Short Cue-target Onset Asynchronies Research Articles

On the putative role of intervening events in exogenous attention.

In exogenous attention, two main behavioural effects are usually observed across time: facilitation at short cue-target onset asynchronies (CTOAs), and Inhibition of Return (IOR) at longer CTOAs. The presentation of an intervening event (IE)-i.e., a cue presented at fixation between the peripheral cue and target period-favours the appearance of IOR. However, although there is a general consensus on this empirical modulation, there is no agreement about the putative role of IEs and/or the mechanism/s underlying their effect. While some authors consider IEs as a "cue-back", automatically reorienting attention to fixation, thus allowing IOR to occur, others have considered IEs as events modulating cue-target integration processes, consequently affecting exogenous cueing. Even in this later case, it is not clear whether IEs modulate cueing by inducing an attentional set (top-down) modulation or by inducing a trial-by-trial (bottom-up) online modulation. To disentangle this issue, in two experiments, we manipulated the proportion of trials in which the IE was presented, thus being able to measure the effect of the presence/absence and proportion of IEs. We observed a gradual influence of the % of IEs over cueing effects, which becomes less positive or more negative as the % of IEs increases. This pattern of findings fits well with the idea that facilitation and IOR depend on cue-target integration processes, and presents critical implications for the open debate about the mechanism/s underlying exogenous spatial cueing effects.

Phasic alertness cues modulate visual processing speed in healthy aging.

Warning signals temporarily increase the rate of visual information in younger participants and thus optimize perception in critical situations. It is unclear whether such important preparatory processes are preserved in healthy aging. We parametrically assessed the effects of auditory alertness cues on visual processing speed and their time course using a whole report paradigm based on the computational Theory of Visual Attention. We replicated prior findings of significant alerting benefits in younger adults. In conditions with short cue-target onset asynchronies, this effect was baseline-dependent. As younger participants with high baseline speed did not show a profit, an inverted U-shaped function of phasic alerting and visual processing speed was implied. Older adults also showed a significant cue-induced benefit. Bayesian analyses indicated that the cueing benefit on visual processing speed was comparably strong across age groups. Our results indicate that in aging individuals, comparable to younger ones, perception is active and increased expectancy of the appearance of a relevant stimulus can increase the rate of visual information uptake.

Sensory adaptation and inhibition of return: dissociating multiple inhibitory cueing effects.

Inhibition of return (IOR) refers to an increase in reaction times to targets that appeared at a previously cued location relative to an uncued location, often investigated using a spatial cueing paradigm. Despite numerous studies that have examined many aspects of IOR, the neurophysiological mechanisms underlying IOR are still in dispute. The objective of the current research is to investigate the plausible mechanisms by manipulating the cue and target types between central and peripheral stimuli in a traditional cue-target paradigm with saccadic responses to targets. In peripheral-cueing conditions, we observed inhibitory cueing effects across all cue-target onset asynchronies (CTOAs) with peripheral targets, but IOR was smaller and arose later with central targets. No inhibition was observed in central-cueing conditions at any CTOAs. Empirical data were simulated using a two-dimensional dynamic neural field model. Our results and simulations support previous work demonstrating that, at short CTOAs, behavioral inhibition is only observed with repeated stimulation-an effect of sensory adaptation. With longer CTOAs, IOR is observed regardless of target type when peripheral cueing is used. Our findings suggest that behaviorally exhibited inhibitory cueing effects can be attributed to multiple mechanisms, including both attenuation of visual stimulation and local inhibition in the superior colliculus.

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.

Returning to "inhibition of return" by dissociating long-term oculomotor IOR from short-term sensory adaptation and other nonoculomotor "inhibitory" cueing effects.

We explored the nature and time course of effects generated by spatially uninformative peripheral cues by measuring these effects with localization responses to peripheral onsets or central arrow targets. In Experiment 1, participants made saccadic eye movements to equiprobable peripheral and central targets. At short cue-target onset asynchronies (CTOAs), responses to cued peripheral stimuli suffered from slowed responding attributable to sensory adaptation while responses to central targets were transiently facilitated, presumably due to cue-elicited oculomotor activation. At the longest CTOA, saccadic responses to central and peripheral targets were indistinguishably delayed, suggesting a common, output/decision effect (inhibition of return; IOR). In Experiment 2, we tested the hypothesis that the generation of this output effect is dependent on the activation state of the oculomotor system by forbidding eye movements and requiring keypress responses to frequent peripheral targets, while probing oculomotor behavior with saccades to infrequent central arrow targets. As predicted, saccades to central arrow targets showed neither the early facilitation nor later inhibitory effects that were robust in Experiment 1. At the long CTOA, manual responses to cued peripheral targets showed the typical delayed responses usually attributed to IOR. We recommend that this late "inhibitory" cueing effect (ICE) be distinguished from IOR because it lacks the cause (oculomotor activation) and effect (response bias) attributed to IOR when it was named by Posner, Rafal, Choate, and Vaughan (1985).

Modeling inhibition of return as short-term depression of early sensory input to the superior colliculus

Inhibition of return (IOR) is an orienting phenomenon characterized by slower behavioral responses to spatially cued, relative to uncued targets, when the cue-target onset asynchronies (CTOAs) are long enough that cue-elicited attentional capture has dispersed. Here, we implement a short-term depression (STD) account of IOR within a neuroscientifically based dynamic neural field model (DNF) of the superior colliculus (SC). In addition to the prototypical findings in the cue-target paradigm (i.e., the biphasic pattern of behavioral enhancement at short CTOAs and behavioral costs at long CTOAs), a variety of findings in the literature are generated with this model, including IOR in averaging saccades and the co-existence of IOR and endogenous orienting at the same location. Many findings that cannot be accommodated by this model could be accounted for by incorporating cortical contributions.

Influences of intra- and crossmodal grouping on visual and tactile Ternus apparent motion

Previous studies of dynamic crossmodal integration have revealed that the direction of apparent motion in a target modality can be influenced by a spatially incongruent motion stream in another, distractor modality. Yet, it remains to be examined whether non-motion intra- and crossmodal perceptual grouping can affect apparent motion in a given target modality. To address this question, we employed Ternus apparent-motion displays, which consist of three horizontal aligned visual (or tactile) stimuli that can alternately be seen as either ‘element motion’ or ‘group motion’. We manipulated intra- and crossmodal grouping by cueing the middle stimulus with different cue-target onset asynchronies (CTOAs). In unimodal conditions, we found Ternus apparent motion to be readily biased towards ‘element motion’ by precues with short or intermediate CTOAs in the visual modality and by precues with short CTOAs in the tactile modality. By contrast, crossmodal precues with short or intermediate CTOAs had no influence on Ternus apparent motion. However, crossmodal synchronous tactile cues led to dominant ‘group motion’ percepts. And for unimodal visual apparent motion, precues with long CTOAs shifted apparent motion towards ‘group motion’ in general. The results suggest that intra- and crossmodal interactions on visual and tactile apparent motion take place in different temporal ranges, but both are subject to attentional modulations at long CTOAs.