The ability to perceive time is innate to humans, but very little is known on the underlying psychological and neural mechanisms. Some peculiar daily life and laboratory phenomena where time appears to be frozen for a brief moment, termed "chronostasis," especially poses a challenge to cognitive neuroscientists. It may also be related to pathological experiences of time lapse in cases such as schizophrenia and drug-addicts. Chronostasis, which usually happens around the hundreds of millisecond range, could occur with or without action, given different perceptual contexts. This particular phenomenon could be a valuable window into how the brain constructs duration perception. With the support from National Science Foundation, Dr. Shinsuke Shimojo and colleagues will use electroencephalogram (EEG) along with a novel method to measure neural activity and its dynamics corresponding to this phenomenon. First, this project will provide further insights into why people perform a challenging task (for example, in sports or games) with concentrated attention sometimes experience "a flow of time." Second, the novel method could lead to a new neural activity index for clinical screening to understanding of mental disorders, because it is known that various types of patients, such as schizophrenics, autistic, and ADHD patients, have problems in time perception. The new knowledge of neural areas and dynamics may also inspire new programs and devices for training or rehabilitation. Third, the conclusions may potentially impact occupations whose performance relies on precise temporal judgments.
Our scientific hypothesis is that duration perception at the hundreds of milliseconds range is mediated by "hierarchical predictive coding," where both familiarity and novelty play a role in modulating perceived duration. The mechanism governing familiarity is likely "repetition suppression," i.e. a relatively automatic decay of neural responses by repetition; the mechanisms subserving novelty detection could be attention orienting. The researchers will isolate these factors with behavioral experiments, and then find corresponding neural correlates with EEG. Specifically, they will use a steady state visual evoked potential (SSVEP) approach to mark the short duration visual stimuli with a tagging temporal frequency. This will give them advantage in subsequent source localization and network connectivity analysis. They expect to discover interactions between low-level and high-level brain areas that co-decide duration perception, which will provide some clues to the ultimate mystery in behavioral neuroscience, that is, how we could experience time lapse, without having peripheral and specific sensory receptors.
