The effect of right and left hemispheric lesions on effortful and automatic memory tasks

The effect of lateralised cerebral damage on two memory tasks - free recall of words and memory of their temporal order - was investigated under intentional, incidental, and "true incidental" learning conditions. Ten Right Brain Damaged patients (RBD), 10 Left Brain Damaged patients (LBD), as well as 15 age-matched and 15 younger control individuals, participated in this study. It was hypothesised that effortful and automatic memory processes involve predominantly the left and right cerebral hemispheres, respectively. Automaticity was defined either by the learning conditions (i.e. incidental-automatic and intentional-effortful) or by the type of task (i.e. temporal-order-automatic and free-recall-effortful) regardless of the learning conditions. In the free recall task the RBD group outperformed the LBD group under all learning conditions. In the temporal order task, the RBD group performed worse than normal controls under all learning conditions while the LBD group performed more poorly than matched controls in the intentional and incidental but not in the "true incidental" learning condition. The results are discussed in terms of the relationship between effortful and automatic memory processes and cerebral lateralisation.