ABSTRACT
Studies of natural development, disease progression, response to external stimuli, and inßuences of new therapies and interventions share a common demand — the ability to characterize or determine some aspect of brain physiology at successive time points. Such studies are facilitated by serial or longitudinal examinations. If the nature of an examination (e.g., brain sectioning or immunohistologic staining) precludes repeated performance, alternative strategies involving large cohorts of similar preparations are required. Samples are drawn at certain stages and assumed to represent the population. To the extent that noninvasive imaging can offer information with sufÞcient physiologic speciÞcity to serve as a reasonable alternative to invasive methods, we can reduce the number of animals required in our neuroscientiÞc investigations while harnessing the statistical power of internal control.
