Page 34 - JCBP-2-2

Journal of Clinical and
Basic Psychosomatics Cognitive modulation of baroreceptor afferents

Figure 1. Stimulus presentation in relation to cardiac cycle phase.
Notes: The three exemplary trials (from the left to the right) indicated a trial of the choice reaction time (CRT) task at cardiac systole, a CRT trial at cardiac
diastole, and a CRT trial with concurrent working memory load at cardiac diastole.
Abbreviation: ECG: Electrocardiography.

2.3. Procedure an established analysis stream as outlined in our previous
After providing informed consent, participants completed study. 35-37 The ex-Gaussian model was then employed to
a health questionnaire and were then attached to ECG fit the RT distribution for each condition. The “retimes”
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electrodes and instructed to watch an affectively neutral package in R statistical software was utilized for the
film clip lasting 180 s. Afterward, participants were ex-Gaussian modeling, which estimated parameters μ, σ,
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35
instructed that there would be several practice trials of red and τ with bootstrapped resampling (1,000 iterations).
or green circles, to press the corresponding key in response In addition, RT data were also analyzed using traditional
to the circle as quickly as possible, and to memorize the mean RTs to check the validity of ex-Gaussian modeling.
digits displayed on the screen and confirm or reject the Mean RTs were calculated as the average score for each
probe digit by pressing the assigned keys. A total of ten condition, with RT outliers falling outside ±3 SD being
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practice trials were delivered before the commencement of excluded from analyses.
the experimental blocks. Each experimental block lasted 2.6. Data analysis
approximately 8 min, with participants given a 2-min rest
between blocks. Following the completion of the final To investigate the impact of cardiac cycle time and WM
block, participants underwent a 2-min recovery period load on behavioral performance, ex-Gaussian parameters
before being thanked for their participation. and accuracy were subjected to 2 (cardiac timing) × 2 (WM
load) repeated measures analyses of variance (ANOVAs).
2.4. Physiological recording Planned contrasts were employed to explore significant
In this study, the BIOPAC MP160 system (BIOPAC main effects and interactions, utilizing two-tailed paired
Systems Inc., Goleta, CA) was used to record physiological t-tests with the Bonferroni correction. Effect sizes in the
signals, which were then digitized at 1,000 Hz (16-bit) analyses were estimated using partial eta-squared and
and analyzed with BIOPAC AcqKnowledge software 5.0. Cohen’s d, respectively.
ECG was recorded in a modified Lead II configuration 3. Results
using disposable, pre-gelled stress-testing spot electrodes
(ConMed Andover Medical, United States). Online At rest, the mean heart rate (HR) was 80.05 bpm
detection of EGC R-waves was performed using an (SD = 13.11 bpm); the mean body mass index was 24.46
AccuSync 71 ECG trigger monitor. The E-Prime software (SD = 4.49). Table 1 shows the descriptive statistics of
on the experimental computer received the trigger to behavioral data. In the WM load condition, the mean response
deliver the stimuli. Cardiac inter-beat intervals (IBIs) and time for the Sternberg task was 1897.81 ms (SD = 766.48 ms),
heart rate were calculated from the raw ECG signals. with an accuracy rate of 90.49% (SD = 12.34%).
2.5. Data reduction 3.1. Effects of cardiac timing and WM load on
response accuracy
The accuracy of sensorimotor responses was assessed as
the percentage of correct responses under each condition. The ANOVA of response accuracy did not show the main
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RTs were analyzed using ex-Gaussian modeling, following effects of interaction (ps > 0.100).

Volume 2 Issue 2 (2024) 4 https://doi.org/10.36922/jcbp.2248