Saccades Methodology Flashcards
(31 cards)
Why did you choose to do only two eye-tracking sessions pre and postexercise?
The decision to conduct only two eye-tracking sessions, one before and one after the exercise intervention, was based on the need to compare baseline oculomotor performance with post-exercise performance. This design is commonly used to identify any immediate effects of exercise on oculomotor function, minimizing participant fatigue and maintaining the integrity of the data by reducing potential confounding factors such as learning or adaptation effects that might occur with multiple testing sessions.
Why did you not choose a longer oculomotor task? Why just 10 minutes?
The 10-minute duration for each block of the oculomotor task was chosen to balance the need for a sufficient number of trials to achieve reliable data with the need to prevent participant fatigue and loss of concentration, which can degrade data quality. Longer tasks can lead to increased variability in participant performance due to fatigue, and the 10-minute duration is a compromise to maintain high-quality, consistent data.
Are 120 trials of pro and antisaccades sufficient to detect changes in oculomotor performance?
Yes, 120 trials of pro- and antisaccades are generally sufficient to detect changes in oculomotor performance. Previous studies have shown that this number of trials provides a reliable measure of saccadic reaction times, accuracy, and errors, allowing for robust statistical analyses. This number of trials strikes a balance between obtaining enough data for statistical power and avoiding participant fatigue.
Describe the calibration technique used before the start of the oculomotor task. What was the reasoning behind the degree of pupil error used?
The calibration technique involved a nine-point calibration of the viewing space, followed by immediate verification to ensure that no point in the calibration space contained more than 1° of error. This high level of accuracy is critical in oculomotor studies to ensure that the measured gaze position accurately reflects the participant’s true gaze. The 1° error threshold is a standard used in eye-tracking studies to ensure data validity and reliability.
Describe what the cut-off parameters were for reaction times, saccade duration, gain, and directional errors.
- Reaction times: Trials with reaction times (RTs) less than 50 ms (anticipatory responses) and RTs greater than 2.5 standard deviations from a participant- and task-specific mean were excluded.
- Saccade duration: Saccade onset was defined as when velocity exceeded 30°/s and acceleration exceeded 8000°/s²; saccade offset was when velocity fell below 30°/s for at least 40 ms. (The saccade was considered to have ended when the eye’s velocity dropped below 30°/s and remained there for at least 40 milliseconds)
- Gain: Analyzed as the ratio of saccade amplitude to target amplitude which was 13.5° for proximal targets and 16.5° for distal targets.
Directional errors: Trials with directional errors, such as performing a prosaccade instead of an instructed antisaccade (or vice versa), were excluded from RT analysis because they involve different planning mechanisms.
How did you pre-process the oculomotor data? What software did you use and why?
The oculomotor data were pre-processed using MATLAB (R2018b) with the Psychophysics Toolbox extensions and the EyeLink Toolbox. Data were filtered offline using a dual-pass Butterworth filter with a low-pass cut-off frequency of 15 Hz. MATLAB and its toolboxes are widely used in psychophysics and oculomotor research due to their flexibility, powerful data analysis capabilities, and compatibility with various eye-tracking hardware.
How did you decide the distance between the monitor and chin-rest for the oculomotor task?
The distance between the monitor and the chin-rest (550 mm) was chosen based on standard practices in eye-tracking research to ensure that visual stimuli are presented within a comfortable and optimal viewing range. This distance helps minimize head movements and maintains a consistent visual angle for all participants, ensuring the accuracy of eye-tracking measurements.
What performance metrics were you privy to in real time during the oculomotor task?
During the oculomotor task, the experimenter had access to real-time point-of-gaze information, trial-by-trial saccade kinematics, and data related to the accuracy of the eye-tracking system. This real-time feedback allowed the experimenter to monitor the performance and accuracy of the eye-tracking system continuously.
How were you able to ensure that experimenter bias did not interfere with oculomotor performance, if you were privy to their performance metrics in real-time?
To minimize experimenter bias, the real-time feedback visible to the experimenter was used solely to monitor technical performance and not to influence participant behavior. Additionally, the experimenter maintained a standardized protocol and remained neutral during task execution to ensure that all participants received the same instructions and conditions, thereby reducing the risk of bias.
Describe “proximal” versus “distal” targets in your oculomotor task. Why were they used, how often did they appear, and was their order random?
- Proximal targets were located 13.5° from the central fixation point, and distal targets were 16.5° away. These different target eccentricities were used to prevent participants from adopting stereotyped responses and to introduce variability in the task. The targets appeared randomly within a block of 60 trials, with the location (left or right) and type of saccade (pro- or antisaccade) being pseudorandomized to ensure a balanced and unpredictable presentation.
Describe the necessity for a “gap paradigm” in your oculomotor task.
The “gap paradigm” involves extinguishing the fixation cross 200 ms before the target onset, creating a temporal gap. This paradigm was used to increase the difficulty of the task and to reduce the predictability of the target onset, thereby increasing the need for rapid and accurate saccadic responses. The gap paradigm is known to elicit shorter reaction times and more express saccades, making it a useful tool for studying oculomotor control.
Why were the targets only presented briefly (i.e., for 50 ms) instead of for the duration of the eye-movement?
Extraretinal feedback refers to the internal monitoring of eye position and movement in the absence of visual input. When a target is presented briefly (50 ms), it disappears before the saccade is completed, preventing participants from using visual feedback to correct their saccade endpoints. By equating pro- and antisaccades for the absence of extraretinal feedback, the study ensures that any observed differences in performance between the two tasks can be attributed to the cognitive processes involved, such as response inhibition and vector inversion, rather than differences in the availability of visual feedback for endpoint correction.
What were the instructions given to the participant regarding how to perform the oculomotor task?
Participants were instructed to perform the saccades “quickly and accurately” in response to the targets. For prosaccades, they were to look directly at the target location, while for antisaccades, they were to look at the mirror-symmetrical location opposite to the target. These instructions were given to ensure clarity and consistency in task performance across all participants.
Why did you choose a separate “block design” instead of a “task-switching” design for the presentation of the saccade types?
A separate block design for pro- and antisaccade trials was chosen to reduce cognitive load and interference effects that might arise from frequent task switching. This design allows participants to focus on one type of saccadic task at a time, leading to more consistent performance and reducing the likelihood of errors that could arise from switching between tasks.
How can you be sure that the reduction in reaction times observed is not due to practice effects?
The antisaccade reaction time (RT) reduction has been shown to be independent of a practice-related performance benefit for several reasons:
○ Frequentist and Bayesian Analyses:
Studies have demonstrated that antisaccade RTs remain equivalent when compared to those interspersed with a non-exercise control interval, as reported in multiple analyses. These findings indicate that the observed reductions in RTs post-exercise are not simply due to repeated exposure or practice effects, but rather are attributable to the effects of exercise itself (Dirk et al., 2020; Dyckman & McDowell, 2005; Klein & Berg, 2001; Samani & Heath, 2018; Shukla & Heath, 2022; Tari et al., 2020, 2023).
○ Antisaccade Durations and Gain Variability:
The fact that antisaccade durations and gain variability did not vary significantly across pre- to post-exercise assessments supports the notion that the post-exercise RT reduction was not due to a change in strategy aimed at reducing RT at the expense of accuracy (Fitts, 1954). If practice effects were responsible, one would expect to see changes in these metrics as participants might trade accuracy for speed (i.e., a speed-accuracy trade-off).
Why did you choose to only dim the lights in the experiment room instead of turning them off completely during the oculomotor task?
The lights were dimmed to an ambient level of 39 cd/m² to reduce glare and reflections on the screen while maintaining enough light for the experimenter to monitor the equipment and participants. Completely dark environments can be uncomfortable for participants and can introduce variability in pupil size and eye-tracking accuracy. The chosen light level strikes a balance between these factors.
Why did you wait for heart rate and blood pressure to return to baseline post-exercise before beginning the second round of oculomotor testing and was 5 minutes sufficient time to wait?
Waiting for heart rate (HR) and blood pressure (BP) to return to baseline ensures that any changes in oculomotor performance can be attributed to the exercise intervention itself rather than residual physiological effects of exercise. Five minutes was considered sufficient based on pilot data and previous literature suggesting that HR and BP typically return to baseline within this period after moderate exercise. Ensuring physiological measures are at baseline reduces confounding variables in the post-exercise assessment.
Was there significant symptom exacerbation post-oculomotor task?
The SCAT-5 symptom frequency and severity did not reliably differ between pre- and post-exercise oculomotor assessments, indicating that there was no significant symptom exacerbation post-oculomotor task. This suggests that the oculomotor assessments were well-tolerated by the participants.
How do you know that the post-exercise reduction in antisaccade reaction times is not just an enhancement of information processing and instead it’s a postexercise EF benefit in inhibitory control?
- The post-exercise reduction in antisaccade reaction times indicates a postexercise EF benefit in inhibitory control rather than just an enhancement of information processing due to several reasons:
○ Antisaccades specifically measure inhibitory control.
○ This task requires suppressing a reflexive prosaccade in favor of a volitional antisaccade, a process heavily reliant on EF (Munoz & Everling, 2004).
○ There is no significant pre- to post-exercise change in prosaccade reaction times.
○ Prosaccades are prepotent and less reliant on EF, suggesting that the reduction in antisaccade RTs is not due to general enhancement in information processing.
○ The improvement in antisaccade performance post-exercise aligns with previous research demonstrating that exercise specifically benefits EF-related tasks rather than general cognitive processing (Heath et al., 2018; Samani & Heath, 2018; Shukla & Heath, 2022).
You suggested that the frequency of antisaccade directional errors might provide a resolution to detect persistent SRC-related EF deficits. Could you elaborate on the potential clinical implications of this finding and how it might inform the assessment and management of SRC?
- The persistence of increased antisaccade directional errors in the SRC group, even after the exercise intervention, suggests that this measure may be a sensitive indicator of lasting EF deficits following concussion.
Clinically, this finding could inform the development of oculomotor-based assessments for concussion diagnosis and recovery monitoring. By tracking changes in antisaccade directional error rates over time, clinicians may be able to detect subtle EF impairments that persist beyond the resolution of other concussion symptoms.
The results showed that the exercise intervention led to a reduction in antisaccade reaction times for both the SRC and HC groups, but did not affect the frequency of directional errors in the SRC group. How do you interpret these findings in terms of the specific cognitive processes involved in antisaccade performance, such as response inhibition and vector inversion?
- The reduction in antisaccade reaction times (RTs) following the exercise intervention in both the SRC and HC groups suggests that acute exercise improves the efficiency of response inhibition and vector inversion processes, which are critical for successful antisaccade performance. Response inhibition involves suppressing the automatic tendency to make a prosaccade towards the target, while vector inversion requires inverting the spatial coordinates of the target to generate a saccade in the opposite direction. The improved RTs indicate that exercise enhances the speed at which these cognitive processes can be executed.
- However, the lack of change in directional error rates for the SRC group suggests that while exercise may enhance the speed of response inhibition and vector inversion processes, it does not necessarily improve their accuracy in individuals with concussion. This finding highlights the dissociation between the efficiency (RT) and effectiveness (accuracy) of cognitive control processes in antisaccade performance.
- The increased frequency of antisaccade directional errors in the SRC group may be related to a failure to evoke the high-level executive function (EF) task-set supporting a non-standard response (Everling & Johnston, 2013). A single bout of exercise might not provide a sufficient stimulus to improve the computational demands associated with adopting the task-set, or task rules, necessary to evoke a directionally correct antisaccade. These findings suggest that the frequency of antisaccade directional errors provides the resolution to detect persistent SRC-related EF deficits.
Antisaccades are not purely inhibitory control tasks (Munoz & Everling, 2004); they also require working memory and cognitive flexibility to maintain the goal of performing an antisaccade instead of a prosaccade. Deliberate practice is necessary to reduce antisaccade directional errors, as they represent a nonstandard task-set (Dyckman & McDowell, 2005). Thus, the increased directional errors in the SRC group, despite return-to-sport clearance, suggest an oculomotor EF deficit (Everling & Johnston, 2013).
You suggested that the frequency of antisaccade directional errors might provide a resolution to detect persistent SRC-related EF deficits. Could you elaborate on the potential clinical implications of this finding and how it might inform the assessment and management of SRC?
The persistence of increased antisaccade directional errors in the SRC group, even after the exercise intervention, suggests that this measure may be a sensitive indicator of lasting EF deficits following concussion. Clinically, this finding could inform the development of oculomotor-based assessments for concussion diagnosis and recovery monitoring. By tracking changes in antisaccade directional error rates over time, clinicians may be able to detect subtle EF impairments that persist beyond the resolution of other concussion symptoms.
Given the promising findings of your study, what future research directions would you propose to further investigate the effects of acute exercise on cognitive function in individuals with SRC, and how might these findings inform the development of exercise-based interventions for SRC recovery?
- Future research could investigate the dose-response relationship between exercise intensity, duration, and cognitive function in individuals with SRC, to determine the optimal exercise parameters for enhancing EF recovery.
- Additionally, longitudinal studies could examine the long-term effects of regular exercise on cognitive function and symptom resolution in SRC patients.
These findings could inform the development of personalized exercise-based interventions for concussion rehabilitation, targeting specific EF domains and tailoring exercise prescriptions to individual recovery trajectories.
Design a follow-up study, not considering funding or resources, to address your limitations and improve upon your methodology
Methods:
* Recruit a larger sample (i.e.,120 SRC participants (60 males, 60 females) and 120 healthy controls
* Match controls on age, sex, BMI, and cardiovascular fitness (i.e., VO2) if possible
* Determine SRC participants’ heart rate threshold (HRt) using the Buffalo Concussion Bike Test.
* Longitudinal assessment of EF pre- and post-exercise at baseline, 2, 4, and 8 weeks post-concussion.
* Monitor CBF changes during exercise using fNIRS and TCD.
* Track SRC symptoms using the complete SCAT5 tool at each time point and 24 hours post-exercise.
* Develop personalized aerobic exercise programs based on HRt.
* Collect data on menstrual cycle.
* Compare outcomes between male and female SRC participants and controls, considering covariates such as years of sport played and lifetime concussion history.
Expected Results:
* Improved EF, symptom resolution, and faster return-to-play in SRC participants following personalized exercise programs.
* Increased CBF during exercise, correlating with EF improvements in both sexes.
Potential sex differences in exercise-induced CBF changes.