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Biological Time Series Analysis Using a Context Free Language: Applicability to Pulsatile Hormone Data

Figure 1

Hierarchically embedded cortisol pulses.

An example adapted from experimental data (black line) with six major cortisol pulses. For a Single Pulse Rise (U₁) starting at time ∼3.5 hours, the single pulse peak is identified with and the starting nadir/valley is identified with a V₁. The pulse rise is defined as the rise in cortisol concentration from the nadir (V₁) to peak (P₁). The pulse rise time (Uw₁) is the time required for the cortisol concentration levels to rise from a sequence of pulses starting with the local nadir (V₁) to the peak (P₁). The Hierarchical (multiple) Pulse Rise (U₂) occurs as the change in concentration from the first nadir (V₂) to last nadir (P₂), which is a local maximum nadir, in the rise portion of this hierarchically organized segment. The hierarchical pulse rise time (Uw₂) is the elapsed time between V₂ and P₂ of the rising portion. The effect of the hierarchical pulses between V₂ and P₂ is an accumulation or increase in cortisol. Similarly, sequences of pulses associated with the dissipation or decrease in cortisol begin at time ∼4.8 hours.

doi: https://doi.org/10.1371/journal.pone.0104087.g001