The question then becomes whether declarative and nondeclarative memory are actually separate or different manifestations of the same neural process. From HM research, we find evidence for the existence of a declarative memory system independent of nondeclarative memory and other forms of intelligence. HM had the ability to retain information in his head for a period of time, suggesting that his working memory was intact (Squire and Wixted, 2011). Further evidence that not all memory is the same is the fact that HM acquired a motor skill despite being unable to remember actually learning the skill, thus showing the difference between episodic memory and semantic memory. Amnesics are able to acquire the perceptual ability to read mirror words at a normal rate compared to controls (Cohen and Squire, 1980), demonstrating that the ability to learn new perceptual skills also remains intact. Among the forms of non-declarative memory, procedural memory involves the cerebellum, the motor cortex and the basal ganglia (General Introduction to Neurobiology...). Therefore, nondeclarative memory can, in some sense, be seen as a more primitive form of memory that is not acquired through the integration and consolidation of neural events in the medial temporal lobe, but rather through associations learned outside the medial temporal lobe.