Models and Mechanistic Insight

" The mission of the Journal of General Physiology is to publish original work of the highest quality that elucidates basic biological, chemical, or physical mechanisms of broad physiological signifi cance. This expectation — that the articles provide mechanistic insight — has served the Journal well; it also has been cause for much uncertainty , mostly pertaining to what actually constitutes mechanistic insight? ... The Journal has a proud tradition of providing a venue where authors are able to convey their work, its signifi cance, and its mechanistic implications , in full. The emphasis on mechanistic insight and the associated scientifi c rigor also means that articles published in the Journal tend to have a very long shelf life, a factor not currently considered in the calculus of ' impact ' " (Andersen, 2008). The January 2008 editorial (re)emphasized the importance of mechanistic insight in the evaluation of submissions. In this editorial, written jointly at the transition of our editorships, we try to fl esh out by example and analysis the nature and the role of models in conveying mech-anistic insight. We do so because the question " what constitutes mechanistic insight " continues to come up in communications with authors and reviewers. To structure the editorial, we selected from the wealth of possibilities in the Journal ' s archives four publications that present diverse examples of models of physiological phenomena — and which continue to be AB(' 74) and BHC(' 02). After briefl y discussing each of the four articles we proceed to discuss the nature and roles of models in general physiology. HSP(' 42) was an experimental effort to determine whether the quantal nature of light energy transfer to visual pigment molecules had implications for vision. They developed an experimental model of a human observer detecting a small, briefl y fl ashed target imaged under night vision conditions: the target was fl ashed for 1 ms on a circular patch of the peripheral retina subtending ‫ف‬ 500 rod photoreceptors. In the model, an observer is hypothesized to detect the target if some criterion minimum number of photons is captured. For 7 observers in 25 different sessions, the average threshold (arbitrarily Abbreviations used in this paper: GHK, Goldman-Hodgkin-Katz; PSF, point-spread function; TTX, tetrodotoxin. defi ned as the light intensity giving rise to 60% detection) was 92 quanta. Physics dictates that the actual number of photons captured on any given …