Time-Encoding Migrates from Prefrontal Cortex to Dorsal Striatum During Learning of a Self-Timed Response Duration Task

ABSTRACTAlthough time is a fundamental dimension of life, we do not know how the brain encodes the temporal information. Several brain areas underlie the temporal information, such as the hippocampus, prefrontal cortex, and striatum, but evidence of how they cooperate to process temporal information is scarce. Notably, the analysis of neural activity during learning are rare, mainly because timing tasks usually take a long time to train. Here we investigated how the time encoding evolves when animals learn to time a 1.5 s interval. We designed a novel training protocol where rats go from naive- to proficient-level timing performance within a single session, allowing us to investigate neuronal activity from very early learning stages. We used pharmacological experiments and machine-learning algorithms to evaluate the level of time encoding in the medial prefrontal cortex and the dorsal striatum. Our results show a double dissociation between the roles of the medial prefrontal cortex and the dorsal striatum during temporal learning, where the former commits to early learning stages while the latter become more engaged as animals become more proficient in the task.

Iterative learning control with applications in energy generation, lasers and health care

Many physical systems make repeated executions of the same finite time duration task. One example is a robot in a factory or warehouse whose task is to collect an object in sequence from a location, transfer it over a finite duration, place it at a specified location or on a moving conveyor and then return for the next one and so on. Iterative learning control was especially developed for systems with this mode of operation and this paper gives an overview of this control design method using relatively recent relevant applications in wind turbines, free-electron lasers and health care, as exemplars to demonstrate its applicability.

Automatic comparison of stimulus durations in the primate prefrontal cortex: the neural basis of across-task interference

Rhesus monkeys performed two tasks, both requiring a choice between a red square and a blue circle. In the duration task, the two stimuli appeared sequentially on each trial, for varying durations, and, later, during the choice phase of the task, the monkeys needed to choose the one that had lasted longer. In the matching-to-sample task, one of the two stimuli appeared twice as a sample, with durations matching those in the duration task, and the monkey needed to choose that stimulus during the choice phase. Although stimulus duration was irrelevant in the matching-to-sample task, the monkeys made twice as many errors when the second stimulus was shorter. This across-task interference supports an order-dependent model of the monkeys' choice and reveals something about their strategy in the duration task. The monkeys tended to choose the second stimulus when its duration exceeded the first and to choose the alternative stimulus otherwise. For the duration task, this strategy obviated the need to store stimulus-duration conjunctions for both stimuli, but it generated errors on the matching-to-sample task. We examined duration coding in prefrontal neurons and confirmed that a population of cells encoded relative duration during the matching-to-sample task, as expected from the order-dependent errors.

More is Less: The Effect of Single and Multiple Interleaved Interruptions on Task Resumption

People experience and handle interruptions on a daily basis. One strategy that people use to manage interruptions is to interleave an interrupting task with a primary task. Past interruptions research has mostly looked at the effects of a single interruption on primary task performance. This study sought to expand on past research by examining primary task performance during a period of interleaved interruptions. In this study, participants experienced either a single interruption or a series of interruptions that increased or decreased in duration. Task resumption in both interleaved interruption conditions was significantly faster than in the single interruption condition. The findings suggest that interleaving interruptions leads to more efficient task resumption than resuming after a single interruption.

Workload Context Effect: An Elusive Phenomenon

The effect of workload context on subsequent performance and workload ratings has crucial implications regarding workload transition. However few studies have examined workload context effects; and those that have, report contradictory results. This study attempts to determine if the failure to find evidence of workload context effects might be attributable to methodological factors such as task duration, task difficulty, and experimental design. Twelve subjects “flew” three sessions of three trials on a computer-based flight simulator, and rated the workload after each trial. A pre-post experimental design presented the first and third trials at a medium level of difficulty while the second (experimental) trial was of low, medium, or high difficulty. Crosswinds of 2, 12, and 22 knots created the levels of low, medium, and high task difficulty. Analyses of the performance and workload data did not reveal significant differences in Trial 3 as a function of prior task difficulty presented in Trial 2. The inability to find workload context effects in the present study suggests that previous inconsistent findings can not be attributed to differences in task duration and experimental design. Rather, it appears that contradictory results may be attributable to differences in the range of task difficulty employed, the workload measurement tool, or both.