all the parameters across the observer were calculated. The scores of both reconstruction methods were compared using a Wilcoxon matched-pairs signed rank test. Inter-reader agreement was calculated using Spearman's rank correlation coefficient. PT was considered significantly superior to VR 3D reconstructions by all readers (p < 0.05). Inter-reader agreement was moderate to strong across four out of five readers. The agreement was stronger with PT images compared to VR images. In conclusion, PT reconstructions are significantly better than VR ones. Although they did not modify patient outcomes, they may improve the post-surgical evaluation of bone-free flap reconstructions following major head and neck surgery

Uncommon Presentations of Pancreatic Neoplasms, Rare Neoplasms, and Peripancreatic Masses

Pancreatic masses with atypical radiological appearance are frequently encountered. Atypical presentation of common pancreatic tumor is also possible. Knowledge of the wide possibilities of intratumoral changes and pathological variants of pancreatic neoplasms may help in the diagnosis. Atypical presentations of pancreatic lesions are uncommon, but they are more frequent than rare pancreatic neoplasms

Imaging presentation of pancreatic neuroendocrine neoplasms

Abstract Pancreatic neuroendocrine neoplasms (P-NENs) are the second most common solid pancreatic neoplasms. P-NENs have a wide range of imaging features presentations and they can be detected with typical and atypical imaging presentations. Typical and atypical appearances can be explained by pathologic correlations. P-NENs are generally hypervascular lesions, showing a typical enhancement behavior after contrast media injection during imaging methods, but they could also have different imaging features, creating some difficulty in differential diagnosis. For this reason, radiologists should be aware of different imaging presentations of these neoplasms. Radiological evaluation has a critical role in P-NENs identification, characterization, and staging of these neoplasms, especially in those cases in which surgery is the treatment of choice. The present paper shows, indicating the underlying pathologic correlations, typical and atypical presentations of NENs. Key Points • P-NENs have a wide range of imaging features presentations, typical and atypical. • Pathology could help in better understanding the typical P-NENs appearance at imaging. • P-NENs are generally hypervascular lesions. • Radiological evaluation has a critical role in P-NENs identification and management. • Radiologists should know every type of different imaging presentation of P-NENs to better diagnose these kinds of lesions