Page 33 - JCBP-2-2

Journal of Clinical and
Basic Psychosomatics Cognitive modulation of baroreceptor afferents

(σ), representing the mean and the standard deviation (SD) psychology courses at Old Dominion University (ODU).
of the normally distributed component, respectively, are Subjects were screened for histories of neurologic and
related to sensory-perceptual processing. 40,41 Cardiac cycle psychiatric disorders, CVD, drug abuse, and psychotropic
phases may have different effects on these parameters. For medication. Other exclusion criteria included smoking
instance, μ, an index of low-order processing, is expected and abnormal color vision. Subjects were also required to
to prolong during cardiac systole. 31,42,43 Furthermore, abstain from alcohol for 12 h, caffeine for 6 h, and vigorous
studies reported an inverse relationship between τ and physical exercise for 2 h before participation. In return
blood pressure elevation during a cognitively demanding for their participation, subjects received course credits.
task, and heart rate variability, a commonly used index of The study was approved by the ODU Institutional Review
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ANS functioning, increased in cognitive tasks. Together, Board (approval code: 1979162).
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these results suggest that baroreceptor afferents reduce
attentional lapses (i.e., τ decreases) when cardiovascular 2.2. Tasks and design
activation occurs. In the choice RT task, subjects were presented with red
The current study aimed to examine the mechanisms and green solid circles at the center of a computer screen
underlying the cognitive modulation of cardiac cycle time as RT stimuli. In each RT trial, the subjects were instructed
on sensorimotor processing. As WM load may serve a to press the left arrow key on a computer keyboard in
critical role in determine the complexity of sensorimotor response to the red circle and the right arrow key for the
responses, we employed a dual-task paradigm and green circle as quickly and accurately as possible. If no key
manipulated concurrent WM load during a choice RT task. press was detected, the RT stimulus remained on screen
To examine potential cardiac cycle time effects, the stimuli for 2,000 ms before ending. The RT stimuli were delivered
in the choice RT task were synchronized with the phases after 300 ms (cardiac systole) or 550 ms (cardiac diastole)
of a cardiac cycle, i.e., cardiac systole and diastole, using a after R-waves that were detected online from the ECG (see
time-locked stimulus presentation with the ECG R-wave. details in later sections). The stimulus delivery schedule
Moreover, we utilized both traditional RT and ex-Gaussian followed the design outlined in prior reports. 16-19,46 Visual
metrics to differentiate cardiac timing effects on various stimuli were displayed on a computer screen positioned
components of sensorimotor processing. 50 cm in front of the subjects using the E-Prime 3.0
software (Psychology Software Tools, Inc., United States).
Based on the prior literature, we hypothesized that
a concurrent WM load would prolong mean RTs and Inter-trial intervals varied, ranging from 3.5–5 s to reduce
the ex-Gaussian μ while also increasing the ex-Gaussian the behavioral effects of subjects’ anticipation of stimulus
parameter τ in both cardiac systole and diastole phases. presentation.
In addition, τ was expected to be smaller during cardiac In this study, WM load was manipulated using the
systole in relative to diastole (hypothesis 1), given that Sternberg memory task, requiring subjects to remember
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attentional lapses are more likely to occur when few three digits. During each trial, the digits were displayed on
cognitive sources (induced by the concurrent WM load) the screen for 1,000 ms. Following the digit presentation,
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are available, and the level of physiological arousal is low subjects completed four-choice RT trials, as described
(cardiac diastole). 43-45 Moreover, we also hypothesized earlier. The probe digit was presented at the end of the RT
that WM load would modulate cardiac timing effects on trials, and subjects were instructed to indicate whether
task performance (hypothesis 2). In specific, when there it matched any of the three digits they had just seen by
was no WM load, response speed, indicated by both mean pressing either “Z” (to confirm the probe) or “X” (to reject
RTs and μ, would be slower and responses would be less the probe) on a keyboard. The duration of the memory
accurate during cardiac systole than those during cardiac maintenance periods lasted for approximately 17,000 ms
diastole, whereas this pattern would be reversed by the (Figure 1).
concurrent WM load. This hypothesis was made based on
documented cardiac cycle time effects on RT responses, 42,45 There were 200 RT trials in total, divided into two
which reflected the recent findings of the specificity of blocks: 100 trials without WM load (i.e., no WM load
cardiac cycle time effects. 24,25 condition) and 100 trials with WM load (WM load
condition). Moreover, 25 WM trials were conducted under
2. Methods the WM load condition. The order of the two blocks was
randomized across participants. Within each block, the
2.1. Participants 100 RT trials were evenly split and presented at cardiac
Forty-seven right-handed subjects (32 female; mean systole (50 trials) and diastole (50 trials), which were also
age = 21.9 years; SD = 2.1 years) were recruited from randomly counterbalanced.

Volume 2 Issue 2 (2024) 3 https://doi.org/10.36922/jcbp.2248