Virtual prism adaptation for spatial neglect: A double-blind study.

ABSTRACTPrismatic adaptation (PA) with wedge prisms is a non-invasive technique used in the rehabilitation of patients suffering from spatial neglect. Unfortunately, as for many behavioural intervention techniques, it is nearly impossible to achieve adequate blinding using wedge prisms, and the potential benefit of PA in the rehabilitation of neglect remains controversial. In order to study an alternative to wedge prism, we examine whether virtual PA at different degrees of deviation may alleviate signs of neglect in a double-blind design. Fifteen neglect patients participated in three adaptation sessions, which differed by the degree of deviation (0°, 15°, or 30°). Performance in line bisection and item cancellation tasks was measured in virtual reality immediately before and after adaptation. Session allocation was concealed from patients and the examiner. Despite the presence of robust, dose-dependent effects of virtual PA on Open-Loop Pointing (OLP), no transfer to line bisection and item cancellation tests were observed. None of the patients were aware of differences between sessions. Virtual PA did not result in visuo-motor transfer effects despite inducing significant adaptation effects in OLP. Together with recent negative findings of randomized-controlled trials, these findings cast doubt on the general efficacy of PA as a rehabilitation method of spatial neglect.

Adaptation to virtual prisms and its relevance for neglect rehabilitation: a single-blind dose-response study with healthy participants.

Prism adaptation (PA) has been applied with mixed success as a rehabilitation method of spatial neglect. Results from many single-case and multiple case studies as well as randomised controlled trials do not produce a clear picture of the efficacy of PA. We here tested a new method of PA, by inducing adaptation effects in the virtual reality. Healthy participants were attributed to one of four groups: no deviation, 10-, 20-, or 30-degrees rightward deviation. In contrast to classical wedge prisms, we induced the visual shift progressively. Participants performed two variants of the bisection and the landmark task to measure cognitive transfer of adaptation effects. Pointing error was directly related to the degree of optical deviation, and was greatest immediately following adaptation. Transfer was only observed in the bisection tasks, and only in the 30-degrees group. Due to the gradual induction of the spatial deviation the majority of participants were unaware of the adaptation effects. These findings show that large rightward deviation may affect sensorimotor performance in healthy participants similarly to neglect patients. Moreover, the finding that only participants adapted to 30-degrees showed biased bisection performance suggests that a critical threshold must be reached in order to induce significant visuomotor transfer.

Resting-state connectivity predicts visuo-motor skill learning.

Spontaneous brain activity at rest is highly organized even when the brain is not explicitly engaged in a task. Functional connectivity (FC) in the alpha frequency band (α, 8-12 Hz) during rest is associated with improved performance on various cognitive and motor tasks. In this study we explored how FC is associated with visuo-motor skill learning and offline consolidation. We tested two hypotheses by which resting-state FC might achieve its impact on behavior: preparing the brain for an upcoming task or consolidating training gains. Twenty-four healthy participants were assigned to one of two groups: The experimental group (n = 12) performed a computerized mirror-drawing task. The control group (n = 12) performed a similar task but with concordant cursor direction. High-density 156-channel resting-state EEG was recorded before and after learning. Subjects were tested for offline consolidation 24h later. The Experimental group improved during training and showed offline consolidation. Increased α-FC between the left superior parietal cortex and the rest of the brain before training and decreased α-FC in the same region after training predicted learning. Resting-state FC following training did not predict offline consolidation and none of these effects were present in controls. These findings indicate that resting-state alpha-band FC is primarily implicated in providing optimal neural resources for upcoming tasks.

Visual but Not Auditory-Verbal Feedback Induces Aftereffects Following Adaptation to Virtual Prisms.

Visuo-motor adaptation with optical prisms that displace the visual scene (prism adaptation, PA) has been widely used to study visuo-motor plasticity in healthy individuals and to decrease the lateralized bias of brain-damaged patients suffering from spatial neglect. Several factors may influence PA aftereffects, such as the degree of optical deviation (generally measured in dioptres of wedge prisms) or the direction of the prismatic shift (leftward vs. rightward). However, the mechanisms through which aftereffects of adaptation in healthy individuals and in neglect affect performance in tasks probing spatial cognition remain controversial. For example, some studies have reported positive effects of PA on auditory neglect, while other studies failed to obtain any changes of performance even in the visual modality. We here tested a new adaptation method in virtual reality to evaluate how sensory parameters influence PA aftereffects. Visual vs. auditory-verbal feedback of optical deviations were contrasted to assess whether rightward deviations influence manual and perceptual judgments in healthy individuals. Our results revealed that altered visual, but not altered auditory-verbal feedback induces aftereffects following adaptation to virtual prisms after 30-degrees of deviation. These findings refine current models of the mechanisms underlying the cognitive effects of virtual PA in emphasizing the importance of visual vs. auditory-verbal feedback during the adaptation phase on visuospatial judgments. Our study also specifies parameters which influence virtual PA and its aftereffect, such as the sensory modality used for the feedback.

Urethral corpus spongiosum amyloidosis presenting with urethrorrhagia during erection.

INTRODUCTION: Urethral amyloidosis is a rare, probably inflammatory condition usually presenting with hematuria and obstructive urinary symptoms, thus mimicking urethral malignancy. After histological confirmation of the diagnosis, treatment can be expectant or symptomatic. AIM. To report an unusual cause of urethrorrhagia occurring only during erection in an otherwise healthy man. METHODS. A 30-year-old man presented with a 5-month history of urethrorrhagia occurring only during erection, and with a painless palpable nodule in his penile urethra clearly visible on urethral US and magnetic resonance imaging, but not on urethroscopy. RESULTS. The patient underwent wide surgical excision of the urethral nodule and grafting of the urethral defect with a pedicled preputial flap. Histological examination revealed isolated amyloid of urethral corpus spongiosum. CONCLUSIONS. Isolated urethrorrhagia during erection and without urinary symptoms can be the presenting sign of urethral amyloidosis involving corpus spongiosum rather than the urethral lumen; in such cases, surgical exploration, wide urethral excision and grafting are mandatory.

How the brain predicts people's behavior in relation to rules and desires. Evidence of a medio-prefrontal dissociation.

Forming and updating impressions about others is critical in everyday life and engages portions of the dorsomedial prefrontal cortex (dMPFC), the posterior cingulate cortex (PCC) and the amygdala. Some of these activations are attributed to "mentalizing" functions necessary to represent people's mental states, such as beliefs or desires. Evolutionary psychology and developmental studies, however, suggest that interpersonal inferences can also be obtained through the aid of deontic heuristics, which dictate what must (or must not) be done in given circumstances. We used fMRI and asked 18 participants to predict whether unknown characters would follow their desires or obey external rules. Participants had no means, at the beginning, to make accurate predictions, but slowly learned (throughout the experiment) each character's behavioral profile. We isolated brain regions whose activity changed during the experiment, as a neural signature of impression updating: whereas dMPFC was progressively more involved in predicting characters' behavior in relation to their desires, the medial orbitofrontal cortex and the amygdala were progressively more recruited in predicting rule-based behavior. Our data provide evidence of a neural dissociation between deontic inference and theory-of-mind (ToM), and support a differentiation of orbital and dorsal prefrontal cortex in terms of low- and high-level social cognition.

Percutaneous nephrostomy in supine position.

INTRODUCTION: Percutaneous nephrostomy has traditionally been performed with the patient in the prone position, probably to reduce the risk of injury to adjacent visceral organs, particularly the colon. The prone position, however, is associated with disadvantages such as patient discomfort and circulatory and ventilatory difficulties, particularly in obese patients. We describe a technique of percutaneous nephrostomy with the patient in the supine anterolateral position using local anesthesia, ultrasound-guided puncture, and fluoroscopy-controlled placement. TECHNICAL CONSIDERATIONS: The supine anterolateral position was obtained by placing towels under the ipsilateral shoulder and gluteus to elevate the flank approximately 30 degrees, thus providing enough space for ultrasound scanning and ultrasound-guided puncture of the collecting system. The ipsilateral arm was placed over the thorax, and the contralateral arm was used for intravenous perfusion. The ipsilateral leg was flexed slightly, and the contralateral leg was flexed and abducted so that its lateral aspect lay on the table, providing adequate space in case of concomitant transurethral manipulation. In this supine position, the colon falls anteromedially and thus well apart from the puncture paths. In contrast, in the prone position, it is pushed against the lateral surface of the kidney in the way of possible puncture paths. CONCLUSIONS: Our experience with 12 consecutive patients showed this technique to be easy, safe, and effective and to prevent the discomfort and ventilation difficulties of the prone position, particularly in obese patients or those in poor general condition or with respiratory problems.