Previous studies have shown that the perceived duration of visual stimuli can be strongly distorted by auditory stimuli presented simultaneously. In this study, we examine whether sounds presented separately from target visual stimuli alter the perceived duration of the target's presentation. The participants' task was to classify the duration of the target visual stimuli as perceived by them into four categories. Our results demonstrate that a sound presented before and after a visual target increases or decreases the perceived visual duration depending on the inter-stimulus interval between the sounds and the visual stimulus. In addition, three tones presented before and after a visual target did not increase or decrease the perceived visual duration. This indicates that auditory perceptual grouping prevents intermodal perceptual grouping, and eliminates crossmodal effects. These findings suggest that the auditory-visual integration, rather than a high arousal state caused by the presentation of the preceding sound, can induce distortions of perceived visual duration, and that inter- and intramodal perceptual grouping plays an important role in crossmodal time perception. These findings are discussed with reference to the Scalar Expectancy Theory.

BACKGROUND: Mismatch negativity (MMN) is the neurophysiological correlate of cognitive integration of novel stimuli. Although MMN is a well-established predictor of awakening in non-sedated comatose patients, its prognostic value in deeply sedated critically ill patients remains unknown. The aim of this prospective, observational pilot study was to investigate the prognostic value of MMN for subsequent awakening in deeply sedated critically ill patients. METHODS: MMN was recorded in 43 deeply sedated critically ill patients on Day 3 of ICU admission using a classical 'odd-ball' paradigm that delivers rare deviant sounds in a train of frequent standard sounds. Individual visual analyses and a group level analysis of recordings were performed. MMN amplitudes were then analysed according to the neurological status (awake vs not awake) at Day 28. RESULTS: Median (inter-quartile range) Richmond Assessment Sedation Scale (RASS) at the time of recording was -5 (range, from -5 to -4.5). Visual detection of MMN revealed a poor inter-rater agreement [kappa=0.17, 95% confidence interval (0.07-0.26)]. On Day 28, 30 (70%) patients had regained consciousness while 13 (30%) had not. Quantitative group level analysis revealed a significantly greater MMN amplitude for patients who awakened compared with those who had not [mean (standard deviation) = -0.65 (1.4) vs 0.08 (0.17) muV, respectively; P=0.003). CONCLUSIONS: MMN can be observed in deeply sedated critically ill patients and could help predict subsequent awakening. However, visual analysis alone is unreliable and should be systematically completed with individual level statistics.

Non-motor symptoms in Parkinson's Disease (PD) predate motor symptoms and substantially decrease quality of life; however, detection, monitoring, and treatments are unavailable for many of these symptoms. Temporal perception abnormalities in PD are generally attributed to altered Basal Ganglia (BG) function. Present studies are confounded by motor control facilitating movements that are integrated into protocols assessing temporal perception. There is uncertainty regarding the BG's influence on timing processes of different time scales and how PD therapies affect this perception. In this study, PD patients using Levodopa (n = 25), Deep Brain Stimulation (DBS; n = 6), de novo patients (n = 6), and healthy controls (n = 17) completed a visual temporal perception task in seconds and sub-section timing scales using a computer-generated graphical tool. For all patient groups, there were no impairments seen at the smaller tested magnitudes (using sub-second timing). However, all PD groups displayed significant impairments at the larger tested magnitudes (using interval timing). Neither Levodopa nor DBS therapy led to significant improvements in timing abilities. Levodopa resulted in a strong trend towards impairing timing processes and caused a deterioration in perceptual coherency according to Weber's Law. It is shown that timing abnormalities in PD occur in the seconds range but do not extend to the sub-second range. Furthermore, observed timing deficits were shown to not be solely caused by motor deficiency. This provides evidence to support internal clock models involving the BG (among other neural regions) in interval timing, and cerebellar control of sub-second timing. This study also revealed significant temporal perception deficits in recently diagnosed PD patients; thus, temporal perception abnormalities might act as an early disease marker, with the graphical tool showing potential for disease monitoring.

BACKGROUND: Current theories of interval timing assume that humans and other animals time as if using a single, absolute stopwatch that can be stopped or reset on command. Here we evaluate the alternative view that psychological time is represented by multiple clocks, and that these clocks create separate temporal contexts by which duration is judged in a relative manner. Two predictions of the multiple-clock hypothesis were tested. First, that the multiple clocks can be manipulated (stopped and/or reset) independently. Second, that an event of a given physical duration would be perceived as having different durations in different temporal contexts, i.e., would be judged differently by each clock. METHODOLOGY/PRINCIPAL FINDINGS: Rats were trained to time three durations (e.g., 10, 30, and 90 s). When timing was interrupted by an unexpected gap in the signal, rats reset the clock used to time the

In the current paper it is proposed that short-term plasticity and dynamic changes in the balance of excitatory-inhibitory interactions may underlie the decoding of temporal information, that is, the generation of temporally selective neurons. Our initial approach was to simulate excitatory-inhibitory disynaptic circuits. Such circuits were composed of a single excitatory and inhibitory neuron and incorporated short-term plasticity of EPSPs and IPSPs and slow IPSPs. We first showed that it is possible to tune cells to respond selectively to different intervals by changing the synaptic weights of different synapses in parallel. In other words, temporal tuning can rely on long-term changes in synaptic strength and does not require changes in the time constants of the temporal properties. When the units studied in disynaptic circuits were incorporated into a larger single-layer network, the units exhibited a broad range of temporal selectivity ranging from no interval tuning to interval-selective tuning. The variability in temporal tuning relied on the variability of synaptic strengths. The network as a whole contained a robust population code for a wide range of intervals. Importantly, the same network was able to discriminate simple temporal sequences. These results argue that neural circuits are intrinsically able to process temporal information on the time scale of tens to hundreds of milliseconds and that specialized mechanisms, such as delay lines or oscillators, may not be necessary.

We all have a sense of time. Yet, there are no sensory receptors specifically dedicated for perceiving time. It is an almost uniquely intangible sensation: we cannot see time in the way that we see color, shape, or even location. So how is time represented in the brain? We explore the neural substrates of metrical representations of time such as duration estimation (explicit timing) or temporal expectation (implicit timing). Basal ganglia (BG), supplementary motor area, cerebellum, and prefrontal cortex have all been linked to the explicit estimation of duration. However, each region may have a functionally discrete role and will be differentially implicated depending upon task context. Among these, the dorsal striatum of the BG and, more specifically, its ascending nigrostriatal dopaminergic pathway seems to be the most crucial of these regions, as shown by converging functional neuroimaging, neuropsychological, and psychopharmacological investigations in humans, as well as lesion and pharmacological studies in animals. Moreover, neuronal firing rates in both striatal and interconnected frontal areas vary as a function of duration, suggesting a neurophysiological mechanism for the representation of time in the brain, with the excitatory-inhibitory balance of interactions among distinct subtypes of striatal neuron serving to fine-tune temporal accuracy and precision.

Individuals with autism spectrum disorder (ASD) have difficulties in social interactions. The cognitive domains that support these interactions include perceptual decision-making, timing, and error-monitoring, which enable one to appropriately understand and react to the other individual in communicative settings. This study constitutes a comprehensive exploration of decision-making and interval timing in ASD as well as the first investigation of error-monitoring abilities of individuals with ASD regarding their performance in the corresponding domains. We found that children with ASD fared similar to typically developing (TD) children in their first-order task performance in two-alternative forced choice perceptual decision-making and temporal reproduction tasks as well as the secondary tasks (signal detection and free finger tapping tasks). Yet, they had a deficit in error-monitoring in both tasks where their accuracy did not predict their confidence ratings, which was the case for the TD group. The difference between ASD and TD groups was limited to error-monitoring performance. This study attests to a circumscribed impairment in error-monitoring in individuals with ASD, which may partially underlie their social interaction problems. This difficulty in cognitively evaluating one's own performance may also relate to theory of mind deficits reported for individuals with ASD, where they struggle in understanding the mental states and intentions of others. This novel finding holds the potential to inform effective interventions for individuals with ASD that can target this error-monitoring ability to have broad-ranging effects in multiple domains involved in communication and social interaction. Autism Res 2019, 12: 239-248 (c) 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Decision-making, timing, and error-monitoring are three of many abilities that underlie smooth social interactions. To date, these domains have been only investigated separately, but given their interactive role in social interactions that are impaired in ASD, we conducted the first study to investigate them together. Children with ASD were as successful as typically developing children in their task performances, but unlike them, were unaware of their errors in both decision-making and timing tasks. This deficit that is limited to error-monitoring can contribute to unraveling the unique cognitive signature of ASD and to formulating interventions with positive implications in multiple domains.

Recent studies have revealed the existence of hippocampal neurons that fire at successive moments in temporally structured experiences. Several studies have shown that such temporal coding is not attributable to external events, specific behaviours or spatial dimensions of an experience. Instead, these cells represent the flow of time in specific memories and have therefore been dubbed 'time cells'. The firing properties of time cells parallel those of hippocampal place cells; time cells thus provide an additional dimension that is integrated with spatial mapping. The robust representation of both time and space in the hippocampus suggests a fundamental mechanism for organizing the elements of experience into coherent memories.

6.5 s. A 2-parameter logistic function was fitted to the proportional choice for lever B (%B responding), yielding estimates of the indifference point (T50) and the Weber fraction (a measure of timing precision). The 5-HT2A antagonist M100907 increased T50, whereas the 5-HT2C antagonist SB-242,084 reduced T50. The results indicate that 5-HT2A and 5-HT2C receptors have countervailing effects on the speed of the internal pacemaker. The hallucinogen 2,5-dimethoxy-4-iodoamphetamine (DOI; 3 mg/kg IP), a 5-HT2 agonist, flattened the response curve at long stimulus intervals and shifted it to the right, causing both T50 and the Weber fraction to increase. The effect of DOI was antagonized by M100907 (0.03 mg/kg SC) but was unaffected by SB-242,084 (0.1 mg/kg SC). Similar to DOI, the selective 5-HT2A agonist 25CN-NBOH (6 mg/kg SC) reduced %B responding at long stimulus intervals, and increased T50 and the Weber fraction. These results demonstrate that hallucinogens alter temporal perception in mice, effects that are mediated by the 5-HT2A receptor. It appears that 5-HT regulates temporal perception, suggesting that altered serotonergic signaling may contribute to the timing deficits observed in schizophrenia and other psychiatric disorders.]]>

While the definition of Autism Spectrum Disorder (ASD) does not include any explicit criteria concerning difficulties of time perception or management, there is growing evidence of atypical temporal perception in individuals with ASD. This review synthesizes the evidence and gaps of the current literature on time processing in ASD. After a brief overview of clinical findings and available assessment tools, we synthetize outcomes of studies evaluating time perception at second and infra-second level, and then, recent literature on the circadian timing system. Findings point that all levels of time processing are atypical in autism (i.e. millisecond, interval and circadian timing). We discuss how time perception abnormalities and ASD core symptoms might intertwine and offer a new perspective for future research on this topic. We advocate the need to systematically assess temporal perception in ASD, and to include these aspects in global functional assessments before intervention. Implementing early intervention techniques to remediate time perception alterations in children with ASD may substantially improve their developmental trajectory.

The neural basis of time perception is unknown. Here we show that neurons in the posterior parietal cortex (area LIP) represent elapsed time relative to a remembered duration. We trained rhesus monkeys to report whether the duration of a test light was longer or shorter than a remembered

Time perception is an important ability that is related closely to humans' and animals' daily activities. It can be distorted by various emotional states. In human studies, experimental pain has been shown to prolong the perception of time. However, related animal studies are lacking. In this study, we used a temporal bisection task to investigate how acute inflammatory pain (induced by hind-paw formalin injection) and chronic neuropathic pain [induced by spinal nerve ligation (SNL)] affected time perception in rats. Rats were trained to recognize

BACKGROUND: Studies at the molecular level aim to integrate genetic and neurobiological data to provide an increasingly detailed understanding of phenotypes related to the ability in time perception. MAIN TEXT: This study suggests that the polymorphisms genetic SLC6A4 5-HTTLPR, 5HTR2A T102C, DRD2/ANKK1-Taq1A, SLC6A3 3'-UTR VNTR, COMT Val158Met, CLOCK genes and GABRB2 A/C as modification factor at neurochemical levels associated with several neurofunctional aspects, modifying the circadian rhythm and built-in cognitive functions in the timing. We conducted a literature review with 102 studies that met inclusion criteria to synthesize findings on genetic polymorphisms and their influence on the timing. CONCLUSION: The findings suggest an association of genetic polymorphisms on behavioral aspects related in timing. However, order to confirm the paradigm of association in the timing as a function of the molecular level, still need to be addressed future research.

Humans and other animals demonstrate the ability to perceive and respond to temporally relevant information with characteristic behavioral properties. For example, the response time distributions in peak-interval timing tasks are well described by Gaussian functions, and superimpose when scaled by the criterion duration. This superimposition has been referred to as the scalar property and results from the fact that the standard deviation of a temporal estimate is proportional to the duration being timed. Various psychological models have been proposed to account for such responding. These models vary in their success in predicting the temporal control of behavior as well as in the neurobiological feasibility of the mechanisms they postulate. A review of the major interval timing models reveals that no current model is successful on both counts. The neurobiological properties of the basal ganglia, an area known to be necessary for interval timing and motor control, suggests that this set of structures act as a coincidence detector of cortical and thalamic input. The hypothesized functioning of the basal ganglia is similar to the mechanisms proposed in the beat frequency timing model [R.C. Miall, Neural Computation 1 (1989) 359-371], leading to a reevaluation of its capabilities in terms of behavioral prediction. By implementing a probabilistic firing rule, a dynamic response threshold, and adding variance to a number of its components, simulations of the striatal beat frequency model were able to produce output that is functionally equivalent to the expected behavioral response form of peak-interval timing procedures.

This study investigated the firing patterns of striatal and cortical neurons in rats in a temporal generalization task. Striatal and cortical ensembles were recorded in rats trained to lever press at 2 possible criterion durations (10 s or 40 s from tone onset). Twenty-two percent of striatal and 15% of cortical cells had temporally specific modulations in their firing rate, firing at a significantly different rate around 10 s compared with 40 s. On 80% of trials, a post hoc analysis of the trial-by-trial consistency of the firing rates of an ensemble of neurons predicted whether a spike train came from a time window around 10 s versus around 40 s. Results suggest that striatal and cortical neurons encode specific durations in their firing rate and thereby serve as components of a neural circuit used to represent duration.

Time is a guiding force in the behavior of all organisms. For both a rat in an experimental setting (e.g. Skinner box) trying to predict when reinforcement will be delivered and a human in a restaurant waiting for his dinner to be served an accurate perception of time is an important determinant of behavior. Recent research has used a combination of pharmacological and behavioral manipulations to gain a fuller understanding of how temporal information is processed. A psychological model of duration discrimination that differentiates the speed of an internal clock used for the registration of current sensory input from the speed of the memory-storage process used for the representation of the durations of prior stimulus events has proven useful in integrating these findings. Current pharmacological research suggests that different stages of temporal processing may involve separate brain regions and be modified by different neurotransmitter systems. For example, the internal clock used to time durations in the seconds-to-minutes range appears linked to dopamine (DA) function in the basal ganglia, while temporal memory and attentional mechanisms appear linked to acetylcholine (ACh) function in the frontal cortex. These two systems are connected by frontal-striatal loops, thus allowing for the completion of the timing sequences involved in duration discrimination.

The effects of selective dopamine (DA) depleting lesions with 6-hydroxydopamine microinjection into the SN, CPu, and NAS, as well as radiofrequency lesions of the CPu on the performance characteristics of rats trained on a single-valued 20-s peak-interval (PI) timing procedure or a double-valued 10-s and 60-s PI procedure were evaluated. A double dissociation in the performance of duration discriminations was found. Rats with CPu lesions were unable to exhibit temporal control of their behavior suggesting complete insensitivity to signal duration but were able to show discrimination of the relative reward value of a signal by differentially modifying their response rates appropriately. In contrast, rats with NAS lesions were able to exhibit temporal control of their behavior by differentially modifying their response rates as a function of signal duration(s), suggesting no impairment of sensitivity to signal duration, but were unable to show discrimination of the relative reward value of a signal.

Animal studies of impulsivity have typically used one of three models: a delay of reward procedure, a differential reinforcement for low rate responding (DRL) procedure, or an autoshaping procedure. In each of these paradigms, we argue, measurement of impulsivity is implicitly or explicitly equated with the effect delay has on the value of reward. The steepness by which delay diminishes value (the temporal discount function) is treated as an index of impulsivity. In order to provide a better analog of human impulsivity, this model needs to be expanded to include the converse of impulsivity - self-control. Through mechanisms such as committing to long range interests before the onset of temptation, or through bundling individual choices into classes of choices that are made at once, human decision-making can often look far less myopic than single trial experiments predict. For people, impulsive behavior may be more often the result of the breakdown of self-control mechanisms than of steep discount functions. Existing animal models of self-control are discussed, and future directions are suggested for psychopharmacological research.

In the present article, the basic research using the mismatch negativity (MMN) and analogous results obtained by using the magnetoencephalography (MEG) and other brain-imaging technologies is reviewed. This response is elicited by any discriminable change in auditory stimulation but recent studies extended the notion of the MMN even to higher-order cognitive processes such as those involving grammar and semantic meaning. Moreover, MMN data also show the presence of automatic intelligent processes such as stimulus anticipation at the level of auditory cortex. In addition, the MMN enables one to establish the brain processes underlying the initiation of attention switch to, conscious perception of, sound change in an unattended stimulus stream.

The purpose of the present experiment was to evaluate timing behavior in spontaneously hypertensive rats (SHR), and compare it to the performance of Wistar Kyoto (WKY), and Wistar (WI) rats. In the first phase of the experiment, the subjects were exposed to a peak-interval procedure, in which fixed-interval 30s trials were alternated with nonreinforced and extended (peak) trials. After 60 sessions, an approximation to a Gaussian probability density function was fitted to the response rate during peak trials in order to estimate the peak time, the peak rate and the Weber fraction. The results showed no difference among the strains in the peak time and the Weber fraction, but a higher peak rate in SHR. In the second phase of the experiment, a gap procedure was introduced; in 80% of the peak trials the stimuli associated with the fixed interval and peak trials were turned off for 9s. Gap trials produced peak time shifts that were longer than those expected if the clock had stopped during the gap but shorter than those had the clock been reset, and no significant differences between the strains were found. Given the great importance that different theories give to temporal processing in the development of the main symptoms of attention deficit hyperactivity disorder (ADHD), and the existence of time perception deficits in humans with ADHD, the present results question the validity of SHR as an animal model of that disorder, and suggest the necessity of exploring the timing behavior of other animal models of ADHD.

Organizing behavior in time is a fundamental process that is highly conserved across species. Here we study the neural basis of timing processes. First, we found that rodents had a burst of stimulus-triggered 4 Hz oscillations in the medial frontal cortex (MFC) during interval timing tasks. Second, rodents with focally disrupted MFC D1 dopamine receptor (D1DR) signaling had impaired interval timing performance and weaker stimulus-triggered oscillations. Prior work has demonstrated that MFC neurons ramp during interval timing, suggesting that they underlie temporal integration. We found that MFC D1DR blockade strongly attenuated ramping activity of MFC neurons that correlated with behavior. These macro- and micro-level phenomena were linked, as we observed that MFC neurons with strong ramping activity tended to be coherent with stimulus-triggered 4 Hz oscillations, and this relationship was diminished with MFC D1DR blockade. These data provide evidence demonstrating how D1DR signaling controls the temporal organization of mammalian behavior.

Medial frontal cortical (MFC) dopamine is essential for the organization of behavior in time. Our prior work indicates that blocking D1 dopamine receptors (D1DR) attenuates temporal processing and low-frequency oscillations by MFC neuronal networks. Here we investigate the effects of focal infusion of the D1DR agonist SKF82958 into MFC during interval timing. MFC D1DR agonist infusion impaired interval timing performance without changing overall firing rates of MFC neurons. MFC ramping patterns of neuronal activity that reflect temporal processing were attenuated following infusion of MFC D1DR agonist. MFC D1DR agonist infusion also altered MFC field potentials by enhancing delta activity between 1 and 4 Hz and attenuating alpha activity between 8 and 15 Hz. These data support the idea that the influence of D1-dopamine signals on frontal neuronal activity adheres to a U-shaped curve, and that cognition requires optimal levels of dopamine in frontal cortex.

We have all experienced that time seems stretched during unpleasant situations. While there is evidence of subjective time overestimation when perceiving external unpleasant stimuli, no study has measured the dilation of time when individuals experience an unpleasant situation in their own body. Here we measured the time dilation induced by a painful homeostatic deviance using temporal bisection task. We show that being in pain leads to an expansion of subjective time whereby a stronger increase in pain perception relative to non-painful stimulation leads to a stronger time-estimate distortion. Neurophysiological studies suggest that time estimation and the perception of self might share a common neural substrate. We propose that, along with bodily arousal and attentional capture, the enhancement of self-awareness may be critical to support dilated subjective time when experiencing pain. As other homeostatic deviances, pain may induce a focus on ourselves contributing to the impression that

Behavioral estimates of time discrimination threshold on animals might be contaminated by the conditioning procedure used and by attentional effects. To avoid such side effects, we measured time discrimination by recording the rat electroencephalographic response to small temporal variations. Freely moving rats were presented with repetitive sounds, some of them being occasionally shorter than the standard, to produce a Mismatch Negativity (MMN) which is known to primarily involve preattentive processes. The smallest difference eliciting a MMN located the discrimination threshold between 16% and 33% of the standard, without attentional confound. Being observed in several species, MMN can be used to decipher both the phylogenetic and ontogenetic evolution of time discrimination, without attentional confound.

Impulsive choice behavior has been proposed as a primary risk factor for other maladaptive behaviors (e.g., gambling, substance abuse). Recent research has suggested that timing processes may play a key role in impulsive choice behavior, and could provide an avenue for altering impulsive choice. Accordingly, the current experiments assessed a set of time-based behavioral interventions to increase self-control while simultaneously assessing effects on timing processes within the impulsive choice task. Three experiments assessed temporal interventions using a differential reinforcement of low rates task (Experiment 1) and exposure to either a variable or fixed interval schedule (Experiments 2-3). The efficacy of the interventions was assessed in Sprague-Dawley (Experiments 1-2) and Lewis (Experiment 3) rat strains. Impulsive choice behavior was assessed by measuring preferences of a smaller-sooner (SS) versus a larger-later (LL) reward, while timing of the SS and LL durations was measured during peak trials within the impulsive choice procedure. The rats showed an increased preference for the LL following all three time-based interventions and also displayed increased temporal precision. These results add to the increasing evidence that supports a possible role for temporal processing in impulsive choice behavior and supply novel behavioral interventions to decrease impulsive behavior.

Pigeons were trained to discriminate the duration of a stimulus. One response in a psychophysical choice situation was reinforced, given the immediately prior presentation of a stimulus duration in one class of durations called short durations, and the other response was reinforced given the immediately prior presentation of a stimulus duration in a second class called long durations. Durations of equal logarithmic difference from the cutoff, whether in the short or long class, yielded equal accuracy. Accuracy was a function not only of the properties of the stimuli to be discriminated, but also of the experimental contingencies used. Accuracy was greater in variable-ratio than in fixed-ratio schedules of reinforcement of the discriminative responses, and was lower at the beginning than later in individual fixed ratios. Proportion of short or long responses (response bias) was affected by sequential dependencies among long and short durations and was effectively controlled through the use of asymmetric reinforcement and fixed-ratio contingencies.

Involvement of the dorsal hippocampus (DHPC) in conditioned-response timing and maintaining temporal information across time gaps was examined in an appetitive Pavlovian conditioning task, in which rats with sham and DHPC lesions were first conditioned to a 15-s visual cue. After acquisition, the subjects received a series of non-reinforced test trials, on which the visual cue was extended (45 s) and gaps of different duration, 0.5, 2.5, and 7.5 s, interrupted the early portion of the cue. Dorsal hippocampal-lesioned subjects underestimated the target duration of 15 s and showed broader response distributions than the control subjects on the no-gap trials in the first few blocks of test, but the accuracy and precision of their timing reached the level of that of the control subjects by the last block. On the gap trials, the DHPC-lesioned subjects showed greater rightward shifts in response distributions than the control subjects. We discussed these lesion effects in terms of temporal versus non-temporal processing (response inhibition, generalisation decrement, and inhibitory conditioning).

BACKGROUND: Depressive patients frequently report to perceive time as going by very slowly. Potential effects of depression on duration judgments have been investigated mostly by means of four different time perception tasks: verbal time estimation, time production, time reproduction, and duration discrimination. Ratings of the subjective flow of time have also been obtained. METHODS: By means of a classical random-effects meta-regression model and a robust variance estimation model, this meta-analysis aims at evaluating the inconsistent results from 16 previous studies on time perception in depression, representing data of 433 depressive patients and 485 healthy control subjects. RESULTS: Depressive patients perceive time as going by less quickly relative to control subjects (g=0.66, p=0.033). However, the analyses showed no significant effects of depression in the four time perception tasks. There was a trend towards inferior time discrimination performance in depression (g=0.38, p=0.079). The meta-regression also showed no significant effects of interval duration. Thus, the lack of effects of depression on timing does not depend on interval duration. However, for time production, there was a tendency towards overproduction of short and underproduction of long durations in depressive patients compared to healthy controls. LIMITATIONS: Several aspects, such as influences of medication and the dopaminergic neurotransmitter system on time perception in depression, have not been investigated in sufficient detail yet and were therefore not addressed by this meta-analysis. CONCLUSIONS: Depression has medium effects on the subjective flow of time whereas duration judgments basically remain unaffected.

Operant procedures combined with pharmacological manipulations have implicated a role for the dopaminergic system in the perception and production of temporal intervals. Because studies have suggested that animals use temporal information to organize food protection behavior, the current study investigates whether dopaminergic systems are involved in timing during this natural behavior. The experiment examined the influence of a dopaminergic agonist (amphetamine) and an antagonist (haloperidol) on food protection behavior initiated to avoid theft by a conspecific. Amphetamine increased the time spent dodging and decreased the time spent bracing during the consumption of a hazelnut. On the other hand, haloperidol decreased the time spent dodging while showing no systematic changes in bracing. Topographic and kinematic analyses of rat movement conflicted with motivational, motoric, and social accounts of drug-induced changes in food protection behavior organization. These observations provide evidence that rats use temporal information to organize movements in the natural behavior of protecting food from theft by a conspecific, and this organization is influenced by both a dopaminergic agonist and an antagonist.

A large number of competing models exist for how the brain creates a representation of time. However, several human and animal studies point to 'climbing neural activation' as a potential neural mechanism for the representation of duration. Neurophysiological recordings in animals have revealed how climbing neural activation that peaks at the end of a timed interval underlies the processing of duration, and, in humans, climbing neural activity in the insular cortex, which is associated with feeling states of the body and emotions, may be related to the cumulative representation of time.