In the present work, electroencephalographic recordings of healthy human participants were performed to study the entrainment of brainwaves using a variety of stimulus. First, periodic entrainment of the brainwaves was studied using two different stimuli in the form of periodic auditory and visual signals. The entrainment with the periodic visual stimulation was consistently observed, whereas the auditory entrainment was inconclusive. Hence, a photic (Visual) stimulus, where two frequencies were presented to the subject simultaneously was used to further explore the bifrequency entrainment of human brainwaves. Subsequently, the evolution of brainwaves as a result of an aperiodic stimulation was explored, wherein an entrainment to the predetermined aperiodic pattern was observed. These results suggest that aperiodic entrainment could be used as a tool for guided modification of brainwaves. This could find possible applications in processes such as epilepsy suppression and biofeedback.Variations in the environment of a system can alter its dynamics. In this work, the phenomenon of the entrainment of human brainwaves to a predetermined aperiodic photic stimulus is presented. As a precursor, entrainment to a single frequency and a bi-frequency signal is studied. Subsequently, the presence of aperiodic entrainment was quantified using short-time Fourier transform (STFT) and by calculating the cross correlation between the STFT of the aperiodic signal and that of the observed EEG dynamics.This guided modification of brainwaves may find possible applications in suppressing some types of epilepsy and in biofeedback.Entrainment is the process of adjusting the dynamics of a system to that of an external rhythm. This is observed in a wide variety of natural as well as laboratory systems [1-6]. In mammals, entrainment of the circadian rhythms as a function of various factors such as illumination, body temperature, social cues and food availability is well documented in literature [3-6]. Another interesting observation in this field is the phenomenon of brainwave entrainment [24]. This phenomenon leads back to the initial experiments done to study the brain dynam-ics [7, 8], wherein flickering lights at different frequencies were used to study the modification of brainwaves in human as well as animal subjects. A recent interest has emerged in the entrainment of brainwaves using a variety of stimulation such as, audio-visual stimulation (AVS) or transcranial alternating current stimulation and its possible applications [9-12]. Research has also been carried out to study the individual effects of auditory [13-15] and photic [16] entrainment of the brainwaves. Noise along with a subthreshold photic stimulus has previously been shown to enhance the periodicity in brainwaves via stochastic resonance [16, 17]. However, there have been contradicting reports regarding the effects of auditory stimulation on the brainwave entrainment [14, 15, 18].The auditory stimulation is conventionally given in the form of binaural beats [11][12][13...

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Periodic and Aperiodic Stochastic Resonance (SR) and Deterministic Resonance (DR) are studied in this paper. To check for the ubiquitousness of the phenomena, two unrelated systems, namely, FitzHugh-Nagumo and a particle in a bistable potential well, are studied. Instead of the conventional scenario of noise amplitude (in the case of SR) or chaotic signal amplitude (in the case of DR) variation, a tunable system parameter ("a" in the case of FitzHugh-Nagumo model and the damping coefficient "j" in the bistable model) is regulated. The operating values of these parameters are defined as the "setpoint" of the system throughout the present work. Our results indicate that there exists an optimal value of the setpoint for which maximum information transfer between the input and the output signals takes place. This information transfer from the input sub-threshold signal to the output dynamics is quantified by the normalised cross-correlation coefficient ( |CCC|). |CCC| as a function of the setpoint exhibits a unimodal variation which is characteristic of SR (or DR). Furthermore, |CCC| is computed for a grid of noise (or chaotic signal) amplitude and setpoint values. The heat map of |CCC| over this grid yields the presence of a resonance region in the noise-setpoint plane for which the maximum enhancement of the input sub-threshold signal is observed. This resonance region could be possibly used to explain how organisms maintain their signal detection efficacy with fluctuating amounts of noise present in their environment. Interestingly, the method of regulating the setpoint without changing the noise amplitude was not able to induce Coherence Resonance (CR). A possible, qualitative reasoning for this is provided.

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