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Journal of Clinical and
Basic Psychosomatics Cognitive modulation of baroreceptor afferents

effects of the cardiac timing manipulation. However, given at cardiac diastole. In the same vein, if an RT stimulus was
the average length of resting IBIs (approximately 750 ms; presented at cardiac diastole, the motor stages of processing
calculated from the mean resting heart rate), the temporal would likely occur at cardiac systole. Therefore, faster RTs
location of R+300 ms and R+550 ms was considered to at cardiac systole under the WM load condition might
correspond to cardiac systole and diastole, respectively, reflect the facilitation of the motor stages of RT responses
across participants. Future studies are expected to include by cardiac diastole. This possible explanation should be
direct measures of baroreceptor activation. tested by future studies using direct neural measures (e.g.,

Importantly, our results revealed that the cardiac timing the lateralized readiness potential, or LRP) that are linked
effect on response speed in the presence of concurrent to different stages in the processing of the RT stimulus.
WM load was in contrast to the effect in the absence of A different line of research adds another possible
WM load, suggesting that WM processes play a critical explanation to our findings. Recent studies focusing on
role in the expression of cardiac timing effects. In a recent cardiac timing effects in affective contexts suggested
study, Larra et al. disentangled cardiac cycle time effects on impulsive decisions are facilitated by cardiac systole,
sensorimotor processes and higher cognitive processing, and increased errors in response inhibition occurred at
and the research team found that spatially compatible cardiac systole rather than diastole. 18,60 Especially, several
sensorimotor responses to an auditory stimulus were studies reported that cardiac systole, rather than diastole,
faster but incompatible sensorimotor responses were enhanced fear processing. 61-64 This pattern of cardiac timing
prolonged during cardiac systole. The authors attributed effects is seemingly consistent with our findings regarding
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these findings to residual activation in response to auditory WM load and cardiac timing effects on sensorimotor
stimuli in the cerebral hemisphere, which, due to partial responses. Garfinkel and Critchley (2016) pointed out that
laterization of auditory processing, suppressed cortical the selective enhancement of fear processing is adaptive
inhibition by baroreceptor afferents. However, the for survival. Moreover, baroreceptor activation facilitates
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current study did not involve auditory stimuli but only the detection of fearful faces and increases activation of the
visual stimuli that are completely processed by the opposite amygdala. 66-68 A closer comparison between cardiac cycle
cerebral hemisphere. Therefore, the account of suppression time effects on sensorimotor processing and emotional
of residual activation may not fully explain our findings. processes indicates that fear processing enhancement by
baroreceptor afferents may reflect the role of interoception
Alternatively, higher central processing may also
override cardiac timing effects, as demonstrated in another in information encoding rather than the behavioral effects
study employing an emotional Stroop task. In the study, of affective processing.
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cardiac cycle time influenced responses in congruent Contrary to our predictions regarding response
trials, in which response selection only involves automatic accuracy, neither WM load nor cardiac timing influenced
processing. Importantly, in the congruent trials requiring errors in sensorimotor responses. This null finding can be
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less mental workload, the effect of cardiac timing on frontal attributed to the high levels of response accuracy (>95%)
EEG was evident, while no such effect was obtained in the observed in all conditions. The accurate responses may be
congruent trials with higher levels of mental workload. As a result of participants slowing down to maintain a high
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frontal EEG activity directly indicates the level of mental level of accuracy. In addition, the low-performance error
workload, our findings align with this study, suggesting rate may have masked the effects of WM load and cardiac
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that WM processes serve as the mechanism underlying timing in statistical tests, preventing sophisticated analysis
the modulation of cardiac timing effects on sensorimotor of information processing.
processing. Physiologically, the modulation of mental workload
Another explanation for the modulation of cardiac on the behavioral effects of baroceptor afferents may
timing effects may not be mutually exclusive to the above be related to hypothalamic stimulation. 69,70 When the
accounts. In specific, due to prolonged RTs under the WM hypothalamic defense area is stimulated, it initiates ANS
load condition, sensorimotor processing was slowed down, activation involving cholinergic vasodilation and increased
potentially extending beyond a certain cardiac phase. In noradrenergic inputs to the cardiovascular system. In
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specific, mean RTs were longer than 700 ms in the WM our study, despite the absence of affective stimuli, WM
load condition, which was longer than two-thirds of the load-induced negative affective experiences, resembling
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length of most cardiac cycles. When an RT stimulus was the effects of hypothalamic stimulation. In other words,
presented at cardiac systole, the motor response would be concurrent WM load may activate noradrenergic
executed approximately 700 ms after the onset of the RT systems and further suppress baroreceptor afferent
stimulus, and thus the motor stages were likely to occur processing through the hypothalamic-NST connection.
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Volume 2 Issue 2 (2024) 7 https://doi.org/10.36922/jcbp.2248