The Cognitive And Neural Mechanism Of Maintaining Information On Time Perception

The cognitive resources or energies are limited in human brain. The more complex the stimulus needed to be processed, the more cognitive resources demanded. Attention is a general, universal mental resource. Decreased timing performance could be explained by the shift of attention, or the reduction of allocated attentional resources. However, selective attention to temporal information differs from the selective attention to other nontemporal dimensions such as color or shape of a stimulus. Time information processing not only occupies perceptual attention, it in a greater extent needs intrinsic attention. The ability of time perception or time estimation reflects the extent of consciousness and thoughts.In normal work and life, even though outside stimulus does not disrupt timing processing, subjective time can be affected by the information stored into human brain. This interfering information might be related to memory, or derive from imagining further scene. In this way, attention model of time perception can not account for the findings, implying that temporal information processing might demand more complex mental resources.Recent years, more researches have pointed out that, time information processing and nontemporal information processing share not only the general attention resources, but also they compete for limited resources within working memory. Working memory (WM) refers to a limited energy system in which a person temporarily stores and manipulates information. In essence, it is an attentional control system of limited capacity, being as the basis for conducting higher cognitive activity. Basing on the effect of working memory on time perception, we could explore the nature of time information as well as its affecting factors from broad areas. Working memory is extremely complex, whose subsystems depend on distinct classification. This study mainly investigates the impact of maintaining working memory on time perception. Time perception is limited to the perception of duration within three seconds.This research included five successive studies, divided into ten experiments, In Experiment1, adopting a dual task paradigm of Sternberg short-term memory and time production, we used magic cube as memory materials, and asked subjects to produce a2500-ms duration during retention of memory information. The results demonstrated that produced time increased with the memory-object size, revealing the impact of maintaining objects on timing, In Experiment2, we combined change detection paradigm and time production task to explore the time course that working memory load and memory materials affected estimated time through ERP technology. The results showed that the amplitude of N1, N470as well as CNV were more negative under low memory load when the stimuli were irregular figures, showing that the WM-based interference were attributed to not only information load as well as material types.We further investigated the impact of maintaining memory information on perceived duration in short time range during study2. We adopted time bisection as time perception task. Besides manipulating memory load, we also changed the interstimuli interval (ISI) from memory task to the onset of timing task. The results demonstrated that working memory load affected the response times. Moreover, when the ISI became shorter, perceived duration decreased and response time was lengthened. This suggests that shift function plays important role In the relationship between maintaining memory information and time perception.During study1and study2, we requested subjects to memorize several stimuli, and manipulated memory load as well as the interstimuli interval to test the impact of working memory on timing. In study3, we would further investigate when the stimuli in time judgment task were relevant with the WM content, whether the attentional orientation derived from WM content could influence time judgment. In Experiment5a, using a dual task paradigm, we made the stimulus in time judgment task match the WM content or not; in Experiment5b, subject were only requested to complete time judgment. The results revealed that the stimulus matching WM content prolonged response times, while perceptual stimulus matching WM content did not generate similar effect. In Experiment6and Experiment7, we explored whether the WM content-based interfering effect was so robust that it changed the internal mental association between time and number, or between time and space. Experiment6b and Experiment7b were taken as control conditions. The results showed that, under memory-matching condition, retention of WM content eliminated the mental link among this magnitude, making the impact of numerical magnitude or spatial dimension on time judgment be not significant. However, under memory-mismatching condition, the impact of number and space on time judgment still existed. Besides, time judgment was affected by memory matching but not perceptin matching stimulus. These results imply that the WM content could guide visual attention, and indirectly disrupted perceived duration.Based on the result from study3, we conducted study4by ERP technology to inspect the time course of maintaining WM content affecting time perception. The experimental and control task were the same to the matching condition of Experiment5a and Experiment5b respectively. Every subject had to complete two tasks in random order. The result showed that memory-matching stimulus prolonged the latency of Nl component and shortened the latency of P2component. The stimuli in Experiment9were Arabic number. The procedure was similar to matching condition in Experiment6a. In order to explore the interfering effect based on WM content was due to retention or perception of the WM digits, we required each subject to conduct two dual tasks which included working memory-time judgment and attention task-time judgment. The results showed that on time-number consistent condition, the latency of Nl component was shorter. However, only memory-matching stimuli shortend the latency of P2when time and number was constent. The amplitude and latency of CNV were not affted by any factors. The results reflected the interfering effect occurred at earlier stage of perceptual processing during timing.In study5, we tested the activation of the brain during working memory and time perception. We found that compared with verbal working memory, time perception mainly activated frontal regions such as inferior frontal gyrus and middle frontal gyrus.Together with the10experiments in the present study, the results indicated that, firstly, the dual task paradigm combing change detection and time perception is a valid method for investing the impact of working memory on time information processing, because it could alone test the role of maintaining stage on perceived duration as well as other interfering factors. Secondly, time perception is affected by stimuli pattern and time interval of memory content. Specifically, stimuli pattern is related to encoding and retention strategies, while the time interval is involved the executive function of working memory system. Thirdly, the attentional orientation derived from the WM content is so robust that it could change the mental association among number, space and time. The results from ERP show the disruption occurs at the early stage of perception. As the target duration is prolonged, the role of inhibition function is heightened. Fourthly, time information processing mainly activated frontal regions such as inferior frontal gyrus and middle frontal gyrus, suggesting time perception demands executive function resources.According to the discussion at home and abroad and the results from this study, we put forward time perception model based on working memory. This model assimilated the range-synthetic models of temporal cognition, stating that time perception is affected not only by attentional resources, encoding pattern, experimental index, but involving in working memory. In particular, firstly, the shared resource between time perception and working is related to stimuli pattern, with that phonological loop is shared by time perception and memory retention required by verbalizable strategy, visuospatial sketchpad is shared by time perception and memory retention required by visupspatial strategy. Secondly, time perception demands central executive function, with that the duration of retention and time range involving in shift and coordination function. Thirdly, time perception is controlled by working memory capacity that have individual, aged and disease difference. In conclusion, the role of working memory is reflected by its control function, coordinating memory, attention and time perception processing.This study enriches time perception model, and provides a value paradigm for further researches engaging in the role of working memory on time perception. We integrate change direction paradigm of working memory and time judgment method to explore the impact of retention information on time perception as well as its other relevant factors, which meet the unambiguous demands on differ mental processing stage.Limited to the time, this study only explores the impact of retention of working memory information on time perception. We might speculate the performance of time perception within different working memory capacity make effect on selecting excellent astronauts, sport player, or early diagnosing, evaluating Parkinson’s disease. These issues will be our research subjects in further.