Successful applications of MSE were seen in studies of HRV, human neuronal spiking patterns, postural sway patterns, and in EEGs of brain maturation, epilepsy, aging, dementia and schizophrenia. Here, we examined the MSE results of both EEG and RR interval time series together and sought to establish what, if any, relationships exist between the dynamics of cardiac and cerebral electrical activity. Photic stimulation is a procedure meant to elicit or accentuate epileptiform discharges during a routine EEG. Both cardiac and neuron cells are spontaneous oscillators. Phase-locked dynamics have been observed in cardiac cells and neurons when they are stimulated by periodic electrical impulses. Mechanical stimulation through ventilator can also produce such phenomenon to neural cells in the respiratory center and sympathetic neurons. The brain is stimulated by periodic lighting impulses during the PS procedure. Despite the widespread utilization, the complete understanding of the brain response to PS is still an open problem. We also checked the signal complexity in the EEGs under repetitive PS. Our results display inverse correlations between the signal complexity of cardiac and cerebral activities. The central autonomic pathways could not fully explain these correlations. The resting-awake EEG was associated to the awake RRI time series in the right frontopolar, central and temporal area, the fastPS EEG was also associated to the awake RRI time series in the bilateral occipital and right central area, whereas the slow-PS EEG was associated to the sleep RRI time series in the right frontopolar SCH772984 company region. These results may imply a strong correlation between the dynamics of heartbeat and brainwaves; and the correlation could be manipulated by photic stimulation, and affected by the sleepwake cycle. A study of EEG under PS found no significant difference between the power spectra of the EEG under PS of frequencies 11 and 20 Hz. We found different signal complexity between the EEGs under different PS frequencies. Compared to the restingawake EEG, an increase of regularity only occurred with the EEG under PS of frequencies equal and above 12 Hz. The fastPS procedure made the EEG dynamics much more regular globally and it also shifted the heart-brain associations topographically into the occipital lobes, the visual cortex. The slow-PS procedure, although not causing any obvious change in the signal complexity of EEG, shifted the presence of heart-brain associations from awake-state into sleep. We assume that the stimulation of fast-PS is very strong that highlights the connection between the heart and brain in the visual cortex, whereas the stimulation of slow-PS is weak and only blocks the background activity in the visual cortex just like what happens during sleep, being eye-closed. Sleep is a state of arousable “loss of consciousness” with slowed heartbeats and brainwaves, and the mechanism of sleep remains unknown. Living organisms are generally believed to behave in a manner of high complexity in order to respond to a broad range of stimuli.