Preparation Of Saccadic Eye Movements Research Articles

Voluntary Saccadic Eye Movements Ride the Attentional Rhythm.

Visual perception seems continuous, but recent evidence suggests that the underlying perceptual mechanisms are in fact periodic-particularly visual attention. Because visual attention is closely linked to the preparation of saccadic eye movements, the question arises how periodic attentional processes interact with the preparation and execution of voluntary saccades. In two experiments, human observers made voluntary saccades between two placeholders, monitoring each one for the presentation of a threshold-level target. Detection performance was evaluated as a function of latency with respect to saccade landing. The time course of detection performance revealed oscillations at around 4 Hz both before the saccade at the saccade origin and after the saccade at the saccade destination. Furthermore, oscillations before and after the saccade were in phase, meaning that the saccade did not disrupt or reset the ongoing attentional rhythm. Instead, it seems that voluntary saccades are executed as part of an ongoing attentional rhythm, with the eyes in flight during the troughs of the attentional wave. This finding for the first time demonstrates that periodic attentional mechanisms affect not only perception but also overt motor behavior.

Visual sensitivity of frontal eye field neurons during the preparation of saccadic eye movements

Primate vision is continuously disrupted by saccadic eye movements, and yet this disruption goes unperceived. One mechanism thought to reduce perception of this self-generated movement is saccadic suppression, a global loss of visual sensitivity just before, during, and after saccadic eye movements. The frontal eye field (FEF) is a candidate source of neural correlates of saccadic suppression previously observed in visual cortex, because it contributes to the generation of visually guided saccades and modulates visual cortical responses. However, whether the FEF exhibits a perisaccadic reduction in visual sensitivity that could be transmitted to visual cortex is unknown. To determine whether the FEF exhibits a signature of saccadic suppression, we recorded the visual responses of FEF neurons to brief, full-field visual probe stimuli presented during fixation and before onset of saccades directed away from the receptive field in rhesus macaques (Macaca mulatta) We measured visual sensitivity during both epochs and found that it declines before saccade onset. Visual sensitivity was significantly reduced in visual but not visuomotor neurons. This reduced sensitivity was also present in visual neurons with no movement-related modulation during visually guided saccades and thus occurred independently from movement-related activity. Across the population of visual neurons, sensitivity began declining ∼80 ms before saccade onset. We also observed a similar presaccadic reduction in sensitivity to isoluminant, chromatic stimuli. Our results demonstrate that the signaling of visual information by FEF neurons is reduced during saccade preparation, and thus these neurons exhibit a signature of saccadic suppression.

Eye Movement Preparation Modulates Neuronal Responses in Area V4 When Dissociated from Attentional Demands

We examined whether the preparation of saccadic eye movements, when behaviorally dissociated from covert attention, modulates activity within visual cortex. We measured single-neuron and local field potential (LFP) responses to visual stimuli in area V4 while monkeys covertly attended a stimulus at one location and prepared saccades to a potential target at another. In spite of the irrelevance of visual information at the saccade target, visual activity at that location was modulated at least as much as, and often more than, activity at the covertly attended location. Modulations of activity at the attended and saccade target locations were qualitatively similar and included increased response magnitude, stimulus selectivity, and spiking reliability, as well as increased gamma and decreased low-frequency power of LFPs. These results demonstrate that saccade preparation is sufficient to modulate visual cortical representations and suggest that the interrelationship of oculomotor and attention-related mechanisms extends to posterior visual cortex.

Visual Sensitivity of Frontal Eye Field Neurons During the Preparation of Saccadic Eye Movements

Primates make frequent saccades to inspect their surroundings and yet must maintain perceptual stability across saccades. The oculomotor system has long been posited to play a role in perceptual st...

Saccades gradually increase the perceived contrast of their targets

The preparation of saccadic eye movements results in pronounced shift of spatial attention to their targets, alerting corresponding locations in early visual cortices and locally improving visual performance as time progresses towards the movement. Here, we show that these attention shifts also lead to a remarkable change in the visual appearance of stimuli presented at the location of the movement goal. Participants fixated a central spot while two standard stimuli (Gabor patches) were flashed in the visual periphery, left and right of fixation. Shortly afterwards, a central movement cue instructed participants to quickly generate a saccade to one of the two stimulus locations. During the latency of the saccade, that is, after the movement cue but before the saccade was actually executed, a test stimulus was flashed at the movement goal. The test stimulus differed from the standard in contrast and, after the execution of the saccade, participants judged this difference in a two alternative forced-choice task, allowing for the assessment of changes in perceived contrast across the time course of saccade preparation. The data show that as time approached the saccade, the test contrast necessary to equate the standard (point of subjective equality) decreased substantially. These results suggest that saccade preparation, like covert attention, alters early visual processing in a way that is similar to increasing the signal strength, revealing perceptual correlates of feedback signals from eye-movement control areas to visual cortex.

Analysis of slow- and fast-alpha band asymmetry during performance of a saccadic eye movement task: Dissociation between memory- and attention-driven systems

This study aimed at analyzing the relationship between slow- and fast-alpha asymmetry within frontal cortex and the planning, execution and voluntary control of saccadic eye movements (SEM), and quantitative electroencephalography (qEEG) was recorded using a 20-channel EEG system in 12 healthy participants performing a fixed (i.e., memory-driven) and a random SEM (i.e., stimulus-driven) condition. We find main effects for SEM condition in slow- and fast-alpha asymmetry at electrodes F3–F4, which are located over premotor cortex, specifically a negative asymmetry between conditions. When analyzing electrodes F7–F8, which are located over prefrontal cortex, we found a main effect for condition in slow-alpha asymmetry, particularly a positive asymmetry between conditions. In conclusion, the present approach supports the association of slow- and fast-alpha bands with the planning and preparation of SEM, and the specific role of these sub-bands for both, the attention network and the coordination and integration of sensory information with a (oculo)-motor response.

Changes in the response rate and response variability of area V4 neurons during saccade preparatio

Event Abstract Back to Event Changes in the response rate and response variability of area V4 neurons during saccade preparatio Nicholas Steinmetz1* and Tirin Moore1 1 Stanford University, United States The visually driven responses of macaque area V4 neurons are modulated during the preparation of saccadic eye movements, but the relationship between presaccadic modulation in area V4 and saccade preparation is poorly understood. Recent neurophysiological studies suggest that the variability across trials of spiking responses provides a more reliable signature of motor preparation than mean firing rate across trials. We compared the dynamics of the response rate and the variability in the rate across trials for area V4 neurons during the preparation of visually guided saccades. As in previous reports, we found that the mean firing rate of V4 neurons was enhanced when saccades were prepared to stimuli within a neuron’s receptive field (RF) in comparison with saccades to a non-RF location. Further, we found robust decreases in response variability prior to saccades and found that these decreases predicted saccadic reaction times for saccades both to RF and non-RF stimuli. Importantly, response variability predicted reaction time whether or not there were any accompanying changes in mean firing rate. In addition to predicting saccade direction, the mean firing rate could also predict reaction time, but only for saccades directed to the RF stimuli. These results demonstrate that response variability of area V4 neurons, like mean response rate, provides a signature of saccade preparation. However, the two signatures reflect complementary aspects of that preparation. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session I Citation: Steinmetz N and Moore T (2010). Changes in the response rate and response variability of area V4 neurons during saccade preparatio. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00090 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 Feb 2010; Published Online: 20 Feb 2010. * Correspondence: Nicholas Steinmetz, Stanford University, Stanford, United States, nick.steinmetz@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Nicholas Steinmetz Tirin Moore Google Nicholas Steinmetz Tirin Moore Google Scholar Nicholas Steinmetz Tirin Moore PubMed Nicholas Steinmetz Tirin Moore Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Changes in the Response Rate and Response Variability of Area V4 Neurons During the Preparation of Saccadic Eye Movements

The visually driven responses of macaque area V4 neurons are modulated during the preparation of saccadic eye movements, but the relationship between presaccadic modulation in area V4 and saccade preparation is poorly understood. Recent neurophysiological studies suggest that the variability across trials of spiking responses provides a more reliable signature of motor preparation than mean firing rate across trials. We compared the dynamics of the response rate and the variability in the rate across trials for area V4 neurons during the preparation of visually guided saccades. As in previous reports, we found that the mean firing rate of V4 neurons was enhanced when saccades were prepared to stimuli within a neuron's receptive field (RF) in comparison with saccades to a non-RF location. Further, we found robust decreases in response variability prior to saccades and found that these decreases predicted saccadic reaction times for saccades both to RF and non-RF stimuli. Importantly, response variability predicted reaction time whether or not there were any accompanying changes in mean firing rate. In addition to predicting saccade direction, the mean firing rate could also predict reaction time, but only for saccades directed to the RF stimuli. These results demonstrate that response variability of area V4 neurons, like mean response rate, provides a signature of saccade preparation. However, the two signatures reflect complementary aspects of that preparation.

Dynamic sensitivity of area V4 neurons during saccade preparation

During the preparation of saccadic eye movements, visual attention is confined to the target of intended fixation and there is a corresponding diminution of visual sensitivity at nontarget locations. Neurons within the macaque visual cortex exhibit correlates of these perceptual changes, such as in area V4, where neuronal responses are enhanced during the preparation of saccades to stimuli within the receptive field (RF), and responses are suppressed during the preparation of saccades to other locations. Both the perceptual and neurophysiological effects suggest that the sensitivity of visual cortical neurons to input is dynamic during saccade preparation. We probed the contrast sensitivity of area V4 neurons to nontarget stimuli at varying times during the preparation of saccades to locations outside of the neuron's receptive field. We found that the contrast sensitivity of many neurons is profoundly altered within 50 ms of saccade onset. The luminance or color contrast sensitivity of individual V4 neurons could increase, decrease, or remain unchanged before saccade onset. For luminance contrast sensitivity, decreases in sensitivity were more frequent and larger in magnitude, resulting in an overall decrement in sensitivity across the population. For color contrast, the effects were smaller and more heterogeneous, resulting in little or no overall change in sensitivity across the population. Our results demonstrate the dynamic influence that saccade preparation has on the sensitivity of visual cortical neurons and suggest a basis for the changes in perception known to occur during saccade preparation.

The time course of presaccadic attention shifts

The dynamics of the allocation of attention during the preparation of saccadic eye movements was studied in a dual task paradigm. As the primary task, participants had to perform a saccade to letter-like items arranged on a clock face. The secondary task was a 2AFC discrimination task in which a discrimination target (DT) ('E' or '3') was presented among distractors, either at the saccade goal, or at a spatially separate, precued location. In the first experiment, the position of the DT was kept constant within an experimental block, while the saccade target location varied. In the second experiment, the location of the DT was varied while the saccade target remained the same within a block. The data demonstrate that attentional dynamics differs between the experiments--attention can shift to the saccade goal early or late during the saccade preparation period, depending on the task. Immediately before saccade onset, however, discrimination performance at the location of the saccade target is always superior to other locations, arguing for a strict and selective coupling between saccade preparation and attention.

Links between eye movement preparation and the attentional processing of tactile events: An event-related brain potential study

Objective We investigated whether the covert preparation of saccadic eye movements results in spatially specific modulations of somatosensory processing. Methods ERPs were recorded in a spatial cueing experiment where auditory cues preceded tactile stimuli delivered to the left or right hand. In the Saccade task, cues signalled that an eye movement towards the left or right hand had to be prepared. In the Covert Attention task, cues signalled the direction of a covert shift of tactile attention. Results A lateralized component previously observed during cued shifts of spatial attention (ADAN) was elicited in the cue–target interval in both tasks. The somatosensory N140 component was enhanced for tactile stimuli presented to the hand on the cued side. This modulation was present not just in the Covert Attention task, but also in the Saccade task. Longer-latency effects of spatial cueing were only present in the Covert Attention task. Conclusions Covert shifts of attention and saccade preparation have similar effects on early stages of tactile processing, suggesting that both are mediated by overlapping control processes. Significance These findings support the premotor theory of attention by demonstrating that the programming of eye movements has spatially selective effects on somatosensory processing.

Saccade landing point selection and the competition account of pro‐ and antisaccade generation: The involvement of visual attention – A review

This paper presents a review and summary of experimental findings on the role of attention in the preparation of saccadic eye movements. The focus is on experiments where performance of prosaccades (saccades towards a suddenly appearing item) and antisaccades (saccades of equal amplitude in the direction opposite to where the target moved) is compared. Evidence suggests that these two opposite responses to the same stimulus event entail competition between neural pathways that generate reflexive movements to the target and neural mechanisms involved in inhibiting the reflex and generating a voluntary gaze shift in the opposite direction to the target appearance. Evidence for such a competition account is discussed in light of a large amount of experimental findings and the overall picture clearly indicates that this competition account has great explanatory power when data on saccadic reaction times and error rates are compared for the two types of saccade. The role of attention is also discussed in particular in light of the finding that the withdrawal of attention by a secondary task 200 to 500 ms before the saccade target appears, leads to speeded antisaccades (without a similar increase in error rates), showing that the results do not simply reflect a speed-accuracy trade-off. This result indicates that the tendency for "reflexive" prosaccades is diminished when attention is engaged in a different task. Furthermore, experiments are discussed that show that as the tendency for a reflexive prosaccade is weakened, antisaccades are speeded up, further supporting the competition account of pro- and antisaccade generation. In the light of evidence from neurophysiology of monkeys and humans, a tentative model of pro- and antisaccade generation is proposed.

Is Direction Position? Position- and Direction-Based Correspondence Effects in Tasks with Moving Stimuli

Five experiments were carried out to test whether (task-irrelevant) motion information provided by a stimulus changing its position over time would affect manual left-right responses. So far, some studies reported direction-based Simon effects whereas others did not. In Experiment 1a, a reliable direction-based effect occurred, which was not modulated by the response mode--that is, by whether participants responded by pressing one of two keys or more dynamically by moving a stylus in a certain direction. Experiments 1a, 1b, and 2 lend support to the idea that observers use the starting position of target motion as a reference for spatial coding. That is, observers might process object motion as a shift of position relative to the starting position and not as directional information. The dominance of relative position coding could also be shown in Experiment 3, in which relative position was pitted against motion direction by presenting a static and dynamic stimulus at the same time. Additionally, we explored the role of eye movements in stimulus-response compatibility and showed in Experiments 1b and 3a that the execution or preparation of saccadic eye movements--as proposed by an attention-shifting account--is not necessary for a Simon effect to occur.

The Role of the Human Dorsolateral Prefrontal Cortex in Ocular Motor Behavior

The dorsolateral prefrontal cortex (DLPFC) is involved in the preparation of saccadic eye movements. Lesion studies and functional magnetic resonance imaging (fMRI) studies suggest that the human DLPFC is located in area 46 of Brodmann. The DLPFC has direct connections with the main cortical ocular motor areas, that is with the frontal eye field (FEF) and the supplementary eye field (SEF) in the frontal lobe; with several (associative, attentional, and motor) areas in the posterior parietal cortex (PPC), including the parietal eye field (PEF); with the cingulate eye field in the anterior cingulate cortex; and directly downstream with the superior colliculus in the brainstem. Lesion and fMRI studies using the antisaccade paradigm have shown that the DLPFC is involved in the inhibition of unwanted reflexive saccades (triggered toward the target by the PEF), whereas the triggering of correct intentional antisaccades (made in the direction opposite to the target) may depend mainly upon the FEF. The DLPFC also controls short-term spatial working memory involved in memory-guided saccades, as shown by lesion and transcranial magnetic stimulation (TMS) studies. By contrast, medium-term spatial memory (after 25 s) may be controlled by the medial temporal cortex (MTC). Recently, TMS studies have suggested that the transmission of memorized information from the integrative parietal areas (PPC) to the MTC is performed via both an indirect pathway comprising the DLPFC (i.e., transmission in series) and a direct pathway bypassing the DLPFC (i.e., transmission in parallel). Furthermore, the DLPFC is involved in the preparation of predictive saccades (i.e., saccades made before the appearance of an expected target) and saccade sequences, and, therefore, also controls some aspects of temporal working memory. Lastly, the involvement of the DLPFC has recently been reported in tasks comprising a target selection or a directional decision to make for the forthcoming saccade. These different functions suggest that the DLPFC plays a major role in the decisional processes governing ocular motor behavior.