The Use of Cognitive Paired Associative Stimulation (C-PAS) in Investigating and Remediating the Effects of Sleep Deprivation on Working Memory in Humans: The Importance of State-Dependency

Sleep deprivation is a global health issue, and the resultant cognitive deficits can be debilitating. A series of studies reported success with individually neuronavigated transcranial magnetic stimulation (TMS), coupled with online task performance, in substantially reducing performance deficits in working memory in healthy adults caused by 2 days of total sleep depression. This paradigm of coupling TMS with online task performance has been referred to as Cognitive Paired Associative Stimulation (C-PAS). This review describes those studies and the research since using various TMS paradigms to remediate working memory deficits in sleep deprivation. Three such studies were found, but none replicated the earlier findings. However, in each case, there were differences in study design that might explain the negative findings and inform future methodological choices and to underline the need to combine TMS with brain imaging guidance. Online task performance during TMS, as done in the C-PAS paradigm, appears to be essential to demonstrating lasting remediation of working memory deficits induced by sleep deprivation. This observation highlights the importance of state-dependency in determining the effects of TMS. Further work needs to be done to clarify the potential role of C-PAS in alleviating the effects of sleep deprivation and studying cognitive processes affected by sleep.