Phase plane portraits in Fig. 10 show that for (D=0.001) the orbit stays near the stable fixed point but for the larger noise values, there are large excursions away from the fixed point when the orbit crosses an "escape" threshold.
If stochastic variation barely reaches an escape threshold, a very weak "wind" may slowly transfer cells to a "downhill" state that will react differently when stimulated.
For example, escape-related neurons have been found in monkeys, in a region analogous to the human MCC (Iwata et al. 2005), and surgical ablation of the MCC increases the escape threshold to nociceptive stimulation (Pastoriza et al. 1996; Donahue et al. 2001).
When the rat did not show any escape response, the threshold was estimated to be 26 g considering the sensitivity limit of this experiment.
In addition, the rat threshold for escape response from cold temperatures is approximately 16 °C whereas the threshold for brainstem reflexes is <5 °C (Vierck 2006).
As such, statistically significant yet spurious alignments (attributed by the remnant segments) can pass off as homologous sequences once they escape the designated statistical threshold.
Thus, the frog started to escape earlier, at smaller threshold angular sizes to compensate for its unsuccessful control of the turn velocity for turns greater than 60° from the midline.
Autocatalytic environmental modification, such as the one triggered by the release of phage, can be seen as a public good that is expensive to produce initially but which can then be amplified at a negligible cost, therefore allowing an escape from the rarity threshold (Brown et al. 2006).
Like cART, such siRNA-based cocktail approaches increase the threshold for mutational escape, and any HIV-1 escape variants that do occur may also result in a loss of viral fitness [ 109– 109].
To test our hypothetical behavioral strategy, we examined correlations between the angular velocity ω and the angular threshold θth in escape turns less than and greater than 60° on either side of the midline (Fig. 6).
