Page 125 - It' about time: Studying the Encoding of Duration

Chapter 6 The distributed view of duration processing raises questions about how different processes support timing behavior. One possibility is that they reflect hierarchical duration processing with each process integrating output from preceding systems. This approach leaves room for multiple types of representation of duration (as described by different models) if we assume that different representations are more suited for different purposes. For example, some duration code such as population responses might be more suited for encoding and storage, while other types of duration coding (e.g. ramping activity) could be more suited for the production of timed behavior. A hierarchal view of duration processing could also bring into perspective the behavioral findings described in the previous paragraphs. In such a case, the adaptation effects originating at different level of visual processing could indicate multiple stages of duration processing that each feed into subsequent processing steps. A similar logic can be applied to the empirical results demonstrating that the DAE does not necessarily reflect adaptation to the duration reported by the same observers (Heron, et al. 2013; chapter 4). In the case of modality specific representation of duration, the unimodal representations of duration could feed into a subsequent processing stage which uses the information to produce a multimodal or amodal representation of duration. Similarly, modulation of perceived duration as a result of increases in temporal frequency content could reflect later processing which is sensitive to multiple sources of temporal information. While these relations are currently speculative, the overall point is clear: hierarchical processing could play an important role in duration processing and could provide us with a basis to unite seemingly contradicting models and empirical results. As such, future research should critically evaluate the possibility that duration-tuned encoding of duration reflects a single processing step, extracting information from sensory input and providing output that can be used and modulated based on additional information during subsequent processing. In contrast to the idea of hierarchical duration processing, different processes involved in duration processing might not necessarily be interconnected or hierarchically structured. Instead, it is worth considering that there is some level of degeneracy in duration processing. That is to say, multiple distinct systems might use different or even the same sources of temporal information to collectively inform timing behavior under different circumstances. These systems could reflect the different mechanisms described 124