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المصدر: Cereb Cortex
مصطلحات موضوعية: genetic structures, Cognitive Neuroscience, Population, Cellular and Molecular Neuroscience, Cognition, Cortex (anatomy), Saccades, medicine, Animals, education, Prefrontal cortex, Visual Cortex, Neurons, education.field_of_study, Eye movement, Pupil, Saccadic masking, eye diseases, medicine.anatomical_structure, Visual cortex, Saccade, Original Article, sense organs, Microsaccade, Psychology, Neuroscience
الوصف: SummaryDecades of research have shown that global brain states such as arousal can be indexed by measuring the properties of the eyes. Neural signals from individual neurons, populations of neurons, and field potentials measured throughout much of the brain have been associated with the size of the pupil, small fixational eye movements, and vigor in saccadic eye movements. However, precisely because the eyes have been associated with modulation of neural activity across the brain, and many different kinds of measurements of the eyes have been made across studies, it has been difficult to clearly isolate how internal states affect the behavior of the eyes, and vice versa. Recent work in our laboratory identified a latent dimension of neural activity in macaque visual cortex on the timescale of minutes to tens of minutes. This ‘slow drift’ was associated with perceptual performance on an orientation-change detection task, as well as neural activity in visual and prefrontal cortex (PFC), suggesting it might reflect a shift in a global brain state. This motivated us to ask if the neural signature of this internal state is correlated with the action of the eyes in different behavioral tasks. We recorded from visual cortex (V4) while monkeys performed a change detection task, and the prefrontal cortex, while they performed a memory-guided saccade task. On both tasks, slow drift was associated with a pattern that is indicative of changes in arousal level over time. When pupil size was large, and the subjects were in a heighted state of arousal, microsaccade rate and reaction time decreased while saccade velocity increased. These results show that the action of the eyes is associated with a dominant mode of neural activity that is pervasive and task-independent, and can be accessed in the population activity of neurons across the cortex.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::90ef2f6e460e74ffd6ae40d2725da41d
https://doi.org/10.1093/cercor/bhab418 -
2
المؤلفون: Ziad M. Hafed, Fatemeh Khademi, Chih-Yang Chen
المصدر: Journal of Neurophysiology. 123:2136-2153
مصطلحات موضوعية: Male, Superior Colliculi, Visual perception, genetic structures, Physiology, Computer science, Fixation, Ocular, Stimulus (physiology), Luminance, Visual Objects, Saccades, Animals, computer.programming_language, Jitter, Neurons, Physics, General Neuroscience, Superior colliculus, Eye movement, Macaca mulatta, Electrophysiological Phenomena, Fixational eye movements, Feature (computer vision), Visual Perception, Spatial frequency, Microsaccade, computer, Neuroscience
الوصف: The primate superior colliculus (SC) is causally involved in microsaccade generation. Moreover, visually-responsive SC neurons across this structure’s topographic map, even at peripheral eccentricities much larger than the tiny microsaccade amplitudes, exhibit significant modulations of evoked response sensitivity when stimuli appear peri-microsaccadically. However, during natural viewing, visual stimuli are normally stably present in the environment and are only shifted on the retina by eye movements. Here we investigated this scenario for the case of microsaccades, asking whether and how SC neurons respond to microsaccade-induced image jitter. We recorded neural activity from two male rhesus macaque monkeys. Within the response field (RF) of a neuron, there was a stable stimulus consisting of a grating of one of three possible spatial frequencies. The grating was stable on the display, but microsaccades periodically jittered the retinotopic RF location over it. We observed clear short-latency visual reafferent responses after microsaccades. These responses were weaker, but earlier (relative to new fixation onset after microsaccade end), than responses to sudden stimulus onsets without microsaccades. The reafferent responses clearly depended on microsaccade amplitude, as well as microsaccade direction relative to grating orientation. Our results indicate that one way for microsaccades to influence vision is through modulating how the spatio-temporal landscape of SC visual neural activity represents stable stimuli in the environment. Such representation strongly depends on the specific pattern of temporal luminance modulations expected from the relative relationship between eye movement vector (size and direction), on the one hand, and spatial visual pattern layout, on the other. Significance statement Despite their small sizes and slow speeds, microsaccades during fixation still jitter retinal images of stable visual objects in the environment. This means that retinotopically organized neurons’ response fields experience temporal modulations of luminance as a visual pattern is shifted by microsaccades. We investigated the impacts of such modulations on superior colliculus (SC) activity. We found that SC neurons exhibit visual reafferent activity bursts with very short latency after microsaccade end. Moreover, these bursts reflect not only the spatial luminance profiles of the patterns, but also how such luminance profiles are temporally modulated by eye movement size and direction. These results indicate that the SC continuously represents visual patterns, even as they are jittered retinotopically by the smallest possible saccades.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::1045989eb66a3da1e0731c30425c2741
https://doi.org/10.1152/jn.00077.2020 -
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المؤلفون: Laurent Goffart, Ziad M. Hafed
المساهمون: Werner Reichardt Centre for Integrative Neuroscience [Tuebingen, Germany], Tuebingen University [Germany] -Institute for Ophthalmology [Tuebingen, Germany], Hertie Institute for Clinical Brain Research [Tubingen], University of Tübingen, Institut de Neurosciences de la Timone (INT), Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)
المصدر: Journal of Neurophysiology
Journal of Neurophysiology, American Physiological Society, 2019, pp.10.1152/jn.00588.2019. ⟨10.1152/jn.00588.2019⟩
Journal of Neurophysiology, 2019, pp.10.1152/jn.00588.2019. ⟨10.1152/jn.00588.2019⟩مصطلحات موضوعية: Adult, Male, Fovea Centralis, Superior Colliculi, genetic structures, Saccadic latency, Computer science, Physiology, Biology, [SCCO]Cognitive science, 03 medical and health sciences, 0302 clinical medicine, Animal model, Memory, biology.animal, Reaction Time, Saccades, Animals, Humans, Primate, Eye Movement Measurements, Balance (ability), 030304 developmental biology, 0303 health sciences, Behavior, Animal, [SDV.NEU.PC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Psychology and behavior, [SCCO.NEUR]Cognitive science/Neuroscience, General Neuroscience, Superior colliculus, Eye movement, [SDV.NEU.SC]Life Sciences [q-bio]/Neurons and Cognition [q-bio.NC]/Cognitive Sciences, Neurophysiology, biology.organism_classification, Macaca mulatta, Gaze, Saccadic masking, Rhesus macaque, [SCCO.PSYC]Cognitive science/Psychology, Saccade, Visual Perception, Female, Visual Fields, Microsaccade, Neuroscience, 030217 neurology & neurosurgery
الوصف: Rigorous behavioral studies made in human subjects have shown that small-eccentricity target displacements are associated with increased saccadic reaction times, but the reasons for this remain unclear. Before characterizing the neurophysiological foundations underlying this relationship between the spatial and temporal aspects of saccades, we tested the triggering of small saccades in the male rhesus macaque monkey. We also compared our results to those obtained in human subjects, both from the existing literature and through our own additional measurements. Using a variety of behavioral tasks exercising visual and nonvisual guidance of small saccades, we found that small saccades consistently require more time than larger saccades to be triggered in the nonhuman primate, even in the absence of any visual guidance and when valid advance information about the saccade landing position is available. We also found a strong asymmetry in the reaction times of small upper versus lower visual field visually guided saccades, a phenomenon that has not been described before for small saccades, even in humans. Following the suggestion that an eye movement is not initiated as long as the visuo-oculomotor system is within a state of balance, in which opposing commands counterbalance each other, we propose that the longer reaction times are a signature of enhanced times needed to create the symmetry-breaking condition that puts downstream premotor neurons into a push-pull regime necessary for rotating the eyeballs. Our results provide an important catalog of nonhuman primate oculomotor capabilities on the miniature scale, allowing concrete predictions on underlying neurophysiological mechanisms. NEW & NOTEWORTHY Leveraging a multitude of neurophysiological investigations in the rhesus macaque monkey, we generated and tested hypotheses about small-saccade latencies in this animal model. We found that small saccades always take longer, on average, than larger saccades to trigger, regardless of visual and cognitive context. Moreover, small downward saccades have the longest latencies overall. Our results provide an important documentation of oculomotor capabilities of an indispensable animal model for neuroscientific research in vision, cognition, and action.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::ad317e0b7e2cce875b2dcfbe2224558e
https://doi.org/10.1152/jn.00588.2019 -
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المؤلفون: Gongchen Yu, James P Herman, Leor N Katz, Richard J Krauzlis
مصطلحات موضوعية: Cued speech, Superior Colliculi, General Immunology and Microbiology, General Neuroscience, Superior colliculus, General Medicine, Fixation, Ocular, Stimulus (physiology), Macaca mulatta, General Biochemistry, Genetics and Molecular Biology, Modulation (music), Saccades, Visual Perception, Animals, Cues, Microsaccade, Psychology, Neuroscience, Biomarkers, Photic Stimulation
الوصف: Recent evidence suggests that microsaccades are causally linked to the attention-related modulation of neurons – specifically, that microsaccades towards the attended location are required for the subsequent changes in firing rate. These findings have raised questions about whether attention-related modulation is due to different states of attention as traditionally assumed or might instead be a secondary effect of microsaccades. Here, in two rhesus macaques, we tested the relationship between microsaccades and attention-related modulation in the superior colliculus, a brain structure crucial for allocating attention. We found that attention-related modulation emerged even in the absence of microsaccades, was already present prior to microsaccades towards the cued stimulus, and persisted through the suppression of activity that accompanied all microsaccades. Nonetheless, consistent with previous findings, we also found significant attention-related modulation when microsaccades were directed towards, rather than away from, the cued location. Thus, in contrast to the prevailing hypothesis, microsaccades are not necessary for attention-related modulation, at least not in the superior colliculus. They do, however, provide an additional marker for the state of attention, especially at times when attention is shifting from one location to another.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::abd99479c3db3fde67b41143c0ac29c6
https://doi.org/10.1101/2021.09.11.459890 -
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المؤلفون: Xiaoguang Tian, Matthias Baumann, Chih-Yang Chen, Ziad M. Hafed, Tong Zhang
المصدر: Journal of neurophysiology. 125(4)
مصطلحات موضوعية: Primates, Fovea Centralis, Superior Colliculi, genetic structures, biology, Behavior, Animal, Eye Movements, Physiology, General Neuroscience, Superior colliculus, Motor Activity, eye diseases, Visual processing, Fixational eye movements, Foveal, biology.animal, Visual Perception, Animals, Primate, sense organs, Microsaccade, Active vision, Neuroscience, Psychomotor Performance
الوصف: The primate superior colliculus (SC) has recently been shown to possess both a large foveal representation as well as a varied visual processing repertoire. This structure is also known to contribute to eye movement generation. Here, we describe our current understanding of how SC visual and movement-related signals interact within the realm of small eye movements associated with the foveal scale of visuomotor behavior. Within the SC’s foveal representation, there is a full spectrum of visual, visual-motor, and motor-related discharge for fixational eye movements. Moreover, a substantial number of neurons only emit movement-related discharge when microsaccades are visually guided, but not when similar movements are generated toward a blank. This represents a particularly striking example of integrating vision and action at the foveal scale. Beyond that, SC visual responses themselves are strongly modulated, and in multiple ways, by the occurrence of small eye movements. Intriguingly, this impact can extend to eccentricities well beyond the fovea, causing both sensitivity enhancement and suppression in the periphery. Because of large foveal magnification of neural tissue, such long-range eccentricity effects are neurally warped into smaller differences in anatomical space, providing a structural means for linking peripheral and foveal visual modulations around fixational eye movements. Finally, even the retinal-image visual flows associated with tiny fixational eye movements are signaled fairly faithfully by peripheral SC neurons with relatively large receptive fields. These results demonstrate how studying active vision at the foveal scale represents an opportunity for understanding primate vision during natural behaviors involving ever-present foveating eye movements.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::9a3f28dff9f9aa041631affc69d0e2fa
https://pubmed.ncbi.nlm.nih.gov/33534661 -
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المؤلفون: Antimo Buonocore, Tatiana Malevich, Ziad M. Hafed
المصدر: Journal of neurophysiology. 125(1)
مصطلحات موضوعية: Male, biology, Physiology, Chemistry, General Neuroscience, Stimulus (physiology), biology.organism_classification, Macaca mulatta, Fixational eye movements, Rhesus macaque, Saccades, Visual Perception, Animals, Microsaccade, Neuroscience, Photic Stimulation
الوصف: Microsaccades have a steady rate of occurrence during maintained gaze fixation, which gets transiently modulated by abrupt sensory stimuli. Such modulation, characterized by a rapid reduction in microsaccade frequency followed by a stronger rebound phase of high microsaccade rate, is often described as the microsaccadic rate signature, owing to its stereotyped nature. Here, we investigated the impacts of stimulus polarity (luminance increments or luminance decrements relative to background luminance) and size on the microsaccadic rate signature. We presented brief, behaviorally irrelevant visual flashes consisting of large or small, white or black stimuli over an otherwise gray image background. Both large and small stimuli caused robust early microsaccadic inhibition, but postinhibition microsaccade rate rebound was significantly delayed and weakened for large stimuli when compared with small ones. Critically, small black stimuli were associated with stronger modulations in the microsaccade rate signature than small white stimuli, particularly in the postinhibition rebound phase, and black stimuli also amplified the incidence of early stimulus-directed microsaccades. Our results demonstrate that the microsaccadic rate signature is sensitive to stimulus size and polarity, and they point to dissociable neural mechanisms underlying early microsaccadic inhibition after stimulus onset and later microsaccadic rate rebound at longer times thereafter. These results also demonstrate early access of oculomotor control circuitry to diverse sensory representations, particularly for momentarily inhibiting saccade generation with short latencies.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b67a1ffe76ea167110f5b24c67ba0409
https://pubmed.ncbi.nlm.nih.gov/33427577 -
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المؤلفون: Alessandro Piras, Andrea Meoni, Milena Raffi
المساهمون: Raffi M., Meoni A., Piras A.
المصدر: Neuroscience letters. 743
مصطلحات موضوعية: 0301 basic medicine, Male, medicine.medical_specialty, Eye movement, Visual perception, genetic structures, Visual space, Eye position, Stimulus (physiology), Attentional bias, Audiology, Macaque, Discrimination Learning, 03 medical and health sciences, 0302 clinical medicine, biology.animal, medicine, Reaction Time, Saccades, Training, Animals, biology, General Neuroscience, Optic flow, Spatial attention, Monkey, Macaca fascicularis, 030104 developmental biology, Visual discrimination, Visual Perception, Microsaccade, Visual system, Psychology, 030217 neurology & neurosurgery, Photic Stimulation, Psychomotor Performance
الوصف: The spatial location indicated by a visual cue can bias microsaccades directions towards or away from the cue. Aim of this work was to evaluate the microsaccades characteristics during the monkey’s training, investigating the relationship between a shift of attention and practice. The monkey was trained to press a lever at a target onset, then an expanding optic flow stimulus appeared to the right of the target. After a variable time delay, a visual cue appeared within the optic flow stimulus and the monkey had to release the lever in a maximum reaction time (RT) of 700 ms. In the control task no visual cue appeared and the monkey had to attend a change in the target color. Data were recorded in 9 months. Results revealed that the RTs at the control task changed significantly across time. The microsaccades directions were significantly clustered toward the visual cue, suggesting that the animal developed an attentional bias toward the visual space where the cue appeared. The microsaccades amplitude differed significantly across time. The microsaccades peak velocity differed significantly both across time and within the time delays, indicating that the monkey made faster microsaccades when it expected the cue to appear. The microsaccades number was significantly higher in the control task with respect to discrimination. The lack of change in microsaccades rate, duration, number and direction across time indicates that the experience acquired during practicing the task did not influence microsaccades generation.
وصف الملف: ELETTRONICO
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المؤلفون: Antimo Buonocore, Ziad M. Hafed, Tatiana Malevich
المصدر: eLife
eLife, Vol 9 (2020)مصطلحات موضوعية: 0301 basic medicine, GAZE FIXATION, Visual perception, genetic structures, Computer science, Macaque, Pupil, 0302 clinical medicine, Foveal, Rhesus macaque, Modulation (music), Biology (General), Physics, biology, General Neuroscience, General Medicine, Eye position, Head Movements, Visual Perception, Medicine, Head movements, Microsaccade, QH301-705.5, Science, Short Report, Fixation, Ocular, Stimulus (physiology), General Biochemistry, Genetics and Molecular Biology, 03 medical and health sciences, biology.animal, Reaction Time, Animals, Vision, Ocular, General Immunology and Microbiology, Eye movement, fixational eye movements, Neurophysiology, Gaze, Macaca mulatta, eye diseases, microsaccades, 030104 developmental biology, Eye tracking, sense organs, Neuroscience, slow ocular position drifts, 030217 neurology & neurosurgery
الوصف: The eyes are never still during maintained gaze fixation. When microsaccades are not occurring, ocular position exhibits continuous slow changes, often referred to as drifts. Unlike microsaccades, drifts remain to be viewed as largely random eye movements. Here we found that ocular position drifts can, instead, be very systematically stimulus-driven, and with very short latencies. We used highly precise eye tracking in three well trained macaque monkeys and found that even fleeting (~8 ms duration) stimulus presentations can robustly trigger transient and stimulus-specific modulations of ocular position drifts, and with only approximately 60 ms latency. Such drift responses are binocular, and they are most effectively elicited with large stimuli of low spatial frequency. Intriguingly, the drift responses exhibit some image pattern selectivity, and they are not explained by convergence responses, pupil constrictions, head movements, or starting eye positions. Ocular position drifts have very rapid access to exogenous visual information.
eLife digest Vision is a highly complex, active process. As we observe and interact with the world around us, we constantly use eye movements to capture the visual information we need. In fact, our eyes continue to make tiny, unconscious movements even when we try to fix our gaze on something. There are two main types of tiny eye movements. The first kind, so called microsaccades, are fast, microscopic flicks that happen every second or half-second. The other kind, termed drift, is a slower, gradual motion that takes place between microsaccades, or at any time when other eye movements are not happening. However, we know far less about drifts than about any other eye movements: both the reason why they occur and the brain mechanisms controlling them are still unclear. Many scientists think that drifts are largely random movements, without any set direction. However, eye drifts do sometimes align with other behaviours – for example, they can help compensate for small, subtle head movements – suggesting that drifts may not be completely random after all. Malevich, Buonocore and Hafed therefore set out to test the hypothesis that eye drifts could, under the right circumstances, in fact be highly directed movements. These experiments used precise sensors to track eye movements in macaque monkeys, which had been trained to fix their gaze on images or shapes (stimuli) presented on a screen. This revealed that presenting new stimuli, even for a few thousandths of a second, could repeatedly trigger drifts. This reaction also happened quickly, starting less than one hundredth of a second after presentation of the stimulus. Further tests, using different images, revealed that the drifts were not only simply reacting to any new stimuli but also appeared to be a partially selective response to specific types of images. These tended to have larger features and less fine detail. For example, a picture of a landscape with large swaths of sky or hilltops would much more reliably trigger the eye drifts than a finely detailed checkerboard pattern, with many small squares alternating between black and white. These results suggested that drifts, far from being random movements, could be another tool for the brain to process visual information. This work sheds new light on the potential role of eye movements in vision, and adds another layer of complexity to the question of how we see. Malevich et al. hope that this study will inspire further research into the brain mechanisms behind ocular drifts. -
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المؤلفون: Francesca Bonetti, Massimo Turatto, Matteo Valsecchi
المساهمون: Bonetti F., Valsecchi M., Turatto M.
مصطلحات موضوعية: Superior Colliculi, Eye Movements, Cognitive Neuroscience, Distractor, Experimental and Cognitive Psychology, Stimulus (physiology), 050105 experimental psychology, Oculomotor capture, 03 medical and health sciences, 0302 clinical medicine, Saccadic programming, Saccades, Animals, 0501 psychology and cognitive sciences, Habituation, Habituation, Psychophysiologic, Superior colliculus, 05 social sciences, Eye movement, Saccadic masking, Inhibition, Psychological, Neuropsychology and Physiological Psychology, Saccade, Fixation (visual), Microsaccade, Psychology, Neuroscience, Photic Stimulation, 030217 neurology & neurosurgery
الوصف: The oculomotor capture triggered by a peripheral onset is subject to habituation, a basic form of learning consisting in a response decrement toward a repeatedly presented stimulus. However, it is unclear whether habituation of reflexive saccades takes place at the saccadic programming or execution stage (or both). To address this issue, we exploited the fact that during fixation the programming of a reflexive saccade exerts a robust but short-lasting phasic inhibition in the absolute microsaccadic frequency. Hence, if habituation of reflexive saccades occurs at the programming stage, then this should also affect the microsaccadic frequency, with a progressive reduction of the inhibitory phase. Conversely, if habituation occurs only at the later stage of saccade execution, the no change in the microsaccadic pattern is expected. Participants were repeatedly exposed to a peripheral onset distractor, and when eye movements were allowed, we replicated the oculomotor capture habituation. Crucially, however, when fixation was maintained the microsaccadic response did not change as exposure to the onset progressed, suggesting that habituation of reflexive saccades does not take place at the programming stage in the superior colliculus (SC), but at the later stage of saccade execution in the brainstem, where the competition between different saccades might be resolved. This scenario challenges one of the main assumptions of the competitive integration model for oculomotor control, which assumes that competition between exogenous and endogenous saccade programs occurs in the (SC). Our results and interpretation are instead in agreement with neurophysiological studies in non-human primates showing that saccadic adaption, another form of oculomotor plasticity, takes place downstream from the SC.
وصف الملف: ELETTRONICO
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::b7be9f37369492bd5d76ba9ada532c66
http://hdl.handle.net/11585/781278 -
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المؤلفون: Joachim Bellet, Chih-Yang Chen, Ziad M. Hafed
المصدر: Journal of Neurophysiology. 118:2789-2805
مصطلحات موضوعية: Adult, Male, 0301 basic medicine, Superior Colliculi, Signal Detection, Psychological, Time Factors, Physiology, Fixation, Ocular, Gating, Functional Laterality, Visual processing, Young Adult, 03 medical and health sciences, 0302 clinical medicine, Rhythm, Reaction Time, Saccades, Animals, Humans, Eye Movement Measurements, Neurons, Communication, business.industry, General Neuroscience, Macaca mulatta, Fixational eye movements, Alpha Rhythm, 030104 developmental biology, Visual Perception, Female, Microsaccade, Beta Rhythm, business, Psychology, Neuroscience, Photic Stimulation, 030217 neurology & neurosurgery, Research Article
الوصف: Microsaccades are tiny saccades that occur during gaze fixation. Even though visual processing has been shown to be strongly modulated close to the time of microsaccades, both at central and peripheral eccentricities, it is not clear how these eye movements might influence longer term fluctuations in brain activity and behavior. Here we found that visual processing is significantly affected and, in a rhythmic manner, even several hundreds of milliseconds after a microsaccade. Human visual detection efficiency, as measured by reaction time, exhibited coherent rhythmic oscillations in the α- and β-frequency bands for up to ~650–700 ms after a microsaccade. Surprisingly, the oscillations were sequentially pulsed across visual hemifields relative to microsaccade direction, first occurring in the same hemifield as the movement vector for ~400 ms and then the opposite. Such pulsing also affected perceptual detection performance. Our results suggest that visual processing is subject to long-lasting oscillations that are phase locked to microsaccade generation, and that these oscillations are dependent on microsaccade direction. NEW & NOTEWORTHY We investigated long-term microsaccadic influences on visual processing and found rhythmic oscillations in behavioral performance at α- and β-frequencies (~8–20 Hz). These oscillations were pulsed at a much lower frequency across visual hemifields, first occurring in the same hemifield as the microsaccade direction vector for ~400 ms before switching to the opposite hemifield for a similar interval. Our results suggest that saccades temporally organize visual processing and that such organization can sequentially switch hemifields.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::c83f25076150ebc1d4a669168b37315a
https://doi.org/10.1152/jn.00253.2017
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