Rhythmic endogenous processes and discrete exogenous inputs: theoretical considerations about their relationship

Rhythmic processes are well known from the brain activity (e.g., alpha rhythm in EEG), the blood circulation (e.g., ECG, heart rate) and the neuromuscular system (e.g, tremor), thus they gained interest of research very early. Typically, these rhythms change the duration of cycles from cycle to cycle in a mainly stochastic manner. All these internal processes can be more or less influenced by sensory stimuli arising from the external environment. This paper focuses on the problem of whether the duration of a cycle of the endogenous rhythmic process is modified by the arriving new input. Experimental observations of physiological tremor indicate a prolongation of the ongoing tremor cycle by a discrete visual input, but theoretical considerations reveal this effect to be possibly caused by the methodological approach