The pedunculopontine nucleus.

In an effort to account for a large number of reported functions mediated by a small portion of the midbrain, a hypothesis is advanced as a basis for discussion and not as established fact and is guided by reports from a large number of laboratories working on the same region but using widely disparate preparations. Overall, the hypothesized model suggests an underlying mechanism of action for what is essentially the ascending reticular activating system. The model proposed will hopefully be tested stringently in order to arrive at a better understanding of brain stem mechanisms modulating a host of rhythmic functions.