Evidence for a global scanpath strategy in viewing abstract compared with realistic images

Scanpaths, the repetitive sequences of saccadic eye movements, occurred when subjects viewed slide projections of both realistic and abstract art. Variance analysis demonstrated that global/local eye movement indices were lower for local scanning by professional art viewers who relied on more global viewing, particularly in abstract images. Non-professional, unsophisticated subjects carried their local scanpath patterns from realistic images on to abstract images. The blink rate of professional subjects viewing abstract images was also significantly lower, indicating increased visual effort. Non-professional viewers showed no difference in blink rates.     

Early and permanent effects of monocular deprivation on pattern discrimination and visuomotor behavior in cats

Visuomotor behavior and pattern discrimination were studied in a group of cats raised with one eye closed by eyelid suturing 7-10 days after birth. At the age of 8-10 months the animals were forced to use their deprived eye by reversal of eye closure (closing the normal eye and opening the deprived one). Visuomotor behavior and pattern discrimination were tested before as well as after reverse closure, to compare performances of the deprived eye with those of the non-deprived eye. In order to get optimal visuomotor experience, the animals were kept in large playrooms for at least 4h each day. Except for normal tactile placing responses, visually triggered extension responses and uncertain jumping, 2 years after reverse closure all other tests (visually guided reaching, visual cliff behavior, obstacle avoidance, tracking, jumping, and visual blink responses) still showed impairments; the optokinetic nystagmus was asymmetric. In contrast with this partial behavioral recovery, pattern discrimination in a simple nose-push training box requiring no complicated visuomotor coordination was found to be positive. Discriminations of gratings of different orientations, starting 4 weeks after reverse closure, appeared to be normal, in comparison with performance using the non-deprived eye of the same cats tested before reverse closure. Form discrimination was also found to be positive; some monocularly deprived cats required more trails than normal cats in upright vs. reversed solid triangles discrimination, but succeeding form problems were mastered within the same range as found in normal cats. Apparently behavioral defects after monocular deprivation are due to deficiencies in visuomotor control rather than in pattern identification.     

Peripheral shift reduces visual sensitivity in cat geniculate neurones

The sudden displacement of the retinal image during a saccade raises the visual threshold of human observers to foveal stimuli. The fall in visual sensitivity observed during this phenomenon, known as saccadic suppression, seems to occur very early in the visual processing chain. The lateral geniculate nucleus (LGN) is a likely locus for the multiple retinal and extraretinal interactions occurring during saccadic eye movements, therefore we used the responses of relay cells of adult cats to simulate a psychophysical experiment. We first measured the responses of X and Y relay cells (27 X and 13 Y) to central spots of optimal size and different contrasts. The spots were presented either alone or time locked with the rapid movement of a large, high-contrast peripheral pattern, referred to as shift. We measured the percentage of trials on which the relay cell fired more spikes when the spot (contrast: 0.03-1.0) was present than when it was absent. In experiments with human observers the task was to indicate, by a keypress, which of two otherwise identical temporal intervals contained the spot. The shift reduces the sensitivity (raises the contrast threshold) of neurones in the cat relay cells to brief, stationary targets presented to the receptive-field center. The suppression of visual sensitivity is significantly greater in Y cells than in X cells (average sensitivity ratios 5.6 +/- 5.4 in Y cells, 1.59 +/- 0.9 in X cells: P < 0.001, U test). The shift also reduces the sensitivity of human observers to the same target. This suggests that the LGN is a potential locus for the modulation of visual responses that leads to saccadic suppression.     

The directional effects of passive eye movement on the directional visual responses of single units in the pigeon optic tectum

We have investigated the visual responses of 184 single units located in the superficial layers of the optic tectum (OT) of the decerebrate, paralysed pigeon. Visual responses were similar to those reported in non-decerebrate preparations; most units responded best to moving visual stimuli, 18% were directionally selective (they had a clear preference for a particular direction of visual stimulus movement), 76% were plane-selective (they responded to movement in either direction in a particular plane). However, we also found that a high proportion of units showed some sensitivity to the orientation of visual stimuli. We examined the effects of extraocular muscle (EOM) afferent signals, induced by passive eye movement (PEM), on the directional visual responses of units. Visual responses were most modified by particular directions of eye movement, although there was no unique relationship between the direction of visual stimulus movement to which an individual unit responded best and the direction of eye movement that caused the greatest modification of that visual response. The results show that EOM afferent signals, carrying information concerning the direction of eye movement, reach the superficial layers of the OT in the pigeon and there modify the visual responses of units in a manner that suggests some role for these signals in the processing of visual information.     

A new pressure ulcer risk assessment scale for individuals with spinal cord injury

The topography of somatosensory evoked magnetic fields (SEFs) following stimulation of the upper and lower lips was investigated in 6 normal subjects. When the lateral side of the upper lip was stimulated, P20m and its counterpart, N20m, were identified in the hemisphere contralateral to the stimulated side. The equivalent current dipoles (ECDs) of N20m-P20m were considered to be located in lip area of the primary sensory cortex (SI). Middle latency deflections (N40m-P40m, N60m-P60m, and N80m-P80m) were identified in bilateral hemispheres. Their ECDs were located in the SI in both hemispheres. Long latency deflections (P110m-N110m) were recognized in both hemispheres, and their ECDs were located inferior to the SI, in an area considered to be the secondary sensory cortex (SII). When the midline of the lip was stimulated, similar short and middle latency deflections was also identified, but SII deflections (P110m-N110m) were decreased in amplitude. When the lower lip was stimulated, the ECDs of short and middle latency deflections were located at a site in the SI inferior to or near those elicited by upper lip stimulation. The ECDs of P110m-N110m were located in an area of the SII similar to that upon stimulation of the upper lip, but their orientations were different.     

Effects of stimulus modality and task condition on blink startle modification and on electrodermal responses

Participants in Experiments 1 and 2 performed a discrimination and counting task to assess the effect of lead stimulus modality on attentional modification of the acoustic startle reflex. Modality of the discrimination stimuli was changed across subjects. Electrodermal responses were larger during task-relevant stimuli than during task-irrelevant stimuli in all conditions. Larger blink magnitude facilitation was found during auditory and visual task-relevant stimuli, but not for tactile stimuli. Experiment 3 used acoustic, visual, and tactile conditioned stimuli (CSs) in differential conditioning with an aversive unconditioned stimulus (US). Startle magnitude facilitation and electrodermal responses were larger during a CS that preceded the US than during a CS that was presented alone regardless of lead stimulus modality. Although not unequivocal, the present data pose problems for attentional accounts of blink modification that emphasize the importance of lead stimulus modality.     

Influence of axial length on visual field defects in primary open-angle glaucoma

With the high frequency of myopia in Taiwan, potential complications or associated conditions, such as glaucoma, are of great concern. To investigate the role of axial length in glaucoma, we enrolled 307 primary open-angle glaucoma (POAG) patients from 1986 through 1996. For the control group, 124 persons were recruited from a survey of a non-glaucoma population and the Ophthalmology Out-patient Department of the National Taiwan University Hospital. Routine eye examination, stereophotography of the optic disc, automated visual field tests, and A-scan ultrasonography were performed on each patient. The Glaucoma Hemifield test was used for analysis of visual field results. The mean axial length was longer in the POAG group than in the control group, especially in the younger age groups (40-59 yr). The POAG group was divided into a short-axial-length (SAL, axial length < 26 mm) group and a long-axial-length (LAL, axial length > or = 26 mm) group. Both subgroups had the deepest visual field defects in the upper and lower nasal areas. The LAL group had deeper visual field defects and the defects were more frequently involved in all sectors analyzed than the SAL group defects. The upper visual field had deteriorated more in the SAL group, whereas the depth of scotoma was similar in the upper and lower hemifields in the LAL group. Our results support the idea that glaucoma patients have a longer axial length than people without glaucoma, and that visual field defects are more pronounced in patients with LAL than in those with SAL.     

Development and application of a nonaqueous capillary electrophoresis system for the analysis of porphyrins and their oligomers (PHOTOFRIN)

We analyzed 577 neurons recorded from visual areas V1, V2, V4, and the inferotemporal area (TEO) of macaque monkeys, which performed a visual fixation task and a spot-off-on (blink) test during the fixation period. Among these neurons, 35% were defined as task-related cells, because they gave responses at the task-start, fixation, or task-end periods but were unresponsive to the spot blink, which was physically identical to these stimuli. Blink-responsive cells accounted for 29% and task-unresponsive cells for 30% of the neurons. The task-related response was large and frequent in V4 (34%) and TEO (41%), but small and less frequent in V1 (31%) and V2 (27%). Other observations further demonstrated nonsensory activities in these areas: In some cells, response to the fixation spot was inhibitory, whereas light stimulation on the fovea was excitatory; some V1 and V2 cells had color-irrelevant responses, and some cells responded to the spot-off only when the monkey regarded it as a task-end cue.     

Harvesting of peripheral blood progenitor cells with different programmes of discontinuous flow systems

PURPOSE: To investigate whether a rapid and practical determination of the temporal frequency characteristic (TFC) of the visual system can be obtained by using the visually evoked potentials (VEPs) elicited by pseudorandom binary sequence (PRBS) stimulation. METHODS: VEPs were recorded from eight volunteers. For the conventional steady state VEPs (S-VEP), the eye was stimulated with five stimulus frequencies. To acquire the PRBS-VEPs, the eye was stimulated with a PRBS stimulus for 40 seconds. The TFC for the S-VEP was calculated from the root mean squared amplitude for each frequency using Fourier transform. For the PRBS stimulus, a cross-correlation function between PRBS (x[t]) and PRBS-VEP (y[t]) was calculated to obtain the TFC. RESULTS: The TFCs obtained by the PRBS and S-VEP methods were highly correlated (P < 0.05), and the TFC curves resembled those in the literature. Most important, the data necessary to determine the TFCs using the PRBS stimulus could be obtained in 4 minutes, whereas that for the S-VEP required 60 minutes for the two eyes. CONCLUSIONS: The high correlation between the TFCs obtained by the two methods indicated that the PRBS technique gives a good measure of the TFC of the human visual system. The significantly shorter time required for this method demonstrated that it is a practical method for determining the linear (and nonlinear) property of the visual system and that it may be useful in clinical applications.     

Spectral characteristics of blink suppression in normal observers

Previous studies of the characteristics of suppression occurring under various visual conditions show similarities and differences which may indicative of the mechanism of suppression. The primary purpose of this study was to determine if the suppression that occurs in response to an eyelid blink (blink suppression) is similar to that which occurs during a saccade (saccadic suppression). In addition, the characteristics of blink suppression and other forms of suppression (i.e. permanent and binocular rivalry suppression) are compared. A test probe paradigm was utilized to determine the effect of blink suppression on the spectral sensitivity function in three normal observers. Employing a two alternative forced choice technique, thresholds were determined for wavelengths from 420 to 680 nm in 20 nm steps. At each wavelength, the threshold was determined at 0 and 400 msec after the onset of a voluntary blink. The magnitude of suppression was taken as the difference between the 0 and 400 msec thresholds. Similar to saccadic suppression, the magnitude of blink suppression increased as the stimuli biased detection towards the luminance channel. These results suggest that blink suppression and saccadic suppression are the result of a single mechanism. Similarities between blink suppression and other forms of visual suppression are also considered.     

Erythrocyte sodium-lithium countertransport activity and total body insulin-mediated glucose disposal in normoalbuminuric normotensive type 1 (insulin-dependent) diabetic patients

PURPOSE: To assess the potential of a clinical method of optic disc measurement in the detection of early neuroretinal rim loss in glaucoma. METHODS: A method of disc biometry based on indirect ophthalmoscopy was used to estimate disc and neuroretinal rim areas in 81 ocular hypertensive eyes of 43 patients and in 28 fellow eyes with normal visual fields of patients with unilateral visual field loss from primary open-angle glaucoma. The results were compared with those from age-matched visually normal patients. RESULTS: Neuroretinal rim area was significantly smaller in both hypertensive and fellow eye groups compared with controls (P < 0.0001; P = 0.0009). Disc area also was smaller in both groups (P = 0.0034; P = 0.046); however, this was inadequate to explain the differences in rim area, which, when corrected for disc size, were still highly significant (P < 0.0001; P = 0.0001). CONCLUSION: The differences in neuroretinal rim area observed are likely to indicate that a proportion of the eyes studied had suffered a reduction of neuroretinal rim area, which was measurable by this method at a stage before the development of demonstrable visual field loss.     

The study on changes of macular light sensitivity before and after photocoagulation for diabetic macular edema

OBJECTIVE: The study was designed to determine whether laser photocoagulation could damage macular visual function in treatment of diabetic macular edema. METHODS: A prospective clinical trial was taken to determine the effects of argon green (514.5nm) laser photocoagulation on macular light sensitivity (MLS) by comparing the self MLS pairing data collected from a Humphrey automatic visual field analyzer before and after the procedure. Nineteen eyes of 15 patients with diabetic macular edema consistent with its diagnostic criteria were enrolled in this study, a follow-up period being 3 months. RESULTS: The mean MLS at the photocoagulation area, non-photocoagulation area, 5 degrees and 13 degrees eccentricity were significantly decreased within 1 week after the treatment, the drops of MLS were 1.85 dB, 1.05 dB, 0.99 dB, 1.66 dB respectively (P < 0.05). The mean reduction of MLS at the fovea within 1 week after the treatment has no statistical significance. The MLS gradually recovered at the 1st and 3rd month after photocoagulation, and the visual acuities in most of the cases were stable or increased. CONCLUSIONS: MLS is affected little by laser photocoagulation, and photocoagulation can reduce the risk of visual loss or increase visual acuity in an eye with diabetic macular edema.     

Blinks of the mind: Memory effects of attentional processes.

If 2 words are presented successively within 500 ms, subjects often miss the 2nd word. This attentional blink reflects a limited capacity to attend to incoming information. Memory effects were studied for words that fell within an attentional blink. Unrelated words were presented in a modified rapid serial visual presentation task at varying stimulus-onset asynchronies, and attention was systematically manipulated. Subsequently, recognition, repetition priming, and semantic priming were measured separately in 3 experiments. Unidentified words showed no recognition and no repetition priming. However, blinked (i.e., unidentified) words did produce semantic priming in related words. When, for instance, ring was blinked, it was easier to subsequently identify wedding than apple. In contrast, when the blinked word itself was presented again, it was not easier to identify than an unrelated word. Possible interpretations of this paradoxical finding are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Activity staining of protein inhibitors of proteases on gelatin-containing polyacrylamide gel electrophoresis

Stimulation of the supraorbital branch of the trigeminal nerve (SO) elicited eye blinks in the rabbit, but did not decrease the amplitude of visual cortical evoked potential from stimulation of the optic chiasm (OX). In addition, the SO stimulation neither induced an inhibitory postsynaptic potential (IPSP) in LGN cells, nor activated inhibitory interneurons in the thalamic reticular nucleus (TRN), which proved to mediate both recurrent inhibition and saccadic suppression in the dorsal lateral geniculate nucleus (LGN). All these indicate that there is no visual suppression in the rabbit LGN during blink reflex.     

Localization of soluble guanylate cyclase activity in the guinea pig cochlea suggests involvement in regulation of blood flow and supporting cell physiology

Foveal pathway visual function was assessed in 11 patients having tumours extending into the suprasellar region but without evidence of visual impairment as assessed by visual acuity and Bjerrum screen campimetry. Psychophysical and routine visual evoked potential (VEP) measurements were obtained from the eye ipsilateral to the maximal suprasellar extension. The sensitivity of luminance and chromatic pathways was assessed psychophysically by measuring increment thresholds for white and red flashes of light presented on a white adapting field. Temporal sensitivity was assessed psychophysically by measuring threshold modulation sensitivity for sinusoidally modulating stimuli (de Lange attenuation characteristic). The patient group showed approximately equal significant psychophysical losses in chromatic, luminance and temporal sensitivities relative to normal controls. Midline VEP P100 latencies of the patient group did not significantly differ from those of the normal control group. It is concluded that tumours extending into the suprasellar region can cause foveal pathway dysfunction affecting both magno- and parvocellular pathways, even in the presence of normal visual acuity and fields suggesting a more widespread and insidious abnormality of the visual pathways in this condition than previously thought.     

A comparison of seven visual fatigue assessment techniques in three data-acquisition VDT tasks

We compared 7 methods of measuring visual fatigue--accommodation power, visual acuity, pupil diameter, critical fusion frequency (CFF), eye movement velocity, subjective rating of visual fatigue, and task performance--for their sensitivity to visual load. In the experiment, 10 participants performed a monitoring task at 2 viewing distances, read articles under 2 levels of screen contrast, and tracked visual targets at 2 different speeds. The same measurement techniques, excluding pupil diameter and eye movement velocity, were compared by extending the task time from 20 to 60 min with the same VDT tasks to test for possible improvement in sensitivity. The results indicated that sensitivities of accommodation power, visual acuity, and CFF were greatly improved by a longer task period, but these 3 measurement techniques did not distinguish among tasks. Pupil diameter, eye movement velocity, and subjective rating of visual fatigue were sensitive in differentiating tracking from reading and monitoring tasks. Eye movement velocity and subjective rating were sensitive to the changes in target velocity of the tracking task. Although task performance was not directly comparable to other measurement techniques, it helped to ensure that participants maintained the same performance level by devoting more resources to the high-load conditions. Actual or potential applications of this research include using some of these assessment techniques for the design of adaptive displays.     

Electrophysiological evidence for a postperceptual locus of suppression during the attentional blink

When an observer detects a target in a rapid stream of visual stimuli, there is a brief period of time during which the detection of subsequent targets is impaired. In this study, event-related potentials (ERPs) were recorded from normal adult observers to determine whether this "attentional blink" reflects a suppression of perceptual processes or an impairment in postperceptual processes. No suppression was observed during the attentional blink interval for ERP components corresponding to sensory processing (the P1 and N1 components) or semantic analysis (the N400 component). However, complete suppression was observed for an ERP component that has been hypothesized to reflect the updating of working memory (the P3 component). Results indicate that the attentional blink reflects an impairment in a postperceptual stage of processing.     

"The attentional blink reflects retrieval competition among multiple rapid serial visual presentation items: Tests of an interference model": Erratum.

Reports an error in "The attentional blink reflects retrieval competition among multiple rapid serial visual presentation items: Tests of an interference model" by Matthew I. Isaak, Kimron L. Shapiro and Jesse Martin (Journal of Experimental Psychology: Human Perception and Performance, 1999[Dec], Vol 25[6], 1774-1792). On p. 1778, the correct Figure 1 was inadvertently replaced in the production process with an erroneous figure. The erratum contains the corrected figure. (The following abstract of the original article appeared in record 2000-15288-019.) When people respond to a target (T1) in a rapid serial visual presentation stream, their perception of a subsequent target (T2) is impaired if the intertarget stimulus onset asynchrony is between about 100 and 500 ms. Three experiments supported the interference model's (K. L. Shapiro, J. E. Raymond, & K. M. Arnell, 1994) claim that this attentional blink reflects competition for retrieval among multiple items in visual short-term memory. Experiments 1 and 2 revealed that items appearing during the blink are named as T2 on an above-chance proportion of trials when T2 must be identified. Experiment 3 demonstrated that both the size of the blink and sensitivity to T2 reflected the number of items competing for retrieval as T2; such competition, moreover, occurred at a conceptual or categorical level rather than at a purely visual one. The relationship between the interference and alternative models of the attentional blink is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Clinical significance of natural killing activity in patients with advanced lymphoma

OBJECTIVE: (1) To determine which facial landmarks show the greatest movement during specific facial animations and (2) to determine the sensitivity of our instrument in using these landmarks to detect putatively abnormal facial movements. DESIGN: Movements of an array of skin-based landmarks on five healthy human subjects (2 men and 3 women; mean age, 27.6 years; range, 26 to 29 years) were observed during the execution of specific facial animations. To investigate the instrument sensitivity, we analyzed facial movements during maximal smile animations in six patients with different types of functional problems. In parallel, a panel was asked to view video recordings of the patients and to rate the degree of motor impairment. Comparisons were made between the panel scores and those of the measurement instrument. RESULTS: Specific regions of the face display movement that is representative of specific animations. During the smile animation, landmarks on the mid- and lower facial regions demonstrated the greatest movement. A similar pattern of movement was seen during the cheek puff animation, except that the infraorbital and chin regions demonstrated minimal movement. For the grimace and eye closure animations, the upper, mid-facial, and upper-lip regions exhibited the greatest movement. During eye opening, the upper and mid-facial regions, excluding the upper lip and cheek, moved the most, and during lip purse, markers on the mid- and lower face demonstrated the most movement. We used the smile-sensitive landmarks to evaluate individuals with functional impairment and found good agreement between instrument rankings based on the data from these landmarks and the panel rankings. CONCLUSION: The present method of three-dimensional tracking has the potential to detect and characterize a range of clinically significant functional deficits.     

Trigeminal inputs to eyeblink motoneurons in the rabbit

The rabbit nictitating membrane and eyeblink response is widely used in studies of classical conditioning. Eyeblinks involve coordinated activation of the orbicularis oculi motoneurons (OOcVII) and accessory abducens motoneurons (AccVI) which close the external eyelids and nictitating membrane, respectively, and inhibition of levator palpebrae motoneurons (LPIII) whose activity raises the upper eyelid. The identification of blink interneurons that may coordinate these responses is an important step in the analysis of mechanisms supporting eyeblink conditioning as they are likely to receive convergent inputs from circuitry associated with learned as well as unlearned responses. We first investigated the distribution of OOcVII motoneurons in the facial nucleus and LPIII motoneurons in the oculomotor nucleus by retrograde tracing of wheat germ-agglutinated horseradish peroxidase (WGA-HRP) injected into the appropriate muscles. We then used an anterograde tracing method to locate trigeminal and paratrigeminal inputs to OOcVII, to AccVI nucleus, and to LPIII. Injections of WGA-HRP were placed into the principal trigeminal nucleus (Vp) and into all divisions of the spinal trigeminal nucleus. We found an area in Vp and the adjacent rostral parts of pars oralis of the spinal trigeminal nucleus that gave clear projections to OOcVII and AccVI motoneurons and adjacent to LPIII motoneurons in the contralateral oculomotor nucleus. We suggest that neurons in this premotor blink area in rabbits can coordinate learned and reflex blink responses involving the external eyelids and the nictitating membrane. In addition, there are direct projections from the pars interpolaris and pars caudalis of the spinal trigeminal nucleus to the facial nucleus that may mediate short latency responses of the external eyelid orbicularis oculi muscle alone.