However, isolating the physiology-the neural implementation-of these behaviorally identified operators has proven notoriously difficult. The broad range of behavioral findings (e.g., Fig 1) shows that continuity fields may be found at every stage of processing. Continuity fields are spatially and temporally tuned operators within which the brain treats different things as being more similar than they are. ![]() ![]() The spatial and temporal range over which the resulting serial dependence happens is called a continuity field ( Fig 1D). The behavior is relatively clear, and it echoes the computational goal of serial dependence: To smooth our experience of the world, the brain recycles information encountered over the last few seconds, within a limited spatial window, as long as the new information is fairly similar. If probed very carefully using behavior and/or physiology at any level, we might therefore find a signature of it. Instead of thinking of serial dependence as a single process or operating at a single level (e.g., only in memory or only in perception), the extensive behavioral work suggests it is a ubiquitous byproduct that emerges at many levels of brain processing. īecause there are so many situations in which serial dependencies occur and have been described behaviorally, no single neural mechanism or module can explain all instantiations of serial dependence. By recycling prior representations, our brain effectively smooths, speeds up, and improves the accuracy of our experience. It was recently proposed that the computational goal of serial dependence is to promote more stable interpretations of the world. In fact, serial dependence probably happens at every level of brain processing, from the earliest to the highest levels. Serial dependence affects processing of visual information on many levels, from perception (-see Fig 1D) (how do things appear, sound, feel?) to decisions (what color is the coat?, which cup should I grasp?) and memory (did I already look here for my keys?). Serial dependence results when the brain biases information to tie together similar things that occur within a close time period, in order to smooth our experience of the world. For a demonstration of serial dependence in perception, see from. Yellow regions show relatively stronger serial dependency. ![]() (D) Continuity fields: regions of space and time within which the brain treats sequential features and objects as being more similar than they are, for the purpose of temporally smoothing representations. This is not an exhaustive list serial dependence occurs for many other stimuli, including at feature and object-selective levels of visual processing, and in other modalities such as audition. (C) Serial dependence in face recognition. Examples of serial dependency effects, in which perceptions, decisions, and memories are biased, pulled toward the past. A recent paper in PLOS Biology by Sheehan and Serences (2022) reveals a possible mechanism for serial dependence in the case of orientation perception and provides an important insight on the difficulty of measuring the neural correlates of serial dependence, in general. Despite a large array of behavioral papers replicating this serial dependence effect in many domains, the physiological mechanism(s) underlying serial dependence have remained stubbornly unclear. This means that images that we encounter over time that are similar to each other will seem even more similar to us than they actually are ( Fig 1A–1C). This is not accidental: It was recently proposed that the visual system smooths our experience of the world by introducing serial dependence in visual representations. Yet, our perception of the world and everything in it appears remarkably stable and effortless. ![]() In principle, our perception should consist of a fluctuating and unstable sequence of visual interpretations, often seemingly unrelated to each other. The visual world at our eyes is relentlessly changing around us-images are in constant motion, and there are multiple sources of uncertainty, both external (e.g., occlusions, fog) and internal (e.g., eye blinks, neural noise, processing delays).
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