Hemispheric asymmetries in episodic memory

The term "episodic memory" refers to our ability to remember past personal experiences. This ability is severely disrupted following bilateral damage to a dedicated neural substrate located symmetrically in the mesial temporal lobes. Milder deficits are also observed following unilateral damage to the same structures. In this chapter, we contrast memory deficits after left and right mesiotemporal damage and review some of the hypotheses proposed to account for the observed differences. As proposed by other authors (e.g., Binder et al., 2010), the observed lesion side effects in memory profiles after unilateral brain damage do not directly reflect specialization across the two symmetric memory substrates. Rather, they depend on the different kinds of information each of the two mesiotemporal structures receives from the ipsilateral hemisphere where other non-memory-specific cognitive systems are asymmetrically housed. In particular, this chapter outlines the role of language, working memory, and visuospatial processes in accounting for side effects in memory profiles. This is because all these systems greatly contribute to the functioning of episodic memory and also show a variable extent of lateralization in the human brain.