Does Cerebellar LTD Mediate Motor Learning? Toward a Resolution without a Smoking Gun

Abstract

It should be clear from the above discussion that the putative role of cerebellar LTD will continue to be a debated issue. There is neither a smoking gun experiment that establishes a causal link nor are all four of our criteria solidly satisfied. Even so, these criteria can serve as a road map leading to firmer ground, and we are struck by how far the journey has progressed. Consider, for example, the relative status of these criteria for cerebellar LTD relative to hippocampal LTP and spatial learning. For LTP, the only criterion that has been addressed seriously is necessity for learning, with results approximately equivalent to LTD and eyelid conditioning. Thus, despite the work remaining to be done, the evidence linking LTD to motor learning is better established than for many other form of plasticity in the vertebrate nervous system. With more work, we may eventually find that Marr's theory was more prophetic than emetic.*To whom correspondence should be addressed.