A consequence of failed sequential learning: A computational account of developmental amnesia

TL;DR

This paper presents a computational model explaining developmental amnesia, showing how hippocampal impairment affects episodic recall but spares semantic memory, aligning with clinical observations.

Contribution

It introduces a novel computational system that simulates developmental amnesia, highlighting the role of impaired sequential learning in hippocampal atrophy.

Findings

Impaired sequential learning causes episodic recall deficits.

Semantic learning remains intact despite hippocampal impairment.

Simulation results align with clinical and previous computational models.

Abstract

Developmental amnesia, featured with severely impaired episodic memory and almost normal semantic memory, has been discovered to occur in children with hippocampal atrophy. This unique combination of characteristics seems to challenge the understanding that early loss of episodic memory may impede cognitive development and result in severe mental retardation. Although a few underlying mechanisms have been suggested, no computational model has been reported that is able to mimic the unique combination of characteristics. In this study, a cognitive system is presented, and developmental amnesia is demonstrated computationally in terms of impaired episodic recall, spared recognition and spared semantic learning. Impaired sequential/spatial learning ability of the hippocampus is suggested to be the cause of such amnesia. Simulation shows that impaired sequential leaning may only result in severe impairment of episodic recall, but affect neither recognition ability nor semantic learning. The spared semantic learning is inline with the view that semantic learning is largely associated with the consolidation of episodic memory, a process in which episodic memory may be mostly activated randomly, instead of sequentially. Furthermore, retrograded amnesia is also simulated, and the result and its mechanism are in agreement with most computational models of amnesia reported previously.