title: [The present in the brain].
abstract: How is the present represented in the brain? This review introduces several theoretical and experimental issues regarding time perception, with special focus on the human visual system. Specifically, it addresses possible ways through which visual information can be processed to allow for the conscious experience of spatio-temporal local relations, object-based temporal localization, object duration, and mental time. We begin with a brief mention of isomorphism and its limitations, and from there we proceed to discuss low-level mechanisms for timing outer events. The concept of spatiotemporal receptive fields with biphasic temporal impulse response functions is introduced. Neurons with such receptive fields are believed to extract elementary information about spatial and temporal inclinations of light intensity. These visual primitives are later reconstructed in biologically meaningful ways to create each perceptual timeline in the brain. The precise mechanism by which each perceptual timeline is created remains unknown; however, for the purpose of this paper, we refer to it as "context", relative to which novel objects are to be spatiotemporally localized by using various cues. Localization involves estimation, including prediction and "postdiction" from currently available cues. As such, many aspects of the subjective present, such as "perceived timing", "subjective duration", and "mental clock" result from estimation and are thus prone to errors, leading often to time illusion. More than one perceptual timeline can exist and serve as an inner clock for multiple objects, multiple attributes, and even for multiple sensory modalities. Calibration across timelines is also a major issue; our ability to exercise flexible recalibration with short-term training or adaptation using salient time markers is briefly argued before ending the review.
authors.affiliation: Department of Psychology, The University of Tokyo.
authors.forename: Ikuya
authors.initials: I
authors.lastname: Murakami
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D001921:Brain / Q000502:physiology*; D006801:Humans; D009474:Neurons / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D013998:Time Perception / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*