QUANTITATIVE ASSESSMENT OF THE MICROSTRUCTURE OF RAT BEHAVIOR .1. F(D), THE EXTENSION OF THE SCALING HYPOTHESIS

Previous studies demonstrated that drug effects on the movement sequen ces of rats in unconditioned motor activity paradigms can be quantifie d by scaling measures that describe the average relationship between a variable of interest and an experimental parameter. However, rats eng age in a wide variety of geometrically distinct movements that can be influenced differentially by drugs. In this investigation, the extende d scaling approach is presented to capture quantitatively the relative contributions of geometrically distinct movement sequences to the ove rall path structure. The calculation of the spectrum of local spatial scaling exponents, f(d), is based on ensemble methods used in statisti cal physics. Results of the f(d) analysis confirm that the amount of m otor activity is not correlated with the geometrical structure of move ment sequences. Changes in the average spatial scaling exponent, d, co rrespond to shifting the entire f(d) function, and indicate overall ch anges in path structure. With the extended scaling approach, straight movement sequences are assessed independently from highly circumscribe d movements. Thus, the f(d) function identifies drug effects on partic ular ranges of movement sequences as defined by the geometrical struct ure of movements. More generally, the f(d) function quantifies the rel ationship between microscopically recorded variables, in this paradigm consecutive (x, y) locations, and the macroscopic behavioral patterns that constitute the animal's response topography.