A neural model of selective attention and object segmentation in the visual scene: An approach based on partial synchronization and star-like architecture of connections

A brain-inspired computational system is presented that allows sequential selection and processing of objects from a visual scene. The system is comprised of three modules. The selective attention module is designed as a network of spiking neurons of the Hodgkin–Huxley type with star-like connections between the central unit and peripheral elements. The attention focus is represented by those peripheral neurons that generate spikes synchronously with the central neuron while the activity of other peripheral neurons is suppressed. Such dynamics corresponds to the partial synchronization mode. It is shown that peripheral neurons with higher firing rates are preferentially drawn into partial synchronization. We show that local excitatory connections facilitate synchronization, while local inhibitory connections help distinguishing between two groups of peripheral neurons with similar intrinsic frequencies. The module automatically scans a visual scene and sequentially selects regions of interest for detailed processing and object segmentation. The contour extraction module implements standard image processing algorithms for contour extraction. The module computes raw contours of objects accompanied by noise and some spurious inclusions. At the next stage, the object segmentation module designed as a network of phase oscillators is used for precise determination of object boundaries and noise suppression. This module has a star-like architecture of connections. The segmented object is represented by a group of peripheral oscillators working in the regime of partial synchronization with the central oscillator. The functioning of each module is illustrated by an example of processing of the visual scene taken from a visual stream of a robot camera.     

Safety and Efficacy of Selective Intra-arterial Thrombolysis for Central Retinal Artery Occlusion

PurposeThe purpose of this study was to determine the efficacy and safety of selective intra-arterial thrombolysis in patients with central retinal artery occlusion (CRAO).MethodsMedical records for 44 eyes of 44 patients diagnosed with acute non-arteritic CRAO and thrombolysis between October 2010 and February 2019 were analyzed retrospectively. Based on visual acuity, fundoscopic findings, and fluorescein angiography, the patients were classified into three stages: incomplete, subtotal, and total. The perfusion state using the best-corrected visual acuity (BCVA), arm to retina time, and arteriovenous passage times, after 1 month, 6 months, and at the final visit after the procedure, were compared with baseline readings.ResultsImprovement of visual acuity was confirmed in 31 out of 44 patients (70.45%). The mean BCVA of 44 patients changed from 1.65 ± 0.78 logarithmic minimum angle of resolution (logMAR) at the first visit to 1.18 ± 0.91 logMAR at the last visit (p = 0.114). The BCVA according to CRAO stage was 0.08 ± 0.11 logMAR for the incomplete stage at the first visit, 0.06 ± 0.05 logMAR (p = 0.933) 1 month after the procedure, and 0.05 ± 0.07 logMAR (p = 0.933) at the last visit. In the subtotal stage, the results were 1.81 ± 0.54 logMAR at the first visit, 1.63 ± 0.76 logMAR (p = 0.035) 1 month after the procedure, and 1.36 ± 0.85 logMAR (p = 0.014) at the last visit. For the total stage of BCVA, the result at the first visit was 2.36 ± 0.25 logMAR, and it was 2.30 ± 0.30 logMAR (p = 0.510) 1 month after the procedure, and 2.42 ± 0.30 logMAR (p = 0.642) at the last visit. Reperfusion was observed in 40 patients out of the 44 (90.91%).ConclusionsSelective intra-arterial thrombolysis can be helpful in patients with subtotal CRAO in terms of visual improvement and retinal arterial reperfusion.     

Cortical connections of the visual pulvinar complex in prosimian galagos (Otolemur garnetti)

The pulvinar complex of prosimian primates is not as architectonically differentiated as that of anthropoid primates. Thus, the functional subdivisions of the complex have been more difficult to determine. In the present study, we related patterns of connections of cortical visual areas (primary visual area, V1; secondary visual area, V2; and middle temporal visual area, MT) as well as the superior colliculus of the visual midbrain, with subdivisions of the pulvinar complex of prosimian galagos (Otolemur garnetti) that were revealed in brain sections processed for cell bodies (Nissl), cytochrome oxidase, or myelin. As in other primates, the architectonic methods allowed us to distinguish the lateral pulvinar (PL) and inferior pulvinar (PI) as major divisions of the visual pulvinar. The connection patterns further allowed us to divide PI into a large central nucleus (PIc), a medial nucleus (PIm), and a posterior nucleus (PIp). Both PL and PIc have separate topographic patterns of connections with V1 and V2. A third, posterior division of PI, PIp, does not appear to project to V1 and V2 and is further distinguished by receiving inputs from the superior colliculus. All these subdivisions of PI project to MT. The evidence suggests that PL of galagos contains a single, large nucleus, as in monkeys, and that PI may have only three subdivisions, rather than the four subdivisions of monkeys. In addition, the cortical projections of PI nuclei are more widespread than those in monkeys. Thus, the pulvinar nuclei in prosimian primates and anthropoid primates have evolved along somewhat different paths. J. Comp. Neurol. 517:493–511, 2009. © 2009 Wiley‐Liss, Inc.     

Factors affecting the number and type of impairments of visual perception and praxis following stroke

Aim:  This study aimed to examine the effect of clinical factors including side of stroke, region of affected cerebral circulation, type of stroke and time since stroke, as well as age on the number and type of impairments of visual perception and praxis in patients following stroke.
Methods:  Two hundred and eight participants with stroke were conveniently sampled from 12 hospitals in Brisbane and the Gold Coast. Background information was collected and each participant was assessed for impairments of visual perception and praxis using the Occupational Therapy Adult Perceptual Screening Test.
Results:  Participants with left-hemisphere stroke were more likely to have impaired body scheme than participants with right-hemisphere stroke. Additionally, participants with right-hemisphere stroke were more likely to have unilateral neglect and impaired constructional skills than those with left-hemisphere stroke. There was a significant relationship between region of affected cerebral circulation and the occurrence of agnosia, unilateral neglect and constructional skill impairment. Moreover, the number of visual perceptual impairments experienced by participants was associated with the region of affected cerebral circulation. Increasing age was significantly related to the occurrence of constructional skill impairment and acalculia.
Conclusions:  Side of stroke, region of affected cerebral circulation and age affected the type of impairments of visual perception and praxis experienced by patients following stroke. Furthermore, region of affected cerebral circulation also influenced the number of impairments of visual perception and praxis in patients after stroke. The results have implications for more specific targeting of assessment and treatment practices following stroke.     

视网膜静脉栓塞治疗中使用阿魏酸钠的临床研究

目的探讨阿魏酸钠注射液治疗视网膜静脉栓塞的临床效果。方法80例（80只眼）视网膜静脉栓塞患者,随机分成治疗组和对照组各40例。对照组给予常规治疗,治疗组给予阿魏酸钠注射液300mg/d静脉滴注,14d为1个疗程。测定治疗前后视力、视网膜中央静脉血流速度、视网膜中央动脉平均收缩期峰值血流速度。结果应用阿魏酸钠治疗后,视力明显改善,视网膜中央静脉血流速度和收缩期峰值血流速度显著提高,与对照组治疗后相比均有显著性差异,疗效优于对照组。结论阿魏酸钠治疗视网膜静脉栓塞疗效显著。     

无痛可视人工流产术麻醉药对生命指征的影响及安全性分析

目的：研究分析无痛可视人工流产术全麻药物对生命指征的影响以及安全保障的最佳用药量。方法：选择五组（瑞芬太尼、瑞芬太尼＋丙泊酚、瑞芬太尼＋咪唑安定、丙泊酚、丙泊酚＋芬太尼）常用的麻醉药。用于无痛可视人工流产术。将受术者随机分为五组,每组60例患者。观察T、R、HR、BP、SpO2等变化情况,计算平均值及标准差并进行组间对比分析。观察各组麻醉用药,探索最佳用药量。结果：五组麻醉药在无痛可视人工流产术中的应用对生命指征的影响以瑞芬太尼＋丙泊酚组最小,经统计学分析,P〈0．05。安全保障的最佳用药量分别为瑞芬太尼0．9～1．4μg/kg、丙泊酚1．9～2．2mg／kg。结论：无痛可视人工流产术全麻药物以“瑞芬太尼＋丙泊酚”组最佳。剂量分别为0．9～1．4tLg／kg、1．9～2．2mg／kg,对生命指征的影响最小,安全系数最高。     

不同类型视标对交叉柱镜检查精确度的影响

目的：探讨蜂窝黑点状视标、最佳矫正视力上一行视标以及包含最佳矫正视力的多行视标对交叉柱镜检查结果的影响。方法：选择本院眼科硕士研究生及进修医生40名（男性11名,女性29名,年龄24~29岁）,采用常规的综合验光仪检查方法,在最大正镜最佳矫正视力（MPMVA）状态下,随机确定3种视标的检查顺序,如发现不同视标的检查结果不一致,则采用散光表帮助判断何种结果残余散光量最小。结果：40名被检者共80眼,其中无散光眼（柱镜度数小于0.25 DC）12只。在其余68眼中,对3种视标反应相同的有19眼（27.9%）;对蜂窝黑点状视标最敏感有23眼（33.8%）;对最佳矫正视力上一行视标最敏感有14眼（20.6%）;对包含最佳矫正视力的多行视标最敏感有12眼（17.6%）。采用非参数检验中的Kruska Wallis Test对数据进行分析得出,三者间对交叉柱镜检查结果的准确程度无显著性差异（χ2 =4.026,P>0.05）。结论：尽管3种视标对于交叉柱镜检查结果的准确程度差异尚无显著性,但综合考虑检查效率、医患交流的难易程度、视标判断的难易程度,推荐首选蜂窝黑点状视标作为交叉柱镜的检查视标。