Saccadic Gaze Research Articles

Exploring the impact of windows on musicians’ experience: a neuroarchitecture perspective

ABSTRACT Performing music can be an enjoyable activity or a source of anxiety and discomfort. Previous studies suggest that it is possible to create spaces that promote well-being by applying knowledge from neuroscience to architectural design. However, this application remains unexplored in the context of music practice spaces. In this study, a virtual replica of a real conservatoire classroom was used to investigate the effect of window size and views through windows on the perception of the built environment. A sample of 61 musicians was recruited, and through questionnaires and eye tracking, participants’ responses to environmental changes while playing their instruments were studied. The results of the experiment indicated a clear preference for larger windows, which significantly contributed to a more positive environment, perceived as more open, light, inviting, calming and spacious. In addition, eye tracking data suggested a reduction in anxiety levels, as evidenced by reduced gaze velocity and saccade ratios. These results demonstrate that windows and related variables such as daylight and views can have a significant impact on the experience of musicians during solo performance. This highlights the need to re-evaluate design considerations in music practice spaces, emphasising the crucial role of environmental elements in enhancing musicians’ well-being.

A Bio-Inspired Visual Perception Transformer for Cross-Domain Semantic Segmentation of High-Resolution Remote Sensing Images

Pixel-level classification of very-high-resolution images is a crucial yet challenging task in remote sensing. While transformers have demonstrated effectiveness in capturing dependencies, their tendency to partition images into patches may restrict their applicability to highly detailed remote sensing images. To extract latent contextual semantic information from high-resolution remote sensing images, we proposed a gaze–saccade transformer (GSV-Trans) with visual perceptual attention. GSV-Trans incorporates a visual perceptual attention (VPA) mechanism that dynamically allocates computational resources based on the semantic complexity of the image. The VPA mechanism includes both gaze attention and eye movement attention, enabling the model to focus on the most critical parts of the image and acquire competitive semantic information. Additionally, to capture contextual semantic information across different levels in the image, we designed an inter-layer short-term visual memory module with bidirectional affinity propagation to guide attention allocation. Furthermore, we introduced a dual-branch pseudo-label module (DBPL) that imposes pixel-level and category-level semantic constraints on both gaze and saccade branches. DBPL encourages the model to extract domain-invariant features and align semantic information across different domains in the feature space. Extensive experiments on multiple pixel-level classification benchmarks confirm the effectiveness and superiority of our method over the state of the art.

Bidirectional brain-body interactions during natural story listening

Narratives can synchronize neural and physiological signals between individuals, but the relationship between these signals, and the underlying mechanism, is unclear. We hypothesized a top-down effect of cognition on arousal and predicted that auditory narratives will drive not only brain signals but also peripheral physiological signals. We find that auditory narratives entrained gaze variation, saccade initiation, pupil size, and heart rate. This is consistent with a top-down effect of cognition on autonomic function. We also hypothesized a bottom-up effect, whereby autonomic physiology affects arousal. Controlled breathing affected pupil size, and heart rate was entrained by controlled saccades. Additionally, fluctuations in heart rate preceded fluctuations of pupil size and brain signals. Gaze variation, pupil size, and heart rate were all associated with anterior-central brain signals. Together, these results suggest bidirectional causal effects between peripheral autonomic function and central brain circuits involved in the control of arousal.

Large eye–head gaze shifts measured with a wearable eye tracker and an industrial camera

We built a novel setup to record large gaze shifts (up to 140∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^\\circ $$\\end{document}). The setup consists of a wearable eye tracker and a high-speed camera with fiducial marker technology to track the head. We tested our setup by replicating findings from the classic eye–head gaze shift literature. We conclude that our new inexpensive setup is good enough to investigate the dynamics of large eye–head gaze shifts. This novel setup could be used for future research on large eye–head gaze shifts, but also for research on gaze during e.g., human interaction. We further discuss reference frames and terminology in head-free eye tracking. Despite a transition from head-fixed eye tracking to head-free gaze tracking, researchers still use head-fixed eye movement terminology when discussing world-fixed gaze phenomena. We propose to use more specific terminology for world-fixed phenomena, including gaze fixation, gaze pursuit, and gaze saccade.

Examining Eye Tracking Metrics and Cognitive Function in Post-Stroke Individuals: A Comparison of Visual Searching Tasks between Those with and without Cognitive Impairment

Introduction: After a stroke, individuals commonly experience visual problems and impaired cognitive function, which can significantly impact their daily lives. In addition to visual neglect and hemianopia, stroke survivors often have difficulties with visual search tasks. Researchers are increasingly interested in using eye tracking technology to study cognitive processing and determine whether eye tracking metrics can be used to screen and assess cognitive impairment in patients with neurological disorders. As such, assessing these areas and understanding their relationship is crucial for effective stroke rehabilitation. Methods: We enrolled 60 stroke patients in this study and evaluated their eye tracking performance and cognitive function through a series of tests. Subsequently, we divided the subjects into two groups based on their scores on the HK-MoCA test, with scores below 21 out of 30 indicating cognitive impairment. We then compared the eye tracking metrics between the two groups and identified any significant differences that existed. Spearman correlation analysis was conducted to explore the relationship between clinical test scores and eye tracking metrics. Moreover, we employed a Mann-Whitney U test to compare eye tracking metrics between groups with and without cognitive impairment. Results: Our results revealed significant correlations between various eye tracking metrics and cognitive tests (p ≤ 0.001–0.041). Furthermore, the group without cognitive impairment demonstrated higher saccade velocity, gaze path velocity, and shorter time to target than the group with cognitive impairment (p ≤ 0.001–0.040). Receiver operating characteristic curve analyses were performed, and the optimal cut-off values for gaze path velocity and saccade velocity were 329.665 (px/s) (sensitivity = 0.80, specificity = 0.533) and 2.150 (px/ms) (sensitivity = 0.733, specificity = 0.633), respectively. Conclusions: Our findings indicate a significant correlation between eye tracking metrics and cognitive test scores. Furthermore, the group with cognitive impairment exhibited a significant difference in these metrics, and a cut-off value was identified to predict whether a client was experiencing cognitive impairment.

Diabetic older women without peripheral neuropathy amplify body sway but are capable of improving postural stability during a saccadic gaze task

BackgroundDiabetic older people tend to present deteriorated performance in balance and locomotion activities, even those without peripheral neuropathy. There is evidence that saccadic eye movements are used to reduce body sway in young and older healthy adults, but it has not been shown that diabetic older people preserve this visuomotor adaptation capacity. Research questionAre diabetic older women without peripheral neuropathy capable of improving postural stability during a saccadic gaze task? MethodsSeventeen type 2 diabetic older women (68.2 ± 10.7 years old) and seventeen healthy women, age-matched controls (66.0 ± 8.4 years old) voluntarily participated in the study. All participants were instructed to stand upright, barefoot, as stable as possible, for 30 s. Participants maintained their feet parallel to each other, at standard and narrow bases of support, while either fixating on a stationary target (fixation condition) or performing horizontal saccadic eye movements to follow a target (eccentricity of 11° of visual angle), which continuously disappeared and reappeared immediately on the opposite side (saccade 0.5 Hz and saccade 1.1 Hz conditions). ResultsResults indicated that the diabetic group clearly had deteriorated postural control, as shown by increased values of mean sway amplitude and mean sway velocity. However, diabetic and control groups were similarly capable of using saccadic eye movements to improve their postural stability, reducing their sway velocity compared to a gaze fixation condition. SignificanceDiabetes per se (without peripheral neuropathy) amplifies postural sway of older women as compared to their healthy age-matched controls. However, diabetic older women without peripheral neuropathy are capable of improving postural stability during a saccadic gaze task.

Changes in oculo‐motor activity during a cognitive challenge can distinguish clinical stages of early Alzheimer’s disease

AbstractBackgroundThe eye adapts to the demands of our behavior [1], its motor activity has proven to be a feasible method for measuring cognition in both health and disease [2]. This study assessed the sensitivity of oculo‐motor features in a benign cognitive challenge model with the purpose of identifying objective efficacy readouts for clinical drug trials in early Alzheimer’s disease (AD).MethodFifty participants, aged 60 to 80 years, performed a reading task in two sessions conducted the same day, morning and evening (i.e. the “cognitive challenge”), with an average inter‐session period of 9.28h, during which participants were not allowed to take naps or consume stimulating beverages. Participants were distributed across four cohorts corresponding to progressive stages of early AD [3]: 1) amyloid negative, cognitively healthy (control group), 2) amyloid positive pre‐symptomatic AD, 3) Mild Cognitive Impairment (MCI) due to AD (pre‐dementia group) and 4) mild AD (mild‐dementia group). ViewMind technology was used to track the oculo‐motor activity [4].ResultNone of the four cohorts reported increased levels of sleepiness during the challenge. However, cohorts showed significantly different oculo‐motor responses during the cognitive challenge (Table 1). The control group showed evidence of learning effects on the reading during the challenge reflected in no change in pupil size, longer saccades, less fixations and shorter gaze. Within the pre‐symptomatic group, however, a negative impact of the challenge was observed in a decrease in pupil size and increase in fixations. However, some learning effects were nevertheless seen in this cohort, in shorter gaze and longer saccades. In pre‐dementia group the learning effects were lost and participants demonstrated difficulty performing the task reflected in decreased pupil size and longer gaze. Finally, the mild‐AD participants showed an increase in fixations, longer gaze and no change in pupil size indicating a pattern of poor reading performance during the challenge.ConclusionOur preliminary results demonstrate that oculo‐motor activity may reflect changes in cognitive resources induced by a benign challenge in progressive clinical stages of early AD. These promising results support continued investigation into the potential of eye‐tracking during reading as a sensitive and objective measure .

Accuracy of clinical versus oculographic detection of pathological saccadic slowing

Saccadic slowing as a component of supranuclear saccadic gaze palsy is an important diagnostic sign in multiple neurologic conditions, including degenerative, inflammatory, genetic, or ischemic lesions affecting brainstem structures responsible for saccadic generation. Little attention has been given to the accuracy with which clinicians correctly identify saccadic slowing. We compared clinician (n = 19) judgements of horizontal and vertical saccade speed on video recordings of saccades (from 9 patients with slow saccades, 3 healthy controls) to objective saccade peak velocity measurements from infrared oculographic recordings. Clinician groups included neurology residents, general neurologists, and fellowship-trained neuro-ophthalmologists. Saccades with normal peak velocities on infrared recordings were correctly identified as normal in 57% (91/171; 171 = 9 videos × 19 clinicians) of clinician decisions; saccades determined to be slow on infrared recordings were correctly identified as slow in 84% (224/266; 266 = 14 videos × 19 clinicians) of clinician decisions. Vertical saccades were correctly identified as slow more often than horizontal saccades (94% versus 74% of decisions). No significant differences were identified between clinician training levels. Reliable differentiation between normal and slow saccades is clinically challenging; clinical performance is most accurate for detection of vertical saccade slowing. Quantitative analysis of saccade peak velocities enhances accurate detection and is likely to be especially useful for detection of mild saccadic slowing.

Reading in Children Who Survived Cerebellar Tumors: Evidence from Eye Movements.

Cerebellar tumors often affect the eye movement centers located in vermis, negatively affecting cognitive development and learning abilities in children. Previous research has established that patients who survived cerebellar tumors tend to demonstrate various saccadic impairments (e.g., hypermetria) and poor gaze stability as compared to healthy controls. The aim of the current study was to evaluate the influence of oculomotor deficits in such patients on reading parameters. A total of 112 children (8–17 y.o.), 65 of whom survived cerebellar tumors, participated in the study. The study design included several oculomotor and reading tasks. Eye movements were recorded every 1/60 s monocularly with an Arrington eye tracker. We observed profound reading impairments in the patients as compared to healthy children, including longer reading time, greater numbers of fixations and regressive saccades, and longer fixation durations. We also found significant correlations between changes in basic oculomotor functions and reading parameters. The patients also demonstrated gaze fixation instability, large number of fixations, and long scanpath reflecting the return of the gaze to the already counted objects. Thus, oculomotor changes caused by cerebellar tumor and its treatment led to disturbances in such neurocognitive activity as reading. Our findings emphasize the necessity of considering these deficits in cerebellar tumor survivors when designing rehabilitation protocols.

The role of eye movements in perceiving vehicle speed and time-to-arrival at the roadside

To avoid collisions, pedestrians depend on their ability to perceive and interpret the visual motion of other road users. Eye movements influence motion perception, yet pedestrians’ gaze behavior has been little investigated. In the present study, we ask whether observers sample visual information differently when making two types of judgements based on the same virtual road-crossing scenario and to which extent spontaneous gaze behavior affects those judgements. Participants performed in succession a speed and a time-to-arrival two-interval discrimination task on the same simple traffic scenario—a car approaching at a constant speed (varying from 10 to 90 km/h) on a single-lane road. On average, observers were able to discriminate vehicle speeds of around 18 km/h and times-to-arrival of 0.7 s. In both tasks, observers placed their gaze closely towards the center of the vehicle’s front plane while pursuing the vehicle. Other areas of the visual scene were sampled infrequently. No differences were found in the average gaze behavior between the two tasks and a pattern classifier (Support Vector Machine), trained on trial-level gaze patterns, failed to reliably classify the task from the spontaneous eye movements it elicited. Saccadic gaze behavior could predict time-to-arrival discrimination performance, demonstrating the relevance of gaze behavior for perceptual sensitivity in road-crossing.

A Developmental Eye Tracking Investigation of Cued Task Switching Performance.

Children perform worse than adults on tests of cognitive flexibility, which is a component of executive function. To assess what aspects of a cognitive flexibility task (cued switching) children have difficulty with, investigators tested where eye gaze diverged over age. Eye‐tracking was used as a proxy for attention during the preparatory period of each trial in 48 children ages 8–16 years and 51 adults ages 18–27 years. Children fixated more often and longer on the cued rule, and made more saccades between rule and response options. Behavioral performance correlated with gaze location and saccades. Mid‐adolescents were similar to adults, supporting the slow maturation of cognitive flexibility. Lower preparatory control and associated lower cognitive flexibility task performance in development may particularly relate to rule processing.

Eye movement biomarkers allow for the definition of phenotypes in Gaucher Disease

BackgroundNeurological forms of Gaucher disease, the inherited disorder of β-Glucosylceramidase caused by bi-allelic variants in GBA1, is a progressive disorder which lacks a disease-modifying therapy. Systemic manifestations of disease are effectively treated with enzyme replacement therapy, however, molecules which cross the blood–brain barrier are still under investigation. Clinical trials of such therapeutics require robust, reproducible clinical endpoints to demonstrate efficacy and clear phenotypic definitions to identify suitable patients for inclusion in trials. The single consistent clinical feature in all patients with neuronopathic disease is the presence of a supranuclear saccadic gaze palsy, in the presence of Gaucher disease this finding serves as diagnostic of ‘type 3’ Gaucher disease.MethodsWe undertook a study to evaluate saccadic eye movements in Gaucher patients and to assess the role of the EyeSeeCam in measuring saccades. The EyeSeeCam is a video-oculography device which was used to run a protocol of saccade measures. We studied 39 patients with non-neurological Gaucher disease (type 1), 21 patients with type 3 (neurological) disease and a series of 35 healthy controls. Mean saccade parameters were compared across disease subgroups.ResultsWe confirmed the saccadic abnormality in patients with type 3 Gaucher disease and identified an unexpected subgroup of patients with type 1 Gaucher disease who demonstrated significant saccade parameter abnormalities. These patients also showed subtle neurological findings and shared a GBA1 variant.ConclusionsThis striking novel finding of a potentially attenuated type 3 Gaucher phenotype associated with a specific GBA1 variant and detectable saccadic abnormality prompts review of current disease classification. Further, this finding highlights the broad spectrum of neuronopathic Gaucher phenotypes relevant when designing inclusion criteria for clinical trials.

Influence of Gaze Direction and Saccades on Hand Location and Orientation Errors in a Memory-Guided Alignment Task

Influence of Gaze Direction and Saccades on Hand Location and Orientation Errors in a Memory-Guided Alignment Task

Image complexity analysis with scanpath identification using remote gaze estimation model.

Analysis of gaze points has been a vital tool for understanding varied human behavioral pattern and underlying psychological processing. Gaze points are analyzed generally in terms of two events of fixations and saccades that are collectively termed as scanpath. Scanpath could potentially establish correlation between visual scenery and human cognitive tendencies. Scanpath has been analyzed for different domains that include visual perception, usability, memory, visual search or low level attributes like color, illumination and edges in an image. Visual search is one prominent area that examines scanpath of subjects while a target object is searched in a given set of images. Visual search explores behavioral tendencies of subjects with respect to image complexity. Complexity of an image is governed by spatial, frequency and color information present in the image. Scanpath based image complexity analysis determines human visual behavior that could lead to development of interactive and intelligent systems. There are several sophisticated eye tracking devices and associated algorithms for recording and classification of scanpath. However, in the present scenario when the chances of viral infections (COVID-19) from known and unknown sources are high, it is very important that the contact less methods and models be designed. In addition, even though the devices acquire and process eye movement data with fair accuracy but are intrusive and costly. The objective of current research work is to establish the complexity of the given set of images while target objects are searched and to present analysis of gaze search pattern. To achieve these objectives a remote gaze estimation and analysis model has been proposed for scanpath identification and analysis. The model is an alternate option for gaze point tracking and scanpath analysis that is non intrusive and low cost. The gaze points are tracked remotely as against sophisticated wearable eye tracking devices available in the market. The model employs easily available softwares and hardware devices. In the current work, complexity is derived on the basis of analysis of fixation and saccade gaze points. Based on the results generated by the proposed model, influence on subjects due to external stimuli is studied. The set of images chosen, act as external stimuli for the subjects during visual search. In order to statistically analyze scanpath for different subjects, certain scanpath parameters have been identified. The model maps and classifies eye movement gaze points into fixations and saccades and generates data for identified parameters. For eye detection and subsequent iris detection voila jones and circular hough transform (CHT) algorithms have been used. Identification by dispersion threshold (I-DT) is implemented for scanpath identification. The algorithms are customized for better iris and scanpath detection. Algorithms are developed for gaze screen mapping and classification of fixations and saccades. The experimentation has been carried on different subjects. Variations during visual search have been observed and analyzed. The present model requires no contact of human subject with any equipment including eye tracking devices, screen or computing devices.

Влияние мозжечковой дисфункции, приобретенной в результате лечения опухоли, на функционирование саккадической системы у детей

Cerebellum plays a crucial role in control of saccadic eye movements and gaze fixation. The cerebellar impairment leads to various disorders of oculomotor behavior and related psychophysiological processes, which, in turn, may affect the efficiency of rehabilitation process of patients who underwent tumor resection surgery on cerebellum. The purpose of this work was to determine the ways and the extent of influence of surgery-related cerebellar dysfunction on visuomotor system of children. We also intended to develop criteria based on these findings to assess the patient’s rehabilitation progress quantitatively as well as qualitatively. 66 children between 9 and 17 years old with surgery-related cerebellar dysfunction were enrolled in this study. The control group consisted of 54 healthy children of the same age. The subjects were to perform 3 oculomotor tasks while their eye movements were recorded using eye tracking technique. We found that children with cerebellar dysfunction had impaired gaze fixation ability, executed more hypermetric saccades and experienced difficulties with visual scanning. These oculomotor system deficiencies inevitably lead to disturbances of various cognitive processes such as visual perception, attention focusing, memory and reading. Also, hypermetric saccades can be treated as a special case of ataxia usually found in patients with cerebellar dysfunction. We conclude that assessment of oculomotor deficiencies should be used to increase the effectiveness of rehabilitation procedures for patients with cerebellar dysfunction.

Semi tandem base of support degrades both saccadic gaze control and postural stability particularly in older adults

Differences in the postural stabilization of older and young adults have been shown to be task-dependent on both visual and postural challenges; however, the gaze behavior during such tasks has rarely been examined. This study investigated the effects of horizontal and vertical saccades on gaze control, center of pressure (CoP) and head displacement of young and older adults on different bases of support. Ten young adults (20.7 ± 3.4 years) and ten older adults (71.6 ± 3.1 years) remained in an upright stance on a force platform wearing an eye-head tracker device. The participants performed 30-second trials according to two bases of support (feet apart and semi-tandem) and three gaze behavior (fixation, horizontal and vertical saccades) conditions. Older adults presented greater CoP amplitude (p < 0.002) and velocity (p < 0.001) (ML axis), and higher head amplitude (ML) (p < 0.002) than young adults during the semi tandem base. Head displacement of both groups presented higher velocity (ML axis) during horizontal (p < 0.001) and vertical saccades (p < 0.01) than the fixation task only on the semi tandem base. There was higher number of fixations (p < 0.001) and lower mean fixation duration (p < 0.001) on the semi-tandem base (p < 0.05). The results showed higher gaze latency variability in vertical saccades for older adults (p < 0.01). Challenging postural tasks may alter postural adjustments and gaze control during saccadic tasks. Particularly, the greater postural instability of older adults increased the gaze latency variability during saccadic tasks, suggesting some deterioration in the posture-gaze relation with aging.

A case of surgically-associated anti GQ1b antibody syndrome accompanied by saccadic ping pong gaze

BackgroundPeriodic alternating ping-pong gaze (PPG) is a rare disease with few reports. To our knowledge, there was no report on anti GQ1b antibody syndrome accompanied by PPG. This paper reported a case of anti GQ1b antibody syndrome with Bickerstaff’s Encephalitis (BBE) overlapping classic Guillain-Barre Syndrome (GBS) after aortic valve replacement, accompanied by an excessive PPG in the course of diagnosis and treatment, this was indeed rarely.Case presentationA 55-year-old male patient was admitted to our hospital with intermittent chest tightness for 3 months, and his condition has worsened in the past 10 days. Aortic valve replacement was performed because of the existence of the moderate and severe stenosis of aortic valve. Horizontal movement of the eyeball was involuntarily slow. The eyeball hovered and returned from one side to the other horizontally for 3–4 s per cycle. In combination with the patient’s typical clinical and laboratory tests, the final diagnosis was anti GQ1b antibody syndrome BBE combined with GBS, accompanied by saccadic ping pong gaze. Intravenous immunoglobulin (0.4 g/kg) was given for immunomodulation, methylprednisolone (1000 mg) therapy and symptomatic treatment were performed in the patient.ConclusionsThe patients were discharged from hospital on the thirtieth day because of economic reasons. After 6 months of follow up, the patients left behind a lack of fluency in speech and limb mobility, but the basic life can be taken care of by himself.

Monitoring Human Visual Behavior during the Observation of Unmanned Aerial Vehicles (UAVs) Videos

The present article describes an experimental study towards the examination of human visual behavior during the observation of unmanned aerial vehicles (UAVs) videos. Experimental performance is based on the collection and the quantitative &amp; qualitative analysis of eye tracking data. The results highlight that UAV flight altitude serves as a dominant specification that affects the visual attention process, while the presence of sky in the video background seems to be the less affecting factor in this procedure. Additionally, the main surrounding environment, the main size of the observed object as well as the main perceived angle between UAV’s flight plain and ground appear to have an equivalent influence in observers’ visual reaction during the exploration of such stimuli. Moreover, the provided heatmap visualizations indicate the most salient locations in the used UAVs videos. All produced data (raw gaze data, fixation and saccade events, and heatmap visualizations) are freely distributed to the scientific community as a new dataset (EyeTrackUAV) that can be served as an objective ground truth in future studies.

Visual Search Efficiency Evaluation Method for Potential Connected Vehicles on Sharp Curves

Accurate discrimination of driving proficiency is essential to improve driving safety. A naturalistic driving experiment was designed and organized to discover the response characteristics among drivers’ eye movement behaviors, driving proficiency, and mountain roads; 20 drivers were recruited to collect corresponding data of eye movement parameters on sharp turns, including gaze behavior and saccade behavior. The data show that on right turning roads, the main range of eye fixation points is −0.1–0.3 m in the horizontal direction, while the range is −0.35–0.2 m for left turn bends. The main range of the eye horizontal gaze angle is 0–30°, the range of the saccade amplitude is 5–25°, and its value increased as the curve radius decreased, showing a logarithmic relationship. Based on the collected eye movement characteristics data, a driver’s visual search modal matrix was built. A principal component analysis was used, and a comprehensive evaluation model of drivers’ eye movement characteristics was established. The result shows that eye movement comprehensive score and driving mileage were positively correlated. The result also indicates that the discrimination model can be used to quantify and discriminate driving proficiency and can provide a novel perspective for connected vehicle performance assessment.

Double Stimulation in a Spiking Neural Network Model of the Midbrain Superior Colliculus.

The midbrain superior colliculus (SC) is a crucial sensorimotor interface in the generation of rapid saccadic gaze shifts. For every saccade it recruits a large population of cells in its vectorial motor map. Supra-threshold electrical microstimulation in the SC reveals that the stimulated site produces the saccade vector specified by the motor map. Electrically evoked saccades (E-saccades) have kinematic properties that strongly resemble natural, visual-evoked saccades (V-saccades), with little influence of the stimulation parameters. Moreover, synchronous stimulation at two sites yields eye movements that resemble a weighted vector average of the individual stimulation effects. Single-unit recordings have indicated that the SC population acts as a vectorial pulse generator by specifying the instantaneous gaze-kinematics through dynamic summation of the movement effects of all SC spike trains. But how to reconcile the a-specific stimulation pulses with these intricate saccade properties? We recently developed a spiking neural network model of the SC, in which microstimulation initially activates a relatively small set of (~50) neurons around the electrode tip, which subsequently sets up a large population response (~5,000 neurons) through lateral synaptic interactions. Single-site microstimulation in this network thus produces the saccade properties and firing rate profiles as seen in single-unit recording experiments. We here show that this mechanism also accounts for many results of simultaneous double stimulation at different SC sites. The resulting E-saccade trajectories resemble a weighted average of the single-site effects, in which stimulus current strength of the electrode pulses serve as weighting factors. We discuss under which conditions the network produces effects that deviate from experimental results.