Research on current situations for functional classification of timing

Time is a fundamental variable that must be quantified by organisms to survive. Depending on the previous functional definition, timing can be divided into explicit timing and implicit timing. For an explicit timing task, the estimation of the stimulus duration is given in the form of perceptual discrimination (perceptual timing) or a motor response (motor timing). For implicit timing, participants can subconsciously (exogenous) or consciously (endogenous) establish temporal expectation. However, the ability of humans to explicitly or implicitly direct attention in time varies with age. Moreover, specific brain mechanisms have been suggested for temporal processing of different time scales (microseconds, hundreds of milliseconds, seconds to minutes, and circadian rhythms). Furthermore, there have been numerous research studies on the neural networks involved in explicit timing during the measurement of sub-second and supra-second intervals. Zhihan Xu Okayama University, Japan Qiong Wu Okayama University, Japan Chunlin Li Capital Medical University, China Yujie Li Central China Normal University, China Hongbin Han Peking University, China Dehua Chui Peking University, China Satoshi Takahashi Okayama University, Japan Jinglong Wu Okayama University, Japan Research on Current Situations for Functional Classification of Timing 223 FUNCTIONAL CLASSIFICATION OF TIMING Temporal processing is crucial for human behavior and cognition. It allows us to determine what is occurring in our environment and when to respond to events. The ability to direct attention to task-relevant information can enhance our behavioral performance. Temporal orienting selective attention is central for optimizing performance by biasing the neural processing of relevant information and suppressing irrelevant items (Moran & Desimone, 1985). Coull and Nobre (2008) suggested that tasks used temporal cues might be divided on the basis of whether the cue is explicitly or implicitly processed. Explicit timing is engaged when the participants make a deliberate estimate of a discrete duration. Implicit timing is engaged, even without a specific instruction to time, whenever sensorimotor information is temporally structured and can be used to predict the duration of future events. In explicit timing, the subjects are instructed to pay attention to the duration of a stimulus. In contrast, implicit timing requires the participants to perform tasks in which timing is important but not the main focus of the task (J. Coull & Nobre, 2008). For example, in a collision judgment task, participants must judge the speed of one or more objects that are moving and then predict the future location of the objects. Thus, this temporal processing focuses on collision judgment; however, time is not central to the task. The critical distinction between explicit timing and implicit timing is whether the task instructions require the participants to afford an overt estimate of duration.