Randomness impacts the building of specific priors, visual exploration, and perception in object recognition.

Recognising objects is a vital skill on which humans heavily rely to respond quickly and adaptively to their environment. Yet, we lack a full understanding of the role visual information sampling plays in this process, and its relation to the individual's priors. To bridge this gap, the eye-movements of 18 adult participants were recorded during a free-viewing object-recognition task using Dots stimuli1. Participants viewed the stimuli in one of three orders: from most visible to least (Descending), least visible to most (Ascending), or in a randomised order (Random). This dictated the strength of their priors along the experiment. Visibility order influenced the participants' recognition performance and visual exploration. In addition, we found that while orders allowing for stronger priors generally led participants to visually sample more informative locations, this was not the case of Random participants. Indeed, they appeared to behave naïvely, and their use of specific object-related priors was fully impaired, while they maintained the ability to use general, task-related priors to guide their exploration. These findings have important implications for our understanding of perception, which appears to be influenced by complex cognitive processes, even at the basic level of visual sampling during object recognition.

The fractal brain: scale-invariance in structure and dynamics.

The past 40 years have witnessed extensive research on fractal structure and scale-free dynamics in the brain. Although considerable progress has been made, a comprehensive picture has yet to emerge, and needs further linking to a mechanistic account of brain function. Here, we review these concepts, connecting observations across different levels of organization, from both a structural and functional perspective. We argue that, paradoxically, the level of cortical circuits is the least understood from a structural point of view and perhaps the best studied from a dynamical one. We further link observations about scale-freeness and fractality with evidence that the environment provides constraints that may explain the usefulness of fractal structure and scale-free dynamics in the brain. Moreover, we discuss evidence that behavior exhibits scale-free properties, likely emerging from similarly organized brain dynamics, enabling an organism to thrive in an environment that shares the same organizational principles. Finally, we review the sparse evidence for and try to speculate on the functional consequences of fractality and scale-freeness for brain computation. These properties may endow the brain with computational capabilities that transcend current models of neural computation and could hold the key to unraveling how the brain constructs percepts and generates behavior.

Development and validity evidence of an objective structured assessment of technical skills score for minimally invasive linear-stapled, hand-sewn intestinal anastomoses: the A-OSATS score.

INTRODUCTION: The aim of this study was to develop a reliable objective structured assessment of technical skills (OSATS) score for linear-stapled, hand-sewn closure of enterotomy intestinal anastomoses (A-OSATS). MATERIALS AND METHODS: The Delphi methodology was used to create a traditional and weighted A-OSATS score highlighting the more important steps for patient outcomes according to an international expert consensus. Minimally invasive novices, intermediates, and experts were asked to perform a minimally invasive linear-stapled intestinal anastomosis with hand-sewn closure of the enterotomy in a live animal model either laparoscopically or robot-assisted. Video recordings were scored by two blinded raters assessing intrarater and interrater reliability and discriminative abilities between novices (n = 8), intermediates (n = 24), and experts (n = 8). RESULTS: The Delphi process included 18 international experts and was successfully completed after 4 rounds. A total of 4 relevant main steps as well as 15 substeps were identified and a definition of each substep was provided. A maximum of 75 points could be reached in the unweighted A-OSATS score and 170 points in the weighted A-OSATS score respectively. A total of 41 anastomoses were evaluated. Excellent intrarater (r = 0.807-0.988, p < 0.001) and interrater (intraclass correlation coefficient = 0.923-0.924, p < 0.001) reliability was demonstrated. Both versions of the A-OSATS correlated well with the general OSATS and discriminated between novices, intermediates, and experts defined by their OSATS global rating scale. CONCLUSION: With the weighted and unweighted A-OSATS score, we propose a new reliable standard to assess the creation of minimally invasive linear-stapled, hand-sewn anastomoses based on an international expert consensus. Validity evidence in live animal models is provided in this study. Future research should focus on assessing whether the weighted A-OSATS exceeds the predictive capabilities of patient outcomes of the unweighted A-OSATS and provide further validity evidence on using the score on different anastomotic techniques in humans.

Time-frequency super-resolution with superlets.

Due to the Heisenberg-Gabor uncertainty principle, finite oscillation transients are difficult to localize simultaneously in both time and frequency. Classical estimators, like the short-time Fourier transform or the continuous-wavelet transform optimize either temporal or frequency resolution, or find a suboptimal tradeoff. Here, we introduce a spectral estimator enabling time-frequency super-resolution, called superlet, that uses sets of wavelets with increasingly constrained bandwidth. These are combined geometrically in order to maintain the good temporal resolution of single wavelets and gain frequency resolution in upper bands. The normalization of wavelets in the set facilitates exploration of data with scale-free, fractal nature, containing oscillation packets that are self-similar across frequencies. Superlets perform well on synthetic data and brain signals recorded in humans and rodents, resolving high frequency bursts with excellent precision. Importantly, they can reveal fast transient oscillation events in single trials that may be hidden in the averaged time-frequency spectrum by other methods.

The Value of Staging Laparoscopy for Optimal Multidisciplinary Treatment in Patients with Gastric Cancer.

Introduction: Despite improvements in the conventional preoperative tools used for staging of gastric cancer, their accuracy still needs to be improved. Laparoscopy has the potential to visualize and characterize the tumor, the peritoneal cavity and the lymph nodes and thus to better select patients for the optimal treatment strategy. Material and Method: Patients with gastric cancer staged initially with contrast enhanced computer tomography and endoscopic ultrasound were also evaluated by laparoscopy and laparoscopic ultrasound in a distinct preoperative staging procedure. The perioperative data was recorded in a prospective database and was used to decide within the multidisciplinary team the optimal treatment protocol for each patient. The database was retrospectively reviewed for this study. Results: Among the 20 CT-scan M0 patients analyzed, peritoneal carcinomatosis was detected in 15% of the cases. In other 15% of patients laparoscopy upstaged the tumor and directed the patient towards neoadjuvant chemotherapy. Laparoscopic guided percutaneous core biopsies settled the definitive diagnosis in 3 further cases. In total, laparoscopic staging brought important information in 65% of cases and changed the treatment plan in 30% of patients. Conclusions: In the era of neoadjuvant chemotherapy, laparoscopy has the potential to overcome some of the limitations of the conventional staging methods and offers additional informations which finally change the treatment plan in as much as a third of patients with gastric cancer.

A 44 bp intestine-specific hermaphrodite-specific enhancer from the C. elegans vit-2 vitellogenin gene is directly regulated by ELT-2, MAB-3, FKH-9 and DAF-16 and indirectly regulated by the germline, by daf-2/insulin signaling and by the TGF-ß/Sma/Mab pathway.

The Caenorhabditis elegans vitellogenin genes are transcribed in the intestine of adult hermaphrodites but not of males. A 44-bp region from the vit-2 gene promoter is able largely to reconstitute this tissue-, stage- and sex-specific-expression. This "enhancer" contains a binding site for the DM-domain factor MAB-3, the male-specific repressor of vitellogenesis, as well as an activator site that we show is the direct target of the intestinal GATA factor ELT-2. We further show that the enhancer is directly activated by the winged-helix/forkhead-factor FKH-9, (whose gene has been shown by others to be a direct target of DAF-16), by an unknown activator binding to the MAB-3 site, and by the full C. elegans TGF-ß/Sma/Mab pathway acting within the intestine. The vit-2 gene has been shown by others to be repressed by the daf-2/daf-16 insulin signaling pathway, which so strongly influences aging and longevity in C. elegans. We show that the activity of the 44 bp vit-2 enhancer is abolished by loss of daf-2 but is restored by simultaneous loss of daf-16. DAF-2 acts from outside of the intestine but DAF-16 acts both from outside of the intestine and from within the intestine where it binds directly to the same non-canonical target site that interacts with FKH-9. Activity of the 44 bp vit-2 enhancer is also inhibited by loss of the germline, in a manner that is only weakly influenced by DAF-16 but that is strongly influenced by KRI-1, a key downstream effector in the pathway by which germline loss increases C. elegans lifespan. The complex behavior of this enhancer presumably allows vitellogenin gene transcription to adjust to demands of body size, germline proliferation and nutritional state but we suggest that the apparent involvement of this enhancer in aging and longevity "pathways" could be incidental.

Membrane resonance enables stable and robust gamma oscillations.

Neuronal mechanisms underlying beta/gamma oscillations (20-80 Hz) are not completely understood. Here, we show that in vivo beta/gamma oscillations in the cat visual cortex sometimes exhibit remarkably stable frequency even when inputs fluctuate dramatically. Enhanced frequency stability is associated with stronger oscillations measured in individual units and larger power in the local field potential. Simulations of neuronal circuitry demonstrate that membrane properties of inhibitory interneurons strongly determine the characteristics of emergent oscillations. Exploration of networks containing either integrator or resonator inhibitory interneurons revealed that: (i) Resonance, as opposed to integration, promotes robust oscillations with large power and stable frequency via a mechanism called RING (Resonance INduced Gamma); resonance favors synchronization by reducing phase delays between interneurons and imposes bounds on oscillation cycle duration; (ii) Stability of frequency and robustness of the oscillation also depend on the relative timing of excitatory and inhibitory volleys within the oscillation cycle; (iii) RING can reproduce characteristics of both Pyramidal INterneuron Gamma (PING) and INterneuron Gamma (ING), transcending such classifications; (iv) In RING, robust gamma oscillations are promoted by slow but are impaired by fast inputs. Results suggest that interneuronal membrane resonance can be an important ingredient for generation of robust gamma oscillations having stable frequency.

Virtual reality does not meet expectations in a pilot study on multimodal laparoscopic surgery training.

BACKGROUND: The purpose of the present study was to determine the value of virtual reality (VR) training for a multimodality training program of basic laparoscopic surgery. MATERIALS AND METHODS: Participants in a two-day multimodality training for laparoscopic surgery used box trainers, live animal training, and cadaveric training on the pulsating organ perfusion (POP) trainer in a structured and standardized training program. The participants were divided into two groups. The VR group (n = 13) also practiced with VR training during the program, whereas the control group (n = 14) did not use VR training. The training modalities were assessed using questionnaires with a five-point Likert scale after the program. Concerning VR training, members of the control group assessed their expectations, whereas the VR group assessed the actual experience of using it. Skills performance was evaluated with five standardized test tasks in a live porcine model before (pre-test) and after (post-test) the training program. Laparoscopic skills were measured by task completion time and a general performance score for each task. Baseline tests were compared with laparoscopic experience of all participants for construct validity of the skills test. RESULTS: The expected benefit from VR training of the control group was higher than the experienced benefit of the VR group. Box and POP training received better ratings from the VR group than from the control group for some purposes. Both groups improved their skill parameters significantly from pre-training to post-training tests [score +17 % (P < 0.01), time -29 % (P < 0.01)]. No significant difference was found between the two groups for laparoscopic skills improvement except for the score in the instrument coordination task. Construct validity of the skills test was significant for both time and score. CONCLUSIONS: At its current level of performance, VR training does not meet expectations. No additional benefit was observed from VR training in our multimodality training program.

Visual exploration and object recognition by lattice deformation.

Mechanisms of explicit object recognition are often difficult to investigate and require stimuli with controlled features whose expression can be manipulated in a precise quantitative fashion. Here, we developed a novel method (called "Dots"), for generating visual stimuli, which is based on the progressive deformation of a regular lattice of dots, driven by local contour information from images of objects. By applying progressively larger deformation to the lattice, the latter conveys progressively more information about the target object. Stimuli generated with the presented method enable a precise control of object-related information content while preserving low-level image statistics, globally, and affecting them only little, locally. We show that such stimuli are useful for investigating object recognition under a naturalistic setting--free visual exploration--enabling a clear dissociation between object detection and explicit recognition. Using the introduced stimuli, we show that top-down modulation induced by previous exposure to target objects can greatly influence perceptual decisions, lowering perceptual thresholds not only for object recognition but also for object detection (visual hysteresis). Visual hysteresis is target-specific, its expression and magnitude depending on the identity of individual objects. Relying on the particular features of dot stimuli and on eye-tracking measurements, we further demonstrate that top-down processes guide visual exploration, controlling how visual information is integrated by successive fixations. Prior knowledge about objects can guide saccades/fixations to sample locations that are supposed to be highly informative, even when the actual information is missing from those locations in the stimulus. The duration of individual fixations is modulated by the novelty and difficulty of the stimulus, likely reflecting cognitive demand.

Considerations concerning design and mechanism of action of a new class of anticancer dual DNA intercalators.

Cancer is one of the most serious and merciless health problems of the mankind, about seven million people dying of cancer every year. Two of the most important and promising targets in cancer chemotherapy include DNA alkylating agents and DNA intercalators. The emphasis of this work was to design, synthetize and formulate a mechanism of action for a new class of dual DNA intercalators. The dual DNA intercalators have three main parts: an alkylating unit (represented by two halo-alkyl-ester chains), an intercalator unit (five- or six-membered ring nitrogen heterocycle) and an acetophenone skeleton linker. As mechanism of action, we consider that these compounds act as dual DNA intercalators, the alkylating unit realizing a covalent bonding via DNA protein "cross-linking effect" while nitrogen heterocycles will realize noncovalent bonding via DNA intercalation with purine and pyrimidine bases from DNA and the amino acids from topoisomerases enzymes. Our hypothesis was confirmed by in vitro anticancer tests against HeLa cell lines, where the newly obtained compounds demonstrated a very good activity.

Feasibility of a high intrathoracic esophagogastric anastomosis without thoracic access after laparoscopic-assisted transhiatal esophagectomy: a pilot experimental study.

INTRODUCTION: The aim of the present study was to evaluate the feasibility of a technique that uses solely the transhiatal approach to create a high intrathoracic esophagogastric anastomosis after laparoscopic transhiatal resection of the distal esophagus. METHOD: Using a laparoscopic approach, the esophagi of 10 midsized pigs were dissected and transected as high as possible in the thorax, and the anvil of a circular stapler was introduced perorally into the esophageal stump. Through a midline short laparotomy, the circular stapler was inserted into the gastric tube and advanced through the hiatus to be connected with the anvil and create the anastomosis. RESULTS: Development of the technique was completed within the first 6 experiments. The last 4 operations were entirely successful, standardized, and easily reproducible. CONCLUSION: The technique is feasible in this experimental setting. Further studies are required to establish if there is a clinical role for this technique in esophageal surgery.

EEG under anesthesia--feature extraction with TESPAR.

We investigated the problem of automatic depth of anesthesia (DOA) estimation from electroencephalogram (EEG) recordings. We employed Time Encoded Signal Processing And Recognition (TESPAR), a time-domain signal processing technique, in combination with multi-layer perceptrons to identify DOA levels. The presented system learns to discriminate between five DOA classes assessed by human experts whose judgements were based on EEG mid-latency auditory evoked potentials (MLAEPs) and clinical observations. We found that our system closely mimicked the behavior of the human expert, thus proving the utility of the method. Further analyses on the features extracted by our technique indicated that information related to DOA is mostly distributed across frequency bands and that the presence of high frequencies (> 80 Hz), which reflect mostly muscle activity, is beneficial for DOA detection.

Properties of multivariate data investigated by fractal dimensionality.

Elaborated data-mining techniques are widely available today. Nevertheless, many non-linear relations among variables remain undiscovered in multi-dimensional datasets. To address this issue we propose a method based on the concept of fractal dimension that explores the structure of multivariate data and apply the method to simulated data, as well as to local field potentials recorded from cat visual cortex. We find that with changes in the analysis scale, the dimensionality of the data often changes, indicating first that the data are not simple fractals with one unique dimension and second, that, at a certain scale, important changes in the geometric structure of the data may occur. The method can be used as a data-mining tool but also as a method for testing a model's fit to the data. We achieve the latter by comparing the dimensionality of the original data to the dimensionality of the data reconstructed from a model's description of the data (here using the general linear model). The method provides indispensable help in estimating the complexity of non-linear relationships within multivariate datasets.

The oscillation score: an efficient method for estimating oscillation strength in neuronal activity.

We present a method that estimates the strength of neuronal oscillations at the cellular level, relying on autocorrelation histograms computed on spike trains. The method delivers a number, termed oscillation score, that estimates the degree to which a neuron is oscillating in a given frequency band. Moreover, it can also reliably identify the oscillation frequency and strength in the given band, independently of the oscillation in other frequency bands, and thus it can handle superimposed oscillations on multiple scales (theta, alpha, beta, gamma, etc.). The method is relatively simple and fast. It can cope with a low number of spikes, converging exponentially fast with the number of spikes, to a stable estimation of the oscillation strength. It thus lends itself to the analysis of spike-sorted single-unit activity from electrophysiological recordings. We show that the method performs well on experimental data recorded from cat visual cortex and also compares favorably to other methods. In addition, we provide a measure, termed confidence score, that determines the stability of the oscillation score estimate over trials.

Neither maternal nor zygotic med-1/med-2 genes play a major role in specifying the Caenorhabditis elegans endoderm.

The med-1 and med-2 genes encode small, highly similar proteins related to GATA-type transcription factors and have been proposed as necessary for specification of both the mesoderm and the endoderm of Caenorhabditis elegans. However, we have previously presented evidence that neither maternal nor zygotic expression of the med-1/2 genes is necessary to specify the C. elegans endoderm. Contradicting our conclusions, a recent report presented evidence, based on presumed transgene-induced cosuppression, that the med-1/2 genes do indeed show an endoderm-specifying maternal effect. In this article, we reinvestigate med-2(-); med-1(-) embryos using a med-2- specific null allele instead of the chromosomal deficiences used previously and confirm our previous results: the large majority (approximately 84%) of med-2(-); med-1(-) embryos express gut granules. We also reinvestigate the possibility of a maternal med-1/2 effect by direct injection of med dsRNA into sensitized (med-deficient) hermaphrodites using the standard protocol known to be effective in ablating maternal transcripts, but again find no evidence for any significant maternal med-1/2 effect. We do, however, show that expression of gut granules in med-1/2-deficient embryos is exquisitely sensitive to RNAi against the vacuolar ATPase-encoding unc-32 gene [present on the same multicopy med-1(+)-containing transgenic balancer used in support of the maternal med-1/2 effect]. We thus suggest that the experimental evidence for a maternal med-1/2 effect should be reexamined and may instead reflect cosuppression caused by multiple transgenic unc-32 sequences, not med sequences.

Robotic-assisted transhiatal esophagectomy.

BACKGROUND: Despite its reduced aggressiveness and excellent results obtained in certain diseases, minimally invasive surgery did not manage to significantly lower the risks of esophageal resections. Further advances in technology led to the creation of robotic systems with their unique maneuverability of the instruments and exceptional view on the operative field, thus setting the prerequisites for performance in complex surgical procedures and offering new possibilities to a disease notorious for its dismal prognosis. MATERIALS AND METHODS: The robotic-assisted transhiatal esophagectomy technique was used in a patient with squamous cell carcinoma of the lower esophagus that had high medical risk for surgical therapy. RESULTS: Esophageal resection and reconstruction were possible through a robotic-assisted minimally invasive transhiatal approach. There were no intraoperative incidents, blood loss was minimal, and lymph node dissection and removal was possible during the procedure. Early ambulation and conservative treatment of the mild complications that occurred offered a favorable postoperative outcome. CONCLUSION: The robotic-assisted transhiatal esophagectomy technique is feasible and safe. Complex procedures become less technically demanding with the help of the robotic system and, thus, the minimally invasive approach can be offered for the benefit of selected patients. Further studies are required to confirm these observations and to establish the role of this procedure in the future.

The brain and other sites of erythropoietin production.

Ischemic hypoxia of the head induced in dogs by carotid compression produces EPO secretion, upon direct cerebral stimulation, and adaptive carotid-respiratory reflexes via sino-carotid stimulation. During hypoxic hypoxia, there also occurs extrarenal EPO production, as shown in binephrectomized rats compared to controls. Ischemic hypoxia of a single kidney transplanted in the neck area (the other kidney being removed) does not induce EPO secretion. An additional factor, of extra-renal origin, is required for the renal production of EPO in a non-hypoxic organism. Section of the spinal cord at C6 level in rats does not abolish EPO secretion induced by hypobaric hypoxia, a fact that suggests that there is no nervous center to control EPO release into a peripheral organ, but EPO might be produced in the brain itself, possibly crossing the blood-brain barrier to reach the blood flow. Stereotactical attempts to locate nervous centers of erythropoiesis regulation also failed. EPO secretion obtained by electrical stimulation of different brain areas suggests the existence of widespread secretory cells, which might be the astrocytes. EPO production along the lymph-forming territories and the involvement of the lining macrophages is reported.

[The clinical, diagnostic and therapeutic characteristics in antral gastric cancer]. / Particularitati clinice, diagnostice si terapeutice în cancerul gastric antral.

This paper is part of a comprehensive study on subphrenic digestive cancer carried out between 1984 and 1988, representing the experience of the III-rd, I-st, IV-th and emergency surgical clinics of Iasi (1530 cases). The peculiarities of gastric cancer with antral site in 231 out of a total of 612 cases, representing the experience of the III-rd Surgical Clinic, are presented. Clinically, the relative early occurrence of the symptoms, the need for an endoscopic examination and biopsy for all gastric ulcer lesions, for the antral ones particularly, are mentioned. The treatment is surgical, but it has to be associated with adjuvant therapy. For the antral site, the oncological subtotal gastrectomy was the surgery of choice (157 cases), the need of restoring the transit in a gastrojejunal manner being underlined. Total gastrectomy was performed in 12 cases.

[The diagnosis and treatment of benign tumors of the subdiaphragmatic digestive tract]. / Diagnosticul si tratamentul tumorilor benigne ale tubului digestiv subdiafragmatic.

One hundred twenty-two benign tumors of subdiaphragmatic digestive tract admitted in the interval 1975-1988 at the III-rd Surgical Clinic of Iasi are reported. Out of these patients 120 required surgical treatment, the remainder of 2 being treated conservatively (diffuse intestinal angiomatosis, Peutz-Jeghers' syndrome). The clinical evolution being atypical, the surgical intervention was required, in most of the cases, due to hemorrhagic and occlusive complications. Histologically, the polyps and schwannomas were prevalent. The diagnostic difficulties, especially in the cases with jejuno-ileal localization, are mentioned.