Viviane Pouthas

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.

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.

Role of the medial temporal lobe in time estimation in the range of minutes

This study examined the role of medial temporal lobe structures in verbal estimation and production of time intervals. Left medial temporal lobe lesions produced deficits in both tasks, whereas right medial temporal lobe lesions only disturbed time production. Although both tasks require adequate use of chronometric units, they seem to be subserved by distinct cognitive processing and to depend on different neural substrates. Verbal estimation of intervals in retrospect seems to depend mainly on contextual memory, and production of intervals depends more specifically on the mental load devoted to time. These findings, documenting for the first time the role of each temporal lobe in duration estimation within the range of minutes, are discussed in light of memory-based and attentional models of time.

Interactions between spatial and kinetic dimensions in movement aftereffect

In some conditions, the surface of the test figure on which one sees an aftereffect of movement does not fit with that part of the visual field previously adapted to a movement. Such an effect, called kinetic-figural effect, may be conceived of as resulting from an interaction between two perceptual systems, each one giving specific information: one for the kinetic aspects which are spatially defined, the other for the spatial relationship inside the visual field. Experiments are presented which indicated the validity of a “law of location” for a movement aftereffect, together with some effects of the spatial relationships between adapting and test fields upon the movement aftereffect.

Is time reproduction sensitive to sensory modalities

To examine the influence of sensory modality on time reproduction, we investigated the location of the indifference interval in the visual and auditory modalities with two ranges of duration (1–5.5 s and 1–10 s). Results showed that in the visual modality, the location of the indifference interval did not shift as a function of duration range and over trials: It was located around 3 s. In the auditory modality, it varied with the duration range: It was also located around 3 s for the first trials and progressively shifted to the mean of both tested ranges. A common mechanism was thus implied in the two modalities, intervals below and above 3 s being differentially processed but with auditory durations, a dynamic process superimposed to this supramodal mechanism. These explanations based on the differential properties of sensory memories and on learning mechanisms taking place during the task are discussed in light of time perception models.

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 Experiences and Time Knowledge in Infancy and Early Childhood

The developmental psychology of time is a vast field, as vast as the complexities of the notion of time itself. No overview can do justice to all areas of exploration. This paper focuses on early temporal experiences and time knowledge. The first section deals with the precursors of some temporal abilities in infancy. Then, three sets of studies are reviewed: studies on the development of representations of temporal structure; studies on transitions over the course of ontogenesis from conditioned responses to time to more cognitively regulated behaviours; and research on the development of childrens conceptions of time as a quantifiable dimension.

Interruption dans la reproduction d'une durée: effet sur la précision du jugement temporel

The effect of an empty break in time estimation was examined in duration reproduction tasks using two visual target durations (1 700 ms and 2 300 ms) . In line with previous research on duration production and discrimination, an effect of break location was observed : the reproduced duration lengthened as the pre-break duration increased (the time between the beginning of the duration to be reproduced and its interruption) . This effect is interpreted as reflecting interference between time estimation processes and expectancy processes which allow the beginning of the interruption to be located. The effect could also be due to a response bias (as described in Vierordts law), which leads to overestima- tion of the short pre-break durations and to underestimation of the long pre- break durations.