I am reading a journal paper about the insulin receptor. The insulin receptor is a receptor tyrosine kinase, and upon ligand binding, undergoes autophosphorylation of intracellular tyrosine residues. Regarding this paper, the terms "basal phosphorylation" or "phosphorylation in the basal state" of the insulin receptor is frequently used. However, I am unsure what the exact definition of basal phosphorylation is.
Is it the phosphorylation the receptor undergoes under physiological/normal conditions in vivo without the addition of exogenous insulin?
For example in the paper, they treat brain slices from wild-type mice with exogenous insulin, and they report that the phosphorylation of the insulin receptor exceeds the basal state.
Any insights are appreciated.