Intentional and Unintentional Contributions to Nonspecific Preparation: Electrophysiological Evidence

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.

Distraction by irrelevant sound during foreperiods selectively impairs temporal preparation

When the interval between a warning signal (WS) and an imperative signal (IS), termed the foreperiod (FP), is variable across trials, reaction time (RT) to the IS typically decreases with increasing FP length. Here we examined the auditory filled-FP effect, which refers to a performance decrement after FPs filled with irrelevant auditory stimulation compared to FPs without additional stimulation. According to one account, irrelevant stimulation distracts individuals from processing time and probability information during the FP (distraction-during-FP hypothesis). This should predominantly affect long-FP trials. Alternatively, the filled-FP effect may arise from a failure to shift attention from FP modality to IS modality (attention-to-modality hypothesis). The first hypothesis focuses on preparatory processing, predicting a selective RT increase on long-FP trials, whereas the second hypothesis focuses on target processing, only predicting a global RT increase irrespective of FP length. Across four experiments, a filled-FP (compared to a blank-FP) condition consistently yielded a selective RT increase on long-FP trials, irrespective of FP-IS modality pairing. This pattern of results contradicts the attention-to-modality hypothesis but corroborates the distraction-during-FP hypothesis. More generally, these data have theoretical implications by supporting a multi-process view of temporal preparation under time uncertainty.

The effect of a cross-trial shift of auditory warning signals on the sequential foreperiod effect

When a warning signal (WS) precedes an imperative signal (IS) by a certain amount of time (the foreperiod, FP), responses are speeded. Moreover, this effect is modulated by the FP length in the previous trial. This sequential FP effect has lately been attributed to a trace-conditioning mechanism according to which individuals learn (and re-learn) temporal relationships between the WS and the IS. Recent evidence suggests that sensory WS attributes are critical to trigger time-related response activation. Specifically, when WS modality is shifted in subsequent trials (e.g., from auditory to visual modality), the sequential FP effect becomes attenuated. This study examined whether the sequential FP effect is reduced only by between-modality shifts or whether this attenuation generalizes to cross-trial shifts of WS attributes within modalities. We compared dimensional (low vs. high tone frequency) and qualitative shifts (pure tone vs. noise) of equal-intense auditory WS events. The results of four experiments revealed that shifts of tone frequency did not, whereas shifts of qualitative tone characteristics did attenuate the sequential FP effect. These results support the view that the WS acts as a trigger cue that unintentionally activates responses at previously reinforced critical moments.

Temporal orienting deficit after prefrontal damage

The aim of this study was to explore, for the first time in patients, the neural bases of temporal orienting of attention as well as the interrelations with two other effects of temporal preparation: the foreperiod effect and sequential effects. We administered an experimental task to a group of 14 patients with prefrontal lesion, a group of 15 control subjects and a group of 7 patients with a basal ganglia lesion. In the task, a cue was presented (a short versus long line) to inform participants about the time of appearance (early versus late) of a target stimulus, and the duration of the cue-target time intervals (400 versus 1400 ms) was manipulated. In contrast to the control group, patients with right prefrontal lesion showed a clear deficit in the temporal orienting effect. The foreperiod effect was also affected in the group of patients with prefrontal lesion (without lateralization of the deficit), whereas sequential effects were preserved. The group of basal ganglia patients did not show deficits in any of the effects. These findings support the voluntary and strategic nature of the temporal orienting and foreperiod effects, which depend on the prefrontal cortex, as well as the more automatic nature of sequential effects, which do not depend on either prefrontal cortex or frontobasal circuits.

Mental fatigue and temporal preparation in simple reaction-time performance

Performance decrements attributed to mental fatigue have been found to be especially pronounced in tasks that involve the voluntary control of attention. Here we explored whether mental fatigue from prolonged time on task (TOT) also impairs temporal preparation for speeded action in a simple reaction-time task. Temporal preparation is enabled by a warning signal presented before the imperative stimulus and usually results in shorter reaction time (RT). When the delay between warning and imperative stimuli - the foreperiod (FP) - varies between trials, responses are faster with longer FPs. This pattern has been proposed to arise from either voluntary attentional processes (temporal orienting) or automatic trial-to-trial learning (trace conditioning). The former account suggests a selective RT increase on long-FP trials with fatigue; the latter account suggests no such change. Over a work period of 51 min, we found the typical increase in overall RT but no selective RT increase after long FPs. This additivity indicates that TOT-induced mental fatigue generally reduces cognitive efficiency but leaves temporal preparation under time uncertainty unaffected. We consider this result more consistent with the trace-conditioning account of temporal preparation.

Generic cognitive adaptations to task interference in task switching

The present study investigated how the activation of previous tasks interferes with the execution of future tasks as a result of temporal manipulations. Color and shape matching tasks were organized in runs of two trials each. The tasks were specified by a cue presented before a task run, cueing only the first trials of each run. Response times (RTs) and error rates were measured for task switching and task repetition conditions. Task interference was varied as a function of response-cue interval (RCI of 300 and 900ms), that is, the interval between the task runs. Keeping the response-stimulus interval within the task runs constant at 300ms allowed the disentangling of the direct effects of RCI manipulation on performance (first trials) from the general effects on performance (both trials in the run). The data showed similar performance improvement due to RCI increase on both trials in the task run. Furthermore, increasing RCI improved both switch and repetition performance to a similar extent. Together, our findings provide further evidence for accounts stressing generic effects of proactive task interference in task switching.

Dynamic adjustment of temporal preparation: shifting warning signal modality attenuates the sequential foreperiod effect

We examined sequential effects in the variable foreperiod (FP) paradigm, which refer to the finding that responses to an imperative signal (IS) are fast when a short FP trial is repeated but slow when it is preceded by a long FP trial. The effect has been attributed to a trace-conditioning mechanism in which individuals learn the temporal relationship between a warning signal (WS) and the IS in a trial-by-trial manner. An important assumption is that the WS in a current trial (i.e., trial FP(n)) acts as a conditioned stimulus, such that it automatically triggers the conditioned response at the exact critical moment that was imperative in the previous trial (i.e., trial FP(n-1)). According to this assumption, a shift from one WS modality in trial FP(n-1) to another modality in trial FP(n) is expected to eliminate or at least reduce the sequential FP effect. This prediction was tested in three experiments that included a random variation of WS modality and FP length within blocks of trials. In agreement with the prediction, a shift in WS modality attenuated the asymmetry of the sequential FP effect.

Automatic sequential response priming and intentional response preparation in choice reaction tasks: evidence from response repetition and response cuing

This study examined the interaction of response repetition and response cuing in a finger cuing task with a short and a long cue-stimulus interval (CSI). We observed shorter reaction times (RTs) with increasing CSI and a substantial response repetition benefit. However, this benefit was abolished at the long CSI, suggesting that response cuing neutralized the repetition effect. According to additive-factors logic, the observed interaction suggests that both repetition and cuing exert their influence on a common processing stage, which we identify as the response selection stage. We argue that cuing and repetition effects are expressions of distinct mental operations: cuing is based on intentional response code activation, whereas repetition is based on sequential, automatic response code priming. Cue-based intentional code activation starts slowly and increases with CSI, but sequential response priming is independent of CSI, explaining why cuing abolishes the response repetition benefit at the long CSI.

Numerical magnitude modulates temporal comparison: an ERP study

Time is believed to be a part of the generalized magnitude system just like space and quantity. Previous research suggests that time perception can be affected by magnitude in some non-temporal dimensions. Here we address two questions. First, could the influence be caused by an abstract magnitude component without perceptual variables? Second, what are the underlying mechanisms of the influence? Participants compared a pair of durations defined by two Arabic digits in a hundreds of milliseconds range. They performed more accurately when the shorter durations were defined by lower numeric value digits (small digits) and the longer durations were defined by higher value digits (large digits) than they did in the reversed condition. Event-Related Potential (ERP) results showed that the CNVs corresponding to the first duration (CNV1), to the second duration (CNV2) and the N1 were all enhanced when durations marked by small digits than that marked by large ones. Combining the electrophysiological data with the behavioral results, we suggest that digits can modulate performance of temporal comparison at the relatively early stage of perceptual processing. One possible explanation of the current results is that selective temporal attention and subsequent expectation may be involved in this modulation.

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.

Cueing method biases in visual detection studies

Questions about attention are usually addressed by cueing tasks assessing whether knowledge of stimulus-related information provided in advance will improve target processing. Here, we test the reliability of this classical paradigm by means of using neutral cues in a simple visual detection task. We compared "mixed-block" (cued/no-cued trials are intermixed in the same block of trials) to "pure-block" (cued/no-cued trials are presented separately) protocols. We report converging evidence with behavioral and fMRI experiments that cueing methods entail competing processes of automatic motor activation (triggered by the cue) and proactive response inhibition (intended to counteract automatic responses to the cue). This competition strongly affects the reaction time baseline necessary to measure the "cueing" effect in a mixed-block design. Indeed, in such a protocol, proactive inhibition cannot be released before target presentation. Accordingly, we suggest that this design inevitably leads to biases in interpreting cueing data, and that the effects classically observed with mixed-block protocols are likely to be artifacts that are not attentional in origin. We conclude that the identification of this methodological issue now calls for a reassessment of the theoretical framework used to interpret some cueing effects with respect to their control baseline.

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.

The neural basis of temporal preparation: Insights from brain tumor patients

When foreperiods (FPs) of different duration vary on a trial-by-trial basis equiprobably but randomly, the RT is faster as the FP increases (variable FP effect), and becomes slower as the FP on the preceding trial gets longer (sequential effects). It is unclear whether the two effects are due to a common mechanism or to two different ones. Patients with lesions on the right lateral prefrontal cortex do not show the typical FP effect, suggesting a deficit in monitoring the FP adequately [Stuss, D. T., Alexander, M. P., Shallice, T., Picton, T. W., Binns, M. A., Macdonald, R., et al. (2005). Multiple frontal systems controlling response speed. Neuropsychologia, 43, 396-417]. The aim of this study was two-fold: (1) to replicate this neuropsychological result testing cerebral tumor patients before and after surgical removal of the tumor located unilaterally in the prefrontal, premotor or parietal cortex, respectively and (2) to investigate whether the sequential effects would change together with the FP effect (supporting single-process accounts) or the two effects can be dissociated across tumor locations (suggesting dual-process views). The results of an experiment with a variable FP paradigm show a significant reduction of the FP effect selectively after excision of tumors on right prefrontal cortex. On the other hand, the sequential effects were reliably reduced especially after surgical removal of tumors located in the left premotor region, despite a normal FP effect. The latter dissociation between the two effects supports a dual-process account of the variable FP phenomena. This study demonstrates that testing acute cerebral tumor patients represents a viable neuropsychological approach for the fractionation and localisation of cognitive processes.

Dissociating the effects of automatic activation and explicit expectancy on reaction times in a simple associative learning task

After repeated associations between two events, E1 and E2, responses to E2 can be facilitated either because participants consciously expect E2 to occur after E1 or because E1 automatically activates the response to E2, or because of both. In this article, the authors report on 4 experiments designed to pit the influence of these 2 factors against each other. The authors found that the fastest responses to a target in a reaction time paradigm occurred when automatic activation was highest and conscious expectancy lowest. These results, when considered together with previous findings indicating that, under most conditions, the relation between expectancy and reaction times is in the opposite direction, are indicative of a reversed association-an interaction pattern that J. C. Dunn and K. Kirsner (1988) demonstrated to be the only one that unambiguously points to the involvement of independent processes.

Neurophysiology of implicit timing in serial choice reaction-time performance

Neural representations of time for the judgment of temporal durations are reflected in electroencephalographic (EEG) slow brain potentials, as established in time production and perception tasks. Here, we investigated whether anticipatory processes in reaction-time procedures are governed by similar mechanisms of interval timing. We used a choice reaction task with two different, temporally regular stimulus presentation regimes, both with occasional deviant interstimulus intervals. Temporal preparation was shown in the form of adjustments in time course of slow brain potentials, such that they reached their maximum amplitude just before a new trial, independent of the duration of the interstimulus interval. Preparation was focused on a brief time window, demonstrated by a drop in amplitude of slow potentials as the standard interval had elapsed in deviant interstimulus intervals. Implicit timing influencing perceptual processing was shown in reduced visual-evoked responses to delayed stimuli after a deviant interstimulus interval and in a reduction of EEG alpha power over the visual cortex at the time when the standard interval had elapsed. In contrast to explicit timing tasks, the slow brain potential manifestations of implicit timing originated in the lateral instead of the medial premotor cortex. Together, the results show that temporal regularities set up a narrow time window of motor and sensory attention, demonstrating the operation of interval timing in reaction time performance. The divergence in slow brain potential distribution between implicit and explicit timing tasks suggests that interval timing for different behaviors relies on qualitatively similar mechanisms implemented in distinct cortical substrates.

Reweighting sequential effects across different distributions of foreperiods: Segregating elementary contributions to nonspecific preparation

In the study of nonspecific preparation, the response time (RT) to an imperative stimulus is analyzed as a function of the foreperiod (FP), the interval between a warning stimulus and the imperative stimulus. When FP is varied within blocks of trials, a downward sloping FP-RT function is usually observed. The slope of this function depends on the distribution of FPs (the more negative the skewness, the steeper the slope) and on intertrial sequences of FP (the longer the FP on the preceding trial, the steeper the slope). Because these determinants are confounded, we examined whether FP-RT functions, observed under three different FP distributions (i.e., uniform, exponential, and peaked) can be predicted, one from the other, by reweighting sequential effects. It turned out that reweighting explained very little variance of the difference between the FP-RT functions, suggesting a dominant role of temporal orienting strategies.

Preparation for speeded action as a psychophysiological concept

Mental preparation aids performance and induces multiple physiological changes that should inform concepts of preparation. To date, however, these changes have been interpreted as being due to a global preparatory process (e.g., attention or alertness). The authors review psychophysiological and performance investigations of preparation. Concepts of the central regulation of action offer an integrative framework for understanding the psychophysiology of preparation. If people process multiple streams of information concurrently, then preparatory processing requires a form of supervisory attention- central regulation to maintain unity of action. This concept is consistent with existing psychophysiological results and links them to current views of information processing. Conversely, psychophysiological measures may provide indices to test concepts within theories of the central regulation of action.