Saccadic Responses Research Articles

Impairment of manual but not saccadic response inhibition following acute alcohol intoxication

BackgroundAlcohol impairs response inhibition; however, it remains contested whether such impairments affect a general inhibition system, or whether affected inhibition systems are embedded in, and specific to, each response modality. Further, alcohol-induced impairments have not been disambiguated between proactive and reactive inhibition mechanisms, and nor have the contributions of action-updating impairments to behavioural ‘inhibition’ deficits been investigated. MethodsForty Participants (25 female) completed both a manual and a saccadic stop-signal reaction time (SSRT) task before and after a 0.8g/kg dose of alcohol and, on a separate day, before and after a placebo. Blocks in which participants were required to ignore the signal to stop or make an additional ‘dual' response were included to obtain measures of proactive inhibition as well as updating of attention and action. ResultsAlcohol increased manual but not saccadic SSRT. Proactive inhibition was weakly reduced by alcohol, but increases in the reaction times used to baseline this contrast prevent clear conclusions regarding response caution. Finally, alcohol also increased secondary dual response times of the dual task uniformly as a function of the delay between tasks, indicating an effect of alcohol on action-updating or execution. ConclusionsThe modality-specific effects of alcohol favour the theory that response inhibition systems are embedded within response modalities, rather than there existing a general inhibition system. Concerning alcohol, saccadic control appears relatively more immune to disruption than manual control, even though alcohol affects saccadic latency and velocity. Within the manual domain, alcohol affects multiple types of action updating, not just inhibition.

Superior colliculus coordinates pupillary and saccadic responses

Superior colliculus coordinates pupillary and saccadic responses

Oculomotor assessment of diurnal arousal variations

Saccadic and pupillary responses are reliable indices of arousal decrement (e.g. fatigue), that might be exploited to improve work schedule guidelines. In this study, we tested the sensitivity of a short 30-s oculomotor test to detect diurnal arousal variations. Twelve participants (5 females, 7 males, 37.7+-11.9 years) volunteered to be assessed every hour (66+-20 min) for three consecutive working days, during their regular office-hours. We used a fully automated testing system, the FIT 2000 Fitness Impairment Tester (Pulse Medical Instruments Inc., Rockville, MD, USA), to measure and record saccadic peak velocity, pupil diameter, and latency and amplitude of the pupillary light reflex. In addition, we collected subjective levels of arousal using the Stanford Sleepiness Scale, and body core temperature. We analyzed the data using a linear mixed model approach for longitudinal data. Both saccadic velocity and subjective alertness decreased over the course of a day, while body core temperature increased (all p-values.05). The data also weakly suggested an increase of the pupil diameter (p 07). The findings support the use of oculomotor indices in the assessment of arousal and fatigue in applied settings.

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.

Multisensory integration in orienting behavior: Pupil size, microsaccades, and saccades

Signals from different sensory modalities are integrated in the brain to optimize behavior. Although multisensory integration has been demonstrated in saccadic eye movements, its influence on other orienting responses, including pupil size and microsaccades, is still poorly understood. We examined human gaze orienting responses following presentation of visual, auditory, or combined audiovisual stimuli. Transient pupil dilation and microsaccade inhibition were evoked shortly after the appearance of a salient stimulus. Audiovisual stimuli evoked larger pupil dilation, greater microsaccade inhibition, and faster saccade reaction times compared to unimodal conditions. Trials with faster saccadic reaction times were accompanied with greater pupil dilation responses. Similar modulation of pre-stimulus pupil-size-change rate was observed between stimulus-evoked saccadic and pupillary responses. Thus, multisensory integration impacts multiple components of orienting, with coordination between saccade and pupil responses, implicating the superior colliculus in coordinating these responses because of its central role in both orienting behavior and multisensory integration.

Social Saliency of the Cue Slows Attention Shifts.

Eye gaze is a powerful cue that indicates where another person’s attention is directed in the environment. Seeing another person’s eye gaze shift spontaneously and reflexively elicits a shift of one’s own attention to the same region in space. Here, we investigated whether reallocation of attention in the direction of eye gaze is modulated by personal familiarity with faces. On the one hand, the eye gaze of a close friend should be more effective in redirecting our attention as compared to the eye gaze of a stranger. On the other hand, the social relevance of a familiar face might itself hold attention and, thereby, slow lateral shifts of attention. To distinguish between these possibilities, we measured the efficacy of the eye gaze of personally familiar and unfamiliar faces as directional attention cues using adapted versions of the Posner paradigm with saccadic and manual responses. We found that attention shifts were slower when elicited by a perceived change in the eye gaze of a familiar individual as compared to attention shifts elicited by unfamiliar faces at short latencies (100 ms). We also measured simple detection of change in direction of gaze in personally familiar and unfamiliar faces to test whether slower attention shifts were due to slower detection. Participants detected changes in eye gaze faster for familiar faces than for unfamiliar faces. Our results suggest that personally familiar faces briefly hold attention due to their social relevance, thereby slowing shifts of attention, even though the direction of eye movements are detected faster in familiar faces.

Visually-guided auditory adaptation and reference frame of the ventriloquism after effect

Ventriloquism aftereffect (VA) is observed as a shift in the perceived locations of auditory stimuli, induced by repeated presentation of audiovisual signals with incongruent locations of auditory and visual components. Since the two modalities use a different reference frame (RF), audition is head-centered (HC) while vision is eye-centered (EC), the representations have to be aligned. A previous study examining RF of VA found inconsistent results: the RF was a mixture of HC and EC for VA induced in the center of the audiovisual field, while it was predominantly HC for VA induced in the periphery [Lin et al., JASA 121, 3095, 2007]. In addition, the study found an adaptation in the auditory space representation even for congruent AV stimuli in the periphery. Here, a computational model examines the origins of these effects. The model assumes that multiple stages of processing interact: (1) the stage of auditory spatial representation (HC), (2) the stage of saccadic eye responses (EC), and (3) some stage at which the representation is mixed (HC + EC). Observed results are most consistent with a suggestion that the neural representation underlying spatial auditory plasticity incorporates both HC and EC auditory information, possibly at different processing stages. [Work supported by VEGA-1/1011/16.]

Dizziness - Runner

HISTORY: A 36 year old previously healthy male presented to the medical tent via wheelchair with acute onset of dizziness and nausea after finishing a marathon. He had met his goal of finishing just under 3 hours. He alternated water and sports drinks for fluid replacement. He described the dizziness as a spinning sensation that began shortly after crossing the finish line associated with emesis. This persisted while lying still with his eyes closed. Symptoms were exacerbated by tilting his head or attempting to look up. No lightheadedness, chest pain, shortness of breath, hearing changes, numbness or altered mental status. No history of vertigo episodes, recent illness or head trauma. In the medical tent, he vomited 3 times. He was laid supine with his legs elevated. Over 45 minutes, he had 5 cups of oral electrolyte replacement, 3 cups of water and a banana without improvement. He was eventually able to walk one lap around the medical tent while keeping his gaze focused downwards. PHYSICAL EXAMINATION: T 0 min: BP 120/58, HR 94, RR 19, O2 94% T 45 min: Supine BP 116/64, HR 63 Standing BP 105/60, HR 72 Rectal temp 97.9F He was mildly ill-appearing with clear mental status, alert and oriented x 4. Cranial nerves II-XII were intact and he demonstrated 5/5 strength in b/l upper and lower extremities. Extraocular movements and smooth pursuit were normal. No signs of spontaneous nystagmus. Nystagmus was observed with change in posture from sitting to supine to side lie. Head impulse testing was positive for compensatory saccade response. Dix-Hallpike maneuver to the right was positive for nystagmus and reproduction of symptoms. DIFFERENTIAL DIAGNOSIS: 1. Exercise associated postural hypotension 2. Exertional Heat Stroke 3. Exercise Associated Hyponatremia 4. Vestibular system dysfunction 5. Central nervous system lesion TESTS AND RESULTS: N/A FINAL/WORKING DIAGNOSIS: Benign paroxysmal positional vertigo (BPPV) TREATMENT AND OUTCOMES: 1. The Epley maneuver was performed, inducing one episode of emesis followed by gradual improvement of symptoms over the following 10 minutes. 2. Instructed to avoid rapid or frequent head movements for the next few days. 3. Gradual return to running after complete resolution of symptoms. 4. Follow up with primary care for any worsening of symptoms.

Speeded saccadic and manual visuo-motor decisions: Distinct processes but same principles

Action decisions are considered an emergent property of competitive response activations. As such, decision mechanisms are embedded in, and therefore may differ between, different response modalities. Despite this, the saccadic eye movement system is often promoted as a model for all decisions, especially in the fields of electrophysiology and modelling. Other research traditions predominantly use manual button presses, which have different response distribution profiles and are initiated by different brain areas. Here we tested whether core concepts of action selection models (decision and non-decision times, integration of automatic and selective inputs to threshold, interference across response options, noise, etc.) generalise from saccadic to manual domains. Using two diagnostic phenomena, the remote distractor effect (RDE) and ‘saccadic inhibition', we find that manual responses are also sensitive to the interference of visual distractors but to a lesser extent than saccades and during a shorter time window. A biologically-inspired model (DINASAUR, based on non-linear input dynamics) can account for both saccadic and manual response distributions and accuracy by simply adjusting the balance and relative timings of transient and sustained inputs, and increasing the mean and variance of non-decisional delays for manual responses. This is consistent with known neurophysiological and anatomical differences between saccadic and manual networks. Thus core decision principles appear to generalise across effectors, consistent with previous work, but we also conclude that key quantitative differences underlie apparent qualitative differences in the literature, such as effects being robustly reported in one modality and unreliable in another.

Stimulus-response incompatibility eliminates inhibitory cueing effects with saccadic but not manual responses.

There are thought to be two forms of inhibition of return (IOR) depending on whether the oculomotor system is activated or suppressed. When saccades are allowed, output-based IOR is generated, whereas input-based IOR arises when saccades are prohibited. In a series of 4 experiments, we mixed or blocked compatible and incompatible trials with saccadic or manual responses to investigate whether cueing effects would follow the same pattern as those observed with more traditional peripheral onsets and central arrows. In all experiments, an uninformative cue was displayed, followed by a cue-back stimulus that was either red or green, indicating whether a compatible or incompatible response was required. The results showed that IOR was indeed observed for compatible responses in all tasks, whereas IOR was eliminated for incompatible trials-but only with saccadic responses. These findings indicate that the dissociation between input- and output-based forms of IOR depends on more than just oculomotor activation, providing further support for the existence of an inhibitory cueing effect that is distinct to the manual response modality.

Early visual processing allows for selective behavior, shifts of attention, and conscious visual experience in spite of masking.

Object-substitution masking (OSM) occurs when a briefly displayed target in a search array is surrounded by a mask, which remains onscreen after the target has disappeared. It has been suggested that OSM results from a specific interference with reentrant visual processing, while the initial feedforward processing is left intact. Here, we tested the prediction that the fastest saccadic responses towards a masked target, supposedly triggered before the onset of reentrant processing, are not impaired by OSM. Indeed, saccades faster than 350ms "escaped" the influence of the mask. Notably, participants' judgements of subjective awareness indicated that stimulus processing during this early stage is not entirely devoid of conscious awareness. Furthermore, the N2pc event-related potential component indicated shifts of spatial attention towards the masked targets on trials with correct fast saccades, suggesting that both target detection and spatial attention can be based on the computations accomplished during the initial feedforward sweep.

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.

Influence of simple action on subsequent manual and ocular responses.

Recent investigations into how action affects perception have revealed an interesting "action effect"-that is, simply acting upon an object enhances its processing in subsequent tasks. The previous studies, however, relied only on manual responses, allowing an alternative stimulus-response binding account of the effect. The current study examined whether the action effect occurs in the presence of changes in response modalities. In Experiment 1, participants completed a modified action effect paradigm, in which they first produced an arbitrary manual response to a shape and then performed a visual search task in which the previous shape was either a valid or invalid cue-responding with a manual or saccadic response. In line with previous studies, the visual search was faster when the shape was a valid cue but only if the shape had been acted upon. Critically, this action effect emerged similarly in both the manual and ocular response conditions. This cross-modality action effect was successfully replicated in Experiment 2, and analysis of eye movement trajectories further revealed similar action effect patterns on direction and numerosity. These results rule out the stimulus-response binding account of the action effect and suggest that it indeed occurs at an attentional level.

Influence of Coactors on Saccadic and Manual Responses.

Two experiments were conducted to investigate the effects of coaction on saccadic and manual responses. Participants performed the experiments either in a solitary condition or in a group of coactors who performed the same tasks at the same time. In Experiment 1, participants completed a pro- and antisaccade task where they were required to make saccades towards (prosaccades) or away (antisaccades) from a peripheral visual stimulus. In Experiment 2, participants performed a visual discrimination task that required both making a saccade towards a peripheral stimulus and making a manual response in reaction to the stimulus’s orientation. The results showed that performance of stimulus-driven responses was independent of the social context, while volitionally controlled responses were delayed by the presence of coactors. These findings are in line with studies assessing the effect of attentional load on saccadic control during dual-task paradigms. In particular, antisaccades – but not prosaccades – were influenced by the type of social context. Additionally, the number of coactors present in the group had a moderating effect on both saccadic and manual responses. The results support an attentional view of social influences.

Where Does Attention Go When Facilitation is Absent?

Attending a location in space facilitates responses to targets at that location when the time between cue and target is short. Certain types of exogenous cues – such as sudden peripheral onsets – have been described as reflexive and automatic. Recent studies however, have been showing many cases where exogenous cues are less automatic than previously believed and do not always result in facilitation. Given a lack of the behavioural facilitation, we propose to test whether this also suggests a lack of underlying attention to that location. We test exogenous cueing with saccadic responses at a range of cue-target onset asynchronies (CTOAs), but also alternate measures linked to the allocation of attention such as saccadic curvature, microsaccades and pupil size. As expected, we find no early facilitation at short CTOAs, and likewise no impact of the cue on microsaccade direction or pupil size. We do observe a small dip in the frequency of microsaccades after the cue as well as a tendency for saccadic curvature away from the cued location at short CTOAs. We interpret these results as evidence of reduced attention at the cued location that is removed or inhibited too quickly to be measured as facilitation of saccadic responses.

The SNARC effect in two dimensions: Evidence for a frontoparallel mental number plane

The existence of an association between numbers and space is known for a long time. The most prominent demonstration of this relationship is the spatial numerical association of response codes (SNARC) effect, describing the fact that participants’ reaction times are shorter with the left hand for small numbers and with the right hand for large numbers, when being asked to judge the parity of a number (Dehaene et al., J. Exp. Psychol., 122, 371–396, 1993). The SNARC effect is commonly seen as support for the concept of a mental number line, i.e. a mentally conceived line where small numbers are represented more on the left and large numbers are represented more on the right. The SNARC effect has been demonstrated for all three cardinal axes and recently a transverse SNARC plane has been reported (Chen et al., Exp. Brain Res., 233(5), 1519–1528, 2015). Here, by employing saccadic responses induced by auditory or visual stimuli, we measured the SNARC effect within the same subjects along the horizontal (HM) and vertical meridian (VM) and along the two interspersed diagonals. We found a SNARC effect along HM and VM, which allowed predicting the occurrence of a SNARC effect along the two diagonals by means of linear regression. Importantly, significant differences in SNARC strength were found between modalities. Our results suggest the existence of a frontoparallel mental number plane, where small numbers are represented left and down, while large numbers are represented right and up. Together with the recently described transverse mental number plane our findings provide further evidence for the existence of a three-dimensional mental number space.

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.

Pseudoneglect in line bisection judgement is associated with a modulation of right hemispheric spatial attention dominance in right-handers

The objective of this study was to validate a line bisection judgement (LBJ) task for use in investigating the lateralized cerebral bases of spatial attention in a sample of 51 right-handed healthy participants. Using functional magnetic resonance imaging (fMRI), the participants performed a LBJ task that was compared to a visuomotor control task during which the participants made similar saccadic and motoric responses. Cerebral lateralization was determined using a voxel-based functional asymmetry analysis and a hemispheric functional lateralization index (HFLI) computed from fMRI contrast images. Behavioural attentional deviation biases were assessed during the LBJ task and a “paper and pencil” symbol cancellation task (SCT). Individual visuospatial skills were also evaluated. The results showed that both the LBJ and SCT tasks elicited leftward spatial biases in healthy subjects, although the biases were not correlated, which indicated their independence. Neuroimaging results showed that the LBJ task elicited a right hemispheric lateralization, with rightward asymmetries found in a large posterior occipito-parietal area, the posterior calcarine sulcus (V1p) and the temporo-occipital junction (TOJ) and in the inferior frontal gyrus, the anterior insula and the superior medial frontal gyrus. The comparison of the LBJ asymmetry map to the lesion map of neglect patients who suffer line bisection deviation demonstrated maximum overlap in a network that included the middle occipital gyrus (MOG), the TOJ, the anterior insula and the inferior frontal region, likely subtending spatial LBJ bias. Finally, the LBJ task-related cerebral lateralization was specifically correlated with the LBJ spatial bias but not with the SCT bias or with the visuospatial skills of the participants. Taken together, these results demonstrated that the LBJ task is adequate for investigating spatial lateralization in healthy subjects and is suitable for determining the factors underlying the variability of spatial cerebral lateralization.

When is inhibition of return input- or output-based? It depends on how you look at it.

Two important diagnostics have been used to infer whether the effect of inhibition of return, when preceded by a saccade, is primarily upon input (i.e., attentional/perceptual level) or output (i.e., response/decision level) processes. Data from antisaccade paradigms involving luminance targets in peripheral vision suggest input effects whereas data from spatially compatible manual responses to centrally presented arrow targets suggest output effects. Here, we combine these diagnostics to resolve the discrepancy. In separate conditions participants made a pro- or antisaccade to a peripheral stimulus. Upon returning gaze to the original fixation, left and right manual responses were made to left- and right-pointing arrows at fixation, respectively. The primary objective of the prosaccade condition was to determine whether an eye movement toward a visual stimulus that was not associated with a manual localization response would bias spatially compatible manual responses against the prior saccade vector. Manual responses were slowest in the direction of the prior saccade, consistent with an output-based attribution (e.g., Posner, Rafal, Choate, & Vaughan, 1985). The primary objective of the antisaccade condition was to determine whether an eye movement away from a visual stimulus would also bias subsequent manual responses. No apparent response bias was detected, consistent with an input-based attribution (e.g., Fecteau, Au, Armstrong, & Munoz, 2004). Collectively, the findings indicate that there are 2, dissociable forms of inhibition depending on saccadic response demands. Converging evidence from other paradigms is discussed. (PsycINFO Database Record

Cognitive Control of Saccadic Eye Movements in Children with Developmental Coordination Disorder.

The ability to use advance information to prepare and execute a movement requires cognitive control of behaviour (e.g., anticipation and inhibition). Our aim was to explore the integrity of saccadic eye movement control in developmental coordination disorder (DCD) and typically developing (TD) children (8–12 years) and assess how these children plan and inhibit saccadic responses, the principal mechanisms within visual attention control. Eye movements and touch responses were measured (separately and concurrently) in Cued and Non-Cued conditions. We found that children with DCD had similar saccade kinematics to the TD group during saccade initiation. Advance information decreased hand movement duration in both groups during Cued trials, but decrements in accuracy were significantly worse in the DCD group. In addition, children with DCD exhibited greater inhibitory errors and inaccurate fixation during the Cued trials. Thus, children with DCD were reasonably proficient in executing saccades during reflexive (Non-Cued) conditions, but showed deficits in more complex control processes involving prediction and inhibition. These findings have implications for our understanding of motor control in children with DCD.