Perception of depth and motion from ambiguous binocular information

AbstractThe visual system can determine motion and depth from ambiguous information contained in images projected onto both retinas over space and time. The key to the way the system overcomes such ambiguity lies in dependency among multiple cues—such as spatial displacement over time, binocular disparity, and interocular time delay—which might be established based on prior knowledge or experience, and stored in spatiotemporal response characteristics of neurons at an early cortical stage. We conducted a psychophysical investigation of whether a single ambiguous cue (specifically, interocular time delay) permits depth discrimination and motion perception. Data from this investigation are consistent with the predictions derived from the response profiles of V1 neurons, which show interdependency in their responses to each cue, indicating that spatial and temporal information is jointly encoded in early vision

ジコ ソシキガタ ガクシュウ カイロ ノ パルス ミツドガタ ディジタル カイロ ニヨル コウセイ

1980年代に始まったニューラルネットワークのリバイバル熱も1990年代半ばのバブルの終演とともに冷え込み、1970年代と同様に落ち着いた研究環境が戻ってきたようである。ただ、いくつかの点で大きな違いがある。その一つ目は、人の脳に関する研究の大切さが理解され、いくつもの大型プロジェクトが走り出していることである。もう一つの違いは、半導体技術である。この10年間の半導体技術の進歩は著しく、最近のパーソナルコンピュータはその速度、記憶容量、磁気ディスクの容量ともに1970年代のIBM370をはじめとする大型計算機をしのぎ、その価格は3桁低くなっている。また、最近の100万ゲート規模のFPGA(Field programmable Gate Array)の開発は、自作の大規模なディジタル回路をクリーンルームなしに容易にVLSI化することを可能にした。本研究は、このような半導体技術の発展を背景に、自己組織型学習回路をディジタル回路で構成し、FPGAに実装し、実時間で学習動作することを確認したものである。 ...研究代表者: 平井有三研究課題番号: 1048006

Mechanical stability of orthodontic miniscrew depends on a thread shape

Background/purpose: Primary stability of orthodontic miniscrew system is of great importance in maintaining stable anchorage during a treatment period. Thus, this study aimed to examine whether the thread shape of orthodontic miniscrew had an effect on its mechanical stability in bone. Materials and methods: Three different types of miniscrews (type A and B with a regular thread shape; type C with a novel thread shape) were placed in artificial bone block with different artificial cortical bone thickness of 1.5, 2.0 and 3.0 mm. Values of maximum insertion torque (MIT), removal torque (RT), torque ratio (TR), screw mobility, static stiffness (K), dynamic stiffness (K∗) and energy dissipation (tan δ) ability were assessed for each miniscrew system. Results: The MIT, RT, TR and K of type C miniscrew were significantly greater than those of type A and B miniscrews when the miniscrews were placed in the thinner artificial bone. Furthermore, the TR value of type C miniscrew was more than 1, indicating the MRT value was larger than the MIT value in the novel miniscrew. The values of K∗ and tan δ were almost similar among the three types of miniscrews. Conclusion: The miniscrew with a novel thread shape showed a higher initial stability compared to those with a regular thread shape. Thus, in order to obtain a sufficient initial stability, it is important to select the type of screw thread that is appropriate for the thickness of the cortical bone

Efficacy of surgical management for recurrent intrahepatic cholangiocarcinoma: A multi-institutional study by the Okayama Study Group of HBP surgery

Background The prognosis of intrahepatic cholangiocarcinoma (ICC) has been poor, because of the high recurrence rate even after curative surgery. This study aimed to evaluate the prognostic impact of surgical resection of recurrent ICC. Patients and methods A total of 345 cases of ICC who underwent hepatectomy with curative intent in 17 institutions were retrospectively analyzed, focusing on recurrence patterns and treatment modalities for recurrent ICC. Results Median survival time and overall 5-year recurrence-free survival rate were 17.8 months and 28.5%, respectively. Recurrences (n = 223) were classified as early (recurrence at 1 year, n = 92). Median survival time was poorer for early recurrence (16.3 months) than for late recurrence (47.7 months,p<0.0001). Treatment modalities for recurrence comprised surgical resection (n = 28), non-surgical treatment (n = 134), and best supportive care (BSC) (n = 61). Median and overall 1-/5-year survival rates after recurrence were 39.5 months and 84.6%/36.3% for surgical resection, 14.3 months and 62.5%/2.9% for non-surgical treatment, and 3 months and 4.8%/0% for BSC, respectively (p<0.0001). Multivariate analysis identified early recurrence, simultaneous intra- and extrahepatic recurrence, and surgical resection of recurrence as significant prognostic factors. In subgroup analyses, surgical resection may have positive prognostic impacts on intra- and extrahepatic recurrences, and even on early recurrence. However, simultaneous intra- and extrahepatic recurrence may not see any survival benefit from surgical management. Conclusion Surgical resection of recurrent ICC could improve survival after recurrence, especially for patients with intra- or extrahepatic recurrence as resectable oligo-metastases

Finding Curved Surfaces from Static and Dynamic Random-Dot Stereograms

this paper we will show that the same network can find curved surfaces from dynamic randomdot stereograms with the same accuracy, but the convergence time is an order of magnitude faster than the static cases. This corresponds to the Julesz&apos;s report that people who could not perceive 3-D surfaces portrayed in static random-dot stereograms could perceive 3-D surfaces portrayed in dynamic random-dot stereograms [2]. 2 The Networ

Reconstruction of Curved Surfaces from Random-Dot Stereograms

Introduction Various constraints have been used to recover 3D structures from 2D images. They are classified into two categories: explicit constraints and implicit ones. In stereo matching algorithms, smoothness constraint is an example of explicit constraints, because it explicitly specifies which binocular pairs are compatible and it forces, for example, to find a planar surface from a pair of random-dot stereograms. As a result most algorithms using the smoothness constraint lack generalizing capability to nonplanar surfaces with non-zero curvatures. Implicit constraints have also been used in stereo matching algorithms. Ordering constraint is such an example. It does not specify which binocular pairs are compatible, but it only specifies which binocular pairs are not compatible. Therefore, it is an implicit constraint from the aspect of recovering surfaces. 2 The model [1] In this work a stereo matcing network using only implicit constraint is proposed an

Hardware implementation of a PCA learning network by an asynchronous PDM digital circuit

We have fabricated a PCA (Principal Component Analysis) learning network in a FPGA (Field Programmable Gate Array) by using an asynchronous PDM (Pulse Density Modulation) digital circuit. The generalized Hebbian algorithm is expressed in a set of ordinary differential equations and the circuits solve them in a fully parallel and continuous manner. The performance of the circuits was tested by a network with two-microphone inputs and two-speaker outputs. By moving a sound source right and left in front of the microphones, the first principal weight vector could continuously track the sound direction in real time.