Neuroimaging in epilepsy

PURPOSE OF REVIEW: Epilepsy neuroimaging is important for detecting the seizure onset zone, predicting and preventing deficits from surgery and illuminating mechanisms of epileptogenesis. An aspiration is to integrate imaging and genetic biomarkers to enable personalized epilepsy treatments. RECENT FINDINGS: The ability to detect lesions, particularly focal cortical dysplasia and hippocampal sclerosis, is increased using ultra high-field imaging and postprocessing techniques such as automated volumetry, T2 relaxometry, voxel-based morphometry and surface-based techniques. Statistical analysis of PET and single photon emission computer tomography (STATISCOM) are superior to qualitative analysis alone in identifying focal abnormalities in MRI-negative patients. These methods have also been used to study mechanisms of epileptogenesis and pharmacoresistance. Recent language fMRI studies aim to localize, and also lateralize language functions. Memory fMRI has been recommended to lateralize mnemonic function and predict outcome after surgery in temporal lobe epilepsy. SUMMARY: Combinations of structural, functional and post-processing methods have been used in multimodal and machine learning models to improve the identification of the seizure onset zone and increase understanding of mechanisms underlying structural and functional aberrations in epilepsy

How Do Established Firms Produce Breakthrough Innovations? Managerial Identity‐Dissemination Discourse and the Creation of Novel Product‐Market Solutions

Despite the legacy of experience, some established firms are able to avoid a mindset, behaviors, and routines that can be expected to lead them down paths of local search and incremental product innovations of ever‐declining value. Indeed, established firms are often adept at introducing successful path‐breaking innovations. To explain this apparent paradox, this article draws on the organizational identity literature to present a model that ascribes breakthrough innovations by established firms to managerial identity‐dissemination discourse (MIDD). MIDD is argued to provide a sense‐giving framework, which fosters an understanding of the firm as a nexus of values around which the firm can be continuously rediscovered and reconstituted in new ways. By exposing the firm as an idea that can assume fresh forms in terms of product‐market combinations, MIDD stimulates and coordinates creative endeavor, thus increasing the disposition to produce breakthrough innovations. The model also suggests that the impact of MIDD is likely to depend on transformational leadership and the level of centralization and formalization in the company. The results of a cross‐sectional empirical study provide support for the model. In contrast to the focus of earlier research on behavioral and structural explanations for breakthroughs by established firms, this article advances understanding by offering a cognitive explanation. In doing so, the article highlights that creativity and innovation in firms are mentally located in an interpretive schema of the firm's identity, which has important implications in relation to organizing for breakthroughs. The article discusses these implications with particular reference to the use of multifunctional teams and advanced information and communication technologies for facilitating breakthroughs

Memory fMRI predicts verbal memory decline after anterior temporal lobe resection.

To develop a clinically applicable memory functional MRI (fMRI) method of predicting postsurgical memory outcome in individual patients

Structural correlates of impaired working memory in hippocampal sclerosis

PURPOSE: Temporal lobe epilepsy (TLE) has been considered to impair long-term memory, whilst not affecting working memory, but recent evidence suggests that working memory is compromised. Functional MRI (fMRI) studies demonstrate that working memory involves a bilateral frontoparietal network the activation of which is disrupted in hippocampal sclerosis (HS). A specific role of the hippocampus to deactivate during working memory has been proposed with this mechanism faulty in patients with HS. Structural correlates of disrupted working memory in HS have not been explored. METHODS: We studied 54 individuals with medically refractory TLE and unilateral HS (29 left) and 28 healthy controls. Subjects underwent 3T structural MRI, a visuospatial n-back fMRI paradigm and diffusion tensor imaging (DTI). Working memory capacity assessed by three span tasks (digit span backwards, gesture span, motor sequences) was combined with performance in the visuospatial paradigm to give a global working memory measure. Gray and white matter changes were investigated using voxel-based morphometry and voxel-based analysis of DTI, respectively. KEY FINDINGS: Individuals with left or right HS performed less well than healthy controls on all measures of working memory. fMRI demonstrated a bilateral frontoparietal network during the working memory task with reduced activation of the right parietal lobe in both patient groups. In left HS, gray matter loss was seen in the ipsilateral hippocampus and parietal lobe, with maintenance of the gray matter volume of the contralateral parietal lobe associated with better performance. White matter integrity within the frontoparietal network, in particular the superior longitudinal fasciculus and cingulum, and the contralateral temporal lobe, was associated with working memory performance. In right HS, gray matter loss was also seen in the ipsilateral hippocampus and parietal lobe. Working memory performance correlated with the gray matter volume of both frontal lobes and white matter integrity within the frontoparietal network and contralateral temporal lobe. SIGNIFICANCE: Our data provide further evidence that working memory is disrupted in HS and impaired integrity of both gray and white matter is seen in functionally relevant areas. We suggest this forms the structural basis of the impairment of working memory, indicating widespread and functionally significant structural changes in patients with apparently isolated HS

Memory network plasticity after temporal lobe resection: a longitudinal functional imaging study

Anterior temporal lobe resection can control seizures in up to 80% of patients with temporal lobe epilepsy. Memory decrements are the main neurocognitive complication. Preoperative functional reorganization has been described in memory networks, but less is known of postoperative reorganization. We investigated reorganization of memory-encoding networks preoperatively and 3 and 12 months after surgery. We studied 36 patients with unilateral medial temporal lobe epilepsy (19 right) before and 3 and 12 months after anterior temporal lobe resection. Fifteen healthy control subjects were studied at three equivalent time points. All subjects had neuropsychological testing at each of the three time points. A functional magnetic resonance imaging memory-encoding paradigm of words and faces was performed with subsequent out-of-scanner recognition assessments. Changes in activations across the time points in each patient group were compared to changes in the control group in a single flexible factorial analysis. Postoperative change in memory across the time points was correlated with postoperative activations to investigate the efficiency of reorganized networks. Left temporal lobe epilepsy patients showed increased right anterior hippocampal and frontal activation at both 3 and 12 months after surgery relative to preoperatively, for word and face encoding, with a concomitant reduction in left frontal activation 12 months postoperatively. Right anterior hippocampal activation 12 months postoperatively correlated significantly with improved verbal learning in patients with left temporal lobe epilepsy from preoperatively to 12 months postoperatively. Preoperatively, there was significant left posterior hippocampal activation that was sustained 3 months postoperatively at word encoding, and increased at face encoding. For both word and face encoding this was significantly reduced from 3 to 12 months postoperatively. Patients with right temporal lobe epilepsy showed increased left anterior hippocampal activation on word encoding from 3 to 12 months postoperatively compared to preoperatively. On face encoding, left anterior hippocampal activations were present preoperatively and 12 months postoperatively. Left anterior hippocampal and orbitofrontal cortex activations correlated with improvements in both design and verbal learning 12 months postoperatively. On face encoding, there were significantly increased left posterior hippocampal activations that reduced significantly from 3 to 12 months postoperatively. Postoperative changes occur in the memory-encoding network in both left and right temporal lobe epilepsy patients across both verbal and visual domains. Three months after surgery, compensatory posterior hippocampal reorganization that occurs is transient and inefficient. Engagement of the contralateral hippocampus 12 months after surgery represented efficient reorganization in both patient groups, suggesting that the contralateral hippocampus contributes to memory outcome 12 months after surgery

Progressive white matter changes following anterior temporal lobe resection for epilepsy.

Anterior temporal lobe resection (ATLR) is an effective treatment for refractory temporal lobe epilepsy (TLE). Widespread abnormalities in diffusion parameters involving the ipsilateral temporal lobe white matter and extending into extratemporal white matter have been shown in cross-sectional studies in TLE. However longitudinal changes following surgery have been less well addressed. We systematically assess diffusion changes in white matter in patients with TLE in comparison to controls before surgery and look at the longitudinal changes following ATLR at two timepoints (3-4 months, 12 months) using a whole brain approach. We find predominantly unilateral baseline changes in temporal and extratemporal structures compatible with altered myelination (reduced fractional anisotropy, increased mean and radial diffusivity). Following surgery, these changes progress in efferent tracts from the resected temporal lobe compatible with Wallerian degeneration. However more superiorly in the corona radiata, internal and external capsules and nearby tracts, changes compatible with plasticity are observed (increased fractional anisotropy and axial diffusivity, reduced radial diffusivity). There is little progression between 3-4 months and 12 months following surgery in patients with left TLE, but the changes become more widespread in patients with right TLE suggesting that plasticity occurs more slowly in this population. The neuropsychological correlates of such plasticity should be explored further

Experience maketh the mind? Top management teams’ experiential background and cognitive search for adaptive solutions

The adaptive strategies of firms depend on executives’ forward-looking cognitive search. We examine how cognitive search is affected by the formative experiences of the executives making up a firm’s top management team (TMT). Drawing on research on adaptive search, cognition, and the upper echelons, we examine the extent to which educational level, diversity of functional expertise, and the length of industry tenure of TMT members will be associated with whether cognitive search centers more on proximal or on distal solutions. Analysis of 10 years of panel-data from US companies shows that whereas a TMT’s educational level does not seem to affect cognitive search, diversity of functional expertise does so, as predicted, and industry tenure does so in a manner we had not fully anticipated. Additional analysis also shows that whether cognitive search is proximal or distal is associated with whether firms enter into related or unrelated new product-markets. The article discusses the implications of these findings

Agro-industrial byproducts as alternate cost-effective medium components for production of polyhydroxybutyrate

631-642Polyhydroxybutyrates (PHBs), biodegradable plastics, having properties similar to conventional plastics, exhibit a high potential for replacing petrochemical-based non-degradable plastics. But a major obstacle in their large-scale commercial production is high production cost, one of the key factors responsible for which is the expensive carbon sources that are currently being used in their manufacturing process. The present work was aimed to study PHB production using cost-effective substrates as carbon sources in the production medium. Inexpensive agro-industrial byproducts (molasses, cheese whey, wheat bran and banana peel, used in different concentrations) were explored for their potential to substitute the conventional costly substrates. Compared to glucose, all the four alternate carbon sources showed an enhancement in PHB production. The mean percent increase in PHB production was in the range of 3.81% to 7.23%. However, some of the bacterial isolates showed an enhancement as high as 23.32% and 19.65%. Highest mean PHB yield was observed in molasses (135.18 mg/mL), followed by cheese-whey (133.79 mg/mL), banana peel, and least in wheat bran based production medium. On dry weight basis, PHB accumulation in cells was observed to be 64.32% and 64.29% of the total dry cell weight with molasses and cheese whey, respectively, as carbon sources. FTIR spectra of extracted PHB were found to be comparable to the spectra of standard PHB, thus, confirming the chemical nature of the extracted polymer

An avalanche-photodiode-based photon-number-resolving detector

Avalanche photodiodes are widely used as practical detectors of single photons.1 Although conventional devices respond to one or more photons, they cannot resolve the number in the incident pulse or short time interval. However, such photon number resolving detectors are urgently needed for applications in quantum computing,2-4 communications5 and interferometry,6 as well as for extending the applicability of quantum detection generally. Here we show that, contrary to current belief,3,4 avalanche photodiodes are capable of detecting photon number, using a technique to measure very weak avalanches at the early stage of their development. Under such conditions the output signal from the avalanche photodiode is proportional to the number of photons in the incident pulse. As a compact, mass-manufactured device, operating without cryogens and at telecom wavelengths, it offers a practical solution for photon number detection.Comment: 12 pages, 4 figure