Brain substrates of classical eyeblink conditioning: a highly localized but also distributed system.

The rabbit classical nictitating membrane/eyeblink conditioning preparation has proven highly valuable for delineating neural structures and systems involved in associative learning. Research conducted over the last 20 years has revealed that the essential neural circuitry for acquisition and performance of this simple, learned, motor response resides in the cerebellum and related brain stem structures. While this system appears to be highly localized, many other brain areas are recruited during eyeblink conditioning. Further, involvement of the cerebellum in associative learning and memory seems to be limited by certain parametric conditions present at the time of learning. These data suggest that classical eyeblink conditioning can also be characterized as a distributed system. Data in support of the highly localized, yet distributed nature of the neural systems involved in classical eyeblink conditioning are presented and discussed here.