Perception Of Intervals Research Articles

Distinct brain dynamics and networks for processing short and long auditory time intervals

Psychophysical studies suggest that time intervals above and below 1.2 s are processed differently in the human brain. However, the neural underpinnings of this dissociation remain unclear. Here, we investigate whether distinct or common brain networks and dynamics support the passive perception of short (below 1.2 s) and long (above 1.2 s) empty time intervals. Twenty participants underwent an EEG recording during an auditory oddball paradigm with .8- and 1.6-s standard time intervals and deviant intervals either shorter (early) or longer (delayed) than the standard interval. We computed the auditory ERPs for each condition at the sensor and source levels. We then performed whole brain cluster-based permutation statistics for the CNV, N1 and P2, components, testing deviants against standards. A CNV was found only for above 1.2 s intervals (delayed deviants), with generators in temporo-parietal, SMA, and motor regions. Deviance detection of above 1.2 s intervals occurred during the N1 period over fronto-central sensors for delayed deviants only, with generators in parietal and motor regions. Deviance detection of below 1.2 s intervals occurred during the P2 period over fronto-central sensors for delayed deviants only, with generators in primary auditory cortex, SMA, IFG, cingulate and parietal cortex. We then identified deviance related changes in directed connectivity using bivariate Granger causality to highlight the networks dynamics associated with interval processing above and below 1.2. These results suggest that distinct brain dynamics and networks support the perception of time intervals above and below 1.2 s.

High-Altitude Exposure and Time Interval Perception of Chinese Migrants in Tibet.

High-altitude exposure can negatively impact one’s ability to accurately perceive time. This study focuses on Chinese migrants who have traveled to the Tibetan plateau and explores the effects of high-altitude exposure on their time interval judgment abilities based on three separate studies. In Study 1, it was found that exposure to high altitudes negatively impacted the time interval judgment functions of the migrants compared with a low-altitude control group; they exhibited a prolonged response time (540 ms: p = 0.006, 95% CI (−1.70 −0.32)) and reduced accuracy (1080 ms: p = 0.032, 95% CI (0.06 1.26)) in certain behavioral tasks. In Study 2, the results showed that high-altitude exposure and sleepiness had an interactive effect on time interval judgment (1080 ms) (p < 0.05, 95% CI (−0.83 −0.40)). To further verify our interaction hypothesis, in Study 3, we investigated the time interval judgment of interactions between acute high-altitude exposure and sleepiness level. The results revealed that the adaptation effect disappeared and sleepiness significantly exacerbated the negative effects of high-altitude exposure on time interval judgment (p < 0.001, 95% CI (−0.85 −0.34)). This study is the first to examine the effects of high-altitude exposure on time interval judgment processing functions and the effects of sleep-related factors on individual time interval judgment.

Perception of time intervals for different functional states of a working person.

Perception of time intervals for different functional states of a working person.

Methylphenidate modifies activity in the prefrontal and parietal cortex accelerating the time judgment

Methylphenidate produces its effects via actions on cortical areas involved with attention and working memory, which have a direct role in time estimation judgment tasks. In particular, the prefrontal and parietal cortex has been the target of several studies to understand the effect of methylphenidate on executive functions and time interval perception. However, it has not yet been studied whether acute administration of methylphenidate influences performance in time estimation task and the changes in alpha band absolute power in the prefrontal and parietal cortex. The current study investigates the influence of the acute use of methylphenidate in both performance and judgment in the time estimation interpretation through the alpha band absolute power activity in the prefrontal and parietal cortex. This is a double-blind, crossover study with a sample of 32 subjects under control (placebo) and experimental (methylphenidate) conditions with absolute alpha band power analysis during a time estimation task. We observed that methylphenidate does not influence task performance (p> 0.05), but it increases the time interval underestimation by over 7s (p< 0.001) with a concomitant decrease in absolute alpha band power in the ventrolateral prefrontal cortex and dorsolateral prefrontal cortex and parietal cortex (p< 0.001). Acute use of methylphenidate increases the time interval underestimation, consistent with reduced accuracy of the internal clock mechanisms. Furthermore, acute use of methylphenidate influences the absolute alpha band power over the dorsolateral prefrontal cortex, ventrolateral prefrontal cortex, and parietal cortex.

Why Do Durations in Musical Rhythms Conform to Small Integer Ratios?

One curious aspect of human timing is the organization of rhythmic patterns in small integer ratios. Behavioral and neural research has shown that adjacent time intervals in rhythms tend to be perceived and reproduced as approximate fractions of small numbers (e.g., 3/2). Recent work on iterated learning and reproduction further supports this: given a randomly timed drum pattern to reproduce, participants subconsciously transform it toward small integer ratios. The mechanisms accounting for this “attractor” phenomenon are little understood, but might be explained by combining two theoretical frameworks from psychophysics. The scalar expectancy theory describes time interval perception and reproduction in terms of Weber's law: just detectable durational differences equal a constant fraction of the reference duration. The notion of categorical perception emphasizes the tendency to perceive time intervals in categories, i.e., “short” vs. “long.” In this piece, we put forward the hypothesis that the integer-ratio bias in rhythm perception and production might arise from the interaction of the scalar property of timing with the categorical perception of time intervals, and that neurally it can plausibly be related to oscillatory activity. We support our integrative approach with mathematical derivations to formalize assumptions and provide testable predictions. We present equations to calculate durational ratios by: (i) parameterizing the relationship between durational categories, (ii) assuming a scalar timing constant, and (iii) specifying one (of K) category of ratios. Our derivations provide the basis for future computational, behavioral, and neurophysiological work to test our model.

Motor Timing and Covariation with Time Perception: Investigating the Role of Handedness.

Time is a fundamental dimension of our behavior and enables us to guide our actions and to experience time such as predicting collisions or listening to music. In this study, we investigate the regulation and covariation of motor timing and time perception functions in left- and right-handers who are characterized by distinct brain processing mechanisms for cognitive-motor control. To this purpose, we use a combination of tasks that assess the timed responses during movements and the perception of time intervals. The results showed a positive association across left- and right-handers between movement-driven timing and perceived interval duration when adopting a preferred tempo, suggesting cross-domain coupling between both abilities when an intrinsic timescale is present. Handedness guided motor timing during externally-driven conditions that required cognitive intervention, which specifies the relevance of action expertise for the performance of timed-based motor activities. Overall, our results reveal that individual variation across domain-general and domain-specific levels of organization plays a steering role in how one predicts, perceives and experiences time, which accordingly impacts on cognition and behavior.

The Time Is Up: Compression of Visual Time Interval Estimations of Bimodal Aperiodic Patterns.

The ability to estimate time intervals subserves many of our behaviors and perceptual experiences. However, it is not clear how aperiodic (AP) stimuli affect our perception of time intervals across sensory modalities. To address this question, we evaluated the human capacity to discriminate between two acoustic (A), visual (V) or audiovisual (AV) time intervals of trains of scattered pulses. We first measured the periodicity of those stimuli and then sought for correlations with the accuracy and reaction times (RTs) of the subjects. We found that, for all time intervals tested in our experiment, the visual system consistently perceived AP stimuli as being shorter than the periodic (P) ones. In contrast, such a compression phenomenon was not apparent during auditory trials. Our conclusions are: first, the subjects exposed to P stimuli are more likely to measure their durations accurately. Second, perceptual time compression occurs for AP visual stimuli. Lastly, AV discriminations are determined by A dominance rather than by AV enhancement.

Temporal Doppler Effect and Future Orientation: Adaptive Function and Moderating Conditions.

The objectives of this study were to examine whether the temporal Doppler effect exists in different time intervals and whether certain individual and environmental factors act as moderators of the effect. Using hierarchical linear modeling, we examined the existence of the temporal Doppler effect and the moderating effect of future orientation among 139 university students (Study 1), and then the moderating conditions of the temporal Doppler effect using two independent samples of 143 and 147 university students (Studies 2 and 3). Results indicated that the temporal Doppler effect existed in all of our studies, and that future orientation moderated the temporal Doppler effect. Further, time interval perception mediated the relationship between future orientation and the motivation to cope at long time intervals. Finally, positive affect was found to enhance the temporal Doppler effect, whereas control deprivation did not influence the effect. The temporal Doppler effect is moderated by the personality trait of future orientation and by the situational variable of experimentally manipulated positive affect. We have identified personality and environmental processes that could enhance the temporal Doppler effect, which could be valuable in cases where attention to a future task is necessary.

Phase interactions between EEG rhythms during short time interval perception

Phase interactions between electroencephalography (EEG) rhythms in the perception of short time intervals were investigated in 27 male and 29 female university students. The study has shown that tight phase relationships are most frequently observed between gammarhythm and other EEG rhythms or between different gamma frequencies. We determined that the discussed phase interactions were susceptible to the effect of factors, such as “gender,” “activity type,” and “activity stage.” Links were also detected between these phase interactions and the levels of intelligence, extraversion, neuroticism, the profile of the lateral organization of the brain, and the accuracy of time perception.

Восприятие и познание времени в пожилом и старческом возрасте (обзор зарубежных исследований)

The process of cognition and perception of time in the elderly (55-75 years) and old (75-90 years) people was always a matter of interest for gerontologists and psychologists looking for the answer to the question why in old age time flows very quickly on one hand and very slowly on the other hand. Studies show that the ability to adequately perceive and prioritize its activities in time in elderly patients depends on the physical, intellectual and social activity, and other factors that determine the quality of life and promote productive aging. The purpose of this article is to familiarize professionals with notions of perception and cognition of time, as well as paradigms of time perception studies in psychology. The article also familiarizes the readers with foreign research aspects of time cognition, i.e, orientation in time, perception of time intervals, time perspective, and mental journey of elderly patients through time

Significant variations in Weber fraction for changes in inter-onset interval of a click train over the range of intervals between 5 and 300 ms.

It is a common psychophysical experience that a train of clicks faster than ca. 30/s is heard as one steady sound, whereas temporal patterns occurring on a slower time scale are perceptually resolved as individual auditory events. This phenomenon suggests the existence of two different neural mechanisms for processing of auditory sequences with fast and slow repetition rates. To test this hypothesis we used Weber’s law, which is known to be valid for perception of time intervals. Discrimination thresholds and Weber fractions (WFs) for 12 base inter-click intervals (ICIs) between 5 and 300 ms were measured from 10 normal hearing subjects by using an “up–down staircase” algorithm. The mean WF, which is supposed to be constant for any perceptual mechanism according to Weber’s law, displayed significant variation with click rate. WFs decreased sharply from an average value of around 5% at repetition rates below 20 Hz to about 0.5% at rates above 67 Hz. Parallel to this steep transition, subjects reported that at rates below 20 Hz they perceived periodicity as a fast tapping rhythm, whereas at rates above 50 Hz the perceived quality was a pitch. Such a dramatic change in WF indicated the existence of two separate mechanisms for processing the click rate for long and short ICIs, based on temporal and spectral features, respectively. A range of rates between 20 and 33 Hz, in which the rate discrimination threshold was maximum, appears to be a region where both of the presumed time and pitch mechanisms are relatively insensitive to rate alterations. Based on this finding, we speculate that the interval-based perception mechanism ceases to function at around 20 Hz and the spectrum-based mechanism takes over at around 33 Hz; leaving a transitional gap in between, where neither of the two mechanisms is as sensitive. Another notable finding was a significant drop in WF for ICI = 100 ms, suggesting a connection of time perception to the electroencephalography alpha rhythm.

Conference report: “Music, mind, and brain” theme program at the Annual Convention of the Association for Psychological Science.

The Association for Psychological Science 24th Annual Convention met in Chicago, Illinois, May 24 -27, 2012. One of the theme programs was Music, Mind, and Brain, with presentations by eminent scientists in the field: Aniruddh Patel from the Neurosciences Institute, Carol Krumhansl from Cornell University, and Daniel J. Levitin from McGill University, who organized the session, as well as Victor Wooten, Grammy-award-winning bassist. As well as reviewing specialized content in the areas of musical rhythm, memory, talent, and training, the talks drew on similar points such as how music moves human beings (both physically and emotionally), how humans can learn music, and how music impacts other species. The program ended with a related poster session, and an evening concert featured two of the presenters.Keywords: APS, conference, music, mind, brainThe 24th annual convention of the Association for Psychological Science (APS), which took place in Chicago, Illinois, at the Sheraton Chicago Hotel & Towers May 24 -27, 2012, included a program titled Music, Mind, and Brain. Three leading cognitive psychologists and neuroscientists specializing in music as well as an internationally renowned musician discussed how structured, organized sound has the power to move us, literally and figuratively.Aniruddh Patel from the Neurosciences Institute (La Jolla, CA) began the program. Carol Krumhansl (Cornell University, Ithaca, NY) gave the second presentation, and was followed by Daniel J. Levitin (McGill University, Montreal, QC, Canada), who had organized the session. The session ended with a talk by Victor Wooten, five-time Grammy award winner and bassist for Bela Fleck and the Flecktones.The PresentationsAniruddh Patel, the Neurosciences Institute: Beat Perception and SynchronizationPatel began his talk Musical Beat Processing in Humans and Other Species by stating that moving to the beat occurs in every human culture. Patel investigated human's underlying mechanisms for singing and moving to the beat (e.g., clapping, tapping, etc.). Some researchers believe animals should be able to move to the beat because they can learn basic sensorimotor tasks. Patel argued the opposing position, that beat-based processing is rare in other animals because this processing is (a) cognitively complex, (b) engages a distinct brain network, and (c) may have evolved for social bonding. Therefore, beat perception and synchronization (BPS) are not possible for most species, including other primates, and these mental capacities associated with BPS rarely co-occur in animals.He elaborated on these mental capacities by discussing the cognitive complexity behind BPS. Beat perception is inherently sensorimotor, a type of temporal processing that depends on a subjective sense of periodicity, and is hierarchical (Palmer & Krumhansl, 1990; Toiviainen, Luck, & Thompson, 2010) and predictive because people actively anticipate the beat (Large & Jones, 1999). Although rhythm is amodal, BPS is primarily biased toward the auditory modality (Patel, Iversen, Chen, & Repp, 2005), even with a metronome (Repp, 2005), and shows limited plasticity. Patel discussed how past work implicates a distributed neural system in time interval perception in that there is no single timing center. Key regions for beat-based perception include (yet are not limited to) premotor cortex, basal ganglia, and dorsolateral prefrontal cortex, all of which interact with the auditory cortex.Beat-based processing is not simply bottom-up processing, but also has a top-down component as well. John Iversen from the Neurosciences Institute exploited top-down processing in a purely perceptual paradigm requiring no motor response, looking at how listeners' different inner metrical interpretations to the same rhythm (simply shifting which beat is the downbeat of a repeating rhythmic pattern) modulate the auditory responses and brain responses (Iversen, Repp, & Patel, 2009). …

More consistent, yet less sensitive: Interval timing in autism spectrum disorders

Even though phenomenological observations and anecdotal reports suggest atypical time processing in individuals with an autism spectrum disorder (ASD), very few psychophysical studies have investigated interval timing, and the obtained results are contradictory. The present study aimed to clarify which timing processes function atypically in ASD and whether they are related to the ASD diagnostic profile. Visual, auditory, and cross-modal interval timing was assessed in 18 individuals with ASD using a repeated standards version of the temporal generalization task. The use of two different standard durations (600 and 1,000 ms) allowed for an assessment of the scalar property of interval timing in ASD, a fundamental characteristic of interval timing. The ASD group showed clearer adherence to the scalar property of interval timing than the control group. In addition, both groups showed the normal effect that auditory stimuli had longer subjective durations than visual ones. Yet, signal detection analysis showed that the sensitivity of temporal discrimination was reduced in the ASD group across modalities, in particular for auditory standards. Moreover, response criteria in the ASD group were related to symptom strength in the communication domain. The findings suggest that temporal intervals are fundamentally processed in the same way in ASD and TD, but with reduced sensitivity for temporal interval differences in ASD. Individuals with ASD may show a more conservative response strategy due to generally decreased sensitivity for the perception of time intervals.

The Association Between Time Interval and Future Event Valence: A Mental Construal Process Perceptive

Consumers are constantly faced with decisions about the events that over time, and time seems to pervade every aspect of consumptive activity. However, the association between event valence and future time perception as well as the mechanism underlying the effects are still not clear. This study investigates the bi-directional relationship between the event valence and time interval perception and a possible mental construal process that may play a role in the associations. This research spans two studies. Study 1 was two 2×2 between-subjects experiments in which we manipulated the time interval (long, short) and event type (high-construal, low-construal). One hundred and four undergraduate students from a major university in Beijing participated in experiment 1a and eighty three undergraduate students from a major university in Beijing participated in experiment 1b. The results showed that the high-construal event was perceived more attractive in distant future, while the low-construal event was perceived more attractive in near future. The results also demonstrated that construal level mediated the impact of time interval on event valence perception. Study 2 was designed to investigate the inverse relationship of time interval and event valence. Forty-nine MBA students from a major university in Beijing participated in the study, in which we manipulated the event valence by ending with gain or loss. The results confirm previous research findings that event ending with loss looms shorter than event ending with gain occurred in the fixed time interval. Moreover, the mechanism underlying this effect is mainly driven by the construal level. That is, the event ending with gain will be construed at a high-level, which in turn makes time interval seem longer than the event ending with loss. These findings may have some important implications. First, the results extend the scope of construal level theory by showing that the association between event valence and temporal distance is a bi-directional relationship. Secondly, the research provides insights into the mental construal process underlying these effects, which elucidates why event ending with loss looms shorter than that with gain and why temporal distance will have an impact on event valence. Thirdly, the impact of temporal distance on event valence perception depends on the type of the event. The research makes a distinction between the two types of events and investigates the effects respectively, which also offers a new perspective on studying the associations between event valence and future time perceptions. Finally, this research contributes to the construal level literature by identifying event valence as a trigger of construal level variation.

Possible mechanisms for the effects of neuromodulators on the perception of time intervals

We propose possible mechanisms for the effects of neuromodulators on the perception of time on the basis of our hypothesis that estimation of intervals between sensory stimuli depends on the beat frequency of a “internal clock,” which is inversely proportional to the latency of reentering excitation of the neocortex. These effects are based on the modification of the efficacy of excitatory inputs to the cortical neurons, as well as inputs from the cortex to the striatum, which are necessary for the disinhibition of thalamic neurons by the basal ganglia and subsequent excitation of the cortex. The character of influence is determined by the concentration of neuromodulators, the types of receptors activated by them on neurons of the striatum and cortex, and the modulation rules. According to the proposed mechanism, an increase in the frequency of the “internal clock” and overestimation of the duration of intervals may result from treatment with dopaminergic drugs, agonists of dopamine D1 and D2 receptors, and opioids and cannabinoids, which promote an increase in the dopamine concentration, as well as antagonists of adenosine A1 and A2A and muscarinic M2 receptors, whose activation facilitates disinhibition of the thalamus by the basal ganglia. Antagonists of A1, M2, and D2 receptors, which prevent depression of excitatory inputs to neocortical pyramidal cells, also can increase the frequency of the “internal clock.” The activation of a large number of D2 receptors on the cortical pyramidal cells, which results from a considerable increase in dopamine concentration, like activation of cannabinoid CB1 receptors, should promote a decrease in the frequency of the “internal clock” and the underestimation of interval duration. The activation of D2 and M2 receptors on the GABAergic interneurons of the cortex under conditions of strong inhibition of pyramidal neurons may increase the beat frequency of the “internal clock.” The proposed mechanism helps to understand the causes of errors in time perception in neurological diseases and to explain the discrepancies in the results of studies on the effects of neuromodulators on the estimation of time. The hypothesis may be experimentally examined by treatment of the striatum or neocortex with agonists and antagonists of various types of receptors and measurement of the drug-induced changes in the interval between the first and second peaks in the distribution of latencies of responses of cortical neurons to sensory stimulus.

Auditory Time-Interval Perception as Causal Inference on Sound Sources

Perception of a temporal pattern in a sub-second time scale is fundamental to conversation, music perception, and other kinds of sound communication. However, its mechanism is not fully understood. A simple example is hearing three successive sounds with short time intervals. The following misperception of the latter interval is known: underestimation of the latter interval when the former is a little shorter or much longer than the latter, and overestimation of the latter when the former is a little longer or much shorter than the latter. Although this misperception of auditory time intervals for simple stimuli might be a cue to understanding the mechanism of time-interval perception, there exists no model that comprehensively explains it. Considering a previous experiment demonstrating that illusory perception does not occur for stimulus sounds with different frequencies, it might be plausible to think that the underlying mechanism of time-interval perception involves a causal inference on sound sources: herein, different frequencies provide cues for different causes. We construct a Bayesian observer model of this time-interval perception. We introduce a probabilistic variable representing the causality of sounds in the model. As prior knowledge, the observer assumes that a single sound source produces periodic and short time intervals, which is consistent with several previous works. We conducted numerical simulations and confirmed that our model can reproduce the misperception of auditory time intervals. A similar phenomenon has also been reported in visual and tactile modalities, though the time ranges for these are wider. This suggests the existence of a common mechanism for temporal pattern perception over modalities. This is because these different properties can be interpreted as a difference in time resolutions, given that the time resolutions for vision and touch are lower than those for audition.

A Neural Correlate of the Processing of Multi-Second Time Intervals in Primate Prefrontal Cortex

Several areas of the brain are known to participate in temporal processing. Neurons in the prefrontal cortex (PFC) are thought to contribute to perception of time intervals. However, it remains unclear whether the PFC itself can generate time intervals independently of external stimuli. Here we describe a group of PFC neurons in area 9 that became active when monkeys recognized a particular elapsed time within the range of 1–7 seconds. Another group of area 9 neurons became active only when subjects reproduced a specific interval without external cues. Both types of neurons were individually tuned to recognize or reproduce particular intervals. Moreover, the injection of muscimol, a GABA agonist, into this area bilaterally resulted in an increase in the error rate during time interval reproduction. These results suggest that area 9 may process multi-second intervals not only in perceptual recognition, but also in internal generation of time intervals.

Body signals, cardiac awareness, and the perception of time

Recent research suggests that our sense of time intervals in the range of seconds is directly related to activity in the insular cortex, which contains the primary sensory area for interoception. We therefore investigated whether performance in a duration reproduction task might correlate with individual interoceptive awareness and with measurable changes in autonomic activity during the task. Thirty-one healthy volunteers participated in an interoceptive (heartbeat) perception task and in repeated temporal reproduction trials using intervals of 8, 14, and 20s duration while skin conductance levels and cardiac and respiratory periods were recorded. We observed progressive increases in cardiac periods and decreases in skin conductance level during the encoding and (less reliably) the reproduction of these intervals. Notably, individuals’ duration reproduction accuracy correlated positively both with the slope of cardiac slowing during the encoding intervals and with individual heartbeat perception scores. These results support the view that autonomic function and interoceptive awareness underpin our perception of time intervals in the range of seconds.

Interval timing with a beat frequency model connecting phase resetting and network response

Time perception is essential for normal physiological and behavioral responses, e.g., recalling stored data and planning future actions, and is deregulated in a series of neuropathologies, e.g., Parkinson’s disease. It is commonly accepted that processing temporal information involves a neural mechanism mimicking a stopwatch such as in the Scalar Expectancy Theory [1]. Organisms have multiple neural timing mechanisms that can span more than 10 orders of magnitude form circadian (24 hours) to interval (minutes) to millisecond timing [2]. Our focus is on modeling neural networks responsible for interval timing. In designing any computational model of interval timing, we must acknowledge an experimentally observed fact: the plot of mean response time versus the standard deviation of the distribution for different timing intervals is linear (scalar property). The established paradigm assumes an internal clock model in which pulses that are emitted regularly by a pacemaker are temporarily stored in an accumulator. At the time of reward or feedback, the number of pulses stored in the accumulator is transferred to the reference memory for future use. During “peak-interval procedure” (in which the participants are asked to reproduce the criterion interval) it is assumed that the internal clock is reset and pulses stored into accumulator until the current count match the memorized value stored during the training. The model we used assumes that timing is an emergent activity originated in the thalamo-cortico-striatal loops [2,3]. In this striatal beat-frequency (SBF) model, timing is based on the coincidental activation of medium spiny neurons in the basal ganglia by cortical neural oscillators [2,3]. The cortical oscillators are assumed to be synchronized at the onset of a trial, and to oscillate at a fixed frequency throughout the criterion interval. In our computational model, the oscillator block is composed of independent spiking neurons with intrinsic frequencies fi which, due to varying factors (biological noise, background neural activity from other cortical areas, etc.), are randomly distributed according to a certain density probability function. The synchronization of cortical oscillations at trial onset and the experience-dependent changes in cortico-striatal transmission are thought to be modulated by the dopaminergic neurons in the substatia nigra pars compacta and ventral tegmental area. A memory block stores the criterion time value c memorized during the training process. However, both storage and retrieval of criterion time to and from memory units is affected by biological context (brain state) and is modeled by randomly distributing criterion time according to a certain density probability function [3]. All timing models must connect the objective time with the subjective time. The subjective time is strongly influenced by brain’s state through neuromodulators. For example, dopamine advances the response whereas achetylcholine can induce a delay of the response in a fixed interval experiment. The mechanism involved could be through a direct change in firing frequency due to neurotransmitter action and it was modeled as a separate clock block. The decision block is an essential component of any timing mechanism that relates internal perception of time intervals with external action. A straightforward mechanism of implementing decision-making uses a set of synaptic weights derived from the memorized criterion time [3]. The weights computed from the memorized criterion constitute the reference vector of weighs. The decision block estimates the projection of the current weights on the vector of weight reference weight. The model correctly reproduced measured behavioral data.

Dissociations between motor timing, motor coordination, and time perception after the administration of alcohol or caffeine

The impacts of psychoactive drugs on timing have usefully informed theories of timing and its substrates. The objectives of the study are to test the effects of alcohol and caffeine on the explicit timing involved in tapping with the implicit timing observed in the coordinated picking up of an object, and with the temporal discrimination. Participants in the "alcohol" experiment (N = 16) received placebo, "low" (0.12 g/kg or 0.14 g/kg for women/men, respectively) or "high" (0.37 g/kg or 0.42 g/kg, respectively) doses of alcohol, and those in the "caffeine" experiment (N = 16) received placebo, 200 or 400 mg caffeine. Time production variability was measured by repetitive tapping of specified intervals, and sources of variance attributable to central timer processes and peripheral motor implementation were dissociated. The explicit timing in tapping was compared with the implicit timing in the coordinated picking up of an object. Time perception was measured as discrimination thresholds for intervals of similar duration. Drug effects on reaction time were also measured. For tapping, alcohol significantly increased timer variability, but not motor variability; it did not affect coordination timing in the grip-lift task. Conversely, for time perception, the low dose of alcohol improved temporal discrimination. Caffeine produced no effects on any of the timing tasks, despite significantly reducing reaction times. The effects of alcohol argue against a common clock process underlying time interval perception and production in the range below 1 s. In contrast to reaction time measures, time perception and time production appear relatively insensitive to caffeine.