Interaction between binocular rivalry and depth in plaid patterns

Binocular rivalry was studied using plaids which were the sum of orthogonal diagonal gratings plus identical vertical gratings in the two eyes. The rivalry alternations sped up as the spatial frequency difference between the vertical and diagonal gratings was increased above about one octave, but slowed down for smaller differences. The interaction between depth and rivalry was studied using similar plaids but with depth introduced in the vertical components. Depth and rivalry coexisted when the spatial frequency difference between the vertical and diagonal gratings was greater than about one octave, but rivalry slowed down and depth perception was reduced for smaller differences. Plaids consisting of square wave gratings were used to compare: (1) added gratings; (2) vertical gratings superimposed on (i.e. occluding) diagonal gratings; (3) diagonal gratings superimposed on vertical gratings. Rivalry alternations were fastest in condition (3), indicating that grouping effects played a role. The final experiment indicated that depth and rivalry coexisted within a spatial frequency band if the orientation difference between the vertical and diagonal components was 60-70 degrees . These results place constraints on models of stereopsis and rivalry, indicating that depth and rivalry can coexist in different spatial frequency and orientation bands but that each interferes with the other in the same band.     

Stereo channels with different temporal frequency tunings

To investigate the spatial and temporal frequency tunings for stereopsis, we measured the contrast sensitivity for depth discrimination with variable spatiotemporal frequencies and disparities using drifting sinusoidal gratings. The results showed that the contrast sensitivity changed with the stimulus disparity and the disparity tuning function varied with the spatial frequency. The disparity in the peak sensitivity decreased proportionally with the spatial frequency (size-disparity correlation). Although the temporal frequency exhibited a limited influence on the peak disparity, the temporal frequency tuning varied with the spatial frequency. The shape of the temporal frequency tuning function was lowpass for higher spatial frequencies, whereas it was bandpass for low spatial frequencies. These results suggest that more than one channel with different temporal as well as spatial frequency tunings contribute to stereopsis.     

From PET detectors to PET scanners

This review describes the properties of available and emerging radiation detector and read-out technologies and discusses how they may affect PET scanner performance. After a general introduction, there is a section in which the physical properties of several different detector scintillators are compared. This is followed by a discussion of recent advances in read-out electronics. Finally, the physical performance of the several commercial PET scanners is summarized.     

Indocyanine green video angiographies help to identify burns requiring operation

The key decision in the treatment of thermal injuries is the determination of the depth of the burn wound and the resultant decision on treatment options. The trend in the treatment of deep dermal and full thickness burns is toward very early excision and grafting to reduce the risk of infection, decrease scar formation, shorten hospital stay, and thereby reducing costs. Traditionally, this has involved serial clinical examinations, which involves primarily subjective judgment. Various objective examination techniques, supplementing the clinical diagnosis, have been suggested, but none has yet achieved widespread clinical acceptance. It has frequently been postulated that the blood flow in injured tissue indicates the extent of tissue damage. In this study, the clinical and scientific impact of indocyanine green (ICG) video angiography was tested in 20 patients. A wide range of depth of injury and etiology was included and analyzed. In all cases considered, video angiography was possible. The measurements and observations correlated well with the actual burn depth, which was assessed clinically (pre- and intraoperative assessment) and histologically (biopsies). In conclusion, ICG video angiography seems to be a practical method to describe vascular patency in a burn wound. The results indicate that ICG fluorescence angiography is a practical, accurate, and effective adjunct to clinical methods for estimating burn wound depth and thereby to assist in the rational assessment of treatment options. Furthermore, it allows an objective, qualitative and quantitative observation of the dynamic changes in burn wound depth, which are observed during the acute post-burn period, thereby indicating optimal timing of the first operation.     

Depth of Subserosal Invasion Predicts Long-Term Survival After Resection in Patients With T2 Gallbladder Carcinoma

Background: This study aimed to identify a subgroup of patients with inapparent T2 gallbladder carcinoma who may be best suited for radical second resection.Methods: A retrospective analysis was conducted of 126 patients with pathologic stage T2 (pT2) gallbladder carcinoma (51 with clinically evident tumor and 75 with inapparent tumor). Depth of subserosal invasion was measured histologically in each gallbladder specimen. The median follow-up period was 113 months.Results: In all 126 patients, depth of subserosal invasion was the strongest independent prognostic factor by univariate (P < .0001) and multivariate (relative risk, 9.27; P < .0001) analyses. Among the 75 patients with inapparent tumor, the outcome after resection was significantly better in patients who had undergone radical second resection than in patients who had undergone cholecystectomy alone (P = .0006). When depth of subserosal invasion was divided into 2 vs. >2 mm, the effectiveness of radical second resection remained only in patients with subserosal invasion >2 mm (P = .0004).Conclusions:Depth of subserosal invasion best predicts postresectional long-term survival of pT2 gallbladder carcinoma patients. Among patients with inapparent pT2 tumors, those with subserosal invasion >2 mm are good candidates for radical second resection.     

Unilateral hippocampal sclerosis with contralateral temporal scalp ictal onset

PURPOSE: To investigate the clinical characteristics and surgical outcomes in patients with unilateral hippocampal sclerosis whose scalp ictal EEG recordings localize to the opposite temporal lobe. METHODS: We retrospectively reviewed the data of all adult patients who had undergone depth electrode implantation for suspected temporal lobe epilepsy (TLE) at UCLA (1993-2000) or the Montreal Neurological Institute (1991-1998) to identify patients who had (a) unilateral hippocampal atrophy, and (b) surface ictal recordings in which the majority of seizures appeared to initiate in the opposite temporal lobe, with few or none that were concordant with the hippocampal atrophy. RESULTS: Of 109 patients with suspected TLE who underwent depth electrode study at the two centers, five patients met the aforementioned criteria. Four of these five had very severe hippocampal atrophy, whereas the fifth had mild atrophy but extensive signal change on magnetic resonance imaging (MRI). Depth electrode recordings in four of the five patients yielded clear ictal onset in the mesial temporal lobe ipsilateral to the imaging abnormality (contralateral to apparent scalp ictal onset). One patient had an unusual bitemporal onset pattern, which was nonetheless suggestive of onset in the sclerotic hippocampus. No patient had intracranial ictal onset contralateral to the imaging abnormality. All patients underwent resection of the structurally abnormal temporal lobe. After follow-up of > or = 2 years, four (80%) of five patients were seizure free, while the fifth showed lesser improvement (class III). CONCLUSIONS: Some patients with severe hippocampal sclerosis (sometimes called a "burned-out hippocampus") have atypical spread of ictal discharges, resulting in apparent gross discordance between imaging and scalp ictal recordings. These patients nonetheless have excellent surgical outcomes on the whole. Whether such patients may forego intracranial recordings requires further study.     

An integrative model of binocular vision: a stereo model utilizing interocularly unpaired points produces both depth and binocular rivalry

Half-occluded points (visible only in one eye) are perceived at a certain depth behind the occluding surface without binocular rivalry, even though no disparity is defined at such points. Here we propose a stereo model that reconstructs 3D structures not only from disparity information of interocularly paired points but also from unpaired points. Starting with an array of depth detection cells, we introduce cells that detect unpaired points visible only in the left eye or the right eye (left and right unpaired point detection cells). They interact cooperatively with each other based on optogeometrical constraints (such as uniqueness, cohesiveness, occlusion) to recover the depth and the border of 3D objects. Since it is contradictory for monocularly visible regions to be visible in both eyes, we introduce mutual inhibition between left and right unpaired point detection cells. When input images satisfy occlusion geometry, the model outputs the depth of unpaired points properly. An interesting finding is that when we input two unmatched images, the model shows an unstable output that alternates between interpretations of monocularly visible regions for the left and the right eyes, thereby reproducing binocular rivalry. The results suggest that binocular rivalry arises from the erroneous output of a stereo mechanism that estimates the depth of half-occluded unpaired points. In this sense, our model integrates stereopsis and binocular rivalry, which are usually treated separately, into a single framework of binocular vision. There are two general theories for what the "rivals" are during binocular rivalry: the two eyes, or representations of two stimulus patterns. We propose a new hypothesis that bridges these two conflicting hypotheses: interocular inhibition between representations of monocularly visible regions causes binocular rivalry. Unlike the traditional eye theory, the level of the interocular inhibition introduced here is after binocular convergence at the stage solving the correspondence problem, and thus open to pattern-specific mechanisms.     

《黄帝内经》针刺浅深量学之思考

从病位、病性、病人的形质、季节时令和经脉及其循行部位等方面就《黄帝内经》对针刺浅深的量化做一综述,同时对目前针刺浅深量化研究作了简要的回顾。笔者以为针刺浅深量化应立足于中医古典文献,并以提高临床疗效为目的,从而为进一步加强针刺手法的研究提供新的思路。     

人工晶状体眼近视力矫正对近立体视的影响

目的 探讨超声乳化白内障吸除及人工晶状体植入术后近立体视改善的方法和手段,为临床改善人工晶状体眼者生活质量提供依据.方法 前瞻性系列病例研究.随机收录年龄相关性白内障患者46例(92只眼),平均年龄(61.3±5.5)岁.其中单眼人工晶状体眼24例(A组),双眼人工晶状体眼22例(B组).测量调节幅度、相对调节、近附加、近立体视.对被收录者人工晶状体眼的一般资料及近附加等计量资料进行t检验,对受检者近立体视分布数据采用X2检验,以P<0.05有统计学意义.结果 A、B组人工晶状体眼移近法单眼调节幅度分别为(2.05±1.12)和(2.35±1.30)D;双眼近附加分别为(2.08±0.37)和(2.13±0.46)D,单眼近附加分别为(2.20±0.42)和(2.01±0.39)D,各组内双眼近附加与单眼近附加差异均有统计学意义(t=2.33,2.20;P<0.05),左右眼单眼近附加差异均有统计学意义(t=3.70,5.02;P<0.01).A、B组配戴单眼近附加时的近立体视优于双眼近附加,差异均有统计学意义(X2=6.46,7.02;P<0.05).结论 单眼近附加作为人工晶状体眼的近附加可以有效改善近屯体视.(中华眼科杂志,2008,44:711-714)     

Gaze direction modulates visual aftereffects in depth and color

Prior physiological studies indicate that gaze direction modulates the gain of neural responses to visual stimuli. Here, we test gaze modulation in the perceptual domain using color and depth aftereffects. After confirming retinotopy of the effects, we employed a balanced alternating adaptation paradigm (adaptation alternates between opponent stimuli) to demonstrate that opposite color and depth aftereffects can co-develop at the same retinal location for different gaze directions. The results provide strong evidence for (a) gaze modulation of aftereffects, (b) generality of gaze modulation across two visual attributes, and (c) perceptual correlates of the modulation of neural activity by gaze direction.