Voluntary presetting of the vestibular ocular reflex permits gaze stabilization despite perturbation of fast head movements

Normal subjects are able to change voluntarily and continuously their head-eye latency together with their compensatory eye movement gain. A continuous spectrum of intent-latency modes of the subject's coordinated gaze through verbal feedback could be demonstrated. It was also demonstrated that the intent to counteract any perturbation of head-eye movement, i.e., the mental set, permitted the subjects to manipulate consciously their vestibular ocular reflex (VOR) gain. From the data, it is inferred that the VOR is always on. It may be, however, variably suppressed by higher cortical control. With appropriate training, head-mounted displays should permit an easy VOR presetting that leads to image stabilization, perhaps together with a decrease of possible misjudgements

Parsing eye movement analysis of scanpaths of naïve viewers of art: How do we differentiate art from non-art pictures?

Relating to G. Buswell’s early work we posed the questions: How do art-naïve people look at pairs of artful pictures and similarly looking snapshots? Does the analysis of their eye movement recordings reveal a difference in their perception? Parsing eye scanpaths using string editing, similarity coefficients can be sorted out and represented for the two measures ‘Sp’ (Similarities of position) and ‘Ss’ (Similarities of sequences). 25 picture pairs were shown 5 times to 7 subjects with no specific task, who were ‘art-naïve’ to avoid confounding of the results through specific art knowledge of the subjects. A significant difference between scanpaths of artful pictures compared to snapshots was not found in our subjects´ repeated viewing sessions. Auto-similarity (same subject viewing the same picture) and cross-similarity (different subjects viewing the same picture) significantly demonstrated this result, for sequences of eye fixations (Ss) as well as their positions (Sp): In case of global (different subjects and different pairs) sequential similarity Ss we found that about 84 percent of the picture pairs where viewed with very low similarity, in quasi random mode within the range of random values. Only in 4 out of 25 artful-picture snapshot pairs was a high similarity found. A specific restricted set of representative regions in the internal cognitive model of the picture is essential for the brain to perceive and eventually recognize the picture: This representative set is quite similar for different subjects and different picture pairs independently of their art–non art features that where in most cases not recognized by our subjects. Furthermore our study shows that the distinction of art versus non-art has vanished, causing confusion about the ratio of signal and noise in the communication between artists and viewers of art

Scanpath Eye Movements during Visual Mental Imagery in a Simulated Hemianopia Paradigm

Several studies have shown that eye movements (EM) are functionally involved in visual imagery. In this study we investigate the impact of a simulated homonymous hemianopia paradigm (SH) with and without foveal masking on scanpath eye movements during visual mental imagery. EM of twenty subjects were recorded under SH condition during viewing and subsequent visual imagery of complex pictures. Using evaluated string editing methods viewing and imagery scanpaths were compared. Our results show that scanpath EM are involved in visual mental imagery and reflect the picture content even under SH. In contrast, additional foveal masking significantly reduces the similarity between viewing and imagery scanpath. This points toward a detrimental effect of foveal masking on subsequent visual imagery performance

Oculomotor fatigue and neuropsychological assessments mirror multiple sclerosis fatigue

Fatigue is a major complaint in MS. Up to now no objective assessment tools have been established which hampers any treatment approach. Previous work has indicated an association of fatigue with cognitive measures of attention. Oculomotor tests have been established in healthy individuals as a read-out of fatigue, and to some extent in MS patients. Based on these observations we compared two groups of MS patients, one with fatigue (n=28) and one without fatigue (n=21) and a group of healthy subjects (n=15) with a stand- ardised computerised measure of alertness and an oculomotor stress test. Patients with fatigue showed highly significant changes of their saccade dynamics as defined by the Main Sequence and Phase Plane plots: They showed slowing of saccades, the characteristical fatigue double peak, and an asymmetrical phase plane. Oculomotor tests differentiated significantly between fatigue and fatigabiliy in our MS patients. They also showed significantly worse performance in the alertness test as well as in the oculomotor task. Significantly slower reaction times were observed for tonic alertness in 2 series without a cue (p=.025 and p=.037) but not in phasic alertness with a cue (p=.24 and p=.34). Performance was influenced by disability as well as by affective state. We conclude, when controlling for disability and depression, saccadic stress tests and alertness tests could be used as an objective read-out for fatigability and fatigue in MS patients

Attention and information acquisition: Comparison of mouse-click with eye-movement attention tracking

Attention is crucial as a fundamental prerequisite for perception. The measurement of attention in viewing and recognizing the images that surround us constitutes an important part of eye movement research, particularly in advertising-effectiveness research. Recording eye and gaze (i.e. eye and head) movements is considered the standard procedure for measuring attention. However, alternative measurement methods have been developed in recent years, one of which is mouse-click attention tracking (mcAT) by means of an on-line based procedure that measures gaze motion via a mouse-click (i.e. a hand and finger positioning maneuver) on a computer screen.Here we compared the validity of mcAT with eye movement attention tracking (emAT). We recorded data in a between subject design via emAT and mcAT and analyzed and compared 20 subjects for correlations. The test stimuli consisted of 64 images that were assigned to eight categories. Our main results demonstrated a highly significant correlation (p<0.001) between mcAT and emAT data. We also found significant differences in correlations between different image categories. For simply structured pictures of humans or animals in particular, mcAT provided highly valid and more consistent results compared to emAT. We concluded that mcAT is a suitable method for measuring the attention we give to the images that surround us, such as photographs, graphics, art or digital and print advertisements

Topology for gaze analyses - Raw data segmentation

Recent years have witnessed a remarkable growth in the way mathematics, informatics, and computer science can process data. In disciplines such as machine learning, pattern recognition, computer vision, computational neurology, molecular biology, information retrieval, etc., many new methods have been developed to cope with the ever increasing amount and complexity of the data. These new methods offer interesting possibilities for processing, classifying and interpreting eye-tracking data. The present paper exemplifies the application of topological arguments to improve the evaluation of eye-tracking data. The task of classifying raw eye-tracking data into saccades and fixations, with a single, simple as well as intuitive argument, described as coherence of spacetime, is discussed, and the hierarchical ordering of the fixations into dwells is shown. The method, namely identification by topological characteristics (ITop), is parameter-free and needs no pre-processing and post-processing of the raw data. The general and robust topological argument is easy to expand into complexsettings of higher visual tasks, making it possible to identify visual strategies. As supplementary file an interactive demonstration of the method can be downloaded

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Pupillary responses to single and sinusoidal light stimul

Pupillary responses to single and sinusoidal light stimuli in diabetic patients

We examined effects of diabetes mellitus (DM) on the pupillary light reflex (PLR). Phasic pupillary response to a single light stimulus (200 ms) (pPLR) and to continuous sinusoidal stimuli with four different frequencies (0.1, 0.3, 0.7, 1.3Hz) (cPLR) were examined in 52 DM patients and 21 control subjects. We asked: does recording and frequency analysis of cPLR together with short time fourier [STFT] analysis of pPLR differentiate better between DM patients and normal subjects than pPLR only? Initial pupil diameter was significantly decreased in the DM group. For pPLR. maximal contraction velocity (Vmax), Vmax of redilation 1, reflex-amplitude and pPLR latency were significantly reduced in those patients who also showed signs of diabetic autonomic neuropathy (DNP). Tests of dynamic pupillary light reflex (cPLR) revealed that all DM patients had a significantly reduced gain at lower frequencies. Pupil phase lag was greater at 0.1 and 0.3Hz and smaller at 0.7 and 1.3 Hz in the DNP group (