Isham, E. | Search bioRxiv

bioRxiv2020

Common and distinct roles of frontal midline theta and occipital alpha oscillations in coding temporal intervals and spatial distances

Judging how far something is and how long it takes to get there are critical to memory and navigation. Yet, the neural codes for spatial and temporal information remain unclear, particularly the involvement of neural oscillations in maintaining such codes. To address these issues, we designed an immersive virtual reality environment containing teleporters that displace participants to a different location after entry. Upon exiting the teleporters, participants made judgements from two given options regarding either the distance they had travelled (spatial distance condition) or the duration they had spent inside the teleporters (temporal duration condition). We wirelessly recorded scalp EEG while participants navigated in the virtual environment by physically walking on an omnidirectional treadmill and traveling through teleporters. An exploratory analysis revealed significantly higher alpha and beta power for short distance versus long distance traversals, while the contrast also revealed significantly higher frontal midline delta-theta-alpha power, and global beta power increases for short versus long temporal duration teleportation. Analyses of occipital alpha instantaneous frequencies revealed their sensitivity for both spatial distances and temporal durations, suggesting a novel and common mechanism for both spatial and temporal coding. We further examined the resolution of distance and temporal coding by classifying discretized distance bins and 250ms time bins based on multivariate patterns of 2-30 Hz power spectra, finding evidence that oscillations code fine-scale time and distance information. Together, these findings support partially independent coding schemes for spatial and temporal information, suggesting that low-frequency oscillations play important roles in coding both space and time.

neuroscience↗

bioRxiv2020

Temporal experience modifies future thoughts: Manipulation of Libet's W influences difficulty assessment during a decision-making task

Past studies have employed the subjective experience of decision time (Libets W) as an index of consciousness, marking the moment at which the agent first becomes aware of a decision. In the current study, we examined whether the temporal experience of W affects subsequent experience related to the action. Specifically, we tested whether W influenced the perception of difficulty in a decision-making task, hypothesizing that temporal awareness of W might influence the sense of difficulty. Consistent with our predictions, when W was perceived as early or late, participants subsequently rated the decision difficulty to be easy or difficult, respectively (Exp.1). Further investigation showed that perceived difficulty, however, did not influence W (Exp.2). Together, our findings suggest a unidirectional relationship such that W plays a role in the metacognition of difficulty evaluation. The results imply that subjective temporal experience of decision time modifies the consequential sense of difficulty. HighlightsO_LIPerceived timing of decision (W) can bias the metacognition of difficulty evaluation in a decision-making task. C_LIO_LIDefined as a temporal index of consciousness, time Ws influence on difficulty evaluation reflects the possibility that the role of consciousness is to modify subsequent thoughts and behaviors. C_LIO_LIExplicit attention is necessary for the timing of decision (W) to be consciously experienced and effectively influential on subsequent thoughts. C_LI

neuroscience↗