Showing papers on "Time perception published in 2003"

Auditory influences on visual temporal rate perception.

Abstract: Visual stimuli are known to influence the perception of auditory stimuli in spatial tasks, giving rise to the ventriloquism effect. These influences can persist in the absence of visual input following a period of exposure to spatially disparate auditory and visual stimuli, a phenomenon termed the ventriloquism aftereffect. It has been speculated that the visual dominance over audition in spatial tasks is due to the superior spatial acuity of vision compared with audition. If that is the case, then the auditory system should dominate visual perception in a manner analogous to the ventriloquism effect and aftereffect if one uses a task in which the auditory system has superior acuity. To test this prediction, the interactions of visual and auditory stimuli were measured in a temporally based task in normal human subjects. The results show that the auditory system has a pronounced influence on visual temporal rate perception. This influence was independent of the spatial location, spectral bandwidth, and intensity of the auditory stimulus. The influence was, however, strongly dependent on the disparity in temporal rate between the two stimulus modalities. Further, aftereffects were observed following approximately 20 min of exposure to temporally disparate auditory and visual stimuli. These results show that the auditory system can strongly influence visual perception and are consistent with the idea that bimodal sensory conflicts are dominated by the sensory system with the greater acuity for the stimulus parameter being discriminated.

Processing of temporal information and the basal ganglia: new evidence from fMRI

Abstract: Temporal information processing is a fundamental brain function, which might include central timekeeping mechanisms independent of sensory modality. Psychopharmacological and patient studies suggest a crucial role of the basal ganglia in time estimation. In this study, functional magnetic resonance imaging (fMRI) was applied in 15 healthy right-handed male subjects performing an auditory time estimation task (duration discrimination of tone pairs in the range of 1,000-1,400 ms) and frequency discriminations (tone pairs differing in pitch, around 1,000 Hz) as an active control task. Task difficulty was constantly modulated by an adaptive algorithm (weighted up-down method) reacting on individual performance. Time estimation (vs rest condition) elicited a distinct pattern of cerebral activity, including the right medial and both left and right dorsolateral prefrontal cortices (DLPFC), thalamus, basal ganglia (caudate nucleus and putamen), left anterior cingulate cortex, and superior temporal auditory areas. Most activations showed lateralisation to the right hemisphere and were similar in the frequency discrimination task. Comparing time and frequency tasks, we isolated activation in the right putamen restricted to time estimation only. This result supports the notion of central processing of temporal information associated with basal ganglia activity. Temporal information processing in the brain might thus be a distributed process of interaction between modality-dependent sensory cortical function, the putamen (with a timing-specific function), and additional prefrontal cortical systems related to attention and memory. Further investigations are needed to delineate the differential contributions of the striatum and other areas to timing.

Does the representation of time depend on the cerebellum?Effect of cerebellar stroke

Abstract: Behaviours that appear to depend on processing temporal information are frequently disrupted after cerebellar damage. The present study examined the role of the cerebellum in explicit timing and its relationship to other psychological processes. We hypothesized that if the cerebellum regulates timekeeping operations then cerebellar damage should disrupt the perception and the reproduction of intervals, since both are thought to be supported by a common timekeeper mechanism. Twenty-one patients with cerebellar damage from stroke and 30 normal controls performed time perception and time reproduction tasks. In the time reproduction task, timing variability was decomposed into a central timing component (clock variability) and a motor component (motor implementation variability). We found impairments only in time reproduction (increased clock variability) in patients with medial and lateral damage involving the middle- to superior-cerebellar lobules. To explore potential reasons for the temporal processing deficits, time reproduction and perception performance were correlated with independent measures of attention, working memory, sensory discrimination and processing speed. Poorer working memory correlated with increased variability in the 'clock' component of time reproduction. In contrast, processing speed correlated best with time perception. The results did not support a role for the cerebellum in timekeeping operations. Rather, deficits in timing movements may be related to a disruption in acquiring sensory and cognitive information relevant to the task, coupled with an additional impairment in the motor-output system.

Early processing stages are modulated when auditory stimuli are presented at an attended moment in time: an event-related potential study.

Abstract: The present study investigated with event-related potentials whether attending to a moment in time modulates the processing of auditory stimuli at a similar early, perceptual level as attending to a location in space. The participants listened to short (600 ms) and long (1,200 ms) intervals marked by white noise bursts. The task was to attend in alternating runs either to the short or to the long intervals and to respond to rare offset markers that differed in intensity from the frequent standard offset markers. Prior to the to-be-attended moment, a slow negative potential developed over the frontal scalp. Stimuli presented at the attended compared to the unattended moments in time elicited an enhanced N1 and an enhanced posteriorly distributed positivity (300-370 ms). The results show that attention can be flexibly controlled in time and that not only late but also early perceptual processing stages are modulated by attending to a moment in time.

Duration judgements in patients with schizophrenia.

Abstract: Background. The ability to encode time cues underlies many cognitive processes. In the light of schizophrenic patients' compromised cognitive abilities in a variety of domains, it is noteworthy that there are numerous reports of these patients displaying impaired timing abilities. However, the timing intervals that patients have been evaluated on in prior studies vary considerably in magnitude (e.g. 1 s, 1 min, 1 h etc.). Method. In order to obviate differences in abilities in chronometric counting and place minimal demands on cognitive processing, we chose tasks that involve making judgements about brief durations of time (<1 s). Results. On a temporal generalization task, patients were less accurate than controls at recognizing a standard duration. The performance of patients was also significantly different from controls on a temporal bisection task, in which participants categorized durations as short or long. Although time estimation may be closely intertwined with working memory, patients' working memory as measured by the digit span task did not correlate significantly with their performance on the duration judgement tasks. Moreover, lowered intelligence scores could not completely account for the findings. Conclusions. We take these results to suggest that patients with schizophrenia are less accurate at estimating brief time periods. These deficits may reflect dysfunction of biopsychological timing processes.

Temporal specificity of perceptual learning in an auditory discrimination task.

Abstract: Although temporal processing is used in a wide range of sensory and motor tasks, there is little evidence as to whether a single centralized clock or a distributed system underlies timing in the range of tens to hundreds of milliseconds We investigated this question by studying whether learning on an auditory interval discrimination task generalizes across stimulus types, intervals, and frequencies The degree to which improvements in timing carry over to different stimulus features constrains the neural mechanisms underlying timing Human subjects trained on a 100- or 200-msec interval discrimination task showed an improvement in temporal resolution This learning generalized to a perceptually distinct duration stimulus, as well as to the trained interval presented with tones at untrained spectral frequencies The improvement in performance did not generalize to untrained intervals To determine if spectral generalization was dependent on the importance of frequency information in the task, subjects were simultaneously trained on two different intervals identified by frequency As a whole, our results indicate that the brain uses circuits that are dedicated to specific time spans, and that each circuit processes stimuli across nontemporal stimulus features The patterns of generalization additionally indicate that temporal learning does not rely on changes in early, subcortical processing, because the nontemporal features are encoded by different channels at early stages

Underestimation of time perception after repetitive transcranial magnetic stimulation

Abstract: The right dorsolateral prefrontal cortex (rDLPFC) may be important in time perception in humans. In the present study, the authors demonstrate that a virtual lesion of the rDLPFC by repetitive transcranial magnetic stimulation (rTMS) leads to underestimation of time perception for brief intervals (lasting a few seconds) in working memory.

The Perceived Onset Time of Self- and Other-Generated Actions

Abstract: Awareness of actions is partly based on the intentions accompanying them. Thus, the awareness of self- and other-generated actions should differ to the extent that access to own and other's intentions differs. Recent studies have found a brain circuit (the mirror-neuron system) that represents self- and other-generated actions in an integrated fashion. This system does not respond to actions made by nonagents, such as machines. We measured the estimated onset time of actions that subjects either executed themselves or observed being executed by someone else or by a machine. In three experiments, the estimates of the machine actions always differed from those of self- and other-generated actions, whereas the latter two were indistinguishable. Our results are consistent with the view that intentions are attributed to others but not to machines. They also raise the interesting possibility that people attribute intentions to themselves in the same way as they do to others.

When time is up: CNV time course differentiates the roles of the hemispheres in the discrimination of short tone durations

Abstract: Numerous studies have suggested that the CNV (contingent negative variation), a negative slow wave developing between a warning and an imperative stimulus, reflects, among other things, temporal processing of the interval between these two stimuli. One aim of the present work was to specify the relationship between CNV activity and the perceived duration. A second aim was to establish if this relationship is the same over the left and right hemispheres. Event-related potentials (ERPs) were recorded for 12 subjects performing a matching-to-sample task in which they had to determine if the duration of a tone (490 ms, 595 ms, 700 ms, 805 ms, and 910 ms) matched that of a previously presented standard (700 ms). CNV activity measured at the FCZ electrode was shown to increase until the standard duration had elapsed. By contrast, right frontal activity increased until the end of the current test duration, even when the standard duration had elapsed. Moreover, for long test durations (805 ms and 910 ms), correlations were observed between CNV peak latency and subjective standard, over left and medial frontal sites. We propose that left and medial frontal activity reflects an accumulation of temporal information that stops once the memorized standard duration is over, while right frontal activity subserves anticipatory attention near the end of the stimulus.

Auditory temporal processing in children with specific reading disability with and without attention deficit/hyperactivity disorder.

Abstract: The auditory temporal deficit hypothesis predicts that children with specific reading disability (RD) will exhibit a deficit in the perception of auditory temporal cues in nonspeech stimuli. Tasks assessing perception of auditory temporal and nontemporal cues were administered to children with (a) RD without attention-deficit/hyperactivity disorder (RD/no-ADHD, n = 40), (b) ADHD alone (ADHD/no-RD, n = 33), (c) RD and ADHD (RD/ADHD, n = 36), and (d) no impairment (NI, n = 41). The presence of RD was associated with a specific deficit in detection of a tone onset time asynchrony, but no reduction in performance on other tasks assessing perception of temporal or nontemporal acoustic cues. The presence of ADHD was associated with a general reduction in performance across tasks. The pattern of results did not indicate a pervasive deficit in auditory temporal function in children with RD, but did suggest a possible sensitivity to backward masking in this group. Results also indicated that the comorbid presence of ADHD is a significant factor in the performance of children with RD on psychoacoustic tasks.

Effects of methamphetamine on duration discrimination.

Abstract: Experiments I and 2 address the controversy regarding the reliability of methamphetamine effects on interval timing. A temporal discrimination procedure was used, in which the rats were reinforced for pressing the left or the right levers after short and long signals, respectively. Methamphetamine (0.5 mg/kg sc) severely disrupted operant performance at 20-100 min after injection, which disabled the measurement of drug effects on temporal perception (Experiment I ). The same dose of methamphetamine shifted the psychometric function to the left at 100-180 min after injection, indicating an increase in subjective durations (Experiment 2). Although these results confirm the role of dopamine in interval timing, that a change in the speed of a neural clock mediates the methamphetamine-induced change in temporal perception is still a working hypothesis.

Orienting in space and time: joint contributions to exogenous spatial cuing effects.

Abstract: We examined whether the time course of exogenous spatial-cuing effects is sensitive to the allocation of attention in time. Expectation for a target within a particular time window following the cue was manipulated by varying the proportion of trials that appeared at each of three stimulus onset asynchronies in both a detection task and a two-alternative forced-choice discrimination task. The time course of spatial-cuing effects was sensitive to the temporal expectation manipulation only in the discrimination task. The results are discussed with reference to the role of attentional set in exogenous spatialcuing paradigms.

Voluntary action expands perceived duration of its sensory consequence

Abstract: When we look at a clock with a hand showing seconds, the hand sometimes appears to stay longer at its first-seen position than at the following positions, evoking an illusion of chronostasis. This illusory extension of perceived duration has been shown to be coupled to saccadic eye movement and it has been suggested to serve as a mechanism of maintaining spatial stability across the saccade. Here, we examined the effects of three kinds of voluntary movements on the illusion of chonostasis: key press, voice command, and saccadic eye movement. We found that the illusion can occur with all three kinds of voluntary movements if such movements start the clock immediately. When a delay is introduced between the voluntary movement and the start of the clock, the delay itself is overestimated. These results indicate that the illusion of chronostasis is not specific to saccadic eye movement, and may therefore involve a more general mechanism of how voluntary action influences time perception.

Context-related representation of timing processes in monkey motor cortex.

Abstract: Precise timing is essential for motor performance, though the neuronal representation of time is unknown. To explore neuronal correlates of timing processes during movement preparation and execution, we compared the activities of neurons recorded in monkey motor cortex during the performance of two tasks requiring correct time estimation in different contextual situations. Despite the fact that both tasks had many common features (e.g. same movements, same time intervals to estimate), they involved different degrees of spatial and temporal uncertainty. Our findings indicate that time is indeed represented in neuronal activity of the motor cortex, albeit strongly dependent on context and not in an invariant manner as a distinct process per se.

Mismatch negativity in detection of interval duration deviation in schizophrenia.

Abstract: Temporal processing deficits have been noted in behavioral studies assessing patients with schizophrenia. The current study sought to explore the physiology of temporal perception while controlling the effects of motivation, attention and other cognitive processes that may contribute to behavioral measures of temporal processing. Mismatch negativity (MMN) waveforms were measured in response to variations in the temporal parameters of an ongoing train of pure tones. A standard inter-stimulus interval of 400 ms was interrupted, on average, every 20th tone by an inter-stimulus interval of 340 ms. Amplitude of MMN waveform elicited by the temporal deviance was significantly reduced in the schizophrenia group compared with controls (p = 0.016). Results suggest that behavioral difficulties on time processing tasks in schizophrenia may reflect a physiological deficit in temporal perception in this population rather than simply more general difficulties in attention or motivation.