Tolerance development in humans with task practice on different limbs of the blood-alcohol curve.

Three groups of male social drinkers were trained on a pursuit rotor task, and subsequently performed the task during five weekly drinking sessions under the same dose (0.83 ml absolute alcohol/kg). During sessions 1-4, group R (N = 10) performed six trials on the task during rising blood-alcohol concentrations (BAC). Group F (N = 10) performed the same number of trials at comparable falling BAC. Group C (N = 5) received three trials at similar BAC during the rising and the falling portions of the alcohol curve. All groups displayed impaired performance on session 1. By session 4, tolerance was evident in groups C and F, but group R remained impaired. The consequences of these different practice treatments were examined in session 5, where all groups performed the task on the rising and the falling limb of the BAC curve. Groups C and F displayed tolerance on both limbs of the curve whereas the R group was impaired on both. Significant acute recovery was evident in the performance of groups F and R, but not in group C. The evidence was considered to support the hypothesis that a compensatory response, which is strengthened by practice, underlies acute recovery and tolerance.