How sleep deprivation degrades task performance: combining experimental analysis with simulations of adenosinergic effects of basal ganglia and cortical circuits

Thesis (Ph.D.)--Boston UniversityHumans configure themselves into "neural machines" to perform optimally on distinct tasks, and they excel at maintaining such configurations for brief episodes. The neural configuration needed for peak performance, however, is subject to perturbations on multiple time scales. This thesis reports new empirical analyses and computational modeling to advance understanding of the variations in reaction time (RT) on simple RT tasks that are associated with the duration of the preceding inter-stimulus interval (order of seconds); the time-on-task duration (order of minutes); and sleep deprivation duration (order of hours to days). Responses from the psychomotor vigilance task (PVT), including anticipations (false alarms), normal RTs, and very long RTs (lapses in attention), were analyzed to discover the effects of: the 1 - 9 second inter-stimulus interval (ISI); the 10-minute task session; up to 50 hours of sleep deprivation (SD); and wake-promoting agents, caffeine and modafinil. Normal RTs and lapses in attention were negatively correlated with ISI length, whereas anticipations were positively correlated. Anticipations, normal RTs, and lapses increased as time-on-task increased, and during SD. Both caffeine and modafinil reduced lapses and anticipations during SD and decreased RT variability. A simple neural network model incorporating both a time-dependent inhibitory process and a time-dependent excitatory process was developed. The model robustly simulated the ISI effect on behavior. The SD effects were reproducible with two parameter adjustments. Informed modeling of drug effects required greater neurobiological detail. In the basal ganglia (BG), adenosine accumulation during SD has two notable effects: it antagonizes dopamine to reduce BG responsiveness to incoming cortical signals, and it reduces cholinergic transmission to parietal and prefrontal cortices, thus reducing attention to visual signals. A detailed computational model of interactions between BG and cortex during PVT was developed to simulate effects of adenosine and their amelioration by caffeine. The model simulates drug, ISI and SD effects on anticipations, RTs, and lapses. This model can be used to describe the effects of SD over a wide range of tasks requiring planned and reactive movements, and can predict and model effects of pharmacological agents acting on the adenosinergic, cholinergic and dopaminergic systems

Mathematical models of damage spread in networks.

This project describes mathematical models for how damage, measured in lost capacity, can spread through an organization. The model allows a company to simulate damage spread and compare different strategies for allocating repair resources after the initial damage has occurred. This project was completed in collaboration with Lehman Brothers investment firm in the aftermath of the terrorist attacks in September 11, 2001

Computer-aided learning in elementary schools.

The goal of this project was to educate the teaching staff of Abington Center Elementary School in the various ways a computer can be used as a teaching tool that can expand the horizons of their students. This goal was attained through providing instruction on basic computer skills, ideas for incorporating computers into current curricula and guidance in using application software to the teaching staff. Two workshops were held for the teaching staff. The first workshop centered on basic skill instruction. This workshop was designed around pre-workshop surveys sent home to the teaching staff during the summer. The second workshop allowed for specific software questions and instruction and was designed on the basis of the responses from a post-workshop survey distributed directly following the first workshop. From the two workshops, the group feels confident that the teaching staff has a renewed interest in incorporating computers into their classrooms and professional lives. Many members of the staff now realize the potential of the computer lab. By providing examples of curriculum based computer exercises for students, and a step-by-step graphic intensive manual for the teaching staff, the group believes that the teaching staff of Abington Center Elementary will introduce new technological media to their students