OKN眼动跟踪在运动文字识别中的作用

用运动文字的阅读眼动实验来研究运动图像识别与眼动控制的关系,并与一般OKN眼动及一般正常阅读进行对比,探讨了速度及位置信息处理与内容信息处理的关系.实验结果表明;(1)一般正常文字阅读的眼动是Saccades眼动与注视停顿;运动文字识别阅读的眼动中没有注视停顿,而是快、慢交替的OKN眼动,在其慢相期间即运动文字与视网膜相对静止期间采集内容信息进行处理,慢相期间既处理文字内容信息又处理运动速度信息,说明对运动速度与内容信息的处理是并行的.(2)在运动文字运动速度高达80°/s以上时,已不能阅读甚至不能识别单字意义,但仍可产生OKN眼动;这一方面证实阅读速度的受限不在于眼球运动的跟踪能力,而在于高级识别中枢的解码速度,另一方面也说明OKN眼动不是在识别后才产生,而是进行运动图象识别的必要条件.(3)运动文字识别阅读的速度不低于一般正常文字阅读的速度.本文的结果还证实OKN眼动的快相眼动有别于Foveating Saccades.     

视觉信息处理:阅读中文和英文时眼动模式的对比研究

文字阅读是一个复杂的视觉模式识别过程,虽然客观测量阅读过程中的脑的活动比较困难,但用记录分析阅读中由脑部控制的眼球活动来研究脑的信息处理特点却是可行的.本文采用两种不同结构的文字——以空间图象为基础的方块汉字和以发音序列为基础的横行英文——作为输入,用红外眼动仪测量阅读时的眼动曲线,再由计算机分析其异同.结果表明:1)阅读注视时程对中文及英文分别为0.260及0.265秒;2)阅读辨认跨度对中文及英文分别为1.7及1.8信息单位.由两者的相似性提示我们:整段理解阅读信息处理能力决定于神经系统高级阅读中枢的解码速率.     

视觉图像辨认眼动中的Top－down信息处理

在视觉图像辨认过程中,眼球不是均匀地扫描全幅图像,而是通过一系列快速的眼球跳动来改变注视点位置,有选择地通过注视停顿来采集图象中的关键信息。通过实验对不同图像刺激时的眼动轨迹进行记录与分析,发现：（１）对于简单的几何图形,眼动注视停顿主要集中在图像中几何特征之处,亦即与周围不同的奇异点上;（２）对复杂图象刺激,眼动注视点位置决定于受试者的已有概念模型及其兴趣所在;（３）对中文单字进行辩认时,其眼动模式也是取决于受试者对该单字的知识（也即概念模型）。以上结果提示,视觉图象辨认主要是通过自上而下（ｔｏｐ－ｄｏｗｎ）的信息处理方式才完成．由中枢控制眼球运动,将注视点落到中枢决定的图形奇点上来,通过注视停顿对中枢认为的关键信息之处进行抽提,以实现辨认。这种处理方式不是只取决于输入的图像信息,也不必对目标图像的每个象素进行处理,而只需对图象中少量的关键信息部位进行重点的检测和处理,从而提高了图象信息处理的能力及效率。     

视觉图像辨认眼动中的Top－down信息处理

在视觉图像辨认过程中,眼球不是均匀地扫描全幅图像,而是通过一系列快速的眼球跳动来改变注视点位置,有选择地通过注视停顿来采集图象中的关键信息。通过实验对不同图像刺激时的眼动轨迹进行记录与分析,发现：（１）对于简单的几何图形,眼动注视停顿主要集中在图像中几何特征之处,亦即与周围不同的奇异点上;（２）对复杂图象刺激,眼动注视点位置决定于受试者的已有概念模型及其兴趣所在;（３）对中文单字进行辩认时,其眼动模式也是取决于受试者对该单字的知识（也即概念模型）。以上结果提示,视觉图象辨认主要是通过自上而下（ｔｏｐ－ｄｏｗｎ）的信息处理方式才完成．由中枢控制眼球运动,将注视点落到中枢决定的图形奇点上来,通过注视停顿对中枢认为的关键信息之处进行抽提,以实现辨认。这种处理方式不是只取决于输入的图像信息,也不必对目标图像的每个象素进行处理,而只需对图象中少量的关键信息部位进行重点的检测和处理,从而提高了图象信息处理的能力及效率。     

不同注意任务类型及难度对猕猴微眼动的影响

微眼动是视觉注视过程中幅度最大、速度最快的眼动,可以消除由于神经系统适应性而产生的视觉衰退现象,在视觉信息处理过程中发挥着重要作用.基于微眼动与视觉感知功能的相关性,设计实验研究猕猴完成显性、隐性注意任务以及不同难度显性注意任务时,视觉注视情况下微眼动的差异.通过对不同难度显性注意任务下微眼动的参数进行比较,发现随着任务难度的增加,微眼动的幅度、速率和频率都被抑制.另一方面,对比不同类型的视觉感知任务(显性注意和隐性注意),发现在相似的实验范式下,隐性注意对微眼动的频率有明显的抑制作用,但幅度和频率没有得到一致的结果,这表明视觉注意任务类型的不同或将导致猕猴完成任务的策略不同.这些工作将为今后进一步研究微眼动产生的神经机制以及视觉注意过程中眼动的作用机制奠定良好的基础.     

不同运动图象同时刺激左右眼时的交替视动震颤(OKN)现象

采用了同时对左右眼分别以不同的运动图象刺激的实验方法,来测量及分析其OKN眼动反应,探索在OKN反映中两眼之间的输入关系以及眼动控制机制。实验结果发现在两眼的刺激图象不一致时,眼动反应为交替的OKN反应,即中枢神经系统根据各眼的刺激速度,交替地控制产生OKN眼动反应。本文还从闭环控制上讨论了视网膜上速度误差信号的作用。     

不同运动图象同时刺激左右眼时的交替视动震颤(OKN)现象

采用了同时对左右眼分别以不同的运动图象刺激的实验方法,来测量及分析其OKN眼动反应,探索在OKN反映中两眼之间的输入关系以及眼动控制机制。实验结果发现在两眼的刺激图象不一致时,眼动反应为交替的OKN反应,即中枢神经系统根据各眼的刺激速度,交替地控制产生OKN眼动反应。本文还从闭环控制上讨论了视网膜上速度误差信号的作用。     

汉字识别的眼动特性-字频效应及信道容量

用眼动测量方法,对字频为４×１０－３至１．６×１０－５范围内笔画数为４至１４的常用汉字进行识别实验,结果表明,汉字识别时间与笔画数无关,而是存在识别时间随字频减小而增大的字频效应,即当汉字字频每减小一个对数单位其识别时间增加约０．０７９秒;识别眼动的注视次数（ｎｕｍｂｅｒｏｆｆｉｘａｔｉｏｎｓ）也随字频减小而增多,注视时程（ｆｉｘａｔｉｏｎｄｕｒａｔｉｏｎ）基本不变;采用＂二决一＂及＂重复显示＂汉字识别实验,证实字频效应反映了识别时间与该字在识别时的先验概率的关系,从而可由实验数据计算出识别的信道容量（ＣｈａｎｎｅｌＣａｐａｃｉｔｙ）约为４２ｂｉｔｓ／ｓ。     

运动图形刺激时家兔的视动震颤反应

旨在用实验方法研究家兔的视动震颤（ＯＫＮ）眼动特点以及单侧前庭迷路损伤对ＯＫＮ的影响,结果表明：单眼刺激时,家兔的ＯＫＮ反应存在着从颞侧到鼻侧方向的方向优势;恒定速度刺激时,刺激开始后,家兔的ＯＫＮ眼动跟踪速度具有从小到大最后趋于稳态的建立过程,刺激消失后,存在眼动速度由大到小直到消失的视动后震颤（ＯＫＡＮ）反应,这两个过程反应了ＯＫＮ系统中可能存在速度存储机制及其对ＯＫＮ眼动的控制作用;单侧前庭     

汉字识别的眼动特性-字频效应及信道容量

用眼动测量方法,对字频为４＊１０＾－３至１．６＊１０＾－５范围内笔画数为４至１４的常用汉字进行识别实验,结果表明,汉字识别时间与笔画数无关,而是存在识别时间随字频减小而增大的字频效应,     

Reading from a Head-Fixed Display during Walking: Adverse Effects of Gaze Stabilization Mechanisms

Reading performance during standing and walking was assessed for information presented on earth-fixed and head-fixed displays by determining the minimal duration during which a numerical time stimulus needed to be presented for 50% correct naming answers. Reading from the earth-fixed display was comparable during standing and walking, with optimal performance being attained for visual character sizes in the range of 0.2° to 1°. Reading from the head-fixed display was impaired for small (0.2-0.3°) and large (5°) visual character sizes, especially during walking. Analysis of head and eye movements demonstrated that retinal slip was larger during walking than during standing, but remained within the functional acuity range when reading from the earth-fixed display. The detrimental effects on performance of reading from the head-fixed display during walking could be attributed to loss of acuity resulting from large retinal slip. Because walking activated the angular vestibulo-ocular reflex, the resulting compensatory eye movements acted to stabilize gaze on the information presented on the earth-fixed display but destabilized gaze from the information presented on the head-fixed display. We conclude that the gaze stabilization mechanisms that normally allow visual performance to be maintained during physical activity adversely affect reading performance when the information is presented on a display attached to the head.     

Properties of 3D rotations and their relation to eye movement control

Rotations of the eye are generated by the torques that the eye muscles apply to the eye. The relationship between eye orientation and the direction of the torques generated by the extraocular muscles is therefore central to any understanding of the control of three-dimensional eye movements of any type. We review the geometrical properties that dictate the relationship between muscle pulling direction and 3D eye orientation. We then show how this relation can be used to test the validity of oculomotor control hypotheses. We test the common modeling assumption that the extraocular muscle pairs can be treated as single bidirectional muscles. Finally, we investigate the consequences of assuming fixed muscle pulley locations when modeling the control of eye movements.     

Using Eye Movements to Evaluate the Cognitive Processes Involved in Text Comprehension

The present article describes how to use eye tracking methodologies to study the cognitive processes involved in text comprehension. Measuring eye movements during reading is one of the most precise methods for measuring moment-by-moment (online) processing demands during text comprehension. Cognitive processing demands are reflected by several aspects of eye movement behavior, such as fixation duration, number of fixations, and number of regressions (returning to prior parts of a text). Important properties of eye tracking equipment that researchers need to consider are described, including how frequently the eye position is measured (sampling rate), accuracy of determining eye position, how much head movement is allowed, and ease of use. Also described are properties of stimuli that influence eye movements that need to be controlled in studies of text comprehension, such as the position, frequency, and length of target words. Procedural recommendations related to preparing the participant, setting up and calibrating the equipment, and running a study are given. Representative results are presented to illustrate how data can be evaluated. Although the methodology is described in terms of reading comprehension, much of the information presented can be applied to any study in which participants read verbal stimuli.     

Both Lexical and Non-Lexical Characters Are Processed during Saccadic Eye Movements

On average our eyes make 3–5 saccadic movements per second when we read, although their neural mechanism is still unclear. It is generally thought that saccades help redirect the retinal fovea to specific characters and words but that actual discrimination of information only occurs during periods of fixation. Indeed, it has been proposed that there is active and selective suppression of information processing during saccades to avoid experience of blurring due to the high-speed movement. Here, using a paradigm where a string of either lexical (Chinese) or non-lexical (alphabetic) characters are triggered by saccadic eye movements, we show that subjects can discriminate both while making saccadic eye movement. Moreover, discrimination accuracy is significantly better for characters scanned during the saccadic movement to a fixation point than those not scanned beyond it. Our results showed that character information can be processed during the saccade, therefore saccades during reading not only function to redirect the fovea to fixate the next character or word but allow pre-processing of information from the ones adjacent to the fixation locations to help target the next most salient one. In this way saccades can not only promote continuity in reading words but also actively facilitate reading comprehension.     

Control and modulation of canal driven vestibulo-ocular reflex.

It has been well known that the canal driven vestibulo-ocular reflex (VOR) is controlled and modulated through the central nervous system by external sensory information (e.g. visual, otolithic and somatosensory inputs) and by mental conditions. Because the origin of retinal image motion exists both in the subjects (eye, head and body motions) and in the external world (object motion), the head motion should be canceled and/or the object should be followed by smooth eye movements. Human has developed a lot of central nervous mechanisms for smooth eye movements (e.g. VOR, optokinetic reflex and smooth pursuit eye movements). These mechanisms are thought to work for the purpose of better seeing. Distinct mechanism will work in appropriate self motion and/or object motion. As the results, whole mechanisms are controlled in a purpose-directed manner. This can be achieved by a self-organizing holistic system. Holistic system is very useful for understanding human oculomotor behavior.     

What We Can Learn about Reading Development from the Analysis of Eye Movements

The paper presents the results of the study on reading mechanisms in children of primary school age performed using eye tracking. The participants were 36 second-grade pupils. Eye movements were registered when reading a specially developed set of sentences containing words with controlled length and frequency. Neuropsychological assessment and reading of words with regular and irregular spelling were also performed. The results confirm the data of reading analysis obtained in other languages and show that characteristics of eye movements during reading depend on the length and frequency of the word. The results indicate a close relationship between the characteristics of the oculomotor activity and the level of the development of reading skills. Analysis of the relationship of eye movements and neuropsychological assessments of the cognitive abilities of children shows that the executive functions and functions for visuospatial information processing are the most important in the second year of reading aquisition. The role of auditory information processing functions requires further investigation.     

A New Font,Specifically Designed for Peripheral Vision,Improves Peripheral Letter and Word Recognition,but Not Eye-Mediated Reading Performance

Reading speed is dramatically reduced when readers cannot use their central vision. This is because low visual acuity and crowding negatively impact letter recognition in the periphery. In this study, we designed a new font (referred to as the Eido font) in order to reduce inter-letter similarity and consequently to increase peripheral letter recognition performance. We tested this font by running five experiments that compared the Eido font with the standard Courier font. Letter spacing and x-height were identical for the two monospaced fonts. Six normally-sighted subjects used exclusively their peripheral vision to run two aloud reading tasks (with eye movements), a letter recognition task (without eye movements), a word recognition task (without eye movements) and a lexical decision task. Results show that reading speed was not significantly different between the Eido and the Courier font when subjects had to read single sentences with a round simulated gaze-contingent central scotoma (10° diameter). In contrast, Eido significantly decreased perceptual errors in peripheral crowded letter recognition (-30% errors on average for letters briefly presented at 6° eccentricity) and in peripheral word recognition (-32% errors on average for words briefly presented at 6° eccentricity).     

Eye-Head Coordination for Visual Cognitive Processing

We investigated coordinated movements between the eyes and head (“eye-head coordination”) in relation to vision for action. Several studies have measured eye and head movements during a single gaze shift, focusing on the mechanisms of motor control during eye-head coordination. However, in everyday life, gaze shifts occur sequentially and are accompanied by movements of the head and body. Under such conditions, visual cognitive processing influences eye movements and might also influence eye-head coordination because sequential gaze shifts include cycles of visual processing (fixation) and data acquisition (gaze shifts). In the present study, we examined how the eyes and head move in coordination during visual search in a large visual field. Subjects moved their eyes, head, and body without restriction inside a 360° visual display system. We found patterns of eye-head coordination that differed those observed in single gaze-shift studies. First, we frequently observed multiple saccades during one continuous head movement, and the contribution of head movement to gaze shifts increased as the number of saccades increased. This relationship between head movements and sequential gaze shifts suggests eye-head coordination over several saccade-fixation sequences; this could be related to cognitive processing because saccade-fixation cycles are the result of visual cognitive processing. Second, distribution bias of eye position during gaze fixation was highly correlated with head orientation. The distribution peak of eye position was biased in the same direction as head orientation. This influence of head orientation suggests that eye-head coordination is involved in gaze fixation, when the visual system processes retinal information. This further supports the role of eye-head coordination in visual cognitive processing.