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The fast orthogonal search method was utilized for the time-series analysis of insulin periodicities based on the 'basic-rest-activity cycle' (BRAC) phenomenon. Time-series analysis of insulin periodicities indicated the lack of autonomy for different systems. The multivariate study also indicated the primary regulatory activities of the autonomic nervous system and the hypothalamus. Furthermore, the autonomic, cardiovascular and neuroendocrine systems exhibited strong coupling and shared periodicities with insulin.

The autonomic, cardiovascular and neuronendocrine systems exhibit periodicity within a 24-hour day in a phenomenon known as ultradian rhythm. Processes such as cardiac output, thoracic fluid index, and the secretion of hormones such as epinephrine, norepineprine and leutinizing hormone were monitored and data was subjected to time-series analysis. These processes occurred in periods of 115-145, 70-100 and 45-60 minutes and point to a single system regulating periodicity.

A letter to the editor is presented commenting on P.T. Macklem's views about the emergent phenomena.