The nature of sensory time perception – centralised or distributed?

Citation

Motala A (2020) The nature of sensory time perception – centralised or distributed?. PhD in Vision Science. Cardiff University. https://orca.cardiff.ac.uk/126722/

Abstract
Using psychophysical methods and human subjects, this work aims to investigate the role of human sensory systems in the perception and passage of time. Specifically, I question the centralised nature of timing and whether a central clock exists to mediate incoming timing signals across the different sensory modalities. The alternative is that our timing mechanisms are embodied within distributed, modality-specific networks, each operating in a dedicated and independent manner. In my first experiment subjects were exposed to a range of rhythms presented to audio, visual and tactile sensory modalities, and were asked to reproduce a test rhythm via a tapping device. Subjects were able to adapt to a range of rhythms; however, the resulting after-effects were only evidenced when the adapting and test sensory modalities matched. My second experiment questioned how we construct sensory rhythms and, using the same method of rhythm adaptation, I used a single empty interval as a test stimulus. Results show that adapting to a given rhythmic rate strongly influences the temporal perception of a single empty interval. This questions the seemingly unique nature of rhythm, suggesting that adaptive distortions in perceived rate of signals within a sequence are, at least in part, a consequence of distortions in the perception of the inter-stimulus interval between the sequence’s component signals. My third experiment focused on more complicated rhythms in the form of anisochrony. I found limited observable after-effects as a result of exposing subjects to patterned rhythms across auditory, visual and tactile sensory modalities. The final experiment demonstrated significant after-effects following exposure to perfectly interleaved auditory and visual rhythms. These results collectively demonstrate mechanisms actively underpinning human perception of time and importantly, present evidence of dynamically distributed mechanisms linked to each sensory modality and processing incoming timing signals in a dedicated manner.