Taxonomical Associative Memory

Assigning categories to objects allows the mind to code experience by concepts, thus easing the burden in perceptual, storage, and reasoning processes. Moreover, maximal efficiency of cognitive resources is attained with categories that best mirror the structure of the perceived world. In this work, we will explore how taxonomies could be represented in the brain, and their application in learning and recall. In a recent work, Sacramento and Wichert (in Neural Netw 24(2):143–147, 2011) proposed a hierarchical arrangement of compressed associative networks, improving retrieval time by allowing irrelevant neurons to be pruned early. We present an extension to this model where superordinate concepts are encoded in these compressed networks. Memory traces are stored in an uncompressed network, and each additional network codes for a taxonomical rank. Retrieval is progressive, presenting increasingly specific superordinate concepts. The semantic and technical aspects of the model are investigated in two studies: wine classification and random correlated data.     

SaOS2 Osteosarcoma Cells as an In Vitro Model for Studying the Transition of Human Osteoblasts to Osteocytes

The central importance of osteocytes in regulating bone homeostasis is becoming increasingly apparent. However, the study of these cells has been restricted by the relative paucity of cell line models, especially those of human origin. Therefore, we investigated the extent to which SaOS2 human osteosarcoma cells can differentiate into osteocyte-like cells. During culture under the appropriate mineralising conditions, SaOS2 cells reproducibly synthesised a bone-like mineralised matrix and temporally expressed the mature osteocyte marker genes SOST, DMP1, PHEX and MEPE and down-regulated expression of RUNX2 and COL1A1. SaOS2 cells cultured in 3D collagen gels acquired a dendritic morphology, characteristic of osteocytes, with multiple interconnecting cell processes. These findings suggest that SaOS2 cells have the capacity to differentiate into mature osteocyte-like cells under mineralising conditions. PTH treatment of SaOS2 cells resulted in strong down-regulation of SOST mRNA expression at all time points tested. Interestingly, PTH treatment resulted in the up-regulation of RANKL mRNA expression only at earlier stages of differentiation. These findings suggest that the response to PTH is dependent on the differentiation stage of the osteoblast/osteocyte. Together, our results demonstrate that SaOS2 cells can be used as a human model to investigate responses to osteotropic stimuli throughout differentiation to a mature osteocyte-like stage.     

Encoding of nested levels of acoustic regularity in hierarchically organized areas of the human auditory cortex

Our auditory system is able to encode acoustic regularity of growing levels of complexity to model and predict incoming events. Recent evidence suggests that early indices of deviance detection in the time range of the middle‐latency responses (MLR) precede the mismatch negativity (MMN), a well‐established error response associated with deviance detection. While studies suggest that only the MMN, but not early deviance‐related MLR, underlie complex regularity levels, it is not clear whether these two mechanisms interplay during scene analysis by encoding nested levels of acoustic regularity, and whether neuronal sources underlying local and global deviations are hierarchically organized. We registered magnetoencephalographic evoked fields to rapidly presented four‐tone local sequences containing a frequency change. Temporally integrated local events, in turn, defined global regularities, which were infrequently violated by a tone repetition. A global magnetic mismatch negativity (MMNm) was obtained at 140–220 ms when breaking the global regularity, but no deviance‐related effects were shown in early latencies. Conversely, Nbm (45–55 ms) and Pbm (60–75 ms) deflections of the MLR, and an earlier MMNm response at 120–160 ms, responded to local violations. Distinct neuronal generators in the auditory cortex underlay the processing of local and global regularity violations, suggesting that nested levels of complexity of auditory object representations are represented in separated cortical areas. Our results suggest that the different processing stages and anatomical areas involved in the encoding of auditory representations, and the subsequent detection of its violations, are hierarchically organized in the human auditory cortex. Hum Brain Mapp 35:5701–5716, 2014. © 2014 Wiley Periodicals, Inc.     

Beta‐band activity in auditory pathways reflects speech localization and recognition in bilateral cochlear implant users

In normal‐hearing listeners, localization of auditory speech involves stimulus processing in the postero‐dorsal pathway of the auditory system. In quiet environments, bilateral cochlear implant (CI) users show high speech recognition performance, but localization of auditory speech is poor, especially when discriminating stimuli from the same hemifield. Whether this difficulty relates to the inability of the auditory system to translate binaural electrical cues into neural signals, or to a functional reorganization of auditory cortical pathways following long periods of binaural deprivation is unknown. In this electroencephalography study, we examined the processing of auditory syllables in postlingually deaf adults with bilateral CIs and in normal‐hearing adults. Participants were instructed to either recognize (“recognition” task) or localize (“localization” task) the syllables. The analysis focused on event‐related potentials and oscillatory brain responses. N1 amplitudes in CI users were larger in the localization compared with recognition task, suggesting an enhanced stimulus processing effort in the localization task. Linear beamforming of oscillatory activity in CI users revealed stronger suppression of beta‐band activity after 200 ms in the postero‐dorsal auditory pathway for the localization compared with the recognition task. In normal‐hearing adults, effects for longer latency event‐related potentials were found, but no effects were observed for N1 amplitudes or beta‐band responses. Our study suggests that difficulties in speech localization in bilateral CI users are not reflected in a functional reorganization of cortical auditory pathways. New signal processing strategies of cochlear devices preserving unambiguous binaural cues may improve auditory localization performance in bilateral CI users. Hum Brain Mapp 35:3107–3121, 2014. © 2013 Wiley Periodicals, Inc .     

Diffractive trifocal lens implantation with or without excimer laser enhancement: is a touch-up procedure a negative predictor for refractive and subjective outcome?

Graefe's Archive for Clinical and Experimental Ophthalmology - To investigate the refractive results of a LASIK enhancement and its impact on treatment safety, efficacy, predictability and...     

Trends in epidemiology and patho-anatomical pattern of proximal humeral fractures

Purpose

Proximal humeral fractures are common and frequently associated with osteoporosis. Little is known about the association between the patho-anatomical fracture pattern of proximal humeral fractures and patient characteristics. The purpose of this six year longitudinal registry analysis of proximal humeral fractures was to study overall numbers, certain predefined pathoanatomical patterns and distribution compared with specific patient characteristics.

Methods

Data of patients treated between 2006 and 2011 in a country hospital that provides care >95 % of the city’s hospitalised patients with fractures was retrospectively reviewed. Data were analysed according to patient characteristics of age, gender, comorbidity, accompanying injuries and radiological analysis of pathoanatomical fracture patterns based on Neer and Arbeitsgemeinschaft für Osteosynthesefragen (AO) classification.

Results

Eight hundred and fifteen proximal humeral fractures (67 % women/33 % men; mean age 66 years, range 19–99) were analysed. During the study period, an overall increase of 42.5 % was found: according to AO classification, 46 % were type A, 22 % type B and 32 % type C. Based on the Neer classification, 86 % were displaced, and 49 % were complex with more than three parts. Of complex fractures, 57 % were female patients >60 years. The number of complex fractures was five times higher in women >60 years than in men of the same age group.

Conclusions

An overall increase of inpatients with displaced proximal tibial fractures was documented. Interestingly, complex displaced proximal humeral fractures, especially in older women with comorbidities, accounted for the majority of cases. These results suggest that health-care planning and hospital-based therapeutic strategies should focus on this patient group.     

Tumor Size Predicts Vascular Invasion and Histologic Grade Among Patients Undergoing Resection of Intrahepatic Cholangiocarcinoma

The association between tumor size and survival in patients with intrahepatic cholangiocarcinoma (ICC) undergoing surgical resection is controversial. We sought to define the incidence of major and microscopic vascular invasion relative to ICC tumor size, and identify predictors of microscopic vascular invasion in patients with ICC ≥5 cm. A total of 443 patients undergoing surgical resection for ICC between 1973 and 2011 at one of 11 participating institutions were identified. Clinical and pathologic data were evaluated using uni- and multivariate analyses. As tumor sized increased, the incidence of microscopic vascular invasion increased: <3 cm, 3.6 %; 3–5 cm, 24.7 %; 5–7 cm, 38.3 %; 7–15 cm, 32.9 %, ≥15 cm, 55.6 %; (p?<?0.001). Increasing tumor size was also found to be associated with worsening tumor grade. The incidence of poorly differentiated tumors increased with increasing ICC tumor size: <3 cm, 9.7 %; 3–5 cm, 19.8 %; 5–7 cm, 24.2 %; 7–15 cm, 21.1 %; >15 cm, 31.6 % (p?=?0.04). The presence of perineural invasion (odds ratio [OR]?=?2.98) and regional lymph node metastasis (OR?=?4.43) were independently associated with an increased risk of microscopic vascular invasion in tumors ≥5 cm (both p?<?0.05). Risk of microscopic vascular invasion and worse tumor grade increased with tumor size. Large tumors likely harbor worse pathologic features; this information should be considered when determining therapy and prognosis of patients with large ICC.     

Transoral parathyroid surgery—a new alternative or nonsense?

Purpose

In recent years, several endoscopic techniques have been explored in thyroid and parathyroid surgery, but only few gained acceptance among patients and surgeons. Based on extensive human cadaver and animal studies, we developed a technique for transoral partial parathyroidectomy (TOPP), which was performed for the first time in a patient with primary hyperparathyroidism (pHPT). We now report on results and the acceptance of this new technique 2 years after its implementation.

Methods

A pilot study was initiated to recruit a total of 10 patients with benign sporadic pHPT and a preoperatively localized parathyroid adenoma eligible for initial parathyroidectomy. The study protocol was approved by the ethics committee, and an insurance for unforeseen complications and risks was procured. Data of all patients evaluated and operated were prospectively collected, and follow-up examinations were carried out for 19 months on average, which included clinical examinations; ultrasonography; Ear, Nose, and Throat (ENT) investigations; and blood testing.

Results

Between January 2010 and May 2012, 75 patients with pHPT and a preoperative localized parathyroid adenoma were eligible for TOPP. After detailed information about the transoral procedure, only five (7 %) female patients consent to undergo TOPP. In three patients, a parathyroid adenoma could be removed via the transoral access, In two patients, the procedure had to be converted to the conventional technique. Median time until resection of a parathyroid adenoma was 122 min (range, 45–175). One patient had a transient recurrent laryngeal nerve palsy, while one patient suffered from a transient palsy of the right hypoglossal nerve and a slight but persisting dysgeusia. Three patients developed a hematoma of the mouth floor and swallowing problems. In four patients, the visual analog scale (VAS) pain score was high (>7) within the first 2 postoperative days.

Conclusions

Although TOPP is feasible, it is poorly accepted by patients and its complication rate is high. Thus, TOPP is nonsense with currently available devices.