Effects of working memory demand on short-term heart-rate- and pulse transit time-variability

The Sternberg memory scanning task provides a measure of processing and working memory retrieval speed. In this test, subjects are presented a set of stimuli of given length. After a delay, one item is presented, and subjects are asked to indicate whether or not the item was part of the set. Performance is assessed by speed and accuracy of the response. Short-term heart rate variability (HRV) analysis is an eligible method for assessing the autonomic nervous system (ANS) mediated response of the cardiovascular system to working memory allocation and retrieval effort. Pulse transit time (PTT), namely the interval between heart systole and arterial blood pulse (PPG) detected in peripheral sites, has also been related to mental stress. The purpose of this study is to analyse HRV and PTT variability (PTTV) in response to a stepwise-increasing difficulty Sternberg task.