The role of physiological arousal in time perception: psychophysiological evidence from an emotion regulation paradigm.

Time perception, crucial for adaptive behavior, has been shown to be altered by emotion. An arousal-dependent mechanism is proposed to account for such an effect. Yet, physiological measure of arousal related with emotional timing is still lacking. We addressed this question using skin conductance response (SCR) in an emotion regulation paradigm. Nineteen participants estimated durations of neutral and negative sounds by comparing them to a previously memorized duration. Instructions were given to attend either to temporal or to emotional stimulus features. Attending to emotion with negative sounds generated longer subjective duration and greater physiological arousal than attending to time. However, a shared-attention condition showed discrepancy between behavioral and physiological results. Supporting the idea of a link between autonomic arousal and subjective duration, our results however suggest that this relation is not as direct as was expected. Results are discussed within recent model linking time perception, emotion and awareness.

How emotional auditory stimuli modulate time perception.

Emotional and neutral sounds rated for valence and arousal were used to investigate the influence of emotions on timing in reproduction and verbal estimation tasks with durations from 2 s to 6 s. Results revealed an effect of emotion on temporal judgment, with emotional stimuli judged to be longer than neutral ones for a similar arousal level. Within scalar expectancy theory (J. Gibbon, R. Church, & W. Meck, 1984), this suggests that emotion-induced activation generates an increase in pacemaker rate, leading to a longer perceived duration. A further exploration of self-assessed emotional dimensions showed an effect of valence and arousal. Negative sounds were judged to be longer than positive ones, indicating that negative stimuli generate a greater increase of activation. High-arousing stimuli were perceived to be shorter than low-arousing ones. Consistent with attentional models of timing, this seems to reflect a decrease of attention devoted to time, leading to a shorter perceived duration. These effects, robust across the 2 tasks, are limited to short intervals and overall suggest that both activation and attentional processes modulate the timing of emotional events.

Basal ganglia and supplementary motor area subtend duration perception: an fMRI study.

Brain imaging studies on duration perception usually report the activation of a network that includes the frontal and mesiofrontal cortex (supplementary motor area, SMA), parietal cortex, and subcortical areas (basal ganglia, thalamus, and cerebellum). To address the question of the specific involvement of these structures in temporal processing, we contrasted two visual discrimination tasks in which the relevant stimulus dimension was either its intensity or its duration. Eleven adults had to indicate (by pressing one of two keys) whether they thought the duration or the intensity of a light (LED) was equal to (right hand) or different from (left hand) that of a previously presented standard. In a control task, subjects had to press one of the two keys at random. A similar broad network was observed in both the duration-minus-control and intensity-minus-control comparisons. The intensity-minus-duration comparison pointed out activation in areas known to participate in cognitive operations on visual stimuli: right occipital gyrus, fusiform gyri, hippocampus, precuneus, and intraparietal sulcus. In contrast, the duration-minus-intensity comparison indicated activation of a complex network that included the basal ganglia, SMA, ventrolateral prefrontal cortex, inferior parietal cortex, and temporal cortex. These structures form several subnetworks, each possibly in charge of specific time-coding operations in humans. The SMA and basal ganglia may be implicated in the time-keeping mechanism, and the frontal-parietal areas may be involved in the attentional and mnemonic operations required for encoding and retrieving duration information.

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--3.2 and 9--13 s) are reported. The stimuli consisted of vibrations applied to the subject's right middle finger. When the vibration ended, the subject estimated an interval identical to its length before pressing a response button. The control task used cued responses with comparable intervals and stimuli. The pattern of activation obtained in the timing task as compared to control mainly included areas having attentional functions (the right dorsolateral prefrontal, inferior parietal, and anterior cingulate cortices), and the supplementary motor area (SMA). No significant difference was seen as a function of the duration range. It is argued, firstly, that involvement of the attentional areas derives from specific relations between attention and the temporal accumulator, as described by dominant timing models; and, secondly, that the SMA, or more probably one of its subregions, subserves time processing.

Does cerebral activity change in middle-aged adults in a visual discrimination task?

The purpose of this study was to assess changes in cerebral activity in middle-aged adults (MA: 50 years) compared to young adults (YA: 20 years). Subjects had to compare the duration or the intensity of a visual stimulus with a previously memorized standard. Evoked potentials were recorded, and a dipole model (obtained from PET data on young adults) was applied for fitting late-latency components. MA performance was poorer than YA performance. Task-specific ERP late components were found (P3 in intensity, CNV in duration), but P3 had a lower amplitude and CNV was less frontal in MAs compared to YAs. The activity of the dipoles that generate late components - cuneus in the intensity task, right frontal in the duration task, and anterior cingulate in both tasks-was less ample or less peaked in MAs than in YAs. This study characterizes neurobiological effects of aging that may already be visible during midlife.

Time estimation in patients with right or left medial-temporal lobe resection.

Patients with either left or right antero-medial-temporal lobe (MTL) resection were investigated as to their ability to reproduce and produce three durations (5, 14, or 38 s) in three conditions (silence, counting, articulatory suppression). The results showed that patients with unilateral MTL lesions did not differ from controls when they had to encode the duration of a visual stimulus in order to reproduce it. By contrast, patients with right MTL lesions underestimated all three durations, compared with controls and with patients with left MTL resection, when they had to produce durations given in chronometric units. This finding suggests that the right MTL retains long-term representations of the conventional units necessary to the accurate production of durations.

Temporal control of rhythmic performance: a comparison between young and old adults.

Young (20-30-year-old) and older (60-76-year-old) adults were tested on two measures of rhythmic performance. The first involved tapping at the subject's own preferred rate, a measure of so-called internal tempo. Over five sessions of testing, tapping rates were consistently and significantly slower on average in the older subjects than the younger ones, but rates were not relatively more variable in older subjects (i.e., coefficients of variation, standard deviation/mean, did not differ between the older and young people). In addition, both old and younger subjects performed on a synchronized-tapping and continuation task of the type used by Wing and Kristofferson (1973, Perception and Psychophysics, 14, 3-12). Target interresponse times were 300, 400, 500, 600, and 700 ms, and in all cases interresponse intervals produced by both the old and young adults matched the target times very closely. Wing and Kristofferson's analytical procedure was used to decompose tapping variance into that attributable to timing processes and that resulting from motor implementation of the timing signal. Both sorts of variance increased with increasing target interresponse time (with timer variance increasing most markedly), but no difference was found in either type of variance in comparisons between the old and younger subjects. If the internal tempo measure directly reflects the speed of internal timing processes, the data suggest that such processes are slower, but not relatively more variable, in older than younger subjects (consistent with some previous evidence and speculation), but that the calibration of performance forced by the synchronization task will make such an age-related difference in "internal clock speed" unobservable on synchronized-tapping tasks.

ERPs and PET analysis of time perception: spatial and temporal brain mapping during visual discrimination tasks.

ERPs were recorded from 12 subjects performing duration and intensity visual discrimination tasks which have been previously used in a PET study. PET data showed that the same network was activated in both tasks [P. Maquet et al., NeuroImage 3:119-126, 1996]. Different ERP waveforms were observed for the late latency components depending on the dimension of the stimulus to be processed: frontal negativity (CNV) for the duration task and parieto-occipital positivity (P300) for the intensity task. Using BESA software, the sources were first modelled with a "PET dipolar model" (right prefrontal, right parietal, anterior cingulate, left and right fusiforms). To obtain a better fit for ERPs recorded in each task, two sources (cuneus, left prefrontal area) had to be added. Consistently with PET findings, dipole modelling indicates that duration and intensity dimensions of a visual stimulus are processed in the same areas. However, ERPs also reveal prominent differences between the time course of the dipole activations for each task, particularly for sources contributing to the late latency ERP components. In the intensity task, dipoles located in the cuneus, the anterior cingulate, and the left prefrontal area yield largest activity within the P300 interval, then activity diminishes rapidly as the stimulus ends, whereas in the duration task, the cuneus and anterior cingulate are still active several hundred milliseconds following stimulus offset. Moreover, in the duration task, the activity of the right frontal dipole parallels the CNV waveform, whereas in the intensity task, this dipole is largely inactive. We assume that the right frontal area plays a specific role in the formation of temporal judgments.

Role of frontal cortex in memory for duration: an event-related potential study in humans.

Event-related potentials were recorded in order to determine how brain activity is lateralized during the encoding and the recognition of visual durations (700 and 2500 ms ranges). It is assumed in the Hemispheric Encoding Retrieval Asymmetry model that the encoding of words, faces and odours involves left frontal areas whereas their recognition involves right frontal areas. The present results indicate that, for temporal information, the hemispheric bias is different: a negativity developed over right frontal electrodes for both encoding and recognition, and for both duration ranges. Thus, the involvement of right frontal areas appears critical for time perception. Conversely to what was expected, contingent negative variation during recognition was large over both left and right frontal electrodes. These results suggest that the involvement of both hemispheres is necessary for recognition of temporal information.

Timing in aging: the role of attention.

This paper questions the issue of attentional capacity in changes in time processing with aging. Performances of young and old subjects were compared in a task involving an attentional sharing between three concurrent estimations of durations (6, 8, or 10 s). Depending upon the experimental condition, the subjects were instructed to simultaneously focus their attention onto one, two, or three target stimuli. The results showed that increased difficulty of the task, that is the increased number of concurrent temporal targets to monitor at a time, led to a greater disruption of timing performance in elderly people than in young adults. Temporal judgments of elderly were less accurate and more variable than those of young adults in the attentional sharing conditions (two or three target durations). The greater sensitivity to interference effects observed in the elderly is discussed in terms of age-related reduction of attentional resources and working-memory deficits.

[Time of consciousness, consciousness of time]. / Le temps de la conscience, la conscience du temps.

Time shapes our behavior: we must estimate the duration of events in our environment in order to anticipate changes and time our activity in function of these changes. However, there is no sensory modality devoted to the perception of time, therefore the question is to know which mechanisms underlie the consciousness that time flows and allow us to estimate time precisely. This article proposes a brief overview of psychological, neuropsychological and brain imaging studies which rely on theoretical models postulating the existence of an internal timer. These studies examine the different components--time base, counter and memory--of this timer: particularly they are aimed at characterising the relationships between the evolution of these components with age or their pathological alterations and changes in temporal judgements. They also attempt to specify the neural bases of these components. From this brief overview comes the idea that, if an internal timer exits, it does not mark objective time but a multitude of subjective times.

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. These areas are assumed to play a major role in time processing, in relation to attention and memory mechanisms.

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. Three tasks were studied: (a) A temporal generalization task (D task) in which the subjects had to judge (by pressing one of two keys) whether the duration of the illumination of a green LED was equal to or different from that of a previously presented standard; (b) An intensity generalization task (I task) in which the judgment concerned the intensity of the LED; and (c) A control task (C task) in which the subjects had to press one of the two keys at random in response to LED illumination. A significant increase in rCBF during the D task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, anterior cingulate cortex, vermis, and a region corresponding to the left fusiform gyrus. A significant increase in rCBF during the I task, compared to that during the C task, was observed in right prefontal cortex, right inferior parietal lobule, right extrastriate cortex, anterior cingulate cortex, left inferior parietal lobule, vermis, and two symmetrical regions corresponding to the fusiform gyri. No significant activation was observed in the D task when compared to that in the I task. We propose that these cortical maps are best explained by the recruitment of visual attention and memory structures, which play a major role in prospective time judgements as indicated by behavioral studies. The data also suggest that the temporal dimension of a visual stimulus is processed in the same areas as other visual attributes.

Temporal learning in 4 1/2- and 6-year-old children: role of instructions and prior knowledge.

The present study investigates effects of different types of instructions (high-rate, interval, and minimal) during training with a fixed-interval schedule as a function of prior acquired temporal knowledge. A pretest was used to assess 4 1/2- and 6-year-old children's ability to understand the temporal parameters of a fixed-interval schedule of reinforcement. The results as a whole show that the control exerted by instructions given by the experimenter or elaborated by the subjects themselves on fixed-interval performance of young children depends on the interaction of two factors: development of verbal self-control skills and mastery of knowledge required by the rules forming the instructions.

Temporal differentiation of response duration in children of different ages: developmental changes in relations between verbal and nonverbal behavior.

Children aged 4.5, 7, or 11 years received an experimental session in which a contingency was placed on button-press duration. Each discrete trial was followed by a brief verbal probe asking a question about the contingency requirement. Other groups of children received an identical task followed by a postexperimental interview. Level of adaptation to the duration contingency tended to increase with age in subjects receiving posttrial verbal probes, but not for those who were interviewed. Eleven-year-olds in the verbal probe condition showed a strong correlation between accurate temporal differentiation and number of verbalizations relating to response duration or timing. The younger subjects, with one exception, showed no association between timing-related verbalizations (which were almost totally absent) and response duration differentiation. This developmental difference occurred even though the younger subjects verbalized after almost every trial. The results suggest that although 11-year-old children apparently produce rule-governed behavior under verbal control as adults do, the behavior of younger children may be controlled directly by reinforcement contingencies even when their verbal repertoires are highly developed.

A developmental study of timing behavior in 4 1/2- and 7-year-old children.

The present study investigated effects of age and instructions on temporal regulations of behavior in children. In the first experiment 4 1/2-year-old and 7-year-old subjects were trained with a DRL (differential reinforcement of low rates) 5-s and a DRL 10-s schedule. Results demonstrate that age and timing performance are related. Seven-year-olds are more efficient than the 4 1/2-year-olds. A striking decline in the 4 1/2-year-old children's capacity to space responses was observed in the DRL 10-s schedule as compared to the DRL 5-s schedule. Analysis of individual performances suggests that the evolution of DRL performance between 4 and 7 years of age depends not only on the development of the capacity to delay responding but also on the acquisition of the ability to represent the reinforcement contingencies, that is, the temporal parameters of the task to oneself. In order to test this hypothesis a second experiment was conducted where instructions to wait between operant responses were given to a group of 4 1/2-year-old subjects at the beginning of a DRL 5-s and a DRL 10-s schedule. The results show that these instructions enhance DRL performance. By directing the 4 1/2-year-old subjects' attention to the temporal requirements of the task, instructions led to efficient performance and accurate timing of responses to the DRL schedule.