The human nervous system can quickly adapt to changes in the environment. When the brain detects an immediate threat the sympathetic branch of the autonomic nervous system engages a pattern of changes on the heart and vasculature. Similar patterns of cardiovascular change are also observed as we encounter performance-critical situations. Indeed, changes in systolic time intervals, cardiac output and vascular resistivity are regularly used as cardiovascular indexes of the psychological processes occurring during motivated and stressful tasks.

Moving ensemble analysis, a new method for characterizing these indexes, is introduced here. Its major innovation is the ability to detect both state and change of cardiovascular indexes during individual experimental trials. This technique is robust to radio frequency and magnetic field artifact present in an MRI environment (chapter 6) as well as respiratory and movement-related artifact normally present in noninvasive recordings. Open-source software implementing this technique as well as validation of its unique processing pipeline are presented in chapter 3.

Task engagement, acute stress and motor performance are difficult phenomena to study simultaneously. The former rapidly decrease over repeated trials while the later often improves as learning occurs. Their relationship must be detectable over a small number of trials where the psychophysiological response is still strong and the motor performance still variable.

State and change of cardiovascular indexes as well as motor performance were studied during high-stakes situations. Participants performed either a maximum grip force output (chapter 4) or a visuomotor tracking (chapter 5) tracking task for monetary rewards or punishments. Significant differences in cardiovascular indexes were observed after the framing of the upcoming trial was presented, as well as changes that predicted performance on the following trial.

In the final study, participants completed easy and very difficult mental arithmetic while functional magnetic resonance images (fMRI) were collected. The near-continuous measurement of cardiovascular indexes was used to detect brain regions likely involved in controlling autonomic/cardiovascular state. Detected regions in the motor system are consistent with recent tract-tracing studies in non-human primates.