Page 21 - It' about time: Studying the Encoding of Duration

Chapter 1 These duration-tuned responses were spatially organized demonstrating chronotropic organization in the brain. This type of topographic organization is often reported for stimulus features that are encoded by feature-tuned neural substrates, such as columnar organization in V1 (Yacoub, Harel, & Ugurbil, 2008) and topographical representations of numerosity (Harvey et al., 2013). Using the DAE to probe duration encoding The studies I have described so far, provide converging evidence for the notion that duration-tuned mechanisms play a role in the encoding of duration. However, so far our understanding of the exact nature of these duration-tuned mechanisms and how they operate is rather limited. For one, many of the assumptions of the duration channel model are based on existing knowledge about the processing of non-temporal sensory features such as orientation and spatial frequency. However, is unknown as to what extent duration-tuned neural structures will mirror the structural and functional properties of the neural structures involved in the encoding of these other sensory features. For example, many of the well-studied visual features such as orientation are encoded by low-level visual areas that show a high level of structural and functional organization. In contrast, feature-tuned encoding of numerosity seems to rely on a more distributed processing network located throughout the association cortex (Harvey & Dumoulin, 2016). Similarly, it is unclear what visual information (or neural input) is used by the brain to extract duration information. Further study is required to understand these basic properties of the duration channel model. It is also unclear how the duration channel model and empirical findings such as the DAE relate to other findings reported in the duration perception literature. As described earlier, there is a wide range of models that has been used to predict and explain findings within the field of duration perception. In many cases, these models (and the related paradigms) rely on unique mechanisms that predict empirical findings that are not easily explained by the duration channel model. In addition, there is a large body of work on timing behavior and temporal illusions that cannot readily be explained by the duration channel model in its current form. This raises questions about the role of duration-tuned mechanisms in our overall ability to encode, store, and use duration information. Answering these questions properly requires a deeper understanding of the structural and functional properties of the neural substrates underlying channel-based duration encoding. 20