Neural signatures of flexible multiple timing

The human ability to track overlapping and asynchronous time intervals is crucial for a myriad of tasks, from engaging in conversation to driving a car. Additionally, unexpected events can trigger rapid, on-the-fly adjustments, necessitating quick updating of both timing intervals and action planning. Such events require immediate recalibration of decision variables to allow the system to promptly adapt to new stimuli and update the timing mechanisms accordingly. In this study, we assessed human male and female participants' ability to track two simultaneous and asynchronous beep trains and determine which one ended first. Due to the stochastic nature of the beeps, participants frequently had to reorient their intended actions in order to identify which train was more likely to have ended. We found that they were able to do this accurately, demonstrating timing performance that was comparable to that of a single train. At the neural level, we recorded slowly evolving EEG potentials that encoded a single interval, the one associated with the currently intended action. Upon an intention switch, when participants had to reorient to a previously unintended action, the EEG response amplitude was reset to reflect the new intended interval. In contrast, when participants were instructed to disregard one of the beep trains, EEG responses solely reflected the intervals of the sequence they attended to. This flexibility in response highlights the brain's ability to dynamically reconfigure cognitive processes in real-time, ensuring that actions remain contextually appropriate despite sudden changes in the environment. Significance statement The human brain exhibits a remarkable ability to track temporal patterns and rapidly adjust timing and action plans in response to unexpected events. Using a novel task, we show that humans can flexibly process two independent, asynchronous sound trains and accurately determine which ends first. The unpredictable nature of the stimuli required frequent shifts in participants' intentions and adjustments in timing. EEG recordings reveal neural signals that mirror this adaptability, dynamically aligning with behavioral changes. These findings highlight the brain's capacity for real-time cognitive flexibility in response to sudden environmental changes, offering new insights into the mechanisms of complex timing behavior.