Shared timing variability in eye and finger movements increases with interval duration: Support for a distributed timing system below and above one second

The origins of the ability to produce action at will at the hundreds of millisecond to second range remain poorly understood. A central issue is whether such timing is governed by one mechanism or by several different mechanisms, possibly invoked by different effectors used to perform the timing task. If two effectors invoke similar timing mechanisms, then they should both produce similar variability increase with interval duration (interonset interval) and thus adhere to Weber's law (increasing linearly with the duration of the interval to be timed). Additionally, if both effectors invoke the same timing mechanism, the variability of the effectors should be highly correlated across participants. To test these possibilities, we assessed the behavioural characteristics across fingers and eyes as effectors and compared the timing variability between and within them as a function of the interval to be produced (interresponse interval). Sixty participants produced isochronous intervals from 524 to 1431?ms with their fingers and their eyes. High correlations within each effector indicated consistent performance within participants. Consistent with a single mechanism, temporal variability in both fingers and eyes followed Weber's law, and significant correlations between eye and finger variability were found for several intervals. These results can support neither the single clock nor the multiple clock hypotheses but instead suggest a partially overlapping distributed timing system.     

The supplementary motor area in motor and perceptual time processing: fMRI studies

The neural bases of timing mechanisms in the second-to-minute range are currently investigated using multidisciplinary approaches. This paper documents the involvement of the supplementary motor area (SMA) in the encoding of target durations by reporting convergent fMRI data from motor and perceptual timing tasks. Event-related fMRI was used in two temporal procedures, involving (1) the production of an accurate interval as compared to an accurate force, and (2) a dual-task of time and colour discrimination with parametric manipulation of the level of attention attributed to each parameter. The first study revealed greater activation of the SMA proper in skilful control of time compared to force. The second showed that increasing attentional allocation to time increased activity in a cortico-striatal network including the pre-SMA (in contrast with the occipital cortex for increasing attention to colour). Further, the SMA proper was sensitive to the attentional modulation cued prior to the time processing period. Taken together, these data and related literature suggest that the SMA plays a key role in time processing as part of the striato-cortical pathway previously identified by animal studies, human neuropsychology and neuroimaging.     

The effects of morphine on the production and discrimination of interresponse times

Recent experiments suggest that the effects of drugs of abuse on the discrimination of the passage of time may differ for experimenter-imposed and subject-produced events. The current experiment examined this suggestion by determining the effects of morphine on the discrimination of interresponse times (IRTs). Pigeons pecked a center key on a random-interval 20-s schedule of matching-to-sample trials. Once the interval had timed out, a choice trial randomly followed either a short (2- to 3-s) or long (6- to 9-s) IRT on the center key. Pecking the side key lit one color produced food after a short IRT, and pecking the side key lit the other color produced food after a long IRT. Two experimental phases differed in the functional role of the different key colors. Under control conditions, the IRT distributions had two modes, one at the lower bound of the short category and a smaller one at the lower bound of the long category. Pigeons accurately categorized the duration of the IRTs: One key color was pecked following short IRTs and the other key color was pecked following long IRTs. Morphine flattened the IRT distribution and reduced the accuracy of categorizing IRTs. Categorization of long IRTs was particularly disrupted. Morphine did not produce overestimation of time as assessed by the production or categorization of IRTs. These results are similar to those obtained previously for the effects of morphine on the discrimination of the duration of experimenter-imposed events.     

Comparison of the Explicit Timing and Interspersal Interventions: Analysis of Problem Completion Rates,Student Preference,and Teacher Acceptability

Explicit timing and interspersal interventions were investigated using a within-subjects design with 45 third-grade students. A control assignment consisted of subtraction of a two digit number from a two digit number (i.e., target problem) and served as a baseline. An explicit timing assignment consisted of similar problems as those for the control assignment. The interspersal assignment consisted of similar problems as those for the control and explicit timing assignments with the addition of subtraction of a one digit number from a one digit number interspersed following every third target problem. Total problem completion rates, target problem completion rates, accuracy on target problems and students' rating regarding difficulty, time, effort, and preference between assignments for class work were collected. Student preference choices were analyzed for fit with the discrete task completion hypothesis. Three trials were administered. Results indicated that: (a) students completed more total problems during interspersal, (b) target problem completion rates were higher during explicit timing, (c) accuracy rates remained constant, (d) students rated the explicit timing assignment as requiring more time and being more difficult for all trials and as requiring more effort for trial 2 and 3, (e) students selected the interspersal assignment to do in class as compared to the explicit timing assignment for all trials, and (f) the data fit the discrete task completion hypothesis relatively well for all trials. Discussion focuses on comparing academic interventions based on problem completion rates, student preference, and acceptability data.     

Speech timing and working memory in profoundly deaf children after cochlear implantation

Thirty-seven profoundly deaf children between 8- and 9-years-old with cochlear implants and a comparison group of normal-hearing children were studied to measure speaking rates, digit spans, and speech timing during digit span recall. The deaf children displayed longer sentence durations and pauses during recall and shorter digit spans compared to the normal-hearing children. Articulation rates, measured from sentence durations, were strongly correlated with immediate memory span in both normal-hearing and deaf children, indicating that both slower subvocal rehearsal and scanning processes may be factors that contribute to the deaf children's shorter digit spans. These findings demonstrate that subvocal verbal rehearsal speed and memory scanning processes are not only dependent on chronological age as suggested in earlier research by. Instead, in this clinical population the absence of early auditory experience and phonological processing activities before implantation appears to produce measurable effects on the working memory processes that rely on verbal rehearsal and serial scanning of phonological information in short-term memory.     

The Timing of Conscious Experience: A Critical Review and Reinterpretation of Libet''s Research

An extended examination of Libet's works led to a comprehensive reinterpretation of his results. According to this reinterpretation, the Minimum Train Duration of electrical brain stimulation should be considered as the time needed to create a brain stimulus efficient for producing conscious sensation and not as a basis for inferring the latency for conscious sensation of peripheral origin. Latency for conscious sensation with brain stimulation may occurafterthe Minimum Train Duration. Backward masking with cortical stimuli suggests a 125–300 ms minimum value for the latency for conscious sensation of threshold skin stimuli. Backward enhancement is not suitable for inferring this latency. For determining temporal relations between stimuli that correspond to subjects' reports, theendof cerebral Minimum Train Duration should be used as reference, rather than its onset. Results of coupling peripheral and cortical stimuli are explained by a latency after the cortical Minimum Train Duration, having roughly the same duration as the latency for supraliminal skin stimuli. Results of coupling peripheral stimuli and stimuli to medial lemniscus (LM) are explained by a shorter LM latency and/or a longer peripheral latency. This interpretation suggests a 230 ms minimum value for the latency for conscious sensation of somatosensory near-threshold stimuli. The backward referral hypothesis, as formulated by Libet, should not be retained. Long readiness potentials preceding spontaneous conscious or nonconscious movements suggest that both kinds of movement are nonconsciously initiated. The validity of Libet's measures of W and M moments (Libet et al., 1983a) is questionable due to problems involving latencies, training, and introspective distinction of W and M. Veto of intended actions may be initially nonconscious but dependent on conscious awareness.     

Response specificity in animal timing.

The stimuli that control responding in the peak procedure were investigated by training rats, in separate sessions, to make two different responses for food reinforcement. During one type of session, lever pressing was normally reinforced 32 s after the onset of a light. During the other type of session, chain pulling was normally reinforced either 8 s after the onset of one auditory cue or 128 s after the onset of a different auditory cue. For both types of sessions, only the appropriate manipulandum was available, and 20% of the trials lasted 240 s and involved no response-contingent consequences. Rats were then tested with the auditory cues in the presence of the lever and the light in the presence of the chain. If the time of reinforcement associated with each stimulus was learned, response rates should peak at these times during transfer testing. However, if a specific response pattern was learned for each stimulus, little transfer should occur. The results did not clearly support either prediction, leading to the conclusion that both a representation of the time of reinforcement and the rat's own behavior may control responding in this situation.     

疼痛背景下时距知觉的变化

时距知觉指对数百毫秒到数个小时时长的知觉, 是日常生活中许多活动的基础。时距知觉受到相当多因素的影响, 如唤醒、注意、动机等。疼痛是一种多维度的心理及生理现象, 包含有感觉分辨、情绪动机、认知评价三个成分。近期研究证明时距知觉会在疼痛背景下发生改变。疼痛背景下时距知觉的相关研究主要涉及三个方面：(1)健康被试对疼痛面孔的时距知觉; (2)实验室诱发疼痛对健康被试时距知觉的影响; (3)临床疼痛患者的时距知觉变化。探索疼痛背景下时距知觉的变化, 可以为理解疼痛的发生发展机制以及时间知觉的机制提供一个新视角。     

时距知觉的动物研究范式及相关神经机制

在探索时距知觉的脑机制的过程中, 相对于人类被试相关研究, 动物研究可以提供较多的药理学、分子生物学、单个神经元电生理学以及光遗传等方面的研究证据。目前较为常用的时距知觉动物研究范式包括时间二分法、峰值间隔法以及低比率差别强化法等。根据不同的研究需求, 动物研究的范式常会进行调整。对时距知觉的动物研究的探讨将基于两方面展开：(1) 常用的时距知觉动物研究范式的介绍及比较; (2) 基于动物研究范式的时距知觉神经机制研究进展, 旨在为深入探索时间知觉的心理学相关研究提供参考。     

About Skinner and time: behavior-analytic contributions to research on animal timing

The article discusses two important influences of B. F. Skinner, and later workers in the behavior-analytic tradition, on the study of animal timing. The first influence is methodological, and is traced from the invention of schedules imposing temporal constraints or periodicities on animals in The Behavior of Organisms, through the rate differentiation procedures of Schedules of Reinforcement, to modern temporal psychophysics in animals. The second influence has been the development of accounts of animal timing that have tried to avoid reference to internal processes of a cognitive sort, in particular internal clock mechanisms. Skinner's early discussion of temporal control is first reviewed, and then three recent theories-Killeen & Fetterman's (1988) Behavioral Theory of Timing; Machado's (1997) Learning to Time; and Dragoi, Staddon, Palmer, & Buhusi's (2003) Adaptive Timer Model-are discussed and evaluated.