Spatial Heterogeneity in Bistable Figure-Ground Perception

The appearance of visual objects varies substantially across the visual field. Could such spatial heterogeneity be due to undersampling of the visual field by neurons selective for stimulus categories? Here, we show that which parts of a bistable vase-face image observers perceive as figure and ground depends on the retinal location where the image appears. The spatial patterns of these perceptual biases were similar regardless of whether the images were upright or inverted. Undersampling by neurons tuned to an object class (e.g., faces) or variability in general local versus global processing cannot readily explain this spatial heterogeneity. Rather, these biases could result from idiosyncrasies in low-level sensitivity across the visual field

Active inference on discrete state-spaces: A synthesis

Active inference is a normative principle underwriting perception, action, planning, decision-making and learning in biological or artificial agents. From its inception, its associated process theory has grown to incorporate complex generative models, enabling simulation of a wide range of complex behaviours. Due to successive developments in active inference, it is often difficult to see how its underlying principle relates to process theories and practical implementation. In this paper, we try to bridge this gap by providing a complete mathematical synthesis of active inference on discrete state-space models. This technical summary provides an overview of the theory, derives neuronal dynamics from first principles and relates this dynamics to biological processes. Furthermore, this paper provides a fundamental building block needed to understand active inference for mixed generative models; allowing continuous sensations to inform discrete representations. This paper may be used as follows: to guide research towards outstanding challenges, a practical guide on how to implement active inference to simulate experimental behaviour, or a pointer towards various in-silico neurophysiological responses that may be used to make empirical predictions

Advanced Scanning Electron Microscopy Methods and Applications to Integrated Circuit Failure Analysis

Semiconductor device failure analysis using the scanning electron microscope (SEM) has become a standard component of integrated circuit fabrication. Improvements in SEM capabilities and in digital imaging and processing have advanced standard acquisition modes and have promoted new failure analysis methods. The physical basis of various data acquisition modes, both standard and new, and their implementation on a computer controlled SEM image acquisition/processing system are discussed, emphasizing the advantages of each method. Design considerations for an integrated, online failure analysis system are also described. Recent developments in the integration of the information provided by electron beam analysis, conventional integrated circuit (IC) testing, computer-aided design (CAD), and device parameter testing into a single system promise to provide powerful future tools for failure analysis

Retrosigmoid approach for a ruptured pontine cavernous malformation, in a 10 years old pacient: Case report

Brainstem cavernous malformations have a high risk of hemorrhage, ranging from 4 to 60%, this risk being even higher in children where larger lesions are encountered. Even small hemorrhages can cause ,severe neurological symptoms because of the high density of cranial nerve nuclei and fiber tracts within the brainstem. The goal of surgical treatment is not only the improvement of neurological symptoms, but also preservation of the patient’s quality of life. We present a case of a 10 years old female pacient who presented after a 5 weeks conservative treatment with right sided weakness and loss of coordination, right hemihipoesthesia, She was diagnosed with a large left pontine cavernous malformation on MRI. The cavernoma was resected using a retrosigmoidian approach , but a small remnant was left, when the surgery had to be stopped due to severe bradicardia. The neurological deficit improved at follow up.The choice of the surgical approach that allows the best exposure of the lesion is mandatory. In this case the lesion was evident on the surface of the brainstem and this facilitated its resection. Traction on the tumor and coagulation near the cranial nerves nuclei should be avoided, but if bradicardia appears the surgery must be stopped.Surgery is the best choice for the patients with symptomatic brainstem cavernomas that present with hemorrhage and neurological deficit, and its objectives should be complete removal and improvement of neurological deficit.&nbsp

Giant extracranial liposarcoma: Case report

Objective: Anaplastic liposarcoma of the head is an extremely rare entity. Seventy-seven cases of head and neck liposarcomas have been reported in the world literature since 1911. Radical surgery is the form of treatment advised.Clinical presentation: Authors report the case of a 62 years old female patient admitted in our institution for a giant extracranial tumor (122/88 mm), developed insidious over a period of 3 years and neglected. The patient agreed surgery only for the epicranial tumor. The lesion was completely removed. Postoperatory outcome was excellent concerning this tumor, although the histopathological result was not that great: high anaplastic liposarcoma.Conclusion: Liposarcoma of the scalp is rare. Diagnosis is made histologically. The histopathologic variant influences clinical behavior and prognosis. The treatment of choice is wide surgical excision.&nbsp

Update on the natural history of infratentorial cavernous malformations

Infratentorial cavernous malformations are still a source of serious controversies in neurosurgery and their natural history and treatment are intensely debated in literature. Recent studies suggest that symptomatic infratentorial cavernous malformations have a more aggressive clinical outcome than the supratentorial ones (the risk of hemorrhage is approximately 30 times that of the supratentorial cavernomas) The optimal therapeutic approach of infratentorial cavernomas need a good understanding of the natural history and also the characteristics that may influence the associated neurological risk, like the patient status at admission, the localization and the genetics of the malformation. Many studies have been published in the last decades to enlight the clinical aspects and the natural history of these vascular malformations. The purpose of this analysis is to make a literature review of the morbidity risk associated to cavernous malformations and their influence on the treatment plan

Brain abscesses: management and outcome analysis in a series of 84 patients during 12 year period

Authors analyze 84 cases of brain abscesses operated between January 2000 and December 2011, in the Fourth Neurosurgical Department by the same surgical team. We underline the general series profile: the mean age was 42.96 years (range: 11-75 years old), 72.62% were males, association with heart defects in seven cases (8.33%), positive bacteriological examination for germs in only 37 cases (44.04%), all negative for HIV infection. The median number of days to diagnosis was 9. Most frequent clinical presentations included headache (40.47%), fever (35.71%), focal neurologic deficits (29.76%), increased intracranial pressure (28.57%) and seizures (11.90%).The majority of cases (76.19%, n=64) presented a supposed medical condition favoring dissemination of a previous infection: malnutrition, tuberculosis, chronic alcoholism, chronic liver malady, neglected dental or ear infections, and only 5 cases (5.95%) had been diagnosed with secondary immunodeficiency syndromes following autoimmune systemic diseases.According to our treatment policy all cases except for two (treated by puncture and aspiration) benefited of open surgery and total removal of the lesions, without local recurrence. Outcome was favorable in 82.14% (n=69) of subjects. General morbidity was 26.19%, and mortality stood at 7.14%. Six cases remained with permanent motor deficit (7.14%) and four (4.76%) with controllable seizures. Out of a total of 33.33% (n=28) of complications, 64.28% were due to medical causes.Follow-up had been extended up to three years for at least 2/3 of patients, who resolved in time medical or surgical conditions which determined cerebral dissemination of the infection. Despite of a poor medical and biological condition, the patients with brain abscess outside of HIV infections benefit from neurosurgical adequate treatment, and if supportive medical and general therapy is continued and sustained, the healing and survival in good neurological status is the rule. Hematogenous spread and advance age were predictors of poor prognosis. Our findings are similar to the results of recent works, although in our series, there is a higher frequency of aerobe germs

Deontological issues - possible misdiagnosis of cerebral metastases

Authors analyses a number of 4588 (52, 24% over 50 years old) patients operated for cerebral tumors in the Clinic Emergency Hospital “Bagdasar-Arseni” from Bucharest, between 2000-2010, with peculiar attention to the concordance between the preoperative and postoperative diagnosis, related to the actual policy to evaluate a neurosurgical patient before surgery. 903 cases were cerebral metastases and 69,5% aged over 50 years old. In 9,7% of cases we recorded a preoperative misdiagnosis of a metastasis due to few main reasons: unavailable information about a present primitive cancer, treacherous MRI image with a single confusing appearance of a cerebral lesion, age less than 50 years old, clinical presentation and biological evaluation inconsistent with malignancy. Authors point that these situations can have serious consequences related to professional competence, deterioration of the patient-doctor relationship, increasing costs for completion of diagnosis and treatment, and inadequate information about patient’s prognosis

Atomic-scale confinement of optical fields

In the presence of matter there is no fundamental limit preventing confinement of visible light even down to atomic scales. Achieving such confinement and the corresponding intensity enhancement inevitably requires simultaneous control over atomic-scale details of material structures and over the optical modes that such structures support. By means of self-assembly we have obtained side-by-side aligned gold nanorod dimers with robust atomically-defined gaps reaching below 0.5 nm. The existence of atomically-confined light fields in these gaps is demonstrated by observing extreme Coulomb splitting of corresponding symmetric and anti-symmetric dimer eigenmodes of more than 800 meV in white-light scattering experiments. Our results open new perspectives for atomically-resolved spectroscopic imaging, deeply nonlinear optics, ultra-sensing, cavity optomechanics as well as for the realization of novel quantum-optical devices

Ultrafast nano-focusing with full optical waveform control

The spatial confinement and temporal control of an optical excitation on nanometer length scales and femtosecond time scales has been a long-standing challenge in optics. It would provide spectroscopic access to the elementary optical excitations in matter on their natural length and time scales and enable applications from ultrafast nano-opto-electronics to single molecule quantum coherent control. Previous approaches have largely focused on using surface plasmon polariton (SPP) resonant nanostructures or SPP waveguides to generate nanometer localized excitations. However, these implementations generally suffer from mode mismatch between the far-field propagating light and the near-field confinement. In addition, the spatial localization in itself may depend on the spectral phase and amplitude of the driving laser pulse thus limiting the degrees of freedom available to independently control the nano-optical waveform. Here we utilize femtosecond broadband SPP coupling, by laterally chirped fan gratings, onto the shaft of a monolithic noble metal tip, leading to adiabatic SPP compression and localization at the tip apex. In combination with spectral pulse shaping with feedback on the intrinsic nonlinear response of the tip apex, we demonstrate the continuous micro- to nano-scale self-similar mode matched transformation of the propagating femtosecond SPP field into a 20 nm spatially and 16 fs temporally confined light pulse at the tip apex. Furthermore, with the essentially wavelength and phase independent 3D focusing mechanism we show the generation of arbitrary optical waveforms nanofocused at the tip. This unique femtosecond nano-torch with high nano-scale power delivery in free space and full spectral and temporal control opens the door for the extension of the powerful nonlinear and ultrafast vibrational and electronic spectroscopies to the nanoscale.Comment: Contains manuscript with 4 figures as well as supplementary material with 2 figure