Abstract

Chronic primary insomnia is characterized by difficulty falling sleep, maintaining sleep and waking up earlier than desired as well as daytime functioning impairment in the absence of an underlying neurological and psychological condition. Daytime functional impairment of patients with chronic primary insomnia is linked to cognitive deficits, including working memory. Functional neuroimaging studies investigating working memory in this population reported abnormal cerebral activation during cognitive abilities testing. This evidence could support altered cognitive functioning. Yet, the same results have not been replicated consistently. Hence, this study aims to provide more nuanced evidence by identifying a map of cerebral activation among patients with insomnia in different phases of working memory using the Sternberg task. This task has never been used for this population. The Sternberg task can evaluate the working memory ability for the encoding and recall phases of working memory separately. Based on our results, we observed that many brain regions that were activated in patients with insomnia were similar to those that were activated in good sleepers in response to a working memory task. Yet, there were key regions within the frontal cortex that were not activated. The differences were more noticeable in the recall phase. This needs to be quantitatively verified by including a control cohort and investigated whether potential working memory impairment in insomnia is phase dependant in future studies. We extended the literature by identifying phase-dependant and load-dependent regions of cerebral activation and deactivation in patients with chronic primary insomnia during the Sternberg task.