bioRxiv (Cold Spring Harbor Laboratory), Apr 29, 2022
Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to transient visu... more Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to transient visual stimuli are known to be sensitive to different stimulus properties, including attention and expectation. In natural vision, transient stimulation of the visual cortex is generated primarily by saccades. Recent studies suggest that the core EEG components in free viewing, induced by saccades (fixation-related potentials, FRPs), are similar to the ERP components with flashed stimuli. We have recently found that the OMI in response to flashed stimuli is sensitive to face familiarity. Here, we investigated whether fixationrelated-potentials (FRPs) and microsaccade inhibition (OMI) in free viewing are sensitive to face familiarity. Observers (N=15) freely watched a slideshow of seven unfamiliar and one familiar world leader's facial images presented randomly for 4-seconds periods, with multiple images per identity. We measured the occipital fixation-related N1 relative to the P1 magnitude as well as the associated fixation-triggered OMI. We found that the average N1 was significantly smaller and the OMI was shorter for the familiar face, compared with any of the 7 unfamiliar faces. Moreover, the P1 was suppressed across saccades for the familiar but not for the unfamiliar faces. Overall, the results indicate that the occipital FRP and the OMI in free viewing are sensitive to face familiarity; this could perhaps be used as a novel physiological measure for studying hidden suppressed memories. .
Involuntary eye movements occur constantly even during fixation and were shown to convey informat... more Involuntary eye movements occur constantly even during fixation and were shown to convey information about cognitive processes. They are inhibited momentarily in response to external stimuli (oculomotor inhibition, OMI), with a time and magnitude that depend on stimulus saliency, attention, and expectations. It was recently shown that the working memory load for numbers modulates the microsaccade rate; however, the generality of the effect and its temporal properties remain unclear. Our goal was to investigate the relationship between OMI and the working memory load for simple colored shapes. Participants (N = 26) maintained their fixation while their eyes were tracked; they viewed briefly flashed colored shapes accompanied by small arrows indicating the shapes to be memorized (1/2/3). After a retention period, a probe shape appeared for matching. The microsaccade rate modulation and temporal properties were analyzed for the memory encoding, maintenance, and retrieval phases. Microsaccade inhibition was stronger when more shapes were memorized, and performance improved when microsaccades were suppressed during maintenance and retrieval. This occurred even though the physical stimuli were identical in number under all conditions. Thus, oculomotor inhibition may play a role in silencing the visual input while processing current stimuli and is generally related to processing time and load. Eye movements, such as saccades and microsaccades, are known to be affected by transient sensory events. Saccades of all sizes are inhibited in response to abrupt stimulation in a process first termed "saccadic inhibition" 1-4. More recently, it has been described as a general Oculomotor Inhibition (OMI) effect or "oculomotor freezing" 5 , since it was found to generalize to eye blinks 6,7 , smooth pursuit, catchup saccades during pursuit 8 , and ocular drift (Malevich et al. 9 , Ziv et al. 10 , paper in review). The vast majority of OMI studies are based on microsaccades, which are small fixational saccades with a rate of 2-3 per second 11. Microsaccades can perform precise exploration 12 and can even be produced voluntarily 13 , but usually they are involuntary, like spontaneous eye blinks and can occur even when there is nothing to explore, as in many experiments with briefly flashed stimuli (e.g. 14). In response to transient stimuli, microsaccades are first inhibited, at around 150 ms, and their probability decreases, then increases above baseline at around 400 ms after stimulus onset, before returning to baseline 15. This stereotypical inhibition and rebound pattern of rate modulation is affected by the stimulus properties as well as by attention and expectation 7,16-21. Perceptual oddballs, auditory or visual, were found to prolong the inhibition 22-25 , whereas increased saliency shortened it, for visual 14 , as well as for auditory stimuli 26 , and also during free viewing when the visual transient is induced by a saccade 14,27,28. The OMI is also affected by the higher-level properties of the stimulus. For instance, OMI duration differs in written language (words vs different types of non-words) 29 , and in auditory cognition 24. The inhibition onset and release are affected by name and face familiarity 30-32 , as well as saccade entrainment to speech segmentation 33. Taken together, these findings indicate that the OMI phenomenon might play a role in suppressing additional transient input caused by saccades during the processing of the current stimulus. The release of inhibition on a timed basis could serve as a synchronization signal in early visual cortex 34. This results in a series of self-generated events (microsaccades) that are like "punctuation marks" for cognitive processing. In the current study, we explored this interpretation regarding working memory load. Working Memory (WM) is a cognitive system that temporarily stores information necessary for complex cognitive processing and manipulation 35. It was first introduced by Baddeley and Hitch 36 as a brain system constructed of a central executive and two Short-term memory (STM) slave components: the phonological loop and the visuo-spatial sketch pad. The capacity of working memory has been suggested to be limited to four chunks 37. To date, only a few studies have examined the relationship between WM capacity and the oculomotor system. WM load has been recently found to reduce the microsaccade rate 38. Another study reported the suppression of reflexive saccades by WM load during anti-saccade tasks 39. It has been suggested that eye movements may
Involuntary eye movements occur constantly even during xation and were shown to convey informatio... more Involuntary eye movements occur constantly even during xation and were shown to convey information about cognitive processes. They are inhibited momentarily in response to external stimuli (oculomotor inhibition, OMI), with a time and magnitude that depend on stimulus saliency, attention, and expectations. It was recently shown that the working memory load for numbers modulates the microsaccade rate; however, the generality of the effect and its temporal properties remain unclear. Our goal was to investigate the relationship between OMI and the working memory load for simple colored shapes. Participants (N = 26) maintained their xation while their eyes were tracked; they viewed brie y ashed colored shapes accompanied by small arrows indicating the shapes to be memorized (1/2/3). After a retention period, a probe shape appeared for matching. The microsaccade rate modulation and temporal properties were analyzed for the memory encoding, maintenance, and retrieval phases. Microsaccade inhibition was stronger when more shapes were memorized, and performance improved when microsaccades were suppressed during maintenance and retrieval. This occurred even though the physical stimuli were identical in number under all conditions. Thus, oculomotor inhibition may play a role in silencing the visual input while processing current stimuli and is generally related to processing time and load.
Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The... more Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The properties of this Oculomotor-Inhibition (OMI) depend on stimulus saliency, anticipation, and attention. Previous studies have shown prolonged saccadic inhibition for auditory oddballs; however, they required active counting of the oddballs. Here we investigated whether the OMI response to auditory deviants can provide a quantitative measure of deviance strength (auditory pitch difference) and studied its dependence on the Inter-Trial Interval (ITI). Participants xated on a central xation stimulus and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (the Oddball paradigm). They did not perform any task or requested to attend to a speci c stimulus. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Moreover, the inhibition onset latency was shorter in proportion to the pitch deviance (the saliency effect), and the release was signi cantly longer for rare deviants (the surprise effect) as long as the ITI was short (<2.5s). Longer ITIs induced higher microsaccade and blink rates together with smaller pupil dilation, indicating a reduction of alertness. Taken together, these results suggest that OMI provides involuntary markers of saliency and surprise, which can be obtained without the participant's response.
In Motion-induced-blindness (MIB; Bonneh et. al., Nature 2001), a salient static pattern may disa... more In Motion-induced-blindness (MIB; Bonneh et. al., Nature 2001), a salient static pattern may disappear and reappear spontaneously in the presence of a global moving pattern. We have previously showed that this phenomenon is unlikely to reflect retinal suppression, sensory masking ...
People with autism spectrum disorder (ASD) and especially the minimally verbal, often fail to lea... more People with autism spectrum disorder (ASD) and especially the minimally verbal, often fail to learn basic perceptual and motor skills. This deficit has been demonstrated in several studies, but the findings could have been due to the nonoptimal adaptation of the paradigms. In the current study, we sought to characterize the skill learning deficit in young minimally verbal children with ASD and explore ways for improvement. For this purpose, we used vestibular stimulation (VS) whose beneficial effects have been demonstrated in the typical population, but the data regarding ASD are limited. We trained 36 children ages 6-13 years, ASD (N = 18, 15 of them minimally verbal) and typical development (TD, N = 18), on a touch version of the visual-motor Serial-Reaction-Time sequence-learning task, in 10 short (few minutes) weekly practice sessions. A subgroup of children received VS prior to each training block. All the participants but two ASD children showed gradual median reaction time improvement with significant speed gains across the training period. The ASD children were overall slower (by~250 msec). Importantly, those who received VS (n = 10) showed speed gains comparable to TD, which were larger (by~100%) than the ASD controls, and partially sequence-specific. VS had no effect on the TD group. These results suggest that VS has a positive effect on learning in minimally verbal ASD children, which may have important therapeutic implications. Furthermore, contrary to some previous findings, minimally verbal children with ASD can acquire, in optimal conditions, procedural skills with few short training sessions, spread over weeks, and with a similar time course as non-ASD controls.
Face familiarity revealed by eye movements. To date, few studies have investigated the pattern of... more Face familiarity revealed by eye movements. To date, few studies have investigated the pattern of eye movements when examining familiar and unfamiliar faces presented for only a few seconds. Longer fixation durations were found when the familiar face had to be reported or concealed 25,29,30. In contrast, shorter fixation durations on familiar faces were recently reported, when observers had to examine and memorize 4 faces for later reporting 31 , presumably because the familiar face requires a shorter memorizing process. These studies, however, do not shed light on OMI because they refer to free viewing of static stimuli and not to the involuntary oculomotor response to visual onsets, which we investigated in the current study. We assumed that OMI would be a better objective measure because it is less prone to top down strategies and potential biases.
Our eyes move constantly but are often inhibited momentarily in response to external stimuli (ocu... more Our eyes move constantly but are often inhibited momentarily in response to external stimuli (oculomotor inhibition [OMI]), depending on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged OMI for auditory oddballs; however, they required counting the oddballs, possibly reflecting voluntary attention. Here, we investigated whether the "passive" OMI response to auditory deviants can provide a quantitative measure of deviance strength (pitch difference) and studied its dependence on the inter-trial interval (ITI). Participants fixated centrally and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (oddballs). In an "active" control experiment, participants counted the deviant or the standard. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Earlier inhibition onset was found in proportion to the pitch deviance (the saliency effect), and a later release was found for oddballs, but only for ITI <2.5 seconds. The active control experiment showed similar results when counting the deviant but longer OMI for the standard when counting it. Taken together, these results suggest that OMI provides involuntary markers of saliency and deviance, which can be obtained without the participant's response.
In this research we present a basis for a solution for Age Related Macular Degeneration (AMD) pat... more In this research we present a basis for a solution for Age Related Macular Degeneration (AMD) patients. The proposed solution is a binocular passive optical device composed of a contact lens and spectacles, both coated by light-reflecting material in order to generate a Fabry-Perot-like resonator. This bounces the light rays several times between the two surfaces, achieving optical simultaneous magnifications for near and far distances as needed for AMD patients in early stages of the disease. Our work has two parts: numerical simulation of the magnification achieved by the device and a clinical experiment, with non-AMD patients, in which we examined visual skills with simultaneous magnifications. The numerical simulations proved mathematically that the device can produce several different magnifications simultaneously, Zemax simulations confirmed this. In the clinical study, simultaneous vision was found to have little effect on visual acuity, but slightly increased reaction time to stimuli. Thus, the proposed device may improve visual capabilities of AMD patients, allow patients in stages where the peripheral retina still functions to use these areas to maximize their remaining visual potential and thus function better in everyday life.
Microsaccades that occur during fixation were studied extensively in response to transient stimul... more Microsaccades that occur during fixation were studied extensively in response to transient stimuli, showing a typical inhibition (Oculomotor Inhibition, OMI), and a later release with a latency that depends on stimulus saliency, attention, and expectations. Here, we investigated the hypothesis that in free viewing every saccade provides a new transient stimulation that should result in a stimulusdependent OMI like a flashed presentation during fixation. Participants (N = 16) freely inspected static displays of randomly oriented Gabor texture images, with varied contrast and spatial frequency (SF) for periods of 10 s each. Eye tracking recordings were divided into epochs triggered by saccade landing (> 1 dva), and microsaccade latency relative to fixation onset was computed (msRT). We found that the msRT in free viewing was shorter for more salient stimuli (higher contrast or lower SF), as previously found for flashed stimuli. It increased with saccade size and decreased across successive saccades, but only for higher contrast, suggesting contrast-dependent repetition enhancement in free viewing. Our results indicate that visual stimulus-dependent inhibition of microsaccades also applies to free viewing. These findings are in agreement with the similarity found between event-related and fixation-related potentials and open the way for studies combining both approaches to study natural vision. Visual active exploration of the environment can be obtained by performing continuous eye movements, termed saccades, which are guided by high-level goals and stimulus-driven mechanisms. However, high spatial resolution details are accrued during the stationary interval between successive saccades ("fixations") by miniature involuntary eye movements including microsaccades and random walk-like ocular drift. Microsaccades during fixation 1-3 were found to prevent retinal image fading 4,5. However, they are very similar to larger saccades when fixation locus correction and precise exploration of small regions are required 6. Saccades and microsaccades are generated by similar neural activity in the superior colliculus (SC) 7. Other cortical regions are also known to be involved in saccade planning, including the lateral intraparietal area and the frontal eye field 8-11. The latter was found to be necessary for microsaccade execution after inhibition induced by transients 12. Moreover, a recent study showed that microsaccades can also be driven by task-relevant goals 6,13. The microsaccade rate, typically one or two per second, is modulated by stimulus presentation. Microsaccades are first inhibited and then released with a latency that depends on the stimulus properties, spatial attention, and anticipation 14-18. Similar temporal dynamics was shown when larger saccades were delayed by irrelevant stimuli 19-22. It has been suggested that saccadic inhibition is a general "freeze effect" 23 or Oculomotor Inhibition (OMI), not specific to saccades. This claim is supported by evidence for eye-blink inhibition 24 , catchup saccade inhibition during smooth pursuit, and pursuit inhibition 25 , all of which show similar stimulus-dependent inhibition in response to flashed stimuli, with a similar inhibitory time course 25-27. For example, in response to a flashed Gabor patch with regular and predictable timing (1 Hz), both the inhibition onset and release times were found to be modulated by the spatial frequency and the contrast of the Gabor, and were found to be correlated with the psychophysical contrast detection threshold (Ref. 28 , Fig. 4). However, it remains unclear whether OMI can be applied to ocular drift. Since our past preliminary evidence 29 might reflect a pupil measurement artifact, recent evidence suggest an opposite effect of increased drift triggered by a randomly presented unanticipated flash in monkeys 30. Furthermore, enhancement rather than inhibition was found for the pursuit and catch-up saccades by a superimposed flash in the pursuit direction 31. Further research is needed to resolve these issues. Event-related responses constitute the vast majority of the psychophysical, electrophysiological, and eye-tracking studies, assuming that these responses reflect the building blocks of perception. Accumulating evidence from recent free viewing electrophysiological studies suggests that the brain responses following a saccade, termed
Texture consists of local variance of grey level or edge intensity values. We have recently prese... more Texture consists of local variance of grey level or edge intensity values. We have recently presented a Generalized Symmetry operator, that captures local spatial relations of image patterns. We show that ac-tivity digerences in the continuous intensity map pro-duced by the local ...
Symmetry is one of the most prominent cues in visual perception as well as in computer vision. We... more Symmetry is one of the most prominent cues in visual perception as well as in computer vision. We have recently presented the Generalized Symmetry Transform that receives as input an edge map, and outputs a symmetry map, where every point mark the intensity and orientation of the local generalized symmetry. In the context of Computer Vision, this map emphasizes points of high symmetry, which, in turn, are used to detect regions of interest for active vision systems. Many psychophysical experiments in texture discrimination use images that consist of various micro-patterns. Since the Generalize Symmetry Transform captures local spatial relations between image edges, we have used it to predict human performance in discrimination tasks. Applying the transform on micro-patterns of some well studied quantitative experiments of human texture discrimination, we show that symmetry, as characterized by our computational scheme, can account for most of them.
The visibility of a local target is in uenced by the global con guration of the stimulus. Colline... more The visibility of a local target is in uenced by the global con guration of the stimulus. Collinear con gurations are a speci c case in which facilitation or suppression of the target has been found to be dependent on the contrast threshold of the target. The role of collinear interactions in perceptual grouping, especially in contour integration, is still controversial. In the current study, the role of collinear interactions in noise was investigated using experimental conditions similar to those utilized in studies of contour integration. The contrast detection paradigm in the presence of similar Gabor elements presented in the background was used. The results show that contrast detection threshold of the target alone is increased (suppression) when it is embedded in randomly oriented background elements. However, when the target is anked by two collinear Gabor elements, the target is facilitated even at higher target contrast levels. Facilitation is not found for orthogonal con gurations. The results suggest that the response to a local element in a contour is modi ed by lateral facilitative and suppressive inputs from elements comprising the smooth contour and randomly oriented background elements, respectively. Thus, detection of elements along a contour should be considered as integration of global neuronal activity rather than as the output of local and individual neurons.
bioRxiv (Cold Spring Harbor Laboratory), Apr 29, 2022
Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to transient visu... more Event-related potentials (ERPs) and the oculomotor inhibition (OMI) in response to transient visual stimuli are known to be sensitive to different stimulus properties, including attention and expectation. In natural vision, transient stimulation of the visual cortex is generated primarily by saccades. Recent studies suggest that the core EEG components in free viewing, induced by saccades (fixation-related potentials, FRPs), are similar to the ERP components with flashed stimuli. We have recently found that the OMI in response to flashed stimuli is sensitive to face familiarity. Here, we investigated whether fixationrelated-potentials (FRPs) and microsaccade inhibition (OMI) in free viewing are sensitive to face familiarity. Observers (N=15) freely watched a slideshow of seven unfamiliar and one familiar world leader's facial images presented randomly for 4-seconds periods, with multiple images per identity. We measured the occipital fixation-related N1 relative to the P1 magnitude as well as the associated fixation-triggered OMI. We found that the average N1 was significantly smaller and the OMI was shorter for the familiar face, compared with any of the 7 unfamiliar faces. Moreover, the P1 was suppressed across saccades for the familiar but not for the unfamiliar faces. Overall, the results indicate that the occipital FRP and the OMI in free viewing are sensitive to face familiarity; this could perhaps be used as a novel physiological measure for studying hidden suppressed memories. .
Involuntary eye movements occur constantly even during fixation and were shown to convey informat... more Involuntary eye movements occur constantly even during fixation and were shown to convey information about cognitive processes. They are inhibited momentarily in response to external stimuli (oculomotor inhibition, OMI), with a time and magnitude that depend on stimulus saliency, attention, and expectations. It was recently shown that the working memory load for numbers modulates the microsaccade rate; however, the generality of the effect and its temporal properties remain unclear. Our goal was to investigate the relationship between OMI and the working memory load for simple colored shapes. Participants (N = 26) maintained their fixation while their eyes were tracked; they viewed briefly flashed colored shapes accompanied by small arrows indicating the shapes to be memorized (1/2/3). After a retention period, a probe shape appeared for matching. The microsaccade rate modulation and temporal properties were analyzed for the memory encoding, maintenance, and retrieval phases. Microsaccade inhibition was stronger when more shapes were memorized, and performance improved when microsaccades were suppressed during maintenance and retrieval. This occurred even though the physical stimuli were identical in number under all conditions. Thus, oculomotor inhibition may play a role in silencing the visual input while processing current stimuli and is generally related to processing time and load. Eye movements, such as saccades and microsaccades, are known to be affected by transient sensory events. Saccades of all sizes are inhibited in response to abrupt stimulation in a process first termed "saccadic inhibition" 1-4. More recently, it has been described as a general Oculomotor Inhibition (OMI) effect or "oculomotor freezing" 5 , since it was found to generalize to eye blinks 6,7 , smooth pursuit, catchup saccades during pursuit 8 , and ocular drift (Malevich et al. 9 , Ziv et al. 10 , paper in review). The vast majority of OMI studies are based on microsaccades, which are small fixational saccades with a rate of 2-3 per second 11. Microsaccades can perform precise exploration 12 and can even be produced voluntarily 13 , but usually they are involuntary, like spontaneous eye blinks and can occur even when there is nothing to explore, as in many experiments with briefly flashed stimuli (e.g. 14). In response to transient stimuli, microsaccades are first inhibited, at around 150 ms, and their probability decreases, then increases above baseline at around 400 ms after stimulus onset, before returning to baseline 15. This stereotypical inhibition and rebound pattern of rate modulation is affected by the stimulus properties as well as by attention and expectation 7,16-21. Perceptual oddballs, auditory or visual, were found to prolong the inhibition 22-25 , whereas increased saliency shortened it, for visual 14 , as well as for auditory stimuli 26 , and also during free viewing when the visual transient is induced by a saccade 14,27,28. The OMI is also affected by the higher-level properties of the stimulus. For instance, OMI duration differs in written language (words vs different types of non-words) 29 , and in auditory cognition 24. The inhibition onset and release are affected by name and face familiarity 30-32 , as well as saccade entrainment to speech segmentation 33. Taken together, these findings indicate that the OMI phenomenon might play a role in suppressing additional transient input caused by saccades during the processing of the current stimulus. The release of inhibition on a timed basis could serve as a synchronization signal in early visual cortex 34. This results in a series of self-generated events (microsaccades) that are like "punctuation marks" for cognitive processing. In the current study, we explored this interpretation regarding working memory load. Working Memory (WM) is a cognitive system that temporarily stores information necessary for complex cognitive processing and manipulation 35. It was first introduced by Baddeley and Hitch 36 as a brain system constructed of a central executive and two Short-term memory (STM) slave components: the phonological loop and the visuo-spatial sketch pad. The capacity of working memory has been suggested to be limited to four chunks 37. To date, only a few studies have examined the relationship between WM capacity and the oculomotor system. WM load has been recently found to reduce the microsaccade rate 38. Another study reported the suppression of reflexive saccades by WM load during anti-saccade tasks 39. It has been suggested that eye movements may
Involuntary eye movements occur constantly even during xation and were shown to convey informatio... more Involuntary eye movements occur constantly even during xation and were shown to convey information about cognitive processes. They are inhibited momentarily in response to external stimuli (oculomotor inhibition, OMI), with a time and magnitude that depend on stimulus saliency, attention, and expectations. It was recently shown that the working memory load for numbers modulates the microsaccade rate; however, the generality of the effect and its temporal properties remain unclear. Our goal was to investigate the relationship between OMI and the working memory load for simple colored shapes. Participants (N = 26) maintained their xation while their eyes were tracked; they viewed brie y ashed colored shapes accompanied by small arrows indicating the shapes to be memorized (1/2/3). After a retention period, a probe shape appeared for matching. The microsaccade rate modulation and temporal properties were analyzed for the memory encoding, maintenance, and retrieval phases. Microsaccade inhibition was stronger when more shapes were memorized, and performance improved when microsaccades were suppressed during maintenance and retrieval. This occurred even though the physical stimuli were identical in number under all conditions. Thus, oculomotor inhibition may play a role in silencing the visual input while processing current stimuli and is generally related to processing time and load.
Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The... more Our eyes move constantly but are often inhibited momentarily in response to external stimuli. The properties of this Oculomotor-Inhibition (OMI) depend on stimulus saliency, anticipation, and attention. Previous studies have shown prolonged saccadic inhibition for auditory oddballs; however, they required active counting of the oddballs. Here we investigated whether the OMI response to auditory deviants can provide a quantitative measure of deviance strength (auditory pitch difference) and studied its dependence on the Inter-Trial Interval (ITI). Participants xated on a central xation stimulus and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (the Oddball paradigm). They did not perform any task or requested to attend to a speci c stimulus. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Moreover, the inhibition onset latency was shorter in proportion to the pitch deviance (the saliency effect), and the release was signi cantly longer for rare deviants (the surprise effect) as long as the ITI was short (<2.5s). Longer ITIs induced higher microsaccade and blink rates together with smaller pupil dilation, indicating a reduction of alertness. Taken together, these results suggest that OMI provides involuntary markers of saliency and surprise, which can be obtained without the participant's response.
In Motion-induced-blindness (MIB; Bonneh et. al., Nature 2001), a salient static pattern may disa... more In Motion-induced-blindness (MIB; Bonneh et. al., Nature 2001), a salient static pattern may disappear and reappear spontaneously in the presence of a global moving pattern. We have previously showed that this phenomenon is unlikely to reflect retinal suppression, sensory masking ...
People with autism spectrum disorder (ASD) and especially the minimally verbal, often fail to lea... more People with autism spectrum disorder (ASD) and especially the minimally verbal, often fail to learn basic perceptual and motor skills. This deficit has been demonstrated in several studies, but the findings could have been due to the nonoptimal adaptation of the paradigms. In the current study, we sought to characterize the skill learning deficit in young minimally verbal children with ASD and explore ways for improvement. For this purpose, we used vestibular stimulation (VS) whose beneficial effects have been demonstrated in the typical population, but the data regarding ASD are limited. We trained 36 children ages 6-13 years, ASD (N = 18, 15 of them minimally verbal) and typical development (TD, N = 18), on a touch version of the visual-motor Serial-Reaction-Time sequence-learning task, in 10 short (few minutes) weekly practice sessions. A subgroup of children received VS prior to each training block. All the participants but two ASD children showed gradual median reaction time improvement with significant speed gains across the training period. The ASD children were overall slower (by~250 msec). Importantly, those who received VS (n = 10) showed speed gains comparable to TD, which were larger (by~100%) than the ASD controls, and partially sequence-specific. VS had no effect on the TD group. These results suggest that VS has a positive effect on learning in minimally verbal ASD children, which may have important therapeutic implications. Furthermore, contrary to some previous findings, minimally verbal children with ASD can acquire, in optimal conditions, procedural skills with few short training sessions, spread over weeks, and with a similar time course as non-ASD controls.
Face familiarity revealed by eye movements. To date, few studies have investigated the pattern of... more Face familiarity revealed by eye movements. To date, few studies have investigated the pattern of eye movements when examining familiar and unfamiliar faces presented for only a few seconds. Longer fixation durations were found when the familiar face had to be reported or concealed 25,29,30. In contrast, shorter fixation durations on familiar faces were recently reported, when observers had to examine and memorize 4 faces for later reporting 31 , presumably because the familiar face requires a shorter memorizing process. These studies, however, do not shed light on OMI because they refer to free viewing of static stimuli and not to the involuntary oculomotor response to visual onsets, which we investigated in the current study. We assumed that OMI would be a better objective measure because it is less prone to top down strategies and potential biases.
Our eyes move constantly but are often inhibited momentarily in response to external stimuli (ocu... more Our eyes move constantly but are often inhibited momentarily in response to external stimuli (oculomotor inhibition [OMI]), depending on the stimulus saliency, anticipation, and attention. Previous studies have shown prolonged OMI for auditory oddballs; however, they required counting the oddballs, possibly reflecting voluntary attention. Here, we investigated whether the "passive" OMI response to auditory deviants can provide a quantitative measure of deviance strength (pitch difference) and studied its dependence on the inter-trial interval (ITI). Participants fixated centrally and passively listened to repeated short sequences of pure tones that contained a deviant tone either regularly or with 20% probability (oddballs). In an "active" control experiment, participants counted the deviant or the standard. As in previous studies, the results showed prolonged microsaccade inhibition and increased pupil dilation following the rare deviant tone. Earlier inhibition onset was found in proportion to the pitch deviance (the saliency effect), and a later release was found for oddballs, but only for ITI <2.5 seconds. The active control experiment showed similar results when counting the deviant but longer OMI for the standard when counting it. Taken together, these results suggest that OMI provides involuntary markers of saliency and deviance, which can be obtained without the participant's response.
In this research we present a basis for a solution for Age Related Macular Degeneration (AMD) pat... more In this research we present a basis for a solution for Age Related Macular Degeneration (AMD) patients. The proposed solution is a binocular passive optical device composed of a contact lens and spectacles, both coated by light-reflecting material in order to generate a Fabry-Perot-like resonator. This bounces the light rays several times between the two surfaces, achieving optical simultaneous magnifications for near and far distances as needed for AMD patients in early stages of the disease. Our work has two parts: numerical simulation of the magnification achieved by the device and a clinical experiment, with non-AMD patients, in which we examined visual skills with simultaneous magnifications. The numerical simulations proved mathematically that the device can produce several different magnifications simultaneously, Zemax simulations confirmed this. In the clinical study, simultaneous vision was found to have little effect on visual acuity, but slightly increased reaction time to stimuli. Thus, the proposed device may improve visual capabilities of AMD patients, allow patients in stages where the peripheral retina still functions to use these areas to maximize their remaining visual potential and thus function better in everyday life.
Microsaccades that occur during fixation were studied extensively in response to transient stimul... more Microsaccades that occur during fixation were studied extensively in response to transient stimuli, showing a typical inhibition (Oculomotor Inhibition, OMI), and a later release with a latency that depends on stimulus saliency, attention, and expectations. Here, we investigated the hypothesis that in free viewing every saccade provides a new transient stimulation that should result in a stimulusdependent OMI like a flashed presentation during fixation. Participants (N = 16) freely inspected static displays of randomly oriented Gabor texture images, with varied contrast and spatial frequency (SF) for periods of 10 s each. Eye tracking recordings were divided into epochs triggered by saccade landing (> 1 dva), and microsaccade latency relative to fixation onset was computed (msRT). We found that the msRT in free viewing was shorter for more salient stimuli (higher contrast or lower SF), as previously found for flashed stimuli. It increased with saccade size and decreased across successive saccades, but only for higher contrast, suggesting contrast-dependent repetition enhancement in free viewing. Our results indicate that visual stimulus-dependent inhibition of microsaccades also applies to free viewing. These findings are in agreement with the similarity found between event-related and fixation-related potentials and open the way for studies combining both approaches to study natural vision. Visual active exploration of the environment can be obtained by performing continuous eye movements, termed saccades, which are guided by high-level goals and stimulus-driven mechanisms. However, high spatial resolution details are accrued during the stationary interval between successive saccades ("fixations") by miniature involuntary eye movements including microsaccades and random walk-like ocular drift. Microsaccades during fixation 1-3 were found to prevent retinal image fading 4,5. However, they are very similar to larger saccades when fixation locus correction and precise exploration of small regions are required 6. Saccades and microsaccades are generated by similar neural activity in the superior colliculus (SC) 7. Other cortical regions are also known to be involved in saccade planning, including the lateral intraparietal area and the frontal eye field 8-11. The latter was found to be necessary for microsaccade execution after inhibition induced by transients 12. Moreover, a recent study showed that microsaccades can also be driven by task-relevant goals 6,13. The microsaccade rate, typically one or two per second, is modulated by stimulus presentation. Microsaccades are first inhibited and then released with a latency that depends on the stimulus properties, spatial attention, and anticipation 14-18. Similar temporal dynamics was shown when larger saccades were delayed by irrelevant stimuli 19-22. It has been suggested that saccadic inhibition is a general "freeze effect" 23 or Oculomotor Inhibition (OMI), not specific to saccades. This claim is supported by evidence for eye-blink inhibition 24 , catchup saccade inhibition during smooth pursuit, and pursuit inhibition 25 , all of which show similar stimulus-dependent inhibition in response to flashed stimuli, with a similar inhibitory time course 25-27. For example, in response to a flashed Gabor patch with regular and predictable timing (1 Hz), both the inhibition onset and release times were found to be modulated by the spatial frequency and the contrast of the Gabor, and were found to be correlated with the psychophysical contrast detection threshold (Ref. 28 , Fig. 4). However, it remains unclear whether OMI can be applied to ocular drift. Since our past preliminary evidence 29 might reflect a pupil measurement artifact, recent evidence suggest an opposite effect of increased drift triggered by a randomly presented unanticipated flash in monkeys 30. Furthermore, enhancement rather than inhibition was found for the pursuit and catch-up saccades by a superimposed flash in the pursuit direction 31. Further research is needed to resolve these issues. Event-related responses constitute the vast majority of the psychophysical, electrophysiological, and eye-tracking studies, assuming that these responses reflect the building blocks of perception. Accumulating evidence from recent free viewing electrophysiological studies suggests that the brain responses following a saccade, termed
Texture consists of local variance of grey level or edge intensity values. We have recently prese... more Texture consists of local variance of grey level or edge intensity values. We have recently presented a Generalized Symmetry operator, that captures local spatial relations of image patterns. We show that ac-tivity digerences in the continuous intensity map pro-duced by the local ...
Symmetry is one of the most prominent cues in visual perception as well as in computer vision. We... more Symmetry is one of the most prominent cues in visual perception as well as in computer vision. We have recently presented the Generalized Symmetry Transform that receives as input an edge map, and outputs a symmetry map, where every point mark the intensity and orientation of the local generalized symmetry. In the context of Computer Vision, this map emphasizes points of high symmetry, which, in turn, are used to detect regions of interest for active vision systems. Many psychophysical experiments in texture discrimination use images that consist of various micro-patterns. Since the Generalize Symmetry Transform captures local spatial relations between image edges, we have used it to predict human performance in discrimination tasks. Applying the transform on micro-patterns of some well studied quantitative experiments of human texture discrimination, we show that symmetry, as characterized by our computational scheme, can account for most of them.
The visibility of a local target is in uenced by the global con guration of the stimulus. Colline... more The visibility of a local target is in uenced by the global con guration of the stimulus. Collinear con gurations are a speci c case in which facilitation or suppression of the target has been found to be dependent on the contrast threshold of the target. The role of collinear interactions in perceptual grouping, especially in contour integration, is still controversial. In the current study, the role of collinear interactions in noise was investigated using experimental conditions similar to those utilized in studies of contour integration. The contrast detection paradigm in the presence of similar Gabor elements presented in the background was used. The results show that contrast detection threshold of the target alone is increased (suppression) when it is embedded in randomly oriented background elements. However, when the target is anked by two collinear Gabor elements, the target is facilitated even at higher target contrast levels. Facilitation is not found for orthogonal con gurations. The results suggest that the response to a local element in a contour is modi ed by lateral facilitative and suppressive inputs from elements comprising the smooth contour and randomly oriented background elements, respectively. Thus, detection of elements along a contour should be considered as integration of global neuronal activity rather than as the output of local and individual neurons.
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Papers by Yoram Bonneh