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Evidence for a pure time perception deficit in children with ADHD.

BACKGROUND: Deficits have been found previously in children with ADHD on tasks of time reproduction, time production and motor timing, implicating a deficit in temporal processing abilities, which has been interpreted as either secondary or primary to core executive dysfunctions. The aim of this study was to explore further the abilities of hyperactive children in skills of time estimation, using a range of time perception tasks in different temporal domains. METHOD: Time estimation was tested in a verbal estimation task of 10 seconds. Time reproduction was also acquired for two time intervals of 5 and 12 seconds. A temporal discrimination task aimed to determine the idiosyncratic threshold of minimum time interval (in milliseconds) necessary to distinguish two intervals differing by approximately 300 milliseconds. Twenty-two children diagnosed with ADHD were compared to 22 healthy children, matched for age, handedness and working memory skills. RESULTS: Children with ADHD were significantly impaired in their time discrimination threshold: on average, time intervals had to be 50 ms longer for the hyperactive children in order to be discriminated when compared with controls. Children with ADHD also responded earlier on a 12-second reproduction task, which however only approached significance after controlling for IQ and short-term memory. No group differences were found for the 5-second time reproduction or verbal time estimation tasks. CONCLUSIONS: The findings suggest that children with ADHD perform poorly on time reproduction tasks which load heavily on impulsiveness and attentional processes and they also suggest that these children may have a perceptual deficit of time discrimination, which may only be detectable in brief durations which differ by several hundred milliseconds. A temporal perception deficit in the range of milliseconds in ADHD may impact upon other functions such as perceptual language skills and motor timing.

Adolescent↗

The impact of mood on time perception, memorization, and acceptance of waiting.

The effects of mood on two cognitive processes, memorization and time perception, were examined. Participants (N = 155) first watched videos that successfully manipulated their mood (happy or sad); then they watched a video simulating a waiting line (Bateson & Hui, 1992; Bosselman & Craik, 1987). A questionnaire was administered to both groups to assess the number of items memorized from the "waiting" video, the estimated waiting time, and the degree of acceptance of waiting time. A series of analyses of variance showed that happy mood enhanced the number of items memorized and the acceptance of waiting but had no significant effect on time estimates. Memorization had no effect on time estimates or on acceptance of waiting; as expected, the longer the perceived waiting time, the less the acceptance of waiting time. A global model based on a system of linear equations (LINEQS) reproduced these results, which are interpreted in terms of both previous studies on mood and time estimate models.

Adaptation, Psychological↗

The role of attention in children's time perception.

This study tested the role of attention in 7- to 9-year-old children's time estimation. Based on an attentional model of time estimation, it was hypothesized that prospective estimates of short intervals are a function of the degree to which a child is occupied with the passage of time and is focusing his or her attention on estimating the exposure time of a stimulus. Two experiments with two different manipulations on attentional focus were conducted. Eighty children were exposed to two types of light bulbs, one a big bulb kindled with high intensity and the other a small one kindled with low intensity. The light bulbs were kindled for different intervals ranging from 3 to 10 s. In both experiments children estimated the lighting time of the bulbs in each condition by a reproduction method. In the first experiment prospective time estimates were found to be significantly longer than retrospective ones. In the second experiment children gave shorter time estimates when their attention was attracted away from the time estimation task than when it was not. In both experiments the attentional hypothesis was supported. In addition, support for the "more is more" hypothesis was obtained. Implications for understanding children's time perception processes are discussed.

Attention↗

Sensory modality and time perception in children and adults.

This experiment investigated the effect of signal modality on time perception in 5- and 8-year-old children as well as young adults using a duration bisection task in which auditory and visual signals were presented in the same test session and shared common anchor durations. Durations were judged shorter for visual than for auditory signals by all age groups. However, the magnitude of this modality difference was larger in the children than in the adults. Sensitivity to time was also observed to increase with age for both modalities. Taken together, these two observations suggest that the greater modality effect on duration judgments for the children, for whom attentional abilities are considered limited, is the result of visual signals requiring more attentional resources than are needed for the processing of auditory signals. Within the framework of the information-processing model of Scalar Timing Theory, these effects are consistent with a developmental difference in the operation of the "attentional switch" used to transfer pulses from the pacemaker into the accumulator. Specifically, although timing is more automatic for auditory than visual signals in both children and young adults, children have greater difficulty in keeping the switch in the closed state during the timing of visual signals.

Acoustic Stimulation↗

The failure of Weber's law in time perception and production.

Weber's law--constancy of the coefficient of variation--is an apparently ubiquitous feature of time perception, and forms the foundation of several theories of timing. We sought evidence for Weber's law in temporal production and categorization experiments. The production task required pigeons to switch between keys within a specified temporal window. The categorization task required them to classify a stimulus duration as either short or long. Weber fractions did not descend to a horizontal asymptote, but were U-shaped: they decreased as a function of target duration, and increased again at intermediate and long durations. This pattern conforms neither to Weber's law, nor to its generalized form (Getty, D.J., 1975. Discrimination of short temporal intervals: a comparison of two models. Percept. Psychophys. 18, 1-8). A model of counter failure accommodated the U-shaped pattern.

Animals↗

[Time perception by patients with depression in manic-depressive psychosis and recurrent schizophrenia].

The author provides the results of a clinicopsychological examination of time perception and surviving by 58 depressive patients with manic-depressive psychosis (MDP) and attack-like schizophrenia. The time surviving and counting off were done in the three clinical variants of depression: hypochondriacal, agitated and apathetic. The surviving of time violation was regarded in the structure of depersonalization disorders, particularly "Ego" stability in time as well as bearing in mind the duration, sequence, localization, rate, tempo and rhythm of the events and emotional experience. The most pronounced and diverse disorders of time surviving were recorded in hypochondriacal depression of MDP, less remarkable and latent in apathetic depression within the framework of schizophrenia.

Adult↗

Dissociable contributions of the prefrontal and neocerebellar cortex to time perception.

We report a series a three psychophysical experiments designed to differentiate the contributions of the neocerebellar and prefrontal cortex to time perception. Comparison of patients with focal, unilateral neocerebellar or prefrontal lesions on temporal discrimination of 400-ms and 4-s intervals (Expt. 1) indicated that neocerebellar damage impaired timing in both millisecond and seconds ranges, whereas prefrontal damage resulted in deficits that were robust only at the longer duration. Patients with prefrontal lesions, however, also exhibited working memory deficits on a non-temporal task (Expt. 2), biases in point of subjective equality indicative of attentional deficits, and were disproportionately sensitive to strategic manipulations in a long-duration discrimination task (Expt. 3). In contrast, the pervasive timing deficits of cerebellar patients were relatively insensitive to strategic support and could not be readily explained by general deficits in working memory or attention. These findings support the hypothesis that neocerebellar regions subserve a central timing mechanism, whereas the prefrontal cortex subserves supportive functions associated with the acquisition, maintenance, monitoring and organization of temporal representations in working memory. Such functions serve to bridge the output of the central timing mechanism with behavior. Together, these regions appear to participate in a working memory system involved in discrimination of durations extending from a few milliseconds to many seconds.

Acoustic Stimulation↗

Time perception: manipulation of task difficulty dissociates clock functions from other cognitive demands.

Previous studies suggest the involvement in timing functions of a surprisingly extensive network of human brain regions. But it is likely that while some of these regions play a fundamental role in timing, others are activated by associated task demands such as memory and decision-making. In two experiments, time perception (duration discrimination) was studied under two conditions of task difficulty and neural activation was compared using fMRI. Brain activation during duration discrimination was contrasted with activation evoked in a control condition (colour discrimination) that used identical stimuli. In the first experiment, the control task was slightly easier than the time task. Multiple brain areas were activated, in line with previous studies. These included the prefrontal cortex, cerebellum, inferior parietal lobule and striatum. In the second experiment, the control task was made more difficult than the time task. Much of the differential time-related activity seen in the first experiment disappeared and in some regions (inferior parietal cortex, pre-SMA and parts of prefrontal cortex) it reversed in polarity. This suggests that such activity is not specifically concerned with timing functions, but reflects the relative cognitive demands of the two tasks. However, three areas of time-related activation survived the task-difficulty manipulation: (i) a small region at the confluence of the inferior frontal gyrus and the anterior insula, bilaterally, (ii) a small portion of the left supramarginal gyrus and (iii) the putamen. We argue that the extent of the timing "network" has been significantly over-estimated in the past and that only these three relatively small regions can safely be regarded as being directly concerned with duration judgements.

Adolescent↗

The effects of diisopropyl phosphorofluoridate (DFP) on time perception in rats.

The hypothesis that DFP alters circadian rhythms by altering the output of an "internal clock" which is also used to time events in behavioral tasks was tested. Since any clock has a mean rate (ticks/unit time) and an associated variance (changes in the rate across time), measures of time perception which depend upon both the mean clock rate and its variance (discriminability, A'), or only the mean clock rate (Bisection Point) were examined. In Experiment 1, two groups of rats were trained to discriminate between a standard duration and six comparison durations of a light. Six weeks following three injections of DFP (1.0 mg/kg/week) or vehicle (saline and 5% alcohol), the discriminability (A') between the standard and comparison durations was reliably reduced for the DFP-treated animals. In Experiment 2, rats were trained to perform on a temporal bisection task. Relative to performance during the weeks following vehicle (peanut oil) treatments, discriminability (A') during the weeks following treatment with DFP (1.0 mg/kg/week) was reliably degraded but measures of the Bisection Point were unaffected. Since Experiments 1 and 2 both used a light duration as a discriminative stimulus, Experiment 3 examined the possibility that DFP treatments produced a change in visual function rather than clock function. Two groups of rats were trained to discriminate between light-on and light-off periods in a standard free-operant successive discrimination paradigm. No changes in discriminability or response rates were evident following two injections of DFP (1.0 mg/kg/week) or vehicle (peanut oil).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

The role of the cerebellum in subsecond time perception: evidence from repetitive transcranial magnetic stimulation.

In three experiments, we investigated the role of the cerebellum in sub- and suprasecond time perception by using repetitive transcranial magnetic stimulation (rTMS). In Experiment 1, subjects underwent four 8-min 1-Hz rTMS sessions in a within-subject design. rTMS sites were the medial cerebellum (real and sham rTMS), left lateral cerebellum, and right lateral cerebellum. Following each rTMS session, subjects completed a subsecond temporal bisection task (stimuli in the range 400-800 msec). Compared with sham rTMS, rTMS applied over the right lateral or medial cerebellum induced a leftward shift of the psychophysical function (perceived lengthening of time). In Experiment 2, a separate sample of subjects underwent the identical rTMS procedure and completed a suprasecond bisection task (stimuli in the 1000-2000 msec range). In this experiment, rTMS to the cerebellar sites did not produce any significant changes compared with sham rTMS. Experiment 3 employed a within-subject design to replicate findings from Experiments 1 and 2. Subjects underwent four rTMS conditions (sub- and suprabisection tasks following medial cerebellar and sham rTMS). rTMS induced a significant leftward shift of psychophysical function in the subsecond bisection, but not in the suprasecond bisection. In this study, we have demonstrated that transient cerebellar stimulation can differently affect the ability to estimate time intervals below and above a duration of 1 sec. The results of this study provide direct evidence for the role of the cerebellum in processing subsecond time intervals. This study further suggests that the perception of sub- and suprasecond intervals is likely to depend upon distinct neural systems.

Adult↗

[Disturbances in time perception in relation to changes in experiencing music in experimental psychosis].

Music is a structure ('Gestalt') in time. The recognition of disturbances of the perception of music enhances the knowledge of disorders of perception of time. Disturbances of perception of music and time in experimental psychoses (psilocybine) are discussed in relation to the studies by Piaget on the development of the notion of time in childhood. The results allow a new interpretation of the disturbances of the perception of time in diencephalic disorders as described in the literature.

Adult↗

Causes and consequences of time perception differences in overweight and normal weight people.

Three experiments considered whether there are differences between overweight and normal weight subjects in time perception which represent the obese subjects' lack of internal responsiveness as well as heightened external reactivity in a noneating setting. In the first study, no time-relevant cues were provided, and overweight subjects were inaccurate in their temporal judgments and showed significantly higher group variability than did normals. In the second study, the effects of differential temporal information generated by interesting and boring cues was considered. The presentation of these time-relevant external cues reduced the judgment variability of the overweight subjects and influenced their perceived passage of time significantly more than normals. The third study examined the influence, on eating behavior, of differences in perceived passage of time as a consequence of manipulating cues for interest or boredom. When bored, overweight subjects perceived time to pass more slowly than did normals and thus ate sooner. Similarly, they delayed eating, judging time to have passed more quickly than it actually had, when they were attending to interesting cues. The implications of a generalized lack of internal sensitivity for a theory about the development and consequences of obesity are discussed.

Attention↗

Interhemispheric changes in alpha rhythm related to time perception.

Each cerebral hemisphere processes environmental information in a different but complementary manner. Structures located in the left hemisphere are assumed to participate in symbolic-logic thinking. Time perception may be considered among such thinking processes. The present study evaluates bilateral occipito-central EEG activity in healthy, right-handed subjects which was produced while they performed a visuomotor monitoring task. The task consisted of two stages. The first stage involved the subject's learning a fixed time interval (10 sec) and the measurement of their reaction time. Subjects responded to an isolated light stimulus by pressing a button with the dominant hand. In the second stage, the subjects accuracy in estimating interval-length was evaluated. Two forms of EEG analysis were used, frequency and alpha ratio, each of which was measured both prior to and subsequent to the motor response. A reversal group was used to carry out a complementary test. Subjects responded in the first block of experiments with the non-dominant (left) hand and with the dominant hand in the second. Results showed that left hemisphere activity was continuous during the interval-learning stage and with optimal reaction times and remained continuous when estimation values approximated the real interval. In addition, in optimal reaction time and near to optimal time estimation responses, the left side showed lower frequency and alpha ratio than did the right. Finally a progressive enhancement in both parameters from the right hemisphere was related to deterioration in test performance. Results from the reversal group did not differ from those of the first group. As evaluated by gross measurements of the EEG, a predominant participation of the left hemisphere in time processing is concluded.

Adult↗