Saccadic Response Time Research Articles

Synchronized refixation saccades in enhanced VVOR test. A new application for PR score.

Main objectives for this study were to develop a quantification method to obtain a Perez-Rey (PR) score adapted to the VVOR test and to evaluate the correlation of the PR score obtained with quantified VVOR with the PR score of the vHIT test. A new PR score calculation method for quantified VVOR test was developed using the MATLAB computational software based on saccadic response time latency variability between each head oscillation cycle of the VVOR test. Retrospective correlation between PR scores in VVOR and vHIT tests, performed in the same vHIT testing session for patients with vestibular neuritis and vestibular neurectomy, was performed to correlate new PR (VVOR) score with the classic PR (vHIT) score. Thirty patients were included: 11 post-neurectomy and 19 subacute vestibular neuritis. Pearson's correlation coefficient (R2) for the overall sample was 0.92 (p < 0.001) and 95% confidence interval was 0.85 -0.96. In the linear mixed-effects statistical model developed, only PRVHIT and PRVVOR scores showed statistical association in Wald X2 test (p = 0.008). The new developed PR score for synchronization measurement of saccadic responses in VVOR testing is a valid method that outputs synchronization values and highly correlates with PR score in vHIT test.

Saccadic eye movements are deployed faster for salient facial stimuli, but are relatively indifferent to their emotional content

The present study explores the threat bias for fearful facial expressions using saccadic latency, with a particular focus on the role of low-level facial information, including spatial frequency and contrast. In a simple localisation task, participants were presented with spatially-filtered versions of neutral, fearful, angry and happy faces. Together, our findings show that saccadic responses are not biased toward fearful expressions compared to neutral, angry or happy counterparts, regardless of their spatial frequency content. Saccadic response times are, however, significantly influenced by the spatial frequency and contrast of facial stimuli. We discuss the implications of these findings for the threat bias literature, and the extent to which image processing can be expected to influence behavioural responses to socially-relevant facial stimuli.

Saccadic as Well as Manual Reaction Times to Targets Given to the Amblyopic Eye are Faster than Those of the Opposite Eye or Normal Eyes

Aim: Amblyopia is caused by a combination of neural and visual impairments caused by abnormal early visual growth. One of the many drawbacks of amblyopia is that the amblyopic eye's saccadic and physical reaction times to targets presented to it are much slower than the other eye or normal eyes.&#x0D; Methodology: Assumed that amblyopic eye's recognized impairments in contrast sensitivity, the question immediately arises if the longer reaction times are merely a result of the stimuli's diminished visibility. Our current research was conducted at People Medical College Hospital Nawabshah from May 2019 to April 2020.&#x0D; Results: RTs to perifoveal stimuli are measured in study 1 as a function of efficient stimulus contrast, i.e., contrasting as measured by the amblyopic eye's comparison threshold. In our anisometropic amblyopes, researchers find that the asymptotic RTs including both eyes are the same when the sensory differences among eyes are minimized or eliminated. Several cross-eyed amblyopes, though, might have had an insurmountable delayed at asymptote. However, after accounting for stimulus sensory changes, these individuals' saccadic response times exhibited considerable interocular discrepancies. According to our results, eliminating the fixation image does slow down the amblyopic eye's reaction time, and that the gap impact is the same in both eyes. Therefore, the amblyopic eye's intrinsic delayed is not eliminated by the gap impact.&#x0D; Conclusion: Last but not least in Experiment 3, we looked at the interocular variations in saccadic and manual reaction times for the same participants. As a result, we were able to determine the relationship between latencies in the two modes.

Testing the unified model of vision and attention: Effects of landmark features, stimulus identity and visual eccentricity on visual orienting and conscious discrimination

ABSTRACTThe unified model of vision and attention (Lambert, A. J., Wilkie, J., Greenwood, A., Ryckman, N., Sciberras-Lim, E., Booker, L.-J., & Tahara-Eckl, L. [2018]. Towards a unified model of vision and attention: Effects of visual landmarks and identity cues on covert and overt attention movements. Journal of Experimental Psychology: Human Perception and Performance, 44, 412–432) was tested by examining effects of centrally and peripherally presented landmark and identity cues on attentional orienting. When presented centrally, both kinds of cue influenced attention; but, when presented peripherally, landmark cues affected attention, but identity cues did not. Effects of peripheral landmark cues on saccadic latencies and manual response times for discriminating between target stimuli were as large as those associated with central landmark cues. Because the dorsal stream represents peripheral vision quite well, whereas the ventral stream does not, these findings are consistent with our proposal that landmark cues tend to recruit dorsal stream encoding, while identity cues rely on ventral stream encoding. When participants discriminated consciously between stimuli employed as cues in the attentional orienting task, centrally presented stimuli were discriminated more rapidly than peripheral stimuli, regardless of cue type. This is consistent with the view that conscious discrimination of the stimuli used as landmark and identity cues in the orienting task, requires vision for perception and recruits ventral stream encoding.

The role of fixation disengagement in the parallel programming of sequences of saccades

One of the core mechanisms involved in the control of saccade responses to selected target stimuli is the disengagement from the current fixation location, so that the next saccade can be executed. To carry out everyday visual tasks, we make multiple eye movements that can be programmed in parallel. However, the role of disengagement in the parallel programming of saccades has not been examined. It is well established that the need for disengagement slows down saccadic response time. This may be important in allowing the system to program accurate eye movements and have a role to play in the control of multiple eye movements but as yet this remains untested. Here, we report two experiments that seek to examine whether fixation disengagement reduces saccade latencies when the task completion demands multiple saccade responses. A saccade contingent paradigm was employed and participants were asked to execute saccadic eye movements to a series of seven targets while manipulating when these targets were shown. This both promotes fixation disengagement and controls the extent that parallel programming can occur. We found that trial duration decreased as more targets were made available prior to fixation: this was a result both of a reduction in the number of saccades being executed and in their saccade latencies. This supports the view that even when fixation disengagement is not required, parallel programming of multiple sequential saccadic eye movements is still present. By comparison with previous published data, we demonstrate a substantial speeded of response times in these condition (“a gap effect”) and that parallel programming is attenuated in these conditions.

Discriminating between anticipatory and visually triggered saccades: measuring minimal visual saccadic response time using luminance.

We describe a novel behavioral method to accurately discriminate anticipatory (i.e., saccades not generated by visual input) from visually triggered saccades and to identify the minimal visual saccadic reaction time (SRT). This method can be used to calculate a feasible lower bound cutoff for latencies of visually triggered saccades within a certain experimental context or participant group. We apply this method to compute the minimal visual SRT for two different saccade target luminance levels. Three main findings are presented: 1) the minimal visual SRT for all participants was 46 ms shorter for bright targets than for dim targets, 2) the transition from non-visually triggered to visually triggered saccades occurred abruptly, independent of target luminance, and 3) although the absolute minimal visual SRTs varied between participants, the response pattern (response to bright targets being faster than to dim targets) was consistent across participants. These results are consistent with variability in saccadic and neural responses to luminance as has been reported in monkeys. On the basis of these results, we argue that differences in the minimal visual SRT can easily occur when stimuli vary in luminance or other saliency features. Applying an absolute cutoff (i.e., 70-90 ms) that approaches the minimal neuronal conduction delays, which is general practice in many laboratories, may result in the wrongful inclusion of saccades that are not visually triggered. It is suggested to assess the lower SRT bound for visually triggered saccades when piloting an experimental setup and before including saccades based on particular latency criteria. NEW & NOTEWORTHY We successfully developed an anticipation paradigm to discriminate between anticipatory and visually triggered saccades by measuring the minimal visual saccadic response time (SRT). We show that the 70- to 90-ms lower bound cutoff for visually triggered saccades should be applied in a flexible way and that the transitional interval is very short. The paradigm can be employed to investigate the effects of different stimulus features, experimental conditions, and participant groups on the minimal visual SRT in humans.

Rhythmic fluctuations of saccadic reaction time arising from visual competition

Recent research indicates that attentional stimulus selection could be a rhythmic process. In monkey, neurons in V4 and IT exhibit rhythmic spiking activity in the theta range in response to a stimulus. When two stimuli are presented together, the rhythmic neuronal responses to each occur in anti-phase, a result indicative of competitive interactions. In addition, it was recently demonstrated that these alternating oscillations in monkey V4 modulate the speed of saccadic responses to a target flashed on one of the two competing stimuli. Here, we replicate a similar behavioral task in humans (7 participants, each performed 4000 trials) and report a pattern of results consistent with the monkey findings: saccadic response times fluctuate in the theta range (6 Hz), with opposite phase for targets flashed on distinct competing stimuli.

Cross-modal integration during value-driven attentional capture

A growing body of evidence suggests that reward may be a powerful determinant of attentional selection. To date, the study of value-based attentional capture has been mainly focused on the visual sensory modality. It is yet unknown how reward information is communicated and integrated across the different senses in order to resolve between competing choices during selective attention. Our study investigated the interference produced by an auditory reward-associated distractor when a semantically-related visual target was concurrently presented. We measured both manual and saccadic response times towards a target image (drum or trumpet), while an irrelevant sound (congruent or incongruent instrument) was heard. Each sound was previously associated with either a high or a low reward. We found that manual responses were slowed by a high-reward auditory distractor when sound and image were semantically congruent. A similar effect was observed for saccadic responses, but only for participants aware of the past reward contingencies. Auditory events associated with reward value were thus capable of involuntarily capturing attention in the visual modality. This reward effect can mitigate cross-modal semantic integration and appears to be differentially modulated by awareness for saccadic vs. manual responses. Together, our results extend previous work on value-driven attentional biases in perception by showing that these may operate across sensory modalities and override cross-modal integration for semantically-related stimuli. This study sheds new light on the potential implication of brain regions underlying value-driven attention across sensory modalities.

Saccadic impairment in chronic traumatic brain injury: examining the influence of cognitive load and injury severity

ABSTRACTObjective: Previous research suggests that saccadic eye movements can be uniquely sensitive to impairment in chronic traumatic brain injury (TBI). This study was conducted to examine saccadic eye movements across varying levels of cognitive load and TBI history/severity. We hypothesized that saccadic impairment in chronic mild and moderate-severe TBI would be most pronounced under conditions of high cognitive load.Methods: In total, 61 participants (including n = 20 with chronic mild TBI, n = 15 with chronic moderate-severe TBI, and 26 uninjured controls) completed a battery of conventional neuropsychological tests and the Fusion n-Back Test, which measures manual and saccadic response time (RT) across varying cognitive load and cueing conditions.Results: Consistent with our hypotheses, chronic mild and moderate-severe TBI were associated with substantial saccadic impairment under conditions of high cognitive load. Participants with moderate-severe TBI also demonstrated saccadic impairment at low levels of cognitive load. TBI groups and uninjured controls did not differ significantly on manual metrics or conventional neuropsychological measures.Conclusions: This study provides additional support for the value of eye tracking for enhanced assessment of TBI. Additionally, findings suggest that TBI is associated with greatest susceptibility to oculomotor interference under high levels of cognitive load.

Attention holding elicited by direct-gaze faces is reflected in saccadic peak velocity.

Manual response times to peripherally presented targets have been reported to be greater in the presence of task-irrelevant pictorial faces at fixation which establish an eye contact with the observer. This effect is interpreted as evidence that direct-gaze faces hold attention. In three experiments, we investigated whether this attention-holding effect is also reflected in saccadic response times. Participants were asked to make a saccade towards a symbolic target that could appear rightwards or leftwards, in the presence of a task-irrelevant centrally placed face with either direct gaze or closed eyes. Unexpectedly, saccadic response times did not show any consistent response pattern as a function of whether the faces were presented with direct gaze vs. closed eyes. Interestingly, saccadic peak velocities were found to be lower in the presence of faces with direct gaze rather than closed eyes (Experiment 1). This effect emerged even in the presence of non-human primate faces (Experiment 2), and no differences between direct gaze and closed eyes emerged when the faces were presented inverted rather than upright (Experiment 3). Overall, these findings suggest that eye contact can have an impact on the saccadic generation system.

Increased risk for age-related impairment in visual attention associated with mild traumatic brain injury: Evidence from saccadic response times.

It was hypothesized that risk for age-related impairment in attention would be greater among those with remote history of mild TBI than individuals without history of head injury. Twenty-seven adults with remote history of mild TBI and a well-matched comparison group of 54 uninjured controls completed a computerized test of visual attention while saccadic and manual response times were recorded. Within the mild TBI group only, older age was associated with slower saccadic responses and poorer saccadic inhibition. Saccadic slowing was mitigated in situations where the timing and location of attention targets was fully predictable. Mild TBI was not associated with age-related increases in risk for neuropsychological impairment or neurobehavioral symptoms. These results provide preliminary evidence that risk for age-related impairment in visual attention may be higher among those with a history of mild TBI. Saccadic measures may provide enhanced sensitivity to this subtle form of cognitive impairment.

Medications influencing central cholinergic pathways affect fixation stability, saccadic response time and associated eye movement dynamics during a temporally-cued visual reaction time task.

Anticholinergic medications largely exert their effects due to actions on the muscarinic receptor, which mediates the functions of acetylcholine in the peripheral and central nervous systems. In the central nervous system, acetylcholine plays an important role in the modulation of movement. This study investigated the effects of over-the-counter medications with varying degrees of central anticholinergic properties on fixation stability, saccadic response time and the dynamics associated with this eye movement during a temporally-cued visual reaction time task, in order to establish the significance of central cholinergic pathways in influencing eye movements during reaction time tasks. Twenty-two participants were recruited into the placebo-controlled, human double-blind, four-way crossover investigation. Eye tracking technology recorded eye movements while participants reacted to visual stimuli following temporally informative and uninformative cues. The task was performed pre-ingestion as well as 0.5 and 2h post-ingestion of promethazine hydrochloride (strong centrally acting anticholinergic), hyoscine hydrobromide (moderate centrally acting anticholinergic), hyoscine butylbromide (anticholinergic devoid of central properties) and a placebo. Promethazine decreased fixation stability during the reaction time task. In addition, promethazine was the only drug to increase saccadic response time during temporally informative and uninformative cued trials, whereby effects on response time were more pronounced following temporally informative cues. Promethazine also decreased saccadic amplitude and increased saccadic duration during the temporally-cued reaction time task. Collectively, the results of the study highlight the significant role that central cholinergic pathways play in the control of eye movements during tasks that involve stimulus identification and motor responses following temporal cues.

Assessment of Performance Validity Using Embedded Saccadic and Manual Indices on a Continuous Performance Test.

In addition to manual (i.e., "button press") metrics, oculomotor metrics demonstrate considerable promise as tools for detecting invalid responding in neurocognitive assessment. This study was conducted to evaluate saccadic and manual metrics from a computerized continuous performance test as embedded indices of performance validity. Receiver operating characteristic analyses, logistic regressions, and ANOVAs were performed to evaluate saccadic and manual metrics in classification of healthy adults instructed to feign deficits ("Fake Bad" group; n = 24), healthy adults instructed to perform their best ("Best Effort" group; n = 26), and adults with a history of mild traumatic brain injury (TBI) who passed a series of validity indices ("mTBI-Pass" group; n = 19). Several saccadic and manual metrics achieved outstanding classification accuracy between Fake Bad versus Best Effort and mTBI-Pass groups, including variability (consistency) of saccadic and manual response time (RT), saccadic commission errors, and manual omission errors. Very large effect sizes were obtained between Fake Bad and Best Effort groups (Cohen's d range: 1.89-2.90; r range: .75-.78) as well as between Fake Bad and mTBI-Pass groups (Cohen's d range: 1.32-2.21; r range: .69-.71). The Fake Bad group consistently had higher saccadic and manual RT variability, more saccadic commission errors, and more manual omission errors than the Best Effort and mTBI-Pass groups. These findings are the first to demonstrate that eye movements can be used to detect invalid responding in neurocognitive assessment. These results also provide compelling evidence that concurrently measured saccadic and manual metrics can detect invalid responding with high levels of sensitivity and specificity.

Multimodal assessment of visual attention using the Bethesda Eye & Attention Measure (BEAM)

ABSTRACTIntroduction: Computerized cognitive tests measuring manual response time (RT) and errors are often used in the assessment of visual attention. Evidence suggests that saccadic RT and errors may also provide valuable information about attention. This study was conducted to examine a novel approach to multimodal assessment of visual attention incorporating concurrent measurements of saccadic eye movements and manual responses. Method: A computerized cognitive task, the Bethesda Eye & Attention Measure (BEAM) v.34, was designed to evaluate key attention networks through concurrent measurement of saccadic and manual RT and inhibition errors. Results from a community sample of n = 54 adults were analyzed to examine effects of BEAM attention cues on manual and saccadic RT and inhibition errors, internal reliability of BEAM metrics, relationships between parallel saccadic and manual metrics, and relationships of BEAM metrics to demographic characteristics. Results: Effects of BEAM attention cues (alerting, orienting, interference, gap, and no-go signals) were consistent with previous literature examining key attention processes. However, corresponding saccadic and manual measurements were weakly related to each other, and only manual measurements were related to estimated verbal intelligence or years of education. Conclusions: This study provides preliminary support for the feasibility of multimodal assessment of visual attention using the BEAM. Results suggest that BEAM saccadic and manual metrics provide divergent measurements. Additional research will be needed to obtain comprehensive normative data, to cross-validate BEAM measurements with other indicators of neural and cognitive function, and to evaluate the utility of these metrics within clinical populations of interest.

The contribution of pre-stimulus neural oscillatory activity to spontaneous response time variability

Large variability between individual response times, even in identical conditions, is a ubiquitous property of animal behavior. However, the origins of this stochasticity and its relation to action decisions remain unclear. Here we focus on the state of the perception–action network in the pre-stimulus period and its influence on subsequent saccadic response time and choice in humans. We employ magnetoencephalography (MEG) and a correlational source reconstruction approach to identify the brain areas where pre-stimulus oscillatory activity predicted saccadic response time to visual targets. We find a relationship between future response time and pre-stimulus power, but not phase, in occipital (including V1), parietal, posterior cingulate and superior frontal cortices, consistently across alpha, beta and low gamma frequencies, each accounting for between 1 and 4% of the RT variance. Importantly, these correlations were not explained by deterministic sources of variance, such as experimental factors and trial history. Our results further suggest that occipital areas mainly reflect short-term (trial to trial) stochastic fluctuations, while the frontal contribution largely reflects longer-term effects such as fatigue or practice. Parietal areas reflect fluctuations at both time scales. We found no evidence of lateralization: these effects were indistinguishable in both hemispheres and for both saccade directions, and non-predictive of choice — a finding with fundamental consequences for models of action decision, where independent, not coupled, noise is normally assumed.

Fronto-central theta oscillations are related to oscillations in saccadic response times (SRT): an EEG and behavioral data analysis.

The phase reset hypothesis states that the phase of an ongoing neural oscillation, reflecting periodic fluctuations in neural activity between states of high and low excitability, can be shifted by the occurrence of a sensory stimulus so that the phase value become highly constant across trials (Schroeder et al., 2008). From EEG/MEG studies it has been hypothesized that coupled oscillatory activity in primary sensory cortices regulates multi sensory processing (Senkowski et al. 2008). We follow up on a study in which evidence of phase reset was found using a purely behavioral paradigm by including also EEG measures. In this paradigm, presentation of an auditory accessory stimulus was followed by a visual target with a stimulus-onset asynchrony (SOA) across a range from 0 to 404 ms in steps of 4 ms. This fine-grained stimulus presentation allowed us to do a spectral analysis on the mean SRT as a function of the SOA, which revealed distinct peak spectral components within a frequency range of 6 to 11 Hz with a modus of 7 Hz. The EEG analysis showed that the auditory stimulus caused a phase reset in 7-Hz brain oscillations in a widespread set of channels. Moreover, there was a significant difference in the average phase at which the visual target stimulus appeared between slow and fast SRT trials. This effect was evident in three different analyses, and occurred primarily in frontal and central electrodes.

Validity and Repeatability of Saccadic Response Times Across the Visual Field in Eye Movement Perimetry

To assess the validity and repeatability of saccadic reaction times (SRT) across the visual field up to 30° using eye movement perimetry (EMP). Eighteen subjects (36 eyes) were shown a central stimulus on a flat monitor screen. Next, peripheral stimuli were shown using an overlap paradigm. Subjects were instructed to look at detected peripheral stimuli and then refixate the central stimulus again. In three repetitive measurement series, a total of 288 visual stimuli (3 series × 24 locations × 4 contrast levels) were presented. Levene's test for equality of variances was applied to test the effect of stimulus location and measurement series on SRT variance. A Wilcoxon signed ranks test was used to compare SRTs between measurement series. A total of 26 eyes were included in the study (72%). On average, 90.5% of the peripheral stimuli were labeled as 'seen' based on eye movement responses. Between the series, the mean SD of SRT differences was approximately 100 ms. Significantly faster SRTs were only found at contrast level 0.8 in series III compared with series II. In series I, SRT variance was independent in 75% of all locations. Across the three series, SRT variance was independent in 87.5% of all locations. The present study demonstrates low variability of SRT across the visual field up to 30° eccentricity and across measurement series. SRT as a measure for visual field responsiveness may be a potential marker to detect risk areas in specific parts of the visual field.

Proportional Hazards Modeling of Saccadic Response Times During Reading

In this article we use proportional hazards models to examine how low-level processes affect the probability of making a saccade over time, through the period of fixation, during reading. We apply the Cox proportional hazards model to investigate how launch distance (relative to word beginning), fixation location (relative to word center), and word frequency affect the hazard of a saccadic response. This model requires that covariates have a constant impact on the hazard over time, the assumption of proportional hazards. We show that this assumption is not supported. The impact of the covariates changes with the time passed since fixation onset. To account for the non-proportional hazards we fit step functions of time, resulting in a model with time-varying effects on the hazard. We evaluate the ability to predict the timing of saccades on held-out fixation data. The model with time-varying effects performs better in predicting the timing of saccades for fixations as short as 100ms and as long as 500ms, when compared both to a baseline model without covariates and a model which assumes constant covariate effects. This result suggests that the time-varying effects model better recovers the time course of low-level processes that influence the decision to move the eyes.

The Relationship between Abnormalities of Saccadic and Manual Response Times in Parkinson's Disease

Clinicians normally use subjective rating scales to estimate the impairment of patients with Parkinson's disease (PD). More objective and quantitative methods of assessment would greatly aid our understanding of the disease. One promising approach is to measure reaction time: the large amount of data recorded in a short period provides precise, reproducible evaluation of the underlying neural decision processes. Manual evoked reaction times and repetitive tapping speed are often used, but differences of experimental design and analysis tend to obscure their interpretation. Saccadic latency, in many ways a simpler and more standardised task, is also normally affected in PD, but its relation to the kind of movement impairment that affects patients' quality of life is less obvious. OBJESTIVE: The aim of this study was to evaluate these tasks in detail and also see whether their use in combination could provide a better measure than each in isolation. We compared three reaction time tasks: saccadometry, and evoked and spontaneous tapping, using protocols as similar as possible, correlating the measurements within a group of PD patients and of age-matched controls. Surprisingly, manual and saccadic performance is uncorrelated in the normal population; but both are similarly affected by PD. The differences between groups are strengthened when the three measures are combined. Saccadic latency can be regarded as an appropriate surrogate for more general kinds of motor impairment. The combination of saccadic and manual parameters enhances their potential use in quantifying disease status and evaluating treatments.

Averaging saccades are repelled by prior uninformative cues at both short and long intervals

When two spatially proximal stimuli are presented simultaneously, a first saccade is often directed to an intermediate location between the stimuli (averaging saccade). In an earlier study, Watanabe (2001) showed that, at a long cue–target onset asynchrony (CTOA; 600 ms), uninformative cues not only slowed saccadic response times (SRTs) to targets presented at the cued location in single target trials (inhibition of return, IOR), but also biased averaging saccades away from the cue in double target trials. The present study replicated Watanabe's experimental task with a short CTOA (50 ms), as well as with mixed short (50 ms) and long (600 ms) CTOAs. In all conditions on double target trials, uninformative cues robustly biased averaging saccades away from cued locations. Although SRTs on single target trials were delayed at previously cued locations at both CTOAs when they were mixed, this delay was not observed in the blocked, short CTOA condition. We suggest that top-down factors, such as expectation and attentional control settings, may have asymmetric effects on the temporal and spatial dynamics of oculomotor processing.