Timing processes: an outline of behavioural and neural indices not systematically considered in timing models.

This paper deals with two questions: what are the main characteristics of timing performance, and how do current timing models account for them? An outline of the most significant behavioural and neural indices of time processing is presented, with particular emphasis on the effects of activation and attention, and on data drawn from an important electrophysiological indice, the Contingent Negative Variation (CNV). A sample of influent timing models is then considered, ranged in two categories depending on whether they provide a representation of the time elapsing online between the limits of a target interval or a representation of the interval limits. The authors support the concept of online "pulse accumulation" as various types of cumulative mechanisms have been described at both neural and behavioural levels.

Contrasting effects of interference and of breaks in interval timing.

When a break is introduced during an interval to be timed, the interval is perceived shorter as break location is delayed. This is interpreted as a result of attention sharing between timing and monitoring the source of the break signal. Similar effects and interpretations are found in another context involving interfering tasks.

Overproduction timing errors in expert dancers.

The authors investigated how expert dancers achieve accurate timing under various conditions. They designed the conditions to interfere with the dancers' attention to time and to test the explanation of the interference effect provided in the attentional model of time processing. Participants were 17 expert contemporary dancers who performed a freely chosen duration while walking and executing a bilateral cyclic arm movement over a given distance.

The supplementary motor area in motor and perceptual time processing: fMRI studies.

The neural bases of timing mechanisms in the second-to-minute range are currently investigated using multidisciplinary approaches. This paper documents the involvement of the supplementary motor area (SMA) in the encoding of target durations by reporting convergent fMRI data from motor and perceptual timing tasks. Event-related fMRI was used in two temporal procedures, involving (1) the production of an accurate interval as compared to an accurate force, and (2) a dual-task of time and colour discrimination with parametric manipulation of the level of attention attributed to each parameter.

Timing functions of the supplementary motor area: an event-related fMRI study.

Two previous studies in which we recorded slow brain potential shifts over the scalp revealed performance-dependent effects that sustained one prominent model of timing mechanisms. These effects seemed to be derived from the supplementary motor area (SMA). Event-related functional magnetic resonance imagery (fMRI) was used to check this hypothesis.

Functional anatomy of the attentional modulation of time estimation.

Attention modulates our subjective perception of time. The less we attend to an event's duration, the shorter it seems to last. Attention to time or color stimulus attributes was modulated parametrically in an event-related functional magnetic resonance imaging study.

The CNV peak: an index of decision making and temporal memory.

A slow brain potential change, the contingent negative variation (CNV), was recorded in a temporal generalization schedule. The task was to judge the duration of a signal (1.250 to 3.

Expectancy, controlled attention and automatic attention in prospective temporal judgments.

Two experiments indicate that prospective judgments of a temporal target are influenced by nontarget temporal features. The basic task was to reproduce a target interval marked by visual events. In addition, visual or auditory interfering events were delivered.

Time processing reflected by EEG surface Laplacians.

We previously described significant relationships between amplitude variations in slow brain potentials and timed between-press intervals (2.5 s). We suggested that these variations are neural traces of timing mechanisms.

Activation of the supplementary motor area and of attentional networks during temporal processing.

This paper first provides a survey of the expanding brain imaging literature in the field of time processing, showing that particular task features (discrete vs rhythmic, perceptual vs motor) do not significantly affect the basic pattern of activation observed. Next, positron emission tomography (PET) data obtained in a timing task (temporal reproduction) with two distinct duration ranges (2.2--3.

The supplementary motor area in motor and sensory timing: evidence from slow brain potential changes.

The present study investigated the processing of durations on the order of seconds with slow cortical potential changes. The question is whether trial-to-trial fluctuations in temporal productions or judgments correspond to variations in the amplitude of surface Laplacians computed over particular scalp regions. Topographical analyses were done using the source derivation method.

Attention and timing: dual-task performance in pigeons.

Pigeons were exposed to an analog of a 'dual-task' procedure used to test attentional models of timing in humans. After separate training on an auditory duration discrimination and on a variable ratio (VR) schedule, VR episodes lasting for 5 s were superimposed on the stimuli to be timed, either early (E) or late (L) during the trial. Trials with VR yielded underestimation of the target durations (increased % of 'short' choices), relative to trials without VR, and this effect was stronger under the L than under the E condition.

Multiple approaches to investigate the existence of an internal clock using attentional resources.

The attentional model of time estimation assumes that specific mechanisms are involved when subjects explicitly process temporal information. Temporal judgments would depend on the amount of attentional resources allocated to a temporal processor (also called timer). The present paper provides some evidence in favor of the existence of such a processor.

Sensory effects on judgments of short time-intervals.

Two experiments were conducted to test the effect of nontemporal factors on duration discrimination. In Exp. 1, a forced-choice adaptive procedure with a standard duration of 400 or 800 ms was employed.

Effects of attention manipulation on judgments of duration and of intensity in the visual modality.

The "attentional model" of time estimation assumes that temporal judgments depend on the amount of attention allocated to the temporal processor (the timer). One of the main predictions of this model is that an interval will be judged shorter when attention is not allocated to the temporal parameters of the task. Previous studies combining temporal and nontemporal tasks (dual-task method) have suggested that the time spent processing the target duration might be a key factor.

The basic pattern of activation in motor and sensory temporal tasks: positron emission tomography data.

Positron emission tomography (PET) data were obtained from subjects performing a synchronization task (target duration 2700 ms). A conjunction analysis was run to identify areas prominently activated both in this task and in a temporal generalization task (target duration 700 ms) used previously. The common pattern of activation included the right prefrontal, inferior parietal and anterior cingulate cortex, the left putamen and the left cerebellar hemisphere.

The "short-long" reaction time effect in duration programming.

The programming processes concerned with response duration were studied in a precueing and in a priming reaction time (RT) paradigm. Participants had to produce a motor response of a specified duration as soon as possible after a response signal (RS) preceded by a warning signal (WS), which could deliver information on 2 response parameters (duration and effector). In Experiment I (precueing; N = 12), 3 effectors (the right hand, the left hand, or the knees) and 3 durations (.

Can the level of prefrontal activity provide an index of performance in humans?

The experiment reported here was aimed at determining whether the level of brain activity can be used as an index of subjects' performance on a temporal task. The discrimination of durations constituted the task. An array of four A's appeared on a screen, and subjects had to decide whether the letters remained on the screen for a short or a long duration as learned in a practice phase.

Brain activation induced by estimation of duration: a PET study.

Duration information about a visual stimulus requires processing as do other visual features such as size or intensity. Using positron emission tomography, iterative H215O infusions, and statistical parametric mapping, we investigated the neural correlates of time processing. Nine normal subjects underwent six serial rCBF.

Programming the duration of a motor sequence: role of the primary and supplementary motor areas in man.

Event-related potentials were recorded in a reaction time (RT) paradigm, where the duration of a learned interval (either 0.7 s or 2.5 s) delimited by two brief button-presses was to be accurately controlled.

Production of short timing responses: a comparative study with a deafferented patient.

How far can proprioception contribute to time keeping? To answer this question, a deafferented patient and neurologically normal subjects produced 1- or 5-sec durations in a sustained (continuous finger press) or discrete (two successive finger taps) manner, with and without Knowledge of Results. The findings were that: (1) proprioceptive afferents contribute to timing regulation in motor production of short durations; (2) this role can be rapidly compensated by Knowledge of Results; (3) the proprioceptive contribution is more important for sustained than for discrete performances; (4) stable performances are produced even when KR is withdrawn, suggesting familiarization with KR leads to the establishment of a mnemonic trace.

Controlled attention sharing influences time estimation.

A seminal attentional model of time estimation predicts that subjective duration will be positively correlated to the amount of attention given to temporal processing. This prediction holds under prospective conditions, in which one is forewarned that judgments of time will be asked, in contrast to retrospective conditions, in which such judgments are required after the relevant period without any prior warning. In three experiments, an attention-sharing method was used.

Programming response duration in a precueing reaction time paradigm.

To determine whether the duration of certain motor activities can be a prespecified dimension of the motor program, we studied the duration of a motor response and the hand to be used, in a precueing paradigm. The response to be produced (a press on a push-button) was either short or long and involved either the right or the left hand. In Experiment 1, 200 and 700 ms (Block 1) or 700 and 2,500 ms (Block 2) were respectively chosen as short and long durations.

Effect of learning on production of duration in variable motor conditions.

It has been suggested that increasing proprioceptive feedback and ensuring its consistency from trial to trial favours timing accuracy. The progressive acquisition of a timing performance with isometric and anisometric responses was investigated in conditions of 'inconsistent feedback', with two different methods: counting seconds or not. Subjects gripped the handle of a dynamometer during precisely 5 seconds in 4 randomly distributed conditions: 'Weak' or 'Strong' constant force, 'Slow' or 'Rapid' variable force.