Scanpath Length Research Articles

Eye-tracking Study on Different Perception of 2D and 3D Terrain Visualisation

The use of computer-generated perspective views, often named as three-dimensional (3D) maps, is growing. These terrain visualisations should be more understandable for users without cartographic education, which are not familiar with contour lines. Within the study, two eye-tracking experiments and online questionnaire were used for investigating the difference between user cognition of classical two-dimensional (2D) visualisation with contour lines and perspective 3D view. Questionnaire was focused on maps understandability, suitability and aesthetics. Results of the questionnaire shows, that the majority of participants prefer 3D visualisation. First eye-tracking experiment was designed as a pair of maps in one stimulus. One shows 2D visualisation, the other 3D visualisation. No significant differences between user preferences of 2D and 3D visualisation were found, but the results were influenced with the order of the maps in the stimuli. Because of that another experiment was designed. In this case stimuli contained only one of two possible visualisations (2D and 3D). ScanPath comparison of this experiment results confirmed that users have different strategies for cognition of 2D and 3D visualisation, although statistically significant difference between both types of visualisation was found in the ScanPath length metric only.

Gaze patterns predicting successful collision avoidance in patients with homonymous visual field defects

Aim of the present study was to identify efficient compensatory gaze patterns applied by patients with homonymous visual field defects (HVFDs) under virtual reality (VR) conditions in a dynamic collision avoidance task. Thirty patients with HVFDs due to vascular brain lesions and 30 normal subjects performed a collision avoidance task with moving objects at an intersection under two difficulty levels. Based on their performance (i.e. the number of collisions), patients were assigned to either an “adequate” (HVFDA) or “inadequate” (HVFDI) subgroup by the median split method. Eye and head tracking data were available for 14 patients and 19 normal subjects. Saccades, fixations, mean number of gaze shifts, scanpath length and the mean gaze eccentricity, were compared between HVFDA, HVFDI patients and normal subjects. For both difficulty levels, the gaze patterns of HVFDA patients (N=5) compared to HVFDI patients (N=9) were characterized by longer saccadic amplitudes towards both the affected and the intact side, larger mean gaze eccentricity, more gaze shifts, longer scanpaths and more fixations on vehicles but fewer fixations on the intersection. Both patient groups displayed more fixations in the affected compared to the intact hemifield. Fixation number, fixation duration, scanpath length, and number of gaze shifts were similar between HVFDA patients and normal subjects. Patients with HVFDs who adapt successfully to their visual deficit, display distinct gaze patterns characterized by increased exploratory eye and head movements, particularly towards moving objects of interest on their blind side. In the context of a dynamic environment, efficient compensation in patients with HVFDs is possible by means of gaze scanning. This strategy allows continuous update of the moving objects’ spatial location and selection of the task-relevant ones, which will be represented in visual working memory.

Current visual scanpath research: a review of investigations into the psychotic, anxiety, and mood disorders

The human visual system is comprised of an array of complex organs, which jointly decode information from visible light to construct a meaningful representation of the surrounding environment. The study of visual scanpaths transpired in a bid to enhance our understanding of the role of eye movements underpinning adaptive functioning as well as psychopathology and was further aided by the advent of modern eye-tracking techniques. This review provides a background to the nature of visual scanpaths, followed by an overview and critique of eye movement studies in specific clinical populations involving the psychotic, anxiety, and mood disorders, and concludes with suggested directions for future research. We performed a Medline and PsycInfo literature search, based on variations of the terms “visual scanpath,” “eye-tracking,” and “eye movements,” in relation to articles published from 1986 to the present. Eye-tracking studies in schizophrenia mostly concurred with the existence of a “restricted” scanning strategy, characterized by fewer number of fixations of increased durations, with shorter scanpath lengths, and a marked avoidance of salient features, especially in relation to facial emotion perception. This has been interpreted as likely reflecting dual impairments in configural processing as well as gestalt perception. Findings from the anxiety and mood disorders have conversely failed to yield coherent results, with further research warranted to provide corroborating evidence and overcome identified methodological limitations. Future studies should also look toward applying similar techniques to related disorders as well as conducting parallel neuroimaging investigations to elucidate potential neurobiological correlates.

Algorithm of the Scanning Path Based on SLC Files in Rapid Prototyping

The paper analyzes the structure of SLC file format which is used in rapid prototyping technology, and studies the algorithm of the scanning path through improving the line-filling algorithm. The scanning path is carried out with VC++ software and the wind power generator blade and car logo are dissected to validate the algorithm. At last, the paper analyzes the influences of the slice thickness and hatch gap on the paths, and compares the file sizes and the scanning path length under different file formats and scanning parameters.

Visual scanning of faces in 22q11.2 deletion syndrome: Attention to the mouth or the eyes?

Previous research demonstrates that people with 22q11.2 deletion syndrome (22q11DS) have social and interpersonal skill deficits. However, the basis of this deficit is unknown. This study examined, for the first time, how people with 22q11DS process emotional face stimuli using visual scanpath technology. The visual scanpaths of 17 adolescents and age/gender matched healthy controls were recorded while they viewed face images depicting one of seven basic emotions (happy, sad, surprised, angry, fear, disgust and neutral). Recognition accuracy was measured concurrently. People with 22q11DS differed significantly from controls, displaying visual scanpath patterns that were characterised by fewer fixations and a shorter scanpath length. The 22q11DS group also spent significantly more time gazing at the mouth region and significantly less time looking at eye regions of the faces. Recognition accuracy was correspondingly impaired, with 22q11DS subjects displaying particular deficits for fear and disgust. These findings suggest that 22q11DS is associated with a maladaptive visual information processing strategy that may underlie affect recognition accuracy and social functioning deficits in this group.

LEARNING TO SELF-REGULATE INSULA CORTEX MODULATES EMOTION RECOGNITION AND NEURAL CONNECTIVITY IN SCHIZOPHRENIA

assessing face emotion and complex stimuli recognition and SPEM tasks while their eye movements were recorded. Results: Post treatment improvement was observed (p=0.001) with both remediation groups showing improvement in emotion recognition. Further, paired sample t-test revealed a significant increase in raw scanpath length for the biofeedback group only post treatment (p<0.05). No pre/post change in SPEM performance was reported for either treatment group. Discussion: Training targeting low level visual processes results in gains in emotion recognition, a process highly relevant to psychosocial functioning in schizophrenia. Further, these gains were observed at a psychophysiological level via the normalisation of some visual scanpath parameters for the bottom-up based remediation alone suggesting that treatments targeted at low level functions have significant downstream effects.

P03-124 - Frontal brain function and visual exploration of natural scenes in schizophrenia

Scanpaths are the patterns of ocular fixations and saccades produced during visual exploration of a scene. Schizophrenia is associated with a restricted style of visual scanning, characterised by fewer fixations and saccades and shorter scanpath lengths compared with well viewers. Such patterns are reflective of chronic dysfunction in real-world visual processing in schizophrenia. Scanpath measures are also emerging as strong discriminatory tools in schizophrenia trait marker research. However, little is understood about the neurocognitive mechanisms underlying atypical viewing patterns. We conducted an exploratory study of the relationships between patterns of visual exploration and neuropsychological test performance in individuals with schizophrenia to further understand the neural substrates of scanpath abnormalities in this group. Fifty-one individuals meeting DSM-IV criteria for schizophrenia completed a range of neuropsychological tests and viewed a battery of static natural scenes while eye movements were recorded using non-invasive infra-red oculography. Restricted scanpath behaviours were unrelated to measures of sustained attention, visual memory, cognitive interference or general cognitive decline. Restricted scanpath patterns were most strongly associated with short term verbal memory, manipulation of information in working memory and verbal fluency performance. Such functions are unlikely to directly impinge on visual exploration in schizophrenia but may be commensurate with dysfunction of the dorsolateral prefrontal cortex, a region known to play a number of key roles in oculomotor control. The results support a role of frontal brain dysfunction in the formation and execution of viewing behaviours in schizophrenia.

Schizotypal personality traits influence idiosyncratic initiation of saccadic face exploration

Visual face exploration is usually biased to the left half of a presented face. Recent findings now indicate that the first saccade in face exploration has a strong idiosyncratic component with around 30% of healthy individuals showing a consistent rightward bias. We investigated in a random sample of 64 right-handed healthy participants whether this rightward bias might relate to individual differences, i.e. a psychotic-like thinking style (schizotypy). Elevated positive (magical ideation) but not negative (physical anhedonia) schizotypy scores accounted for a pronounced left-face preference for first saccades. Furthermore, when using magical ideation and physical anheonia to group individuals according to their median scale scores into four groups (either both scores elevated or low, or mixed with one score elevated, one low), participants with both scores elevated exhibited the most pronounced left-face preference and participants with both scores low the least. The same participant groups did not differ with respect to their side preference in exploring fractals nor for other exploration parameters such as first fixation duration, number of saccades or scanpath length. These findings indicate pronounced right-hemispheric dominance for face exploration in healthy individuals with elevated positive schizotypal thought. These findings contrast with expectations from studies with schizophrenic patients, and point to the relevance of individual differences in lateralized face processing.

Individual differences in scanpaths correspond with serotonin transporter genotype and behavioral phenotype in rhesus monkeys (Macaca mulatta)

Scanpaths (the succession of fixations and saccades during spontaneous viewing) contain information about the image but also about the viewer. To determine the viewer-dependent factors in the scanpaths of monkeys, we trained three adult males (Macaca mulatta) to look for 3 s at images of conspecific facial expressions with either direct or averted gaze. The subjects showed significant differences on four basic scanpath parameters (number of fixations, fixation duration, saccade length, and total scanpath length) when viewing the same facial expression/gaze direction combinations. Furthermore, we found differences between monkeys in feature preference and in the temporal order in which features were visited on different facial expressions. Overall, the between-subject variability was larger than the within- subject variability, suggesting that scanpaths reflect individual preferences in allocating visual attention to various features in aggressive, neutral, and appeasing facial expressions. Individual scanpath characteristics were brought into register with the genotype for the serotonin transporter regulatory gene (5-HTTLPR) and with behavioral characteristics such as expression of anticipatory anxiety and impulsiveness/hesitation in approaching food in the presence of a potentially dangerous object.

Audio-visual stimulation improves oculomotor patterns in patients with hemianopia

Patients with visual field disorders often exhibit impairments in visual exploration and a typical defective oculomotor scanning behaviour. Recent evidence [Bolognini, N., Rasi, F., Coccia, M., & Làdavas, E. (2005b). Visual search improvement in hemianopic patients after audio-visual stimulation. Brain, 128, 2830–2842] suggests that systematic audio-visual stimulation of the blind hemifield can improve accuracy and search times in visual exploration, probably due to the stimulation of Superior Colliculus (SC), an important multisensory structure involved in both the initiation and execution of saccades. The aim of the present study is to verify this hypothesis by studying the effects of multisensory training on oculomotor scanning behaviour. Oculomotor responses during a visual search task and a reading task were studied before and after visual (control) or audio-visual (experimental) training, in a group of 12 patients with chronic visual field defects and 12 controls subjects. Eye movements were recorded using an infra-red technique which measured a range of spatial and temporal variables. Prior to treatment, patients’ performance was significantly different from that of controls in relation to fixations and saccade parameters; after Audio-Visual Training, all patients reported an improvement in ocular exploration characterized by fewer fixations and refixations, quicker and larger saccades, and reduced scanpath length. Overall, these improvements led to a reduction of total exploration time. Similarly, reading parameters were significantly affected by the training, with respect to specific impairments observed in both left- and right-hemianopia readers. Our findings provide evidence that Audio-Visual Training, by stimulating the SC, may induce a more organized pattern of visual exploration due to an implementation of efficient oculomotor strategies. Interestingly, the improvement was found to be stable at a 1 year follow-up control session, indicating a long-term persistence of treatment effects on the oculomotor system.

Penggunaan Algoritma Huffman Untuk Kompres Teks

Method compression of text by using algorithm Huffman gives storage thrift of data. This method is algorithm that is most famous to compress of text. This algorithm applies system encoding with bit network, where character which the frequency is often is decoded with short bit network and character which the frequency seldom be decoded with long bit network. There is three steps in using algorithm Huffman that is first phase of forming of tree Huffman where at this phase by using this Huffman tree minimization of scanning path length will by the way of putting down information often emerges close to root and information which seldom emerge far from root, second phase is encoding that is way is compiling string binary read from root up to tree leaf Huffman, and third phase that is decoding returns from code which has been formed. Keywords : Huffman’s Algorithm, Huffman Tree, Encoding, Decoding

Demonstration of scan path optimization in proton therapy

A three-dimensional (3D) intensity modulated proton therapy treatment plan to be delivered by magnetic scanning may comprise thousands of discrete beam positions. This research presents the minimization of the total scan path length by application of a fast simulated annealing (FSA) optimization algorithm. Treatment plans for clinical prostate and head and neck cases were sequenced for continuous raster scanning in two ways, and the resulting scan path lengths were compared: (1) A simple back-and-forth, top-to-bottom (zigzag) succession, and (2) an optimized path produced as a solution of the FSA algorithm. Using a first approximation of the scanning dynamics, the delivery times for the scan sequences before and after path optimization were calculated for comparison. In these clinical examples, the FSA optimization shortened the total scan path length for the 3D target volumes by approximately 13%-56%. The number of extraneous spilled particles was correspondingly reduced by about 13%-54% due to the more efficient scanning maps that eliminated multiple crossings through regions of zero fluence. The relative decrease in delivery time due to path length minimization was estimated to be less than 1%, due to both a high scanning speed and time requirements that could not be altered by optimization (e.g., time required to change the beam energy). In a preliminary consideration of application to rescanning techniques, the decrease in delivery time was estimated to be 4%-20%.

Long-term efficacy of aripiprazole to treat psychosis in schizophrenia: Sub-analysis of two double-blind, haloperidol controlled studies

We used a psychophysiological marker of visual attention (the visual scanpath) to investigate the effects of atypical (risperidone) vs. typical (haloperidol) antipsychotic medication on facial emotion perception in schizophrenia (n=28) and healthy control (n=28) groups. Of the schizophrenia subjects, 15 were prescribed risperidone. Visual scanpaths to ‘happy’, ‘sad’ and ‘neutral’ faces were recorded using video-oculography, and concurrent emotion-recognition accuracy was assessed using multiple-option tasks. Compared to control subjects, both schizophrenia subgroups showed a restriction in visual scanning (reduced total fixation number and decreased scanpath length). Haloperidol-treated schizophrenia subjects exhibited an additional and consistent pattern of reduced attention (fixation) to salient features for neutral and happy. By contrast, risperidone-treated subjects showed a relatively greater attention to salient features for these expressions, in which they did not differ from controls. Recognition accuracy for happy and neutral showed a similar lack of impairment. These findings suggest that risperidone may play a specific role in schizophrenia in the ability to attend to salient features, and to integrate this information into an accurate percept for neutral and positive expressions in particular.

Visual scanning deficits in schizophrenia and their relationship to executive functioning impairment

Abnormal visual scanning of faces, objects, and line drawings has been observed in patients with schizophrenia and is thought to reflect neurocognitive impairment. In this study, a simultaneous measurement approach was used to assess whether schizophrenia patients demonstrate restricted visual scanning when confronted with a complex problem-solving stimulus, and whether visual scanning deficits are predictive of inflexible thinking. Thirty-eight schizophrenia patients and 30 comparison participants were presented with Rorschach inkblots while eye movements were monitored and verbal responses to the stimuli were recorded and scored for inflexible thinking using the Rorschach Repetition and Perseveration Scale. Schizophrenia patients demonstrated fewer and longer visual fixations and shorter total scanpath relative to comparison participants but did not differ on mean scanpath length. Among patients, fewer fixations were associated with a higher frequency of verbal perseverations. Correlations between scanning measures and symptoms showed that negative symptoms were related to a minimal scanning or “staring” approach. Results support previous findings of restricted visual scanning in schizophrenia patients, are consistent with previously observed relationships between visual scanning and symptom profiles, and suggest that visual organizational deficits during complex problem-solving tasks may be related to cognitive inflexibility and frontal-executive dysfunction.

Face to face: visual scanpath evidence for abnormal processing of facial expressions in social phobia

Cognitive models of social phobia propose that cognitive biases and fears regarding negative evaluation by others result in preferential attention to interpersonal sources of threat. These fears may account for the hypervigilance and avoidance of eye contact commonly reported by clinicians. This study provides the first objective examination of threat-related processing in social phobia. It was predicted that hyperscanning (hypervigilance) and eye avoidance would be most apparent in social phobia for overt expressions of threat. An infrared corneal reflection technique was used to record visual scanpaths in response to angry, sad, and happy vs. neutral facial expressions. Twenty-two subjects with social phobia were compared with age- and sex-matched normal controls. As predicted, social phobia subjects displayed hyperscanning, (increased scanpath length) and avoidance (reduced foveal fixations) of the eyes, particularly evident for angry faces. The results could not be explained by either medication or co-morbid depression. These findings are consistent with theories emphasising the role of information processing biases in social phobia, and show promise in the application to treatment evaluation in this disorder.

Emotion perception in schizophrenia: an eye movement study comparing the effectiveness of risperidone vs. haloperidol

We used a psychophysiological marker of visual attention (the visual scanpath) to investigate the effects of atypical (risperidone) vs. typical (haloperidol) antipsychotic medication on facial emotion perception in schizophrenia ( n=28) and healthy control ( n=28) groups. Of the schizophrenia subjects, 15 were prescribed risperidone. Visual scanpaths to ‘happy’, ‘sad’ and ‘neutral’ faces were recorded using video-oculography, and concurrent emotion-recognition accuracy was assessed using multiple-option tasks. Compared to control subjects, both schizophrenia subgroups showed a restriction in visual scanning (reduced total fixation number and decreased scanpath length). Haloperidol-treated schizophrenia subjects exhibited an additional and consistent pattern of reduced attention (fixation) to salient features for neutral and happy. By contrast, risperidone-treated subjects showed a relatively greater attention to salient features for these expressions, in which they did not differ from controls. Recognition accuracy for happy and neutral showed a similar lack of impairment. These findings suggest that risperidone may play a specific role in schizophrenia in the ability to attend to salient features, and to integrate this information into an accurate percept for neutral and positive expressions in particular.

Visual scanpaths to threat-related faces in deluded schizophrenia

This study examined visuo-cognitive processing of threat-related (anger, fear) and non-threat faces (happy, sad, neutral) in deluded schizophrenia ( n=11), non-deluded schizophrenia ( n=8), and healthy control ( n=22) participants. Focal analyses examined scanpath aberrations for particular facial expressions in sub-groups of schizophrenia patients determined by the presence or absence of overt delusions. Deluded schizophrenia subjects exhibited significantly fewer fixations of shorter duration for all faces, and fewer fixations of reduced duration to the feature areas of negative facial expressions (anger, sad), compared with healthy controls. Compared with non-deluded schizophrenia subjects, deluded subjects exhibited fewer fixations to fear expressions and more fixations to the feature areas of happy expressions. These findings were revealed in the context of restricted scanning (reduced number and duration of fixations, shorter scanpath length and shorter duration of fixations to facial features) in the entire schizophrenia group ( n=19) compared with healthy controls. The findings suggest a controlled attentional bias away from the feature areas of negative facial expressions in deluded schizophrenia, that is, specific to threat-related expressions compared with non-deluded schizophrenia subjects. This controlled bias away from negative social stimuli in deluded schizophrenia is discussed in terms of an attentional style of ‘vigilance–avoidance’ operating across early and late stages of information processing.

Defining the temporal threshold for ocular fixation in free-viewing visuocognitive tasks

Patterns of ocular fixation in free-viewing tasks reflect aspects of visual attention and cognition. To quantify these patterns, fixations must be identified in raw eye movement data by applying explicit spatial and temporal thresholds. A temporal threshold of 200 ms is commonly used in clinical visuocognitive research, despite having been originally derived from a study of eye movements in reading. We systematically explored temporal fixation thresholds below 200 ms, using biologically relevant (human face) and abstract (complex geometric) stimuli. Short fixations (<200 ms) significantly altered spatiotemporal patterns of fixation for both the face and geometric stimuli, by increasing the number of fixations and the scanpath length. A threshold of 100 ms was found to discriminate fixations from other oculomotor activity effectively, and was consistent with current physiological and visuocognitive models. Statistical examination of fixation duration data for each subject suggested the median was a less biased and more robust measure of central tendency than the mean.

A meta-analysis of studies of antisaccade performance in biological relatives of schizophrenia patients

Background: Impaired processing of faces in patients with schizophrenia may underlie aspects of disturbance in their social interaction. This study examined patterns of eye fixation in subjects with schizophrenia and non-psychiatric controls, while processing a high resolution picture of a neutral face and a nonbiological complex geometric stimulus.Methods: Ten-second sequences of eye movement were recorded video-oculographically (50 samples/sec) while subjects were “free-viewing” the stimuli. An essential element of the study was customized software that ensured stimulus presentation on a video display only after subjects were fixated upon a centre-screen cue, so that all subjects began stimulus processing from the same point.Results: Compared with the control group, subjects with schizophrenia exhibited reduced scanpath lengths and a tendency toward fewer fixations for the face stimulus. They also showed an initial relative right spatial hemineglect (for the first voluntary fixation) when viewing the Rey figure, but not when viewing the face stimulus. Overall, there were no significant differences between the schizophrenia and control groups in the lateral distribution of subsequent fixations for either stimulus.Conclusions: Disturbed spatial and temporal patterns of eye movement in some people with schizophrenia may reflect sub-optimal processing of face stimuli, that may predispose these individuals to dysfunctional interpretation of facial communication cues.

Schizophrenia and affective disorder show different visual scanpath patterns to faces and facial expressions: Is this a trait versus state-based distinction?

Background: Impaired processing of faces in patients with schizophrenia may underlie aspects of disturbance in their social interaction. This study examined patterns of eye fixation in subjects with schizophrenia and non-psychiatric controls, while processing a high resolution picture of a neutral face and a nonbiological complex geometric stimulus.Methods: Ten-second sequences of eye movement were recorded video-oculographically (50 samples/sec) while subjects were “free-viewing” the stimuli. An essential element of the study was customized software that ensured stimulus presentation on a video display only after subjects were fixated upon a centre-screen cue, so that all subjects began stimulus processing from the same point.Results: Compared with the control group, subjects with schizophrenia exhibited reduced scanpath lengths and a tendency toward fewer fixations for the face stimulus. They also showed an initial relative right spatial hemineglect (for the first voluntary fixation) when viewing the Rey figure, but not when viewing the face stimulus. Overall, there were no significant differences between the schizophrenia and control groups in the lateral distribution of subsequent fixations for either stimulus.Conclusions: Disturbed spatial and temporal patterns of eye movement in some people with schizophrenia may reflect sub-optimal processing of face stimuli, that may predispose these individuals to dysfunctional interpretation of facial communication cues.