Procedural learning in a patient with amnesia due to hypoxia.

It has been claimed that procedural learning on a broad range of perceptuomotor and cognitive tasks is normal in amnesic patients whose severe deficits in acquiring declarative knowledge can be well documented. To evaluate the generality of this proposition we studied procedural learning on three different tasks in an amnesic patient who displayed no signs of intellectual deterioration including problem-solving difficulty. The patient showed normal improvement in learning to read transformed script and normal within-session improvement on a mirror-reading task. However, his retention of the mirror-reading skill from one day to the next was impaired, and he learned the Tower of Hanoi puzzle more slowly than normal. This patient's performance demonstrates that even amnesics without problem-solving difficulties do not perform normally on all tasks that are said to measure procedural learning. In the absence of a clear operational definition of procedural learning the usefulness of the concept remains heuristic.