Circulatory changes during mental stress in tetraplegic and paraplegic man

Hemodynamics and cerebral oxygenation during acute exercise in moderate normobaric hypoxia and with concurrent cognitive task in young healthy males

The present investigation aimed to study the cardiovascular responses and the cerebral oxygenation (Cox) during exercise in acute hypoxia and with contemporary mental stress. Fifteen physically active, healthy males (age 29.0 ± 5.9 years) completed a cardiopulmonary test on a cycle ergometer to determine the workload at their gas exchange threshold (GET). On a separate day, participants performed two randomly assigned exercise tests pedaling for 6 min at a workload corresponding to 80% of the GET: (1) during normoxia (NORMO), and (2) during acute, normobaric hypoxia at 13.5% inspired oxygen (HYPO). During the last 3 min of the exercise, they also performed a mental task (MT). Hemodynamics were assessed with impedance cardiography, and peripheral arterial oxygen saturation and Cox were continuously measured by near-infrared spectroscopy. The main results were that both in NORMO and HYPO conditions, the MT caused a significant increase in the heart rate and ventricular filling rate. Moreover, MT significantly reduced (74.8 ± 5.5 vs. 62.0 ± 5.2 A.U.) Cox, while the reaction time (RT) increased (813.3 ± 110.2 vs. 868.2 ± 118.1 ms) during the HYPO test without affecting the correctness of the answers. We conclude that in young, healthy males, adding an MT during mild intensity exercise in both normoxia and acute moderate (normobaric) hypoxia induces a similar hemodynamic response. However, MT and exercise in HYPO cause a decrease in Cox and an impairment in RT.

Validation of Affect-tag Affective and Cognitive Indicators

The Affect-tag solution measures physiological signals to deliver indicators derived from cognitive science. To provide the most accurate and effective results, a database of electrodermal activity (EDA) signals acquired using the Affect-tag A1 band was created. An experimental paradigm was designed to measure action-taking, autonomic regulation, cognitive load (CL), emotions, and stress, affects, and social stress. The Affect-tag emotional power (EP), emotional density (ED), and CL affective and cognitive indicators were refined based on the physiological responses of 48 participants during these tasks. Statistical significance was obtained for all indicators in tasks they were designed to measure, resulting in a total accuracy score of 89% for the combined indicators. Data obtained during this study will be further analyzed to define emotional and affective states.

Sympathetic activity is influenced by task difficulty and stress perception during mental challenge in humans

1. Our aim was to determine the influence of the type of task, the absolute and relative difficulty of the task, and the perceived stress associated with performance of the task on sympathetic circulatory regulation during cognitive challenge in humans. 2. Sympathetic nerve activity to skeletal muscle (MSNA) determined from peroneal microneurography, heart rate and arterial blood pressure were recorded continuously in twelve subjects during a modified Stroop colour word test (CWT) and mental arithmetic (MA), each performed over six levels of increasing absolute task difficulty. Performance (percentage correct) on each task was assessed and ratings of perceived stress obtained. Responses to CWT and MA were compared at similar levels of performance and perceived stress. 3. MSNA decreased at task onset, remained below baseline levels at low levels of difficulty which were not perceived as stressful, increased above baseline levels at higher levels of difficulty which were perceived as stressful, and increased further during recovery. Thus, the regulation of MSNA was stress dependent. At similar levels of stress perception there were no differences in MSNA between CWT and MA. Although performance declined as task difficulty increased, there was no particular 'threshold' level of performance associated with the stimulation of MSNA. 4. Arterial pressure and heart rate were elevated above baseline levels throughout the mental tasks. Arterial pressure increased over the first 3-4 levels of each task and then plateaued whereas heart rate did not vary across increasing levels of task difficulty. Heart rate and arterial pressure responses to CWT were higher than those to MA. 5. These data demonstrate that during cognitive challenge the stimulation of MSNA is governed primarily by perceived stress which is dependent, in part, on the absolute level of task difficulty. In contrast, neither performance nor the type of cognitive task appear to be important determinants of MSNA. Arterial pressure is influenced by the task and level of difficulty. Heart rate is independent of task difficulty but may be task dependent.