Production of Time Intervals by Aged Subjects

Characteristics of time perception by aged subjects of both sexes aged 60–91 years were studied. They assessed time intervals of 1, 3, 5, 7, and 10 s. It was found that the 1-s interval is significantly overestimated, while the other intervals are underestimated. The maximum error in time measurement was found in women. The subjective time scale in aged subjects is more narrow than the physical scale, and the value of the psychophysical measurement function is significantly smaller than unity (p 0.05).     

The electrodermal indices of the subjective perception of performance errors during drowsy changes in consciousness

The study was aimed at searching for objective criteria of subject's perception of errors in performance due to drowsiness and estimating the time between the onset of errors and the moment of their awareness. Healthy subjects (n = 64) with the pronounced EEG alpha were examined under conditions without sleep deprivation. Experiments (n = 280) lasted for 40 min. During the experiments, the EEG, EOG, EDR, EKG, and button pressings were recorded and subject's reports were registered. The subjects were waken up after the onset of errors or 20 min after the beginning of the performance independently of errors. The error onset was shown to be preceded by the EEG "drowsy pattern" and decrease in the rate of spontaneous EDR. The performance reappearance after the error was accomplished by alpha-rhythm independently from error awareness. The interrogation of subjects after the error and activity revival demonstrated a correlation between the error subjective perception and appearance of the EDR. The interval between the error and the first following EDR (mean 10.1 s) was significantly (p < 0.001, t-test for dependent samples) shorter than the interval between the error and the last preceding EDR (mean 69.8 s). It is suggested that the subjective perception of an error is a significant endogenous stimulus, which evokes the orienting response and accompanying sympathetic activation.     

The invariance of subjective time scales

Organization of subjective time scales was studied by various methods of duration scaling (reproduction, fractionation, multiplication, evaluation, measuring and cross-model selection). Computation of linear correlation coefficients between physical time and its subjective expression for various methods of scaling in different coordinate systems allows to make a conclusion about a degree form of psychophysical dependence. The value of function degree index varies in the range of 0.80-0.88 for verbal evaluation and 0.93-1.07 for other methods. The concept is suggested about the "active" and "passive" time.     

Genetic basis of time perception in athletes

The association between the subjective time perception and polymorphism of some genes, regulating activity of serotonin and dopamine, was studied in 89 synchronized swimmers. COMT gene, responsible for dopamine destruction, influences on reproduction of short time intervals (1-2 s). 5-HT2A and MAOA genes, regulating activity of serotonin, influence on subjective time flow. 5-HTT and COMT genes, regulating activity of serotonin and dopamine respectively, are related with accuracy of orientation in time. Association of time perception with different genes and mediators suggests different perception mechanisms, in different time ranges, in concordance with the previous physiological studies. The current study reveals that these physiological mechanisms have different molecular-neurochemical basis that helps to overcome the gap between the investigation on systemic and molecular levels.     

Mouse Activity across Time Scales: Fractal Scenarios

In this work we devise a classification of mouse activity patterns based on accelerometer data using Detrended Fluctuation Analysis. We use two characteristic mouse behavioural states as benchmarks in this study: waking in free activity and slow-wave sleep (SWS). In both situations we find roughly the same pattern: for short time intervals we observe high correlation in activity - a typical 1/f complex pattern - while for large time intervals there is anti-correlation. High correlation of short intervals ( to : waking state and to : SWS) is related to highly coordinated muscle activity. In the waking state we associate high correlation both to muscle activity and to mouse stereotyped movements (grooming, waking, etc.). On the other side, the observed anti-correlation over large time scales ( to : waking state and to : SWS) during SWS appears related to a feedback autonomic response. The transition from correlated regime at short scales to an anti-correlated regime at large scales during SWS is given by the respiratory cycle interval, while during the waking state this transition occurs at the time scale corresponding to the duration of the stereotyped mouse movements. Furthermore, we find that the waking state is characterized by longer time scales than SWS and by a softer transition from correlation to anti-correlation. Moreover, this soft transition in the waking state encompass a behavioural time scale window that gives rise to a multifractal pattern. We believe that the observed multifractality in mouse activity is formed by the integration of several stereotyped movements each one with a characteristic time correlation. Finally, we compare scaling properties of body acceleration fluctuation time series during sleep and wake periods for healthy mice. Interestingly, differences between sleep and wake in the scaling exponents are comparable to previous works regarding human heartbeat. Complementarily, the nature of these sleep-wake dynamics could lead to a better understanding of neuroautonomic regulation mechanisms.     

Internal Representations of Temporal Statistics and Feedback Calibrate Motor-Sensory Interval Timing

Humans have been shown to adapt to the temporal statistics of timing tasks so as to optimize the accuracy of their responses, in agreement with the predictions of Bayesian integration. This suggests that they build an internal representation of both the experimentally imposed distribution of time intervals (the prior) and of the error (the loss function). The responses of a Bayesian ideal observer depend crucially on these internal representations, which have only been previously studied for simple distributions. To study the nature of these representations we asked subjects to reproduce time intervals drawn from underlying temporal distributions of varying complexity, from uniform to highly skewed or bimodal while also varying the error mapping that determined the performance feedback. Interval reproduction times were affected by both the distribution and feedback, in good agreement with a performance-optimizing Bayesian observer and actor model. Bayesian model comparison highlighted that subjects were integrating the provided feedback and represented the experimental distribution with a smoothed approximation. A nonparametric reconstruction of the subjective priors from the data shows that they are generally in agreement with the true distributions up to third-order moments, but with systematically heavier tails. In particular, higher-order statistical features (kurtosis, multimodality) seem much harder to acquire. Our findings suggest that humans have only minor constraints on learning lower-order statistical properties of unimodal (including peaked and skewed) distributions of time intervals under the guidance of corrective feedback, and that their behavior is well explained by Bayesian decision theory.     

Event-related covariances during a bimanual visuomotor task. I. Methods and analysis of stimulus- and response-locked data

A new method that measures between-channel, event-related covariances (ERCs) from scalp-recorded brain signals has been developed. The method was applied to recordings of 26 EEG channels from 7 right-handed men performing a bimanual visuomotor judgment task that required fine motor control. Covariance and time-delay measures were derived from pairs of filtered, laplacian-derived, averaged wave forms, which were enhanced by rejection of outlying trials, in intervals spanning event-related potential components. Stimulus- and response-locked ERC patterns were consistent with functional neuroanatomical models of visual stimulus processing and response execution. In early post-stimulus intervals, ERC patterns differed according to the physical properties of the stimulus; in later intervals, the patterns differed according to the subjective interpretation of the stimulus. The response-locked ERC patterns suggested 4 major cortical generators for the voluntary fine motor control required by the task: motor, somesthetic, premotor and/or supplementary motor, and prefrontal. This new method may thus be an advancement toward characterizing, both spatially and temporally, functional cortical networks in the human brain responsible for perception and action.     

运动对时距知觉的影响及其神经机制

在运动过程中,时距知觉的能力非常重要,能帮助个体对时长进行判断及对事件的发生做出预测和准备.近年来,越来越多的研究发现运动本身会直接影响个体的时距知觉.本文分别从运动参数、运动阶段、视觉运动刺激和运动有关的个体因素四个方面梳理了运动对时距知觉产生影响的行为学证据.目前已经有大量研究从不同角度证明,大脑运动系统组成了支持...     

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.     

Wrist activity monitoring in air crew members: a method for analyzing sleep quality following transmeridian and north-south flights

Home base recordings of motor activity during bedtime, and of subjective sleep parameters, were obtained from air crew members before and after the following routes with multiple flight segments: (1) south-north (SN) across 1 time zone; (2) west-east (WE) across 17 time zones; (3) east-west (EW) across 7 time zones. For the EW route, recordings were also obtained during layover. Only after return from the EW route was bedtime motor activity (measured by a wrist-worn ambulatory monitor) enhanced, was the percentage of bedtime immobility periods reduced, and were frequency and duration of self-assessed waking after sleep onset increased. The subjects rated their sleep as less quiet and felt less rested than during baseline. The various parameters gradually reverted toward baseline during the first 4 days at home. Although sleep showed only minor impairments during the EW route, the subjective jet-lag score was high during layover and after return to home base. Ambulatory activity monitoring is a useful method for assessing sleep quality after long-haul flights.     

Cross-modal distortion of time perception: demerging the effects of observed and performed motion

Temporal information is often contained in multi-sensory stimuli, but it is currently unknown how the brain combines e.g. visual and auditory cues into a coherent percept of time. The existing studies of cross-modal time perception mainly support the "modality appropriateness hypothesis", i.e. the domination of auditory temporal cues over visual ones because of the higher precision of audition for time perception. However, these studies suffer from methodical problems and conflicting results. We introduce a novel experimental paradigm to examine cross-modal time perception by combining an auditory time perception task with a visually guided motor task, requiring participants to follow an elliptic movement on a screen with a robotic manipulandum. We find that subjective duration is distorted according to the speed of visually observed movement: The faster the visual motion, the longer the perceived duration. In contrast, the actual execution of the arm movement does not contribute to this effect, but impairs discrimination performance by dual-task interference. We also show that additional training of the motor task attenuates the interference, but does not affect the distortion of subjective duration. The study demonstrates direct influence of visual motion on auditory temporal representations, which is independent of attentional modulation. At the same time, it provides causal support for the notion that time perception and continuous motor timing rely on separate mechanisms, a proposal that was formerly supported by correlational evidence only. The results constitute a counterexample to the modality appropriateness hypothesis and are best explained by Bayesian integration of modality-specific temporal information into a centralized "temporal hub".     

Detrended Fluctuation Analysis and Adaptive Fractal Analysis of Stride Time Data in Parkinson's Disease: Stitching Together Short Gait Trials

Variability indicates motor control disturbances and is suitable to identify gait pathologies. It can be quantified by linear parameters (amplitude estimators) and more sophisticated nonlinear methods (structural information). Detrended Fluctuation Analysis (DFA) is one method to measure structural information, e.g., from stride time series. Recently, an improved method, Adaptive Fractal Analysis (AFA), has been proposed. This method has not been applied to gait data before. Fractal scaling methods (FS) require long stride-to-stride data to obtain valid results. However, in clinical studies, it is not usual to measure a large number of strides (e.g., strides). Amongst others, clinical gait analysis is limited due to short walkways, thus, FS seem to be inapplicable. The purpose of the present study was to evaluate FS under clinical conditions. Stride time data of five self-paced walking trials ( strides each) of subjects with PD and a healthy control group (CG) was measured. To generate longer time series, stride time sequences were stitched together. The coefficient of variation (CV), fractal scaling exponents (DFA) and (AFA) were calculated. Two surrogate tests were performed: A) the whole time series was randomly shuffled; B) the single trials were randomly shuffled separately and afterwards stitched together. CV did not discriminate between PD and CG. However, significant differences between PD and CG were found concerning and . Surrogate version B yielded a higher mean squared error and empirical quantiles than version A. Hence, we conclude that the stitching procedure creates an artificial structure resulting in an overestimation of true . The method of stitching together sections of gait seems to be appropriate in order to distinguish between PD and CG with FS. It provides an approach to integrate FS as standard in clinical gait analysis and to overcome limitations such as short walkways.     

The influence of size perception and internal modeling on the control process while lifting

The present study sought to verify object size perception through internal modeling while lifting an object. Electromyography (EMG) activity of the upper limb muscles was recorded while 20 healthy females alternately lifted two containers of the same weight, but were unequal in size. When subjects lifted the small container, a significant increase was observed in the EMG activity. Most subjects determined that the small container was heavier than the large container, and predicted that the large container would be heavier than the small container due to size difference. The results may be explained by supporting that subjects predict object weight based on perception of size through internal modeling; however, predictions are cross-checked and modified through sensory feedback based on subjective weight.     

Evaluation and reproduction of time intervals in 7-10-year old children

We examined 200 children at the age of 7-10 (100 boys and 100 girls). The subjects had to estimate and reproduce time intervals in the range of 15-90 s. It was found that the children reproduced the intervals better and with lesser deviations than they estimated the intervals. The precision of time estimation increased with age and was best in ten-ear-old children. The findings confirm the authors' hypothesis about the "active" and "passive" time perception.     

Estimation by humans of signals simulating different sound movement directions and specificity of the perception of these signals by patients with temporal epilepsy

The perception of moving sound stimuli that imitate directional sound source movement was studied in healthy subjects and in patients with temporal lobe lesions, as well as in a group of patients with simultaneous lesions of the temporal cortex and hippocampus. Under the conditions of dichotic stimulation of patients with the rightor left-side foci of convulsive activity, the nature and length of the trajectories of the emerging subjective sound images (SSI) were estimated depending on the direction of movement and interaural time difference (700, 400, 200 μs). The audiograms of all patients did not differ from those of healthy subjects, suggesting that the auditory sensitivity of patients remained unimpaired. However, in the patients, the trajectories were shorter than the trajectories in healthy subjects at all the values of the initial time delay and at all the directions of SSI movements. In patients with the cortical temporal epilepsy, changes of the subjective sound field were the most significant in the case of the right-side localization of foci of the convulsive activity. In patients with simultaneous lesions of the temporal cortex and hippocampus, the averaged trajectories of SSI movement differed significantly from those in the group of healthy subjects (p < 0.01) and in patients with a relatively isolated lesion of the temporal cortex (p < 0.05); these trajectories were independent of the initial delay. The mediobasal structures of the temporal lobe that are involved in the epileptic process proved to play a significant role in the perception and estimation of the moving sound stimuli, although they do not belong to the auditory system proper. The possible mechanisms underlying disorders in patients with temporal epilepsy are discussed.     

Some scaling principles for the immune system

Using recent progress in biological scaling, we explore the way in which the immune system of an animal scales with its mass (M). It is shown that the number of cells in a single clone of B cells should scale as M and that the B-cell repertoire scales as ln (cM), where c is a constant. The time that a B cell needs to circulate once through the organism is shown to scale as M(1/4)ln (cM). It is suggested that the scaling of other cell populations in the immune system could be derived from these scaling relations for B cells.     

Complications inherent in scaling the basal rate of metabolism in mammals

The scaling of the basal rate of metabolism in mammals is reexamined. Both the power and level of the scaling function are sensitive to various factors that interact with body mass and rate of metabolism, including the precision of temperature regulation, food habits, and activity level. This sensitivity implies that the rate of metabolism is a highly plastic character in the course of evolution. Consequently, the singular effect of mass on the rate of metabolism is most effectively analyzed in ecologically and physiologically uniform sets of species, rather than in taxonomically defined groups, which often are ecologically and physiologically diverse. Otherwise, all fitted curves for mammals integrate a variety of competing factors, thereby reflecting the species used and denying unique analytic significance to the power in scaling relations. Kleiber's eutherian curve may represent a relatively uniform set of data because all the species included were domesticated and because selection for high rates of production (and high rates of metabolism) occurred in the process of domestication. In the analysis of scaling relationships, the standard error of estimate (Sy.x) is a more valuable measure of the residual variation than is (1.0-r2) because r2 is a non-linear measure of the conformation of data to the relation and because Sy.x, unlike r2, is independent of the units used in the scaling relationship. At present the best estimate indicates that total rate of metabolism scales proportionally to approximately m0.60 at small masses (less than 300 g), as long as small species do not enter torpor, and scales proportionally to approximately m0.75 at large masses (greater than or equal to 300 g). Physiological properties other than metabolism are potentially sensitive to secondary factors, so their scaling functions also would be most clearly defined for physiologically uniform groups of species. This view suggests that insight into the significance of scaling relations can be obtained by examining the residual variation around a scaling function as well as by examining conformation to the function.     

Scaling effects and spatio-temporal multilevel dynamics in epileptic seizures

Epileptic seizures are one of the most well-known dysfunctions of the nervous system. During a seizure, a highly synchronized behavior of neural activity is observed that can cause symptoms ranging from mild sensual malfunctions to the complete loss of body control. In this paper, we aim to contribute towards a better understanding of the dynamical systems phenomena that cause seizures. Based on data analysis and modelling, seizure dynamics can be identified to possess multiple spatial scales and on each spatial scale also multiple time scales. At each scale, we reach several novel insights. On the smallest spatial scale we consider single model neurons and investigate early-warning signs of spiking. This introduces the theory of critical transitions to excitable systems. For clusters of neurons (or neuronal regions) we use patient data and find oscillatory behavior and new scaling laws near the seizure onset. These scalings lead to substantiate the conjecture obtained from mean-field models that a Hopf bifurcation could be involved near seizure onset. On the largest spatial scale we introduce a measure based on phase-locking intervals and wavelets into seizure modelling. It is used to resolve synchronization between different regions in the brain and identifies time-shifted scaling laws at different wavelet scales. We also compare our wavelet-based multiscale approach with maximum linear cross-correlation and mean-phase coherence measures.