A neural code for time and space in the human brain.

Time and space are primary dimensions of human experience. Separate lines of investigation have identified neural correlates of time and space, yet little is known about how these representations converge during self-guided experience. Here, 10 subjects with intracranially implanted microelectrodes play a timed, virtual navigation game featuring object search and retrieval tasks separated by fixed delays. Time cells and place cells activate in parallel during timed navigation intervals, whereas a separate time cell sequence spans inter-task delays. The prevalence, firing rates, and behavioral coding strengths of time cells and place cells are indistinguishable-yet time cells selectively remap between search and retrieval tasks, while place cell responses remain stable. Thus, the brain can represent time and space as overlapping but dissociable dimensions. Time cells and place cells may constitute a biological basis for the cognitive map of spatiotemporal context onto which memories are written.

Using a picture (or a thousand words) for supporting spatial knowledge of a complex virtual environment.

External representations powerfully support and augment complex human behavior. When navigating, people often consult external representations to help them find the way to go, but do maps or verbal instructions improve spatial knowledge or support effective wayfinding? Here, we examine spatial knowledge with and without external representations in two studies where participants learn a complex virtual environment. In the first study, we asked participants to generate their own maps or verbal instructions, partway through learning. We found no evidence of improved spatial knowledge in a pointing task requiring participants to infer the direction between two targets, either on the same route or on different routes, and no differences between groups in accurately recreating a map of the target landmarks. However, as a methodological note, pointing was correlated with the accuracy of the maps that participants drew. In the second study, participants had access to an accurate map or set of verbal instructions that they could study while learning the layout of target landmarks. Again, we found no evidence of differentially improved spatial knowledge in the pointing task, although we did find that the map group could recreate a map of the target landmarks more accurately. However, overall improvement was high. There was evidence that the nature of improvement across all conditions was specific to initial navigation ability levels. Our findings add to a mixed literature on the role of external representations for navigation and suggest that more substantial intervention-more scaffolding, explicit training, enhanced visualization, perhaps with personalized sequencing-may be necessary to improve navigation ability.

Diagnostic Performance of Electromagnetic Navigation versus Virtual Navigation Bronchoscopy-Guided Biopsy for Pulmonary Lesions in a Single Institution: Potential Role of Artificial Intelligence for Navigation Planning.

Navigation bronchoscopy is an emerging technique used to evaluate pulmonary lesions. Using Veran's SPiN electromagnetic navigation bronchoscopy (ENB) and Archimedes virtual bronchoscopy navigation (VBN), this study aimed to compare the accuracy and safety of these procedures for lung lesions and to identify potentially relevant knowledge for the application of artificial intelligence in interventional pulmonology in a single institute. This single-center, retrospective study compared the ENB and VBN results in patients with pulmonary lesions unsuitable for biopsy via percutaneous transthoracic needle biopsy methods. A total of 35 patients who underwent navigation bronchoscopy for pulmonary lesion diagnosis were enrolled. Nineteen patients were stratified in the ENB group, and sixteen were in the VBN group. The mean age of this cohort was 67.6 ± 9.9 years. The mean distance of the lesion from the pleural surface was 16.1 ± 11.7 mm (range: 1.0-41.0 mm), and most lesions were a solid pattern (n = 33, 94.4%). There were 32 cases (91.4%) of pulmonary lesions with an air-bronchus sign. A statistically significant difference was found between pulmonary size and transparenchymal nodule access (p = 0.049 and 0.037, respectively). The navigation success rate was significantly higher in the VBN group (93.8% vs. 78.9%). Moreover, no procedure-related complications or mortality were noted. The radiographic characteristics, such as size or solid component, can affect the selection of the biopsy procedure, either ENB or VBN. Navigation bronchoscopy-guided biopsy demonstrated acceptable accuracy and a good safety profile in evaluating pulmonary lesions when the percutaneous approach was challenging or life threatening.

Visual-spatial processing impairment in the occipital-frontal connectivity network at early stages of Alzheimer's disease.

Introduction: Alzheimer's disease (AD) is the leading cause of dementia worldwide, but its pathophysiological phenomena are not fully elucidated. Many neurophysiological markers have been suggested to identify early cognitive impairments of AD. However, the diagnosis of this disease remains a challenge for specialists. In the present cross-sectional study, our objective was to evaluate the manifestations and mechanisms underlying visual-spatial deficits at the early stages of AD. Methods: We combined behavioral, electroencephalography (EEG), and eye movement recordings during the performance of a spatial navigation task (a virtual version of the Morris Water Maze adapted to humans). Participants (69-88 years old) with amnesic mild cognitive impairment-Clinical Dementia Rating scale (aMCI-CDR 0.5) were selected as probable early AD (eAD) by a neurologist specialized in dementia. All patients included in this study were evaluated at the CDR 0.5 stage but progressed to probable AD during clinical follow-up. An equal number of matching healthy controls (HCs) were evaluated while performing the navigation task. Data were collected at the Department of Neurology of the Clinical Hospital of the Universidad de Chile and the Department of Neuroscience of the Faculty of Universidad de Chile. Results: Participants with aMCI preceding AD (eAD) showed impaired spatial learning and their visual exploration differed from the control group. eAD group did not clearly prefer regions of interest that could guide solving the task, while controls did. The eAD group showed decreased visual occipital evoked potentials associated with eye fixations, recorded at occipital electrodes. They also showed an alteration of the spatial spread of activity to parietal and frontal regions at the end of the task. The control group presented marked occipital activity in the beta band (15-20 Hz) at early visual processing time. The eAD group showed a reduction in beta band functional connectivity in the prefrontal cortices reflecting poor planning of navigation strategies. Discussion: We found that EEG signals combined with visual-spatial navigation analysis, yielded early and specific features that may underlie the basis for understanding the loss of functional connectivity in AD. Still, our results are clinically promising for early diagnosis required to improve quality of life and decrease healthcare costs.

Real-Time Navigation in Google Street View® Using a Motor Imagery-Based BCI.

Navigation in virtual worlds is ubiquitous in games and other virtual reality (VR) applications and mainly relies on external controllers. As brain-computer interfaces (BCI)s rely on mental control, bypassing traditional neural pathways, they provide to paralyzed users an alternative way to navigate. However, the majority of BCI-based navigation studies adopt cue-based visual paradigms, and the evoked brain responses are encoded into navigation commands. Although robust and accurate, these paradigms are less intuitive and comfortable for navigation compared to imagining limb movements (motor imagery, MI). However, decoding motor imagery from EEG activity is notoriously challenging. Typically, wet electrodes are used to improve EEG signal quality, including a large number of them to discriminate between movements of different limbs, and a cuedbased paradigm is used instead of a self-paced one to maximize decoding performance. Motor BCI applications primarily focus on typing applications or on navigating a wheelchair-the latter raises safety concerns-thereby calling for sensors scanning the environment for obstacles and potentially hazardous scenarios. With the help of new technologies such as virtual reality (VR), vivid graphics can be rendered, providing the user with a safe and immersive experience; and they could be used for navigation purposes, a topic that has yet to be fully explored in the BCI community. In this study, we propose a novel MI-BCI application based on an 8-dry-electrode EEG setup, with which users can explore and navigate in Google Street View®. We pay attention to system design to address the lower performance of the MI decoder due to the dry electrodes' lower signal quality and the small number of electrodes. Specifically, we restricted the number of navigation commands by using a novel middle-level control scheme and avoided decoder mistakes by introducing eye blinks as a control signal in different navigation stages. Both offline and online experiments were conducted with 20 healthy subjects. The results showed acceptable performance, even given the limitations of the EEG set-up, which we attribute to the design of the BCI application. The study suggests the use of MI-BCI in future games and VR applications for consumers and patients temporarily or permanently devoid of muscle control.

Neural basis of topographical disorientation in the primate posterior cingulate gyrus based on a labeled graph.

Patients with lesions in the posterior cingulate gyrus (PCG), including the retrosplenial cortex (RSC) and posterior cingulate cortex (PCC), cannot navigate in familiar environments, nor draw routes on a 2D map of the familiar environments. This suggests that the topographical knowledge of the environments (i.e., cognitive map) to find the right route to a goal is represented in the PCG, and the patients lack such knowledge. However, theoretical backgrounds in neuronal levels for these symptoms in primates are unclear. Recent behavioral studies suggest that human spatial knowledge is constructed based on a labeled graph that consists of topological connections (edges) between places (nodes), where local metric information, such as distances between nodes (edge weights) and angles between edges (node labels), are incorporated. We hypothesize that the population neural activity in the PCG may represent such knowledge based on a labeled graph to encode routes in both 3D environments and 2D maps. Since no previous data are available to test the hypothesis, we recorded PCG neuronal activity from a monkey during performance of virtual navigation and map drawing-like tasks. The results indicated that most PCG neurons responded differentially to spatial parameters of the environments, including the place, head direction, and reward delivery at specific reward areas. The labeled graph-based analyses of the data suggest that the population activity of the PCG neurons represents the distance traveled, locations, movement direction, and navigation routes in the 3D and 2D virtual environments. These results support the hypothesis and provide a neuronal basis for the labeled graph-based representation of a familiar environment, consistent with PCG functions inferred from the human clinicopathological studies.

Virtual navigation bronchoscopy-guided intraoperative indocyanine green localization in simultaneous surgery for multiple pulmonary nodules.

BACKGROUND: Accurate localization of pulmonary nodules is the main difficulty experienced in wedge resection. Commonly used localization methods have their own advantages and disadvantages. However, clinical work has demonstrated that intraoperative indocyanine green localization under electromagnetic navigation bronchoscopy/virtual navigation bronchoscopy (VNB) is more advantageous than conventional methods for patients with multiple pulmonary nodules undergoing simultaneous surgery, especially for those undergoing bilateral lung surgery. METHODS: Data of patients undergoing simultaneous surgery for multiple pulmonary nodules with preoperative methylene blue localization by computed tomography (CT)-guided percutaneous lung puncture (methylene blue group) or intraoperative indocyanine green localization under VNB (virtual navigation group) were retrospectively analyzed. Patient characteristics, pulmonary nodule features, localization time, preoperative location time, location success rate, operation time, complication incidence, visceral pleural staining rate after localization, and pulmonary nodule primary resection success rate were compared between the two groups. RESULTS: The methylene blue and virtual navigation groups comprised 39 and 20 patients with 119 and 67 pulmonary nodules resected, respectively. Sex, age, number of pulmonary nodules resected simultaneously, unilateral/bilateral lung surgery, pulmonary nodule size, distance between pulmonary nodules and the visceral pleura, pulmonary nodule consolidation-to-tumor ratio, location of pulmonary nodules in the pulmonary lobe, postoperative pathology, visceral pleura staining rate, primary pulmonary nodule resection success rate, and surgical duration did not differ significantly between the groups (p > 0.05). The localization time of the virtual navigation group was significantly shorter than that of the methylene blue group (p < 0.05), regardless of unilateral or bilateral multiple nodules. In the methylene blue group, 25.64% (10/39) of patients presented complications, all of which were pneumothorax, whereas no complications were found in the virtual navigation group. CONCLUSIONS: For patients with multiple pulmonary nodules undergoing simultaneous surgery, indocyanine green injection under VNB can achieve a similar effect on pulmonary nodule localization as classical methylene blue injection under CT-guided percutaneous lung puncture, with shorter localization time and fewer complications.

Stress-induced HPA activation in virtual navigation and spatial attention performance.

BACKGROUND: Previous research has shown that spatial performance (e.g. navigation, visuospatial memory, attention) can be influenced by acute stress; however, studies have produced mixed findings sometimes showing an improvement after stress, other times showing impairment or no overall effect. Some of these discrepancies may be related to: the type of stress system activated by the stressor (sympathetic adrenal medulla [SAM] or hypothalamic-pituitary-adrenocortical [HPA]); whether cortisol responders vs. nonresponders are analyzed subsequent to main effects; and sex differences in stress responses. In the present study, we examine the influence of HPA activation from an acute laboratory stressor (Socially Evaluated Cold Pressor test [SECPT]) on performance during two spatial tasks: Useful Field of View (UFOV; a measure of spatial attention) and virtual reality (VR) navigation. We assigned 31 males and 30 females to either the SECPT or a Non-Stress condition prior to the two spatial tasks. Cardiovascular measures including heart rate and blood pressure, and salivary cortisol biosamples were obtained at specific time points. RESULTS: Participants in the Stress condition showed increases in heart rate, systolic and diastolic blood pressure indicating sympathetic adrenal medulla (SAM) axis activation. Stress also led to increases in salivary cortisol, suggesting hypothalamic-pituitary-adrenocortical (HPA) activation. Stress did not influence overall performance in the spatial attention UFOV or the VR navigation task. However, a sex difference in spatial attention was detected when participants were divided into Stress-cortisol responders and non-responders in the UFOV task. Male Stress-cortisol responders (n = 9) showed better UFOV accuracy than female Stress-cortisol responders (n = 6); no sex differences were found among the Non-Stress control group. Furthermore, for females in the stress condition (n = 14), higher cortisol responses were associated with lower spatial attention performance. CONCLUSIONS: Socially Evaluated Cold Pressor stress resulted in no change in speed or accuracy in a VR navigation task. For the spatial attention task, the SECPT led to a sex difference among Stress-cortisol responders with males showing improved accuracy over females. The relationship between HPA activation and prefrontal cortex activity may be necessary to understand sex differences in spatial attention performance.

Total laparoscopic resection by medial-retroperitoneal approach using virtual navigation: two case reports of primary retroperitoneal schwannoma.

BACKGROUND: We report two rare cases of retroperitoneal schwannoma completely resected by a laparoscopic medial-retroperitoneal approach aided by virtual navigation. Three-dimensional images have been used in liver and lung surgery, but there are few prior reports on retroperitoneal surgery. CASE PRESENTATION: These two case reports are of a 60-year-old man and a 40-year-old man with asymptomatic retroperitoneal schwannoma. In both cases, the tumors were located in the right renal hilum and were close to the duodenum, right ureter, and inferior vena cava. Simulation using three-dimensional images was performed before surgery, and a medial-retroperitoneal approach was performed to secure a wide surgical field. During the operation, we confirmed the location of the main feeder and the relationship between the tumor and organs with those shown on the three-dimensional images and performed total laparoscopic resection. CONCLUSION: The medial-retroperitoneal approach provides operative safety. Preoperative simulation and intraoperative navigation with three-dimensional images, which can be freely rotated and interactively visualized from any angle, are useful methods to enhance the surgeon's understanding of a patient's specific anatomy and are especially effective when resecting a retroperitoneal tumor that is located in an anatomically deep and complex location.

Prospective Evaluation of Ultrasound in a Novel Position with MRI Virtual Navigation for MRI-Detected Only Breast Lesions: A Pilot Study of a More Efficient and Economical Method.

The aim of this study was to evaluate the clinical utility of ultrasound (US) with magnetic resonance imaging (MRI) virtual navigation in a novel prone position for MRI-detected incidental breast lesions. Between June 2016 and June 2020, 30 consecutive patients with 33 additional Breast Imaging Reporting and Data System (BI-RADS) category 4 or 5 lesions that were detected on MRI but occult on second-look US were enrolled in the study. All suspicious lesions were located in real-time US using MRI virtual navigation in the prone position and then followed by US-guided biopsy or surgical excision. Pathological results were taken as the standard of reference. The detection rate of US with MRI virtual navigation was calculated. The MRI features and pathological types of these lesions were analyzed. A total of 31 lesions were successfully located with real-time US with MRI virtual navigation and then US-guided biopsy or localization, and the detection rate was 93.9% (31/33). Twenty-seven (87.1%, 27/31) proved to be benign lesions and four (12.9%, 4/31) were malignant lesions at pathology. Of the 33 MRI-detected lesions, 31 (93.9%, 31/33) were non-mass enhancements and two (6.1%, 2/33) were masses. This study showed that real-time US with prone MRI virtual navigation is a novel efficient and economical method to improve the detection and US-guided biopsy rate of breast lesions that are detected solely on MRI.

The Feasibility of Using Virtual Reality and Eye Tracking in Research With Older Adults With and Without Alzheimer's Disease.

Aim: To examine the feasibility of using large scale spatial, self-mobile, virtual reality, and eye tracking in older adults with and without Alzheimer's disease (AD). Methods: Older adults with early stage AD (n = 38) and a control group without AD (n = 50) were asked to find their way in a large, projected VR simulation of a retirement community repeatedly over 10 trials for each of 2 days, while wearing eye tracking glasses. Feasibility measures, including tolerance, side effects, and ability to complete the VR and eye tracking were collected. This study reports the analysis of the feasibility data for the VR and eye tracking and comparison of findings between the groups. Results: Over 80% of the subjects were able to complete the VR portion of the study. Only four subjects, all in the AD group, could not use the joystick and were excluded. Withdrawal rate (18%) was similar between the groups [X 2 (2) = 2.82, N = 88, p = 0.245] with most withdrawals occurring after the fourth trial. Simulation sickness was not significantly different between the groups. Only 60% of the subjects had completed eye tracking videos; more subjects in the AD group had complete eye tracking videos than the control group; X 2 (1) = 7.411, N = 88, p = 0.006. Eye tracking incompletion was primarily due to inability to calibration issues. Conclusion: Virtual reality testing and eye tracking can be used in older adults with and without AD in a large-scale way-finding task, but that there are some limitations.

Multi-Dimensional Display of Wang's Lymph Node Map Using Virtual Bronchoscopic Navigation System.

Background: Transbronchial needle aspiration (TBNA) is a classical technique for diagnosing mediastinal-hilar lymph node enlargement. However, the diagnostic value of conventional TBNA (cTBNA) is limited in small lymph nodes. Methods: Here, we generated an innovative multi-dimensional virtual lymph node map on top of Wang's lymph node map using a Lungpoint Virtual Bronchoscopic Navigation System. Results: The virtual bronchoscopic navigation (VBN) system was combined with computed tomography (CT) images to generate extrabronchial, endobronchial, sagittal, coronal as well as horizontal views of the 11 intrathoracic lymph node stations and their adjacent tissues and blood vessels. We displayed the specific puncture site of each lymph node station. The 11 stations were divided into four groups: right mediastinal stations, left mediastinal stations, central mediastinal stations and hilar stations. Conclusion: The VBN system provides a precise view of the intrabronchial landmarks, which may increase the diagnostic accuracy of intrathoracic lymph node adenopathy and assist bronchoscopists with practicing TBNA.

Craniopagus twin: pre- and post-natal 3-dimensional virtual and physical models and virtual navigation created with free or open source software-an option for low-resource centers.

BACKGROUND: Craniopagus twins represent a rare and complex congenital malformation characterized by conjoined twins fused at the cranium. Craniopagus is challenging for patients' families and surgeons, and accurate confirmation of the extent of cranial fusion is a complex process. Most information regarding the surgical anatomy of this rare condition is obtained through analysis of ultrasonographic, magnetic resonance, or computed tomographic images. A multidisciplinary team plays a key role in obtaining such information and in parental counseling and coordination of various complex processes for optimal postnatal care of these twins. The extent of fusion is usually determined based on conventional clinical methods, such as imaging studies. METHODS: Imaging software is being used in recent times to create three-dimensional reconstruction images and for virtual navigation to investigate the skulls and brains of craniopagus twins. However, the acquisition and maintenance costs of such sophisticated medical software may be unaffordable for medical centers in developing countries. To overcome this limitation, we investigated the role of open or free source software for accurate determination of complex malformations of the skull and brain of craniopagus twins.

Virtual navigation for the improvement of parents counseling and the planning of fetal endoscopic myelomeningocele repair.

BACKGROUND: Myelomeningocele (MMC) is the most severe form of spina bifida with intrauterine repairs becoming more prevalent. The development of three-dimensional ultrasound (3DUS) and magnetic resonance imaging (MRI) has drastically improved the visualization of fetal anatomy. METHODS: Virtual Navigation (VN) results from a technology that uses software generated realistic images to replicate the immersive feeling of a real environment. CONCLUSION: This report aims to demonstrate VN in a Chiari II malformation case, obtained from 3DUS and MRI files, comparing this with the fetal endoscopic surgery for MMC.

Complications after 100 sessions of cone-beam computed tomography-guided lung radiofrequency ablation: a single-center, retrospective experience.

Objective: To evaluate complications after consecutive 100 sessions of cone-beam computed tomography (CBCT)-guided radiofrequency ablation (RFA) of lung tumorsMaterials and methods: A retrospective study was conducted from January 2016 and October 2018. All procedures were performed using a CBCT virtual navigation guidance system, combining three-dimentional CBCT, needle planning software, and real-time fluoroscopy. Complications were evaluated for each RFA session in 63 consecutive patients (31 male, 32 female; mean age 58.0 years) with 121 lung tumors who underwent 100 sessions of CBCT-guided lung ablation with an internally cooled RFA system. Complications were recorded using the Common Terminology Criteria of Adverse Events (CTCAE) 5.0. A major complication was defined as a grade 3 or 4 adverse event.Results: There was no postprocedural mortality. The major and minor complication rates were 5% and 28%, respectively. The major complications were significant pulmonary hemorrhage (1%), large hemothorax requiring drainage (1%), pneumonia treated with antibiotics (2%), and delayed bronchopleural fistula (1%). The minor complications were pneumothorax (15%), hemoptysis (11%), and subcutaneous emphysema (2%). Of the 15 pneumothoraces, percutaneous catheter drainage was required in six sessions. Pneumothorax was more likely to occur if RFA was performed on two or more tumors at one session. Immediate, periprocedural and delayed complications were 23%, 9%, and 1%, respectively.Conclusion: CBCT-guided RFA of lung tumors is a relatively safe procedure with acceptable morbidity.

The comparison of electromagnetic with virtual bronchoscopic navigation accuracy at hybrid operating room in patient with sternal wires.

We describe a case of a 63-year-old lady with an incidental small right upper lobe ground glass opacity (GGO) lesion, who had history of open-heart surgery with bypass grafts for coronary artery disease. Video-assisted thoracic surgery (VATS) excisional biopsy with pre-operative localization was planned. Localization by percutaneous approach is challenging due to position of GGO shielded by both the scapular and ribs. Electromagnetic navigation accuracy may be affected by steel sternal wires but its effect has not been reported on literature. Both virtual and electromagnetic navigation bronchoscopy platforms were used with real-time cone-beam CT confirmation in the hybrid operating room to perform dye marking. Both navigation methods successfully marked the GGO for lung resection. Our case demonstrated that the accuracy of electromagnetic navigation in the presence of steel sternal wire is satisfactory for dye marking and the use of intra-operative cone-beam CT in hybrid operating room is invaluable for the success of navigational bronchoscopy.

Advances in interventional diagnostic bronchoscopy for peripheral pulmonary lesions.

Introduction: The incidence of peripheral pulmonary lesions (PPLs) is growing following the adoption of lung cancer screening by low-dose chest CT. Although CT-guided transthoracic needle aspiration has been the standard method to diagnose PPLs, the field of interventional bronchoscopy is rapidly advancing to overcome complications of the transthoracic approach yet maintain the yield. Areas covered: This article reviews the clinical evidence of recent emerging interventional bronchoscopic techniques for diagnosis of PPLs. Expert opinion: Recent advances in interventional bronchoscopy contribute to not only the safety of transbronchial approaches to PPLs but also the higher diagnostic yield. To perform accurate sampling of PPLs, bronchoscopists must select the correct airway, approach the target as close as possible, and confirm the location of the target before sampling. These key steps can be assisted by recently developed technologies. However, it is important for bronchoscopists to understand the strengths and limitations of these emerging technologies.

Current status of diagnostic and therapeutic bronchoscopy in Japan: 2016 national survey of bronchoscopy.

BACKGROUND: The safety management committee of the Japan Society for Respiratory Endoscopy (JSRE) conducted national surveys to clarify the state of diagnostic and therapeutic bronchoscopy in 2016. METHODS: Questionnaire forms were mailed to 532 JSRE-accredited facilities throughout Japan. We surveyed the actual condition of clinical practice and cases of bronchoscopy during 2016. RESULTS: Four hundred and thirty-three facilities responded giving a response rate of 81.4%; 67.6% held more than 400 beds. The average number of board accredited senior Fellows and Fellows per facility was 1.9 and 3.2, respectively. Diagnostic bronchoscopy was performed in a hospitalized setting in 74.6% of all facilities. The radial type ultrasound probe was operated in 51.7% of all facilities. The number of facilities has markedly increased compared with that reported in the 2010 survey (19.6%). The bronchoscopic navigation system had been in operation in 41.7% of all facilities. Antithrombotic drugs were adjusted before biopsy in 96.8% of all facilities. For intravenous sedation, midazolam was the first choice in 76.9% of all facilities. Endobronchial ultrasound guided transbronchial lymph node needle aspiration (EBUS-TBNA) has become popular over the decade (19.6% in 2010 to 68.1% in 2016). The mean number of the board accredited senior Fellows and board accredited Fellows increased in comparison with that in 2010. As a new technique, radial type ultrasound-guided peripheral approach has become popular. CONCLUSIONS: Through this survey, the advanced safety of bronchoscopic examination has been secured in many facilities. A continuous monitoring of bronchoscopic practices with respect to safety management is recommended.

Generalisation decrement and not overshadowing by associative competition among pairs of landmarks in a navigation task with humans.

In three experiments, a virtual preparation for humans of the Morris water task (VMWT) was used. Experiment 1 established that four landmarks were of similar salience. Then, in Experiments 2 and 3, participants were trained to locate a hidden platform in the presence or either two or four of the previous landmarks. In Experiment 2, one pair of groups was trained with four visual landmarks spaced at equal intervals around the edge of the pool, while a second pair was trained with two landmarks only, either relatively close to or far from the hidden platform. After training, a reciprocal overshadowing effect was found: on a test without the platform with two landmarks only (either close to or far from the platform position), the participants trained with four landmarks spent less time in the platform quadrant than those trained with only two. Finally, Experiment 3 showed that at least participants trained with two landmarks relatively close to the platform and then tested with four also performed worse on test than those trained and tested with two close landmarks only. This result suggests that generalisation decrement, rather than associative competition, could provide a sufficient explanation for the overshadowing observed in Experiment 2 in the proximal groups. The present set of experiments extend, although only partially, the generalisation decrement results documented in rats to human participants.

Can we study 3D grid codes non-invasively in the human brain? Methodological considerations and fMRI findings.

Recent human functional magnetic resonance imaging (fMRI) and animal electrophysiology studies suggest that grid cells in entorhinal cortex are an efficient neural mechanism for encoding knowledge about the world, not only for spatial location but also for more abstract cognitive information. The world, be it physical or abstract, is often high-dimensional, but grid cells have been mainly studied on a simple two-dimensional (2D) plane. Recent theoretical studies have proposed how grid cells encode three-dimensional (3D) physical space, but it is unknown whether grid codes can be examined non-invasively in humans. Here, we investigated whether it was feasible to test different 3D grid models using fMRI based on the direction-modulated property of grid signals. In doing so, we developed interactive software to help researchers visualize 3D grid fields and predict grid activity in 3D as a function of movement directions. We found that a direction-modulated grid analysis was sensitive to one type of 3D grid model - a face-centred cubic (FCC) lattice model. As a proof of concept, we searched for 3D grid-like signals in human entorhinal cortex using a novel 3D virtual reality paradigm and a new fMRI analysis method. We found that signals in the left entorhinal cortex were explained by the FCC model. This is preliminary evidence for 3D grid codes in the human brain, notwithstanding the inherent methodological limitations of fMRI. We believe that our findings and software serve as a useful initial stepping-stone for studying grid cells in realistic 3D worlds and also, potentially, for interrogating abstract high-dimensional cognitive processes.