Landmark Guidance Research Articles

Imaging Guidance Improves the Results of Viscosupplementation with HANOX-M-XL in Patients with Ankle Osteoarthritis: Results of a Clinical Survey in 50 Patients Treated in Daily Practice.

BACKGROUNDThe objective of this survey was to assess retrospectively the interest of performing viscosupplementation using imaging guidance in patients suffering from ankle osteoarthritis (OA).PATIENTS AND METHODSThis is a multicenter retrospective survey using a standardized questionnaire. Fifty patients suffering from ankle OA and treated, in daily clinical practice, with a single intra-articular injection of a novel viscosupplement made of a combination of a non-animal cross-linked hyaluronan and mannitol, HANOX M-XL, were included in the survey. The injection procedure (imaging or landmark guidance), demographic data, patient’s self-evaluation of pain, satisfaction, treatment efficacy, and tolerability were collected. Predictive factors of both efficacy and patient’s satisfaction were investigated.RESULTSThe percentages of patients very satisfied/satisfied and not really satisfied/dissatisfied with the treatment were 68% and 32%, respectively. Efficacy was rated as very good, good, moderate, and poor by 38%, 30%, 12%, and 20% of the cases, respectively. Efficacy was unrelated to gender and age and was highly correlated with pain score (P < 0.0001). In satisfied patients, the decrease in consumption of analgesics/non-steroidal anti-inflammatory drugs was >75% in 64% of the cases. Efficacy was significantly different with regard to imaging guidance. There was a statistically significant difference in efficacy and satisfaction between landmark-guided and imaging-guided injections (P = 0.02). The success rate was 2.3 times higher in the imaging-guided group than in the landmark-guided group. No significant difference was found between patients injected under fluoroscopy or ultrasound guidance, despite a trend favoring ultrasound (P = 0.09). Tolerability was rated as very good/good in 47 patients, moderate in two, and poor in one and was unrelated to the type of guidance.CONCLUSIONThis preliminary study suggests that the use of imaging guidance significantly optimizes the success rate of ankle viscosupplementation. No safety concern was observed.LEVEL OF EVIDENCEIII.

Three-dimensional models of natural environments and the mapping of navigational information.

Much evidence has accumulated in recent years, demonstrating that the degree to which navigating insects rely on path integration or landmark guidance when displaced depends on the navigational information content of their specific habitat. There is thus a need to quantify this information content. Here we present one way of achieving this by constructing 3D models of natural environments using a laser scanner and purely camera-based methods that allow us to render panoramic views at any location. We provide (1) ground-truthing of such reconstructed views against panoramic images recorded at the same locations; (2) evidence of their potential to map the navigational information content of natural habitats; (3) methods to register these models with GPS or with stereo camera recordings and (4) examples of their use in reconstructing the visual information available to walking and flying insects. We discuss the current limitations of 3D modelling, including the lack of spectral and polarisation information, but also the opportunities such models offer to map the navigational information content of natural habitats and to test visual navigation algorithms under 'real-life' conditions.

Food searches and guiding structures in North African desert ants, Cataglyphis.

North African desert ants, Cataglyphis fortis, use path integration as their primary means of navigation. The ants also use landmarks when these are available to improve navigation accuracy. Extended landmarks, such as walls and channels, may serve further functions, for example, local guidance or triggering of local vectors. The roles of such structures were usually examined in homing animals but not during food searches. When searching for familiar feeding sites, Cataglyphis may show intriguing deviations from expected search performances. These may result from the presence of extended landmarks, namely experimental channels. Here we scrutinise this hypothesis of landmark guidance in food searches. We prevented the ants from seeing the channel walls by covering their eyes, except the dorsal rim area. This experiment was repeated in the open test field with an alley of black cylinders to extend our findings to a more normal foraging environment. Ants with covered eyes did not deviate from expected search performances, whereas ants with normal eyes extended their searches along the axis of the leading structures by 15–20 %, in both channels and landmark alleys. This demonstrates that Cataglyphis orients along extended landmarks when searching for familiar food sources and alters its search pattern accordingly.

Performance of central venous catheterization by medical students: a retrospective study of students' logbooks.

BackgroundMedical students often learn the skills necessary to perform a central venous catheterization in the operating room after simulator training. We examined the performance of central venous catheterization by medical students from the logbooks during their rotation in department of anesthesiology.MethodsFrom the logbooks of medical students rotating in our department between January 2011 and June 2012, we obtained the kind and the number of central venous catheterization students had done, the results of the procedures whether they were success or failed, the reasons of the failures, complications, and the student self-reported confidence and satisfaction of their performance.ResultsThere were 93 medical students performed 875 central venous catheterizations with landmark guidance on patients in the operating theater, and the mean number of catheterizations performed per student was 9.4 ± 2.0, with a success rate of 67.3%. Adjusted for age, sex, body mass index, surgical category, ASA score and insertion site, the odds of successful catherization improved with cumulative practice (odds ratio 1.10 per additional central venous catheterization performed; 95% confidence interval 1.05–1.15). The major challenge students encountered during the procedure was the difficulty of finding the central veins, which led to 185 catheterizations failed. The complication rate of central venous catheterization by the students was 7.8%, while the most common complication was puncture of artery. The satisfaction and confidence of students regarding their performance increased with each additional procedure and decreased significantly if failure or complications had occurred.ConclusionA student logbook is a useful tool for recording the actual procedural performance of students. From the logbooks, we could see the students’ performance, challenges, satisfaction and confidence of central venous catheterization were improved through cumulative clinical practice of the procedure.

Part I—The Historical and Legal Background Leading to the Office of Civil Rights “Dear Colleague Letter”

Part I of the feature describes the historical path of the Dear Colleague Letter and discusses the specific road to this landmark guidance, what it means, and how the leadership and action of the Office for Civil Rights will pave the way for students with disabilities to participate in sports the same way that Title IX has enabled participation for women.

Navigational Efficiency of Nocturnal Myrmecia Ants Suffers at Low Light Levels

Insects face the challenge of navigating to specific goals in both bright sun-lit and dim-lit environments. Both diurnal and nocturnal insects use quite similar navigation strategies. This is despite the signal-to-noise ratio of the navigational cues being poor at low light conditions. To better understand the evolution of nocturnal life, we investigated the navigational efficiency of a nocturnal ant, Myrmecia pyriformis, at different light levels. Workers of M. pyriformis leave the nest individually in a narrow light-window in the evening twilight to forage on nest-specific Eucalyptus trees. The majority of foragers return to the nest in the morning twilight, while few attempt to return to the nest throughout the night. We found that as light levels dropped, ants paused for longer, walked more slowly, the success in finding the nest reduced and their paths became less straight. We found that in both bright and dark conditions ants relied predominantly on visual landmark information for navigation and that landmark guidance became less reliable at low light conditions. It is perhaps due to the poor navigational efficiency at low light levels that the majority of foragers restrict navigational tasks to the twilight periods, where sufficient navigational information is still available.

The Clavicular Notch as an Alternate Anatomical Landmark for Internal Jugular Vein Cannulation in Infants and Children: A Descriptive Study

Objective: To evaluate an alternate anatomical landmark technique for internal jugular vein cannulation in infants and children. Aim: To evaluate the success and safety of the clavicular notch as a bony landmark for central venous cannulation in infants and children. Background: Central venous cannulation can be particularly difficult in infants and children. While ultrasound-guided techniques are well established, the majority of central venous catheters are placed using landmark guidance with variable success rate. This prospective study documents the success and safety of a modified landmark technique using the clavicular notch as a bony landmark for central venous cannulation in this group of patients. Materials and methods: One hundred and fifty children under 12 years of age belonging to ASA grade I to III were included in the study. All children were placed in 150 trendelenberg position with head rotated 40o to the opposite side. The relationship of the IJV to the carotid artery was noted by audio Doppler. The notch technique was used only if the IJV was detected by Doppler at the notch. Using the standard seldinger technique the IJV was cannulated and the complications were noted. The traditional approach was our rescue method. Results: The IJV was localized at the clavicular notch in 95.33% (143/150) cases by audio Doppler and the overall successful cannulation rate was 98.6% (141/143). We encountered complications in 13 (8.6%) cases, none of which had any adverse outcome. Conclusion: This study confirms the consistent location of IJV at the clavicular notch. Therefore, the ‘Notch technique’ can be used successfully for IJV cannulation in infants and children.

Anatomical variations of the internal jugular vein in relation to carotid artery : an ultrasound study

Background: In developing country like India, central venous catheter is still inserted using anatomical landmark guidance with success rate up to 97.6% and complications up to 15%. Aims & Objective: This study was aimed to determine the anatomical variations of the internal jugular vein (IJV) in relation with carotid artery (CA) with the help of 2-D ultrasound. Material and Methods: This prospective randomized study was conducted in a teaching and tertiary care hospital on 100 young healthy volunteers of either sex, aged 20 years to 40 years. Each volunteer was placed supine with 15˚ down trendlenberg position with 45˚ neck rotation on contra-lateral side. Linear array probe with 7.5 M Hz of “Sonosite Micromaxx” ultrasound machine was placed perpendicular to the apex of the triangle formed by two heads of sternocleidomastoid muscle and clavicle. Vessels were visualized in transverse section in 2-D ultrasound. Exact location of IJV was identified in relation to the CA on ultrasound and recorded as lateral, antero-lateral, anterior, medial, and posterior. The diameter of IJV and CA, distance from skin to IJV were recorded on both sides of neck for each volunteer. Anterior position of IJV in relation to CA was defined as dangerous position. Small sized IJV was defined as diameter ≤7 mm. Data were analyzed using Graphpad prism software version 5.1. P value < 0.05 was taken as significant. Results: The mean diameter of IJV was 13.23 (2.52) mm in right and 10.25(2.29) mm in left side of neck (p=0.0001). Small sized IJV was in 1% in right and 8% in left side (p=0.0349). 15% and 28% of volunteers had dangerous position of IJV in relation to CA on right and left side of neck respectively (p=0.0381). Conclusion: Significant number of healthy young volunteers had anatomical variations in terms of size and position of IJV (left side > right side) in relation of CA by ultrasound screening. Thus, anatomical landmarks are not sufficient, alternative measures like ultrasound scanning should be implemented prior to catheterization to identify the individual with potentially difficult catheterization.

Comparison of Anatomic Landmarks and Ultrasound Guidance for Intercostal Nerve Injections in Cadavers

Intercostal nerve (ICN) injections are routinely performed under anatomic landmark or fluoroscopic guidance for acute and chronic pain indications. Ultrasound (US) is being used increasingly to perform ICN injections, but there is lack of evidence to support categorically the benefits of US over conventional techniques. We compared guidance with US versus anatomic landmarks for accuracy and safety of ICN injections in cadavers in a 2-phase study that included evaluation of deposition of injected dye by dissection and spread of contrast on fluoroscopy. A cadaver experiment was performed to validate US as an imaging modality for ICN blocks. In the first phase of the study, 12 ICN injections with 2 different volumes of dye were performed in 1 cadaver using anatomic landmarks on one side and US-guidance on the other (6 injections on each side). The cadaver was then dissected to evaluate spread of the dye. The second phase of the study consisted of 74 ICN injections (37 US-guided and 37 using anatomic landmarks) of contrast dye in 6 non-embalmed cadavers followed by fluoroscopy to evaluate spread of the contrast dye. In the first phase of the study, the intercostal space was identified with US at all levels. Injection of 2 mL of dye was sufficient to ensure compete staining of the ICN for 5 of 6 US-guided injections but anatomic landmark guidance resulted in correct injection at only 2 of 6 intercostal spaces. No intravascular injection was found on dissection with either of the guidance techniques. In the second phase of the study, US-guidance was associated with a higher rate of intercostal spread of 1 mL of contrast dye on fluoroscopy compared with anatomic landmarks guidance (97% vs 70%; P = 0.017). Ultrasound confers higher accuracy and allows use of lower volumes of injectate compared with anatomic landmarks as a guidance method for ICN injections in cadavers. Ultrasound may be a viable alternative to anatomic landmarks as a guidance method for ICN injections.

Resident accuracy in locating the common femoral vein in normal weight vs. obese patients

Objectives: Ultrasound guidance increases the success of internal jugular central venous catheter (CVC) placement. The common femoral vein (CFV) is considered an easier site and physicians frequently place CFV CVCs using anatomical landmark guidance. No research has demonstrated the effect of patient weight on placement of a femoral CVC. The authors hypothesized that resident physicians could determine by anatomical landmarks the insertion site of a femoral CVC in normal and overweight adults. Methods: Investigators consented adult patients in the Emergency Department to serve as study models. Patients were grouped by BMI: Normal (BMI (BMI > 25). PGYI-III Emergency Medicine residents who volunteered to participate were included. Residents inspected and palpated the inguinal regions on a patient and marked the patient’s skin directly over the CFV. A faculty member assessed success using a 10 MHz linear probe (Sonosite Micro Maxx) centered over the mark. The attempt was successful if the mark was directly over the CFV and unsuccessful if distal, lateral, or medial to the CFV. Results: Nineteen residents (6 PGYI, 7 PGY II, and 6 PGYIII) assessed 17 patients. There were 43 attempts on Normal patients and 57 attempts on Overweight patients. The success rate on Normal patients was 74% and on Overweight patients was 42% (p = 0.0021). Conclusion: Residents were more successful in correctly identifying the CFV by anatomical landmarks in Normal patients. Training year had no effect on success. Ultrasound guidance may increase the success rate of placing a femoral CVC in patients with BMI > 25.

English

BACKGROUND: Context: A central venous line access is very importance in management of the critically ill patients even though, it may carry a risk of complications. AIMS: Objective of this study is to assess and compare success rate, attempts of cannulation and complications like inadvertent arterial puncture, hematoma, and pneumothorax occurred during the Central Venous Catheter (CVC) placement using ultrasound guidance (USG) & anatomical landmark guidance (ALG). SETTINGS AND DESIGN: The prospective randomized study was carried out in 64 patients for right sided internal jugular vein CVC placement. Using computer generated randomization chart, all patients were divided randomly into two groups: Group USG and Group ALG. METHODS AND MATERIAL: Right sided internal jugular vein (IJV) was cannulated with the guidance of ultrasound and anatomical landmark, respectively in group USG and group ALG. Patients were observed & data were recorded for success rate, no. of attempts, and complications like inadvertent arterial puncture, hematoma, and pneumothorax STATISTICAL ANALYSIS USED : Database was analysed using graphpad prism 5 software. RESULTS: Success rate is 31 out of 32 (96.88%) in group USG while 24 out of 32 (75%) in group ALG (p =0.031). Placement of central venous catheter with 1st attempt is 28 out of 32 (87.50%) in group USG while 18 out of 32 (56.25%) in group ALG (p =0.012). Hematoma and overall complications are 0 versus 6 (18.75%) in group USG & ALG respectively. CONCLUSIONS: Ultrasound guided central venous catheter placement is easy, safer & prudent approach than the anatomical landmark guided central venous catheter placement. KEY MESSAGES: We believe that Ultrasound guidance should be encouraged for all central venous catheter placements in patients & thereby improving patient's safety and quality care.

Image-guided versus blind glucocorticoid injection for shoulder pain

Traditionally, glucocorticoid injection for the treatment of shoulder pain has been performed guided by anatomical landmarks alone. With the advent of readily available imaging tools such as ultrasound, image-guided injections have increasingly become accepted into routine care. While there is some evidence that the use of imaging improves accuracy, it is unclear from current evidence whether or not it improves patient-relevant outcomes. The aim of this review was to assess whether image-guided glucocorticoid injections improve patient-relevant outcomes compared to landmark-guided or systemic intramuscular injections in patients with shoulder pain. We searched the Cochrane Central Register of Controlled Trials (CENTRAL, via The Cochrane Library), MEDLINE (Ovid), and EMBASE (Ovid) to June 2011. We also searched the World Health Organisation International Clinical Trials Registry Platform (http://www.who.int/trialsearch/Default.aspx) to identify ongoing trials and screened reference lists of retrieved review articles and trials to identify potentially relevant studies. We included randomised controlled trials (RCTs) and quasi-randomised controlled clinical trials that compared image-guided glucocorticoid injection to landmark-guided or systemic intramuscular injection. Outcomes of interest included pain, function, range of motion, proportion of participants with overall improvement and adverse events. There were no restrictions on language or date of publication. Two review authors independently selected the studies for inclusion, extracted the data and performed a risk of bias assessment. Disagreement about inclusion or exclusion of individual studies and risk of bias was resolved by a third review author. Five studies (290 participants) were included in the review. The image-guided groups in all trials used ultrasound to guide injection. Four studies included participants with rotator cuff disease; in three the comparator was local landmarks to direct injection into the subacromial bursa and in the fourth the comparator was systemic intramuscular injection into the upper gluteal muscles in the buttock region. One study included participants with adhesive capsulitis and injection was directed into the glenohumeral joint by either ultrasound or anatomical landmark guidance.No significant differences between groups were observed with respect to reduction in pain at one to two weeks (two trials, 146 participants, standardized mean difference (SMD) -1.44, 95% CI -4.14 to 1.26), or function at one to two weeks (two trials, 146 participants, SMD 0.95, 95% confidence interval (CI) -1.29 to 3.20; back-translated to mean difference (MD) 4 points, 95% CI -5 to 13, on a 0 to 100 point scale, higher score means better function) or six weeks (three trials, 207 participants, SMD 0.63, 95% CI -0.06 to 1.33; back-translated to MD -3 points, 95% CI -11 to 5, on a 0 to 100 point scale) and the sensitivity analyses did not alter these results. While there was a significant difference between groups with respect to reduction in pain at six weeks favouring image guidance (three trials, 207 participants, SMD -0.80, 95% CI -1.46 to -0.14), there was considerable statistical heterogeneity and after removing trials with inadequate allocation concealment and inadequate blinding in a sensitivity analysis, the difference was no longer significant (one trial, 106 participants, MD -0.60 points, 95% CI -1.44 to 0.24 points on a 9-point scale).No statistical difference in adverse events between groups was identified (10/104 image-guided group versus 16/103 comparator; risk ratio (RR) 0.55, 95% CI 0.17 to 1.85). Minor adverse events reported included transient post-injection pain, facial redness and warmth. Based upon moderate evidence from five trials, our review was unable to establish any advantage in terms of pain, function, shoulder range of motion or safety, of ultrasound-guided glucocorticoid injection for shoulder disorders over either landmark-guided or intramuscular injection. The lack of any added benefit of ultrasound guided subacromial bursal injection over glucocorticoid injection administered into the upper gluteal muscles of the buttock suggests that the benefits of glucocorticoid may arise through systemic rather than local effects. Therefore, although ultrasound guidance may improve the accuracy of injection to the putative site of pathology in the shoulder, it is not clear that this improves its efficacy to justify the significant added cost.

Navigational knowledge of homebound Australian sugar ants, Camponotus consobrinus.

Navigational knowledge of homebound Australian sugar ants, Camponotus consobrinus.

Phrenic nerve palsy after internal jugular venous catheter placement

Central venous catheters are usually inserted to measure the central venous pressure or use as an administration route for fluid or medication. There are reports that complications, such as arterial puncture, pneumothorax, occur in approximately 15% of cases when inserting it [1,2]. Phrenic nerve palsy is a very rare complication attributed to central venous catheter insertion. It can be caused when inserting the catheter into the subclavian vein or internal jugular vein, as well as when venal puncture is attempted several times with a thick needle, and can also occur when the needle is inserted too deeply, directly injuring the nerves. We recently had a case of phrenic nerve palsy, which was discovered late and its cause suspected to be central venous catheter insertion. The patient, a 75 year old female, underwent left nephroureterectomy for papillary urothelial carcinoma. At the time, there were no abnormalities in the preoperative physical examinations and laboratory tests including a chest x-ray. A central venous catheter was inserted through land mark guidance, by means of the anterior approach, into the right internal jugular vein [1]. There were no difficulties or specific events during the procedure. The operation proceeded without any complications, yet the chest x-ray taken on the same day after the surgery, indicated pulmonary congestion and atelectasis on the right lower lobe. Two days after the surgery, the central venous catheter was removed. The ABGA, performed on the third day post surgery showed pH 7.42, PaCO2 40.7 mmHg, and PaO2 64.1 mmHg in room air and the chest x-ray showed no differences when compared to the one before. Ten days after the surgery, the patient was discharged with no specific symptoms and was advised to take deep breaths and cough. Six months later, the patient visited the outpatient clinic with dyspnea, which began occurring a month prior without any other symptoms, such as coughing or sputum. Atelectasis in the right lower lobe was observed in the chest x-ray taken, which was similar to the chest x-ray from six months before. In the dynamic chest CT, the right diaphragm had risen and segmental atelectasis could be observed in the right middle and lower lobes. Both an electroneurography and electromyography were performed on the right upper and lower limbs under the suspicion of phrenic nerve palsy. The results showed an abnormal electrophysiological finding that suggested right cervical radiculopathy (C 4, 5, 7) and right phrenic neuropathy. The right median nerve, ulnar nerve, lower limb nerve, and left phrenic nerve, were all normal. In the Jolly test performed, in order to rule out abnormalities in the neuromuscular junction, no abnormal electrophysiological findings were observed. The patient did not complain of other symptoms in the upper or lower limbs, other than dyspnea. Also, with the exception of the history of central venous catheter insertion six months prior, there were no other causes for the phrenic nerve palsy, such as tumor or infection. Hence, the central venous catheter insertion was suspected as the most probable cause for the phrenic nerve palsy. The patient complained of dyspnea continuously, so a diaphragm plication was performed. The pulmonary function test, performed nine days after the surgery, showed FVC 1,510 (67%) ml and FEV1 1,030 (68%) ml, which had improved from

Path integration controls nest-plume following in desert ants

Event Abstract Back to Event Path integration controls nest-plume following in desert ants Cornelia Buehlmann1*, Bill S. Hansson1 and Markus Knaden1 1 Max Planck Institute for Chemical Ecology, Evolutionary Neuroethology, Germany The desert ant Cataglyphis fortis is equipped with sophisticated navigational skills for returning to its nest after foraging. The ant’s primary means for long-distance navigation is path integration, which provides a continuous readout of the ant’s approximate distance and direction from the nest. The nest is pinpointed additionally with the aid of landmarks. Here we show that homing ants move upwind along nest-derived odor plumes to approach their nest. The ants only respond to odor plumes if the state of their path integrator tells them that they are near the nest. This influence of path integration is important because we could experimentally provoke ants to follow odor plumes from a foreign, conspecific nest and enter that nest. We identified CO2 as one nest-plume component that can by itself induce plume following in homing ants. Taken together, the results suggest that path-integration information enables ants to avoid entering the wrong nest, where they would inevitably be killed by resident ants. This project was supported by the Max Planck Society. Keywords: Cataglyphis, Desert ants, Landmark guidance, navigation, Olfaction, path integration, Plume following Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for participant symposium and student poster award) Topic: Orientation and Navigation Citation: Buehlmann C, Hansson BS and Knaden M (2012). Path integration controls nest-plume following in desert ants. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00080 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Mar 2012; Published Online: 07 Jul 2012. * Correspondence: Miss. Cornelia Buehlmann, Max Planck Institute for Chemical Ecology, Evolutionary Neuroethology, Jena, 07745, Germany, cbuehlmann@ice.mpg.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Cornelia Buehlmann Bill S Hansson Markus Knaden Google Cornelia Buehlmann Bill S Hansson Markus Knaden Google Scholar Cornelia Buehlmann Bill S Hansson Markus Knaden PubMed Cornelia Buehlmann Bill S Hansson Markus Knaden Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Visual discrimination, sequential learning and memory retrieval in the Australian desert ant Melophorus bagoti

Bees, wasps and ants--so-called central-place foragers--need potent homing strategies to return to their nest. Path integration and view-based landmark guidance are the key strategies for the ants' navigation. For instance, they memorise different views in a sequence (sequential memory) but also have a step counter that informs them about the covered distance during each foraging trip (odometer). The sequential memory and the odometer information can act as contextual cues during travel for retrieving the appropriate stored view. When and which cue is used at different stages and lengths of the foraging trips is still unknown. In this study, we examined how the Australian desert ant Melophorus bagoti uses sequential memory and odometric information to retrieve visual memories. Using a set-up made out of channels and two-choice boxes (Y-mazes), we demonstrate first that M. bagoti foragers are able to learn and discriminate a variety of visual stimuli in a sequence of views along the inbound trip back to the nest. We then forced the homing ants to encounter a fixed sequence of two visual patterns during their inbound trips. By manipulating the position and distance of the visual stimuli and decision boxes, we could set the two contextual cues (sequential memory and odometer) into conflict. After the short 4-m outbound distance, a preference for odometric information as a contextual cue was found, but after the long 8-m outbound distance, ants relied primarily on their sequential memory retrieval. Odometer precision deteriorates with increasing travel distance, and accordingly, our findings imply that desert ants may be relying on the most reliable contextual cue for retrieving visual memories.

No Need for a Cognitive Map: Decentralized Memory for Insect Navigation

In many animals the ability to navigate over long distances is an important prerequisite for foraging. For example, it is widely accepted that desert ants and honey bees, but also mammals, use path integration for finding the way back to their home site. It is however a matter of a long standing debate whether animals in addition are able to acquire and use so called cognitive maps. Such a ‘map’, a global spatial representation of the foraging area, is generally assumed to allow the animal to find shortcuts between two sites although the direct connection has never been travelled before. Using the artificial neural network approach, here we develop an artificial memory system which is based on path integration and various landmark guidance mechanisms (a bank of individual and independent landmark-defined memory elements). Activation of the individual memory elements depends on a separate motivation network and an, in part, asymmetrical lateral inhibition network. The information concerning the absolute position of the agent is present, but resides in a separate memory that can only be used by the path integration subsystem to control the behaviour, but cannot be used for computational purposes with other memory elements of the system. Thus, in this simulation there is no neural basis of a cognitive map. Nevertheless, an agent controlled by this network is able to accomplish various navigational tasks known from ants and bees and often discussed as being dependent on a cognitive map. For example, map-like behaviour as observed in honey bees arises as an emergent property from a decentralized system. This behaviour thus can be explained without referring to the assumption that a cognitive map, a coherent representation of foraging space, must exist. We hypothesize that the proposed network essentially resides in the mushroom bodies of the insect brain.

Ocelli contribute to the encoding of celestial compass information in the Australian desert antMelophorus bagoti

Many animal species, including some social hymenoptera, use the visual system for navigation. Although the insect compound eyes have been well studied, less is known about the second visual system in some insects, the ocelli. Here we demonstrate navigational functions of the ocelli in the visually guided Australian desert ant Melophorus bagoti. These ants are known to rely on both visual landmark learning and path integration. We conducted experiments to reveal the role of ocelli in the perception and use of celestial compass information and landmark guidance. Ants with directional information from their path integration system were tested with covered compound eyes and open ocelli on an unfamiliar test field where only celestial compass cues were available for homing. These full-vector ants, using only their ocelli for visual information, oriented significantly towards the fictive nest on the test field, indicating the use of celestial compass information that is presumably based on polarised skylight, the sun's position or the colour gradient of the sky. Ants without any directional information from their path-integration system (zero-vector) were tested, also with covered compound eyes and open ocelli, on a familiar training field where they have to use the surrounding panorama to home. These ants failed to orient significantly in the homeward direction. Together, our results demonstrated that M. bagoti could perceive and process celestial compass information for directional orientation with their ocelli. In contrast, the ocelli do not seem to contribute to terrestrial landmark-based navigation in M. bagoti.

Polarised skylight and the landmark panorama provide night-active bull ants with compass information during route following

Navigating animals are known to use a number of celestial and terrestrial compass cues that allow them to determine and control their direction of travel. Which of the cues dominate appears to depend on their salience. Here we show that night-active bull ants attend to both the pattern of polarised skylight and the landmark panorama in their familiar habitat. When the two directional cues are in conflict, ants choose a compromise direction. However, landmark guidance appears to be the primary mechanism of navigation used by forager ants, with those cues in the direction of heading having the greatest influence on navigation. Different colonies respond to the removal of these cues to different degrees, depending on the directional information provided by the local landmark panorama. Interestingly, other parts of the surrounding panorama also influence foraging speed and accuracy, suggesting that they too play a role in navigation.

Ultrasound-guided external jugular vein cannulation for central venous access by inexperienced trainees

The insertion of central venous catheters via the external jugular vein (EJV) is not always practical because of the relatively frequent failure rate; thus, the internal jugular approach is generally used. Data from the literature suggest that ultrasound-guided catheterization of the internal jugular vein is superior to the surface anatomy landmark technique and, therefore, should be the method of choice. We evaluated the value of ultrasound guidance in the learning process of central venous cannulation via EJV by similarly inexperienced trainees. In this prospective randomized study, 60 patients were assigned to two groups: group SA (surface anatomy; n = 30) underwent insertion of the central venous catheter using landmark guidance and group US (ultrasound; n = 30) underwent insertion using ultrasound guidance. In all patients, catheter insertion through the right EJV was performed by trainees in their second year of training. Ultrasound guidance was carried out by the same ultrasound specialist. The following parameters were evaluated in all patients: the number of successful punctures of the right EJV, the total number of attempts and the time to vein puncture; the number of successful insertions of the central venous catheter, the number of attempts and the duration of catheterization (from puncture of EJV to external fixation of the catheter); and the incidence of complications. The study was approved by the institutional ethics committee, and all patients gave written informed consent. Data were expressed as mean +/- SD. Student's t-test, Mann-Whitney test and chi2-test were used for analysis and P < 0.05 was considered statistically significant. The power of the study was 85%. The EJV puncture was successful in 24 out of 30 (80%) patients from group SA and in 22 out of 30 (73%) patients from group US (P = NS). There were no statistically significant differences between the groups regarding the mean time to perform the vein puncture and the number of attempts. The insertion of the central venous catheter was performed successfully in 10 (33%) patients from group SA and six (20%) patients from group US. The success rate of central cannulation via the EJV approach was 10 out of 24 (42%) in group SA and six out of 22 (27%) in group US (P = NS). The total time for insertion and the number of attempts were similar in both groups (P = NS). Local haematoma occurred in 11 patients in group SA and in three patients in group US (P = NS). Our results demonstrate no significant differences between the conventional surface anatomy landmark technique and the ultrasound-guided technique for the insertion of a central venous catheter via EJV by inexperienced trainees.