Operant task performance dose-response

Ginseng extract improves the spatial learning performance of aged rats in an eight-arm radial maze and operant discrimination task (Nitta et al. 1995). It also improves memory performance in active-avoidance (shuttle-box) and passive-avoidance (step-down) tasks, and reinforces staircase-maze learning in both young and aged rats. (Petkov and Mosharrof 1987 Petkov et al. 1990 Petkov et al. 1992). The effects were also very dose dependent, with inverted U-shape dose-response curves. 

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