Locus of the effect of temporal preparation: evidence from the lateralized readiness potential

The time course of temporal preparation in an applied setting: a study of gaming behavior

We examined the time course of temporal preparation in the practice of computer gaming. Participants held an infrared rifle to shoot animated figures ("terrorists") that appeared from an elevator that opened briefly after the sound of a bell. The sound was either loud or soft and the interval between the sound and the opening of the elevator varied between 100 and 600ms. We found that shooting latency decreased exponentially as a function of interval, reflecting growing temporal preparation towards an optimum. When the sound was soft, this function was shifted to the right as compared to when the sound was loud. These findings are consistent with a model assuming that preparation starts upon the detection of a warning (i.e., later for the soft than for the loud sound) and continues until the detection of a target (i.e., longer as the interval increases). These results signify a successful application of a theoretical model in an applied setting.

Responses to loud auditory stimuli indicate that movement-related activation builds up in anticipation of action

Previous research using a loud acoustic stimulus (LAS) to investigate motor preparation in reaction time (RT) tasks indicates that responses can be triggered well in advance of the presentation of an imperative stimulus (IS). This is intriguing given that high levels of response preparation cannot be maintained for long periods (≈ 200 ms). In the experiments reported here we sought to assess whether response-related activation increases gradually over time in simple RT tasks. In experiment 1, a LAS was presented at different times just prior to the presentation of the IS to probe the level of activation for the motor response. In experiment 2, the same LAS was presented at different times after the presentation of the IS. The results provide evidence that response-related activation does increase gradually in anticipation of the IS, but it remains stable for a short time after this event. The data display a pattern consistent with the response being triggering by the LAS, rather than a reaction to the IS.

Dissociable spatial and temporal effects of inhibition of return

Inhibition of return (IOR) refers to the relative suppression of processing at locations that have recently been attended. It is frequently explored using a spatial cueing paradigm and is characterized by slower responses to cued than to uncued locations. The current study investigates the impact of IOR on overt visual orienting involving saccadic eye movements. Using a spatial cueing paradigm, our experiments have demonstrated that at a cue-target onset asynchrony (CTOA) of 400 ms saccades to the vicinity of cued locations are not only delayed (temporal cost) but also biased away (spatial effect). Both of these effects are basically no longer present at a CTOA of 1200 ms. At a shorter 200 ms CTOA, the spatial effect becomes stronger while the temporal cost is replaced by a temporal benefit. These findings suggest that IOR has a spatial effect that is dissociable from its temporal effect. Simulations using a neural field model of the superior colliculus (SC) revealed that a theory relying on short-term depression (STD) of the input pathway can explain most, but not all, temporal and spatial effects of IOR.

Implicit temporal expectation attenuates auditory attentional blink

Attentional blink (AB) describes a phenomenon whereby correct identification of a first target impairs the processing of a second target (i.e., probe) nearby in time. Evidence suggests that explicit attention orienting in the time domain can attenuate the AB. Here, we used scalp-recorded, event-related potentials to examine whether auditory AB is also sensitive to implicit temporal attention orienting. Expectations were set up implicitly by varying the probability (i.e., 80% or 20%) that the probe would occur at the +2 or +8 position following target presentation. Participants showed a significant AB, which was reduced with the increased probe probability at the +2 position. The probe probability effect was paralleled by an increase in P3b amplitude elicited by the probe. The results suggest that implicit temporal attention orienting can facilitate short-term consolidation of the probe and attenuate auditory AB.

Arousal modulates temporal preparation under increased time uncertainty: Evidence from higher-order sequential foreperiod effects

When the foreperiod (FP) is unpredictably varied in reaction-time tasks, responses are slow at short but fast at long FPs (variable-FP effect), and further vary asymmetrically as a function of FP sequence (sequential FP effect). A trace-conditioning model attributes these phenomena to time-related associative learning, while a dual-process model views them as resulting from combined effects of strategic preparation and trial-to-trial changes in arousal. Sometimes, responses are slower in long-long than in short-long FP sequences. This pattern is not predicted from the trace-conditioning account, since FP repetitions should speed up, rather than slow down, responses (due to reinforcement). The effect, however, might indicate the contribution of arousal, which according to the dual-process model, is heightened after a short FP(n-1) but decreased after a long FP(n-1). In five experiments, we examined higher-order sequential FP effects on performance, with a particular emphasis on analyzing performance in long-FP(n) trials as a function of FP length in the two preceding trials, varying temporal FP context (i.e. average FP length) and reaction mode (simple vs. choice reaction). Slower responses in long-long-long (compared with short-short-long) FP sequences were not found within a short-FP context (Exps. 1 & 2) but clearly emerged within a long-FP context (Exps. 3-5). This pattern supports the notion that transient arousal changes contribute to sequential performance effects in variable-FP tasks, in line with the dual-process account of temporal preparation.

Decomposition of warning effects in Parkinson's disease

Neutral warning signals speed voluntary reactions by reducing temporal uncertainty and by triggering a brief burst of arousal. We attempted to isolate the phasic arousal mechanism in people with Parkinson's disease (PD) using a clock display to minimize temporal uncertainty. In this condition, the speeding of responses in a color-discrimination task by an accessory stimulus was the fully equivalent to the effect in age-matched control subjects. This indicates preserved phasic arousal in PD. Temporal preparation based on warning cues also appeared to be normal. By contrast, in a condition with high temporal uncertainty, the accessory stimulus (an air puff to the foot) impaired accuracy for the patients but not the neurologically normal subjects. The data are consistent with the view that PD disrupts internal but not external control of alertness.

The time course of attention: selection is transient

The time course of attention has often been investigated using a spatial cuing task. However, attention likely consists of multiple components, such as selectivity (resolving competition) and orienting (spatial shifting). Here we sought to investigate the time course of the selective aspect of attention, using a cuing task that did not require spatial shifting. In several experiments, targets were always presented at central fixation, and were preceded by a cue at different cue-target intervals. The selection component of attention was investigated by manipulating the presence of distractors. Regardless of the presence of distractors, an initial rapid performance enhancement was found that reached its maximum at around 100 ms post cue onset. Subsequently, when the target was the only item in the display, performance was sustained, but when the target was accompanied by irrelevant distractor items, performance declined. This temporal pattern matches closely with the transient attention response that has been found in spatial cuing studies, and shows that the selectivity aspect of attention is transient.

Dissociative patterns of foreperiod effects in temporal discrimination and reaction time tasks

This study examined whether the process of temporal preparation for a target stimulus is the same regardless of the task required by the target stimulus. To this end, the same variable-foreperiod design was used in a temporal discrimination task (Experiment 1) and a reaction time task (Experiment 2). In Experiment 1, both temporal sensitivity and perceived duration increased as a function of foreperiod, whereas in Experiment 2, foreperiod did not influence reaction time. Furthermore, both temporal sensitivity and perceived duration revealed an asymmetric sequential effect of foreperiod, but the pattern of this effect was opposite to the pattern observed in the reaction time task. Together these dissociative patterns of foreperiod effects suggest that the mechanism of temporal preparation depends on the task required by the target stimulus.

Does temporal preparation increase the rate of sensory information accumulation?

Recent studies showed that temporal preparation, i.e., the ability to prepare for an upcoming stimulus, improves perceptual processing. The mechanisms underlying this benefit are still controversial. Based upon the theoretical framework of accumulation models, it has been proposed that the accumulation of sensory stimulus information begins earlier when participants are temporally prepared than when they are unprepared. Alternatively, however, temporal preparation might also affect the accumulation rate of sensory information. In the present study, we examined these possibilities. Specifically, in three experiments, we manipulated participants' decision criterion. This manipulation should interact with any experimental manipulation affecting the rate of information processing, but produce additive effects with any manipulation affecting the onset of information accumulation rather than its rate. We obtained additive effects on RT, irrespective of whether the decision criterion was manipulated by increasing catch trial proportion or nogo trial proportion. These results suggest that temporal preparation improves perceptual processing by operating on the onset of sensory information accumulation rather than the rate of sensory information accumulation.

Implicit, predictive timing draws upon the same scalar representation of time as explicit timing

It is not yet known whether the scalar properties of explicit timing are also displayed by more implicit, predictive forms of timing. We investigated whether performance in both explicit and predictive timing tasks conformed to the two psychophysical properties of scalar timing: the Psychophysical law and Weber's law. Our explicit temporal generalization task required overt estimation of the duration of an empty interval bounded by visual markers, whereas our temporal expectancy task presented visual stimuli at temporally predictable intervals, which facilitated motor preparation thus speeding target detection. The Psychophysical Law and Weber's Law were modeled, respectively, by (1) the functional dependence between mean subjective time and real time (2) the linearity of the relationship between timing variability and duration. Results showed that performance for predictive, as well as explicit, timing conformed to both psychophysical properties of interval timing. Both tasks showed the same linear relationship between subjective and real time, demonstrating that the same representational mechanism is engaged whether it is transferred into an overt estimate of duration or used to optimise sensorimotor behavior. Moreover, variability increased with increasing duration during both tasks, consistent with a scalar representation of time in both predictive and explicit timing. However, timing variability was greater during predictive timing, at least for durations greater than 200 msec, and ascribable to temporal, rather than non-temporal, mechanisms engaged by the task. These results suggest that although the same internal representation of time was used in both tasks, its external manifestation varied as a function of temporal task goals.

Corticospinal excitability during preparation for an anticipatory action is modulated by the availability of visual information

To intercept rapidly moving objects, people must predict the right time to initiate their actions. The timing of movement initiation in interceptions is thought to be determined when a perceptual variable specifying time to contact reaches a criterion value. If a response needs to be aborted, the performer must make a decision before this moment. It has been recently shown that the minimal time to suppress an anticipatory action takes longer during motion extrapolation than during continuous visual information. In experiment 1, we sought to determine whether or not the availability of visual information would 1) affect the latency to inhibit an anticipatory action, and 2) modulate the level of excitability in the motor cortex (M1). The behavioral results showed that the absence of visual information prolonged the latency to stop the movement as previously reported. The neurophysiological data indicated that corticospinal excitability levels were affected by the availability of visual information. In experiment 2, we sought to verify whether corticospinal excitability levels would also differ between the two visual conditions when the task did not involve response suppression. The results of experiment 2 indicated that excitability levels did not differ between visual conditions. Overall, our findings indicated that the buildup of motor activation can also play a role in determining different latencies to inhibit an anticipatory action. They also suggest that the buildup of motor activation in the corticospinal pathways can be strategically modulated to the requirements of the task during continuous visual information.

Temporal Preparation Decreases Perceptual Latency: Evidence from a Clock Paradigm

A clock paradigm was employed to assess whether temporal preparation decreases the time to detect the onset of a stimulus—that is, perceptual latency. In four experiments participants watched a revolving clock hand while listening to soft or loud target tones under high or low temporal preparation. At the end of each trial, participants reported the clock hand position at the onset of the target tone. The deviation of the reported clock hand position from the actual position indexed perceptual latency. As expected, perceptual latency decreased with target tone intensity. Most importantly, however, greater temporal preparation decreased perceptual latency in all four experiments, especially for soft tones, which supports rather directly the idea that temporal preparation diminishes the duration of perceptual processing.

Temporal Cueing of Target-Identity and Target-Location

In four experiments either a short or a long foreperiod preceded the presentation of one of two targets, presented either in the center of the screen (Experiment 1) or at one of two locations (Experiments 2–4). Participants were to identify the presented target by pressing a left or a right button as quickly as possible. In Experiment 1, each of the two targets and in Experiment 2, each of the two locations appeared frequently after one and infrequently after the other foreperiod. Experiments 3 and 4 explored the combined effects of disparate frequency distributions of targets and locations to the two foreperiods. Reaction times and error rates revealed faster processing and/or less errors for respectively those targets and locations which were frequent after the current foreperiod. The data suggest that besides location-specific target expectancies ( Hoffmann & Kunde, 1999 ) also time-specific expectancies for those targets and target-locations are formed which are likely at the respective point in time.

The Effects of Accessory Stimuli on Information Processing: Evidence from Electrophysiology and a Diffusion Model Analysis

People typically respond faster to a stimulus when it is accompanied by a task-irrelevant accessory stimulus presented in another perceptual modality. However, the mechanisms responsible for this accessory-stimulus effect are still poorly understood. We examined the effects of auditory accessory stimulation on the processing of visual stimuli using scalp electrophysiology (Experiment 1) and a diffusion model analysis (Experiment 2). In accordance with previous studies, lateralized readiness potentials indicated that accessory stimuli do not speed motor execution. Surface Laplacians over the motor cortex, however, revealed a bihemispheric increase in motor activation—an effect predicted by nonspecific arousal models. The diffusion model analysis suggested that accessory stimuli do not affect parameters of the decision process, but expedite only the nondecision component of information processing. Consequently, we conclude that accessory stimuli facilitate stimulus encoding. The visual P1 and N1 amplitudes on accessory-stimulus trials were modulated in a way that is consistent with multisensory energy integration, a possible mechanism for this facilitation.

Time and decision making in humans

Decision making requires evaluating alternatives that differ on a number of attributes. During this evaluation process, selection of options depends on the duration of the options, the duration of the expected delay for realizing the options, and the time available to reach a decision. This article reviews the relationship between time and decision making in humans with respect to this evaluation process. Moreover, the role of psychological time, as compared with physical time, is accentuated. Five topics have been selected that illustrate how time and mental representations of time affect decision making. These are (1) the duration of options, (2) temporal decision making, (3) the time between having made a decision and experiencing the consequences of that decision, (4) the temporal perspective of decision makers, and (5) the duration of the decision process. The discussion of each topic is supplemented by suggestions for further research. It is shown that psychological time is often neglected in human decision making but seems to play an important role in the making of choices.

Lengthening fixed preparatory foreperiod durations within a digit magnitude classification task serves mainly to shift distributions of response times upwards

In this study, the effect of lengthening foreperiod duration (i.e. the time between the presentation of a warning signal and a subsequent target stimulus) on choice RTs is examined. The foreperiod durations used were either 2 or 8s and were fixed within pure blocks of trials. The task was to determine whether a single-digit target stimulus was either smaller or larger than 5 and responses were provided manually. An additive relation between foreperiod duration length and numerical distance from 5 was present in the mean RTs. Subsequent ex-Gaussian analyses of the shapes of the RT distributions indicated that they become shifted upwards as the foreperiod increased with relatively smaller increases in the sizes of their tails. It is argued mainly that the latter finding is incompatible with the strategic time estimation view of the fixed foreperiod duration effect.

Functional Locus of Intensity Effects in Choice Reaction Time Tasks

Long reaction times (RT) paradoxically occur with extremely loud auditory stimuli ( Van der Molen & Keuss, 1979 , 1981 ) or with ultrabright and large visual stimuli ( Jaśkowski & Włodarczyk, 2006 ) when the task requires a response choice. Van der Molen and Keuss (1981 ) hypothesized that this effect results from an arousal-driven elongation of response-selection processes. We tested this hypothesis using visual stimuli and chronopsychophysiological markers. The results showed that the latency of both early (P1 recorded at Oz) and late (P300) evoked potentials decreased monotonically with intensity. In contrast, the latency of stimulus-locked lateralized readiness potentials (LRP) abruptly increased for the most intense stimuli, thus mirroring the reaction time–intensity relationship. Response-locked LRPs revealed no dependency on intensity. These findings suggest that the processes responsible for the van der Molen-Keuss effect influence processing stages that are completed before the onset of LRP. The van der Molen-Keuss effect likely occurs later than those represented by early sensory potentials. This is in keeping with the hypothesis of van der Molen-Keuss.

Sequential effects within a short foreperiod context: evidence for the conditioning account of temporal preparation

Responses to an imperative stimulus (IS) are especially fast when they are preceded by a warning signal (WS). When the interval between WS and IS (the foreperiod, FP) is variable, reaction time (RT) is not only influenced by the current FP but also by the FP of the preceding trial. These sequential effects have recently been proposed to originate from a trace conditioning process, in which the individuals learn the temporal WS-IS relationship in a trial-by-trial manner. Research has shown that trace conditioning is maximal when the temporal interval between the conditioned and unconditioned stimulus is between 0.25 and 0.60s. Consequently, one would predict that sequential effects occur especially within short FP contexts. However, this prediction is contradicted by Karlin [Karlin, L. (1959). Reaction time as a function of foreperiod duration and variability. Journal of Experimental Psychology, 58, 185-191] who did not observe the typical sequential effects with short FPs. To investigate temporal preparation for short FPs, three experiments were conducted, examining the sequential FP effect comparably for short and long FP-sets (Experiment 1), assessing the influence of catch trials (Experiment 2) and the case of a very dense FP-range (Experiment 3) on sequential FP effects. The results provide strong evidence for sequential effects within a short FP context and thus support the trace conditioning account of temporal preparation.

Neural modulation by regularity and passage of time

The current study tested whether multiple rhythms could flexibly induce temporal expectations (temporal orienting) and whether these expectations interact with temporal expectations associated with the passage of time (foreperiod effects). A visual stimulus that moved following a regular rhythm was temporarily occluded for a variable duration (occlusion foreperiod). The task involved making a speeded perceptual discrimination about the target stimulus that reappeared after the occlusion. Temporal-orienting effects were measured by comparing performance and event-related potentials on conditions in which the timing for target reappearance was predictable (valid) versus unpredictable (invalid) according to the rhythm. Foreperiod effects were measured by comparing conditions in which the target was occluded for progressively longer periods of time (short, medium, and long foreperiods) and hence were increasingly predictable. The results showed strong interactions between temporal orienting and foreperiod effects during the facilitation of behavior and neural activity associated with late perceptual and response selection processes. Temporal orienting attenuated the N2 amplitude and decreased the P3 latency only at short foreperiods. Temporal preparation related to foreperiod effects abolished temporal orienting effects at medium and long foreperiods. Likewise, foreperiod effects attenuated the N1 and N2 amplitudes and decreased the P3 latency only in the invalid orienting condition as preparation related to temporal orienting abolished foreperiod effects in the valid condition. This high degree of neural overlap between the effects of temporal orienting driven by rhythms and foreperiod effects associated with the passage of time suggests the involvement of a common mechanism for temporal preparation.

Grip force control during gait initiation with a hand-held object

When walking with a hand-held object, grip force is coupled in an anticipatory manner to changes in inertial force resulting from the accelerations and decelerations of gait. However, it is not known how grip and inertial forces are organized at the onset of gait, and if the two forces are coupled in the early phases of gait initiation. Moreover, initiating walking with an object involves the coordination of anticipatory postural (e.g., ground reaction force changes) and grasping adjustments. The aim of this study was to investigate the relationship of ground reaction, grip, and inertial force onsets, and the subsequent development of the coupling of grip and inertial forces during gait initiation with a hand-held object. Ten subjects performed gait initiation with a hand-held object following predictable and unpredictable start signals. We found that ground reaction and grip force onsets were closely linked in time regardless of the predictability of the start signal. In the early period of gait initiation, the grip force started to increase prior to inertial force changes. While the strength of the coupling of grip and inertial forces was moderate in this early phase, it increased to values observed during steady-state gait after the swing foot left the ground. The early grip force increase and the coupling of grip and inertial forces represent an anticipatory control process. This process establishes an appropriate grip-inertial force ratio to ensure object stability during acceleration after foot-off and maintains this increased ratio thereafter. The results suggest that grasping and whole body movements are governed by a common internal representation.

Effects of response sequence length on motor programming: a chronometric analysis

The present experiment studied choice response context effects on the programming of response sequences using behavioural and electrophysiological methods. Participants were asked to produce responses differing in sequence length (1-key vs. 3-key responses) with either their left or right hand in a choice reaction time (RT) task. The choice response context was manipulated by a blocked or mixed execution of 1-key and 3-key responses. A sequence length effect on RT was observed in the blocked but not in the mixed condition. The time course of the lateralized readiness potential indicates a motoric locus of the sequence length effect, suggesting that the response hand is activated before the entire motor program is established.

Maintaining Grip: Anticipatory and Reactive EEG Responses to Load Perturbations

Previous behavioral work has shown the existence of both anticipatory and reactive grip force responses to predictable load perturbations, but how the brain implements anticipatory control remains unclear. Here we recorded electroencephalographs while participants were subjected to predictable and unpredictable external load perturbations. Participants used precision grip to maintain the position of an object perturbed by load force pulses. The load perturbations were either distributed randomly over an interval 700- to 4,300-ms (unpredictable condition) or they were periodic with interval 2,000 ms (predictable condition). Preparation for the predictable load perturbation was manifested in slow preparatory brain potentials and in electromyographic and force signals recorded concurrently. Preparation modulated the long-latency reflex elicited by load perturbations with a higher amplitude reflex response for unpredictable compared with predictable perturbations. Importantly, this modulation was also reflected in the amplitude of sensorimotor cortex potentials just preceding the long-latency reflex. Together, these results support a transcortical pathway for the long-latency reflex and a central modulation of the reflex grip force response.

The hazards of time

Temporal expectations are continuously formed and updated, and interact with expectations about other relevant attributes of events, in order to optimise our interaction with unfolding sensory stimulation. In this paper, we will highlight some evidence revealing the pervasive effects of temporal expectations in modulating perception and action, and reflect on the current state of understanding about their underlying neural systems and mechanisms.

Temporal uncertainty degrades perceptual processing

When participants are required to react to a stimulus, reaction times (RTs) are usually reduced when temporal uncertainty about stimulus occurrence is minimized. Contrary to the common assumption attributing this RT benefit solely to the speeding of motor processes, recent evidence suggests that temporal uncertainty might rather influence premotoric processing levels. We employed a backward-masking procedure to further confine the locus of the temporal uncertainty effect. Participants performed a discrimination task and indicated whether a spatial gap within a square was on the right or the left side. In addition to the shorter RTs, visual discrimination accuracy was improved when temporal uncertainty was low. This result demonstrates that temporal uncertainty influences stimulus processing at a perceptual level.

Localization of temporal preparation effects via trisected reaction time

Previous research using nonchronometric measures in humans and animals has shown that warning signals can influence stages of processing throughout the reaction time (RT) interval. However, latency measures indicate that warning effects on RT are not due to the speeding of motor processes, at least not late ones. To better isolate the chronometric effects of temporal preparation, we used lateralized event-related potentials to divide mean RT into three time segments. Foreperiod duration had only a small, nonsignificant influence on the first and last segments (early visual and late motor processes, respectively). The chronometric effect was mainly restricted to the middle interval, which extended from onset of the N2pc component to onset of the lateralized readiness potential. The results imply that temporal preparation primarily speeds late perception, response selection or early motor processes.

Accessory stimuli modulate effects of nonconscious priming

In a recent study, it was shown that subliminal priming (SP) effects are affected by the temporal predictability of a stimulus onset. If predictability is not given, SP effects are eliminated (Naccache, Blandin, & Dehaene, 2002). In two experiments, we investigated how different levels of preparation for target processing affect SP effects. For this purpose, an accessory tone stimulus was presented at different times prior to a subliminal priming task. The results demonstrate a clear modulation of the SP effects at different foreperiod intervals. Relative to conditions without an accessory stimulus, SP effects were smaller for short foreperiod intervals of the accessory stimulus, and larger for long foreperiod intervals. The results suggest that the presentation of an accessory stimulus facilitates response activation processes because of the participants' enhanced level of preparation for stimulus processing.