A Consequence of Failed Sequential Learning: A Computational Account of Developmental Amnesia

摘要

Developmental amnesia, featured with severely impaired episodic memory and almost normal semantic memory, has been discovered to occur in children with hippocampal atrophy. Such amnesia seems to challenge the understanding that early loss of episodic memory may impede cognitive development and result in severe mental retardation. While the underlying mechanism is still unclear, no computational model has been reported to simulate developmental amnesia. A cognitive and computational system is presented, for the first time, to simulate the unique characteristics of the amnesia: impaired episodic recall, spared recognition, and spared semantic learning. The lesioned sequential/spatial learning ability of the hippocampus is suggested to be able to cause severe impairment of episodic recall, but affect neither recognition ability nor semantic learning. Semantic learning is generally thought to largely associate with the consolidation of episodic memory, a process in which sequential activation of episodic memory may not be necessary. Semantic learning through memory consolidation featured with random activation of stored experiences is performed, and the acquired knowledge is demonstrated to have the flexibility that is one of the key characteristics of semantic memory.