This has been proved to be a valid index of experimental, clinical and chronic pain [ 7].
These robust intercorrelations suggest that hormonal concentrations used as continuous regressors for BOLD signal are a valid index of pubertal development.
Vagal tone is assessed by the root mean square of successive differences in these interbeat intervals (RMSSD), that has previously been proven to be a valid index of vagal tone.
This measure has been shown to be a valid index of self-reported pain with seniors who have mild to moderate dementia in that scores increase from baseline to painful situations [ 47]. (9) Gait speed (6 metre walk test).
In several large adult cohort studies, AVR has been shown to be a valid index for an increased risk of hypertension, stroke and higher cardiovascular mortality [ 41, 42].
The OF may induce more anxiety than the other two tests if defecation is considered a valid index of emotionality in the OF test [ 95]; however, others have questioned the validity of OF defecation as index of emotionality of rats [ 96, 97].
Circulating levels of adhesion molecules have been regarded as a valid index of endothelial activation.
Nonetheless, even if there is still an ongoing debate on the specific processes that underlie the N2pc, it is widely accepted as a valid index of visual selective attention (for a review, see [24]).
