SMR neurofeedback for improving sleep and memory – Two studies in primary insomnia

Abstract

Introduction: A non-pharmacological intervention, namely instrumental conditioning of 12-15 Hz oscillations (ISC), for improving sleep quality and memory is tested. This frequency range is known to be abundant during (i) quiet but alert wakefulness (sensorimotorrhythm, SMR) as well as in (ii) light NREM sleep-spindles. ISC is known to influence sleep quality. Materials and methods: In two studies we here intend to clarify the nature of these effects and apply neurofeedback (NFT) to (sub- )clinical insomnia patients. In the first study 24 young subjects with sub-clinical symptoms of primary insomnia were tested. A counterbalanced within-subjects design (19 lab visits over the course of 3-6 weeks) was adopted. Each patient participated in an ISCNFT as well as a sham-NFT training block. Polysomnographic sleep recordings were scheduled before and after training blocks. In a similar manner we then also conducted a counter-balanced double-blind follow-up study with 30 primary insomnia patients and 30 (sex and age matched) controls. Results: Data of the first study confirm a significant increase of 12-15 Hz activity over the course of the 10 SMR training sessions which was also positively related to overnight memory consolidation changes. Number of awakenings were reduced and slowwave sleep was increased following ISC but not sham. Last but not least N3 sleep spindles were found to be enhanced after SMR training. Preliminary results of study 2 indicate that patients suffering from more severe insomnia do not benefit in sleep or memory over the 12 ISC sessions. However, all groups (healthy controls, sleep state mispercept, and insomnia patients) do enhance SMR-power (and fast spindles) exclusively in the SMR (but not placebo) condition. Subjectively the sleep complaint decreased over both conditions. With respect to susceptibility to interference it becomes evident that interference affects the declarative (but not procedural) memory domain. Forgetting from initial evening learning to a delayed recall after a week (as well as after interference) is also found more pronounced in insomnia patients than healthy controls. Last but not least, analyses of the sleep EEG and sleep spindles reveal a traitlike relationship between fast spindle activity (SpA) and the initial learning levels in the declarative memory. Conclusion: Current results indicate that besides healthy individuals also young people suffering from (sub-clinical) primary insomnia can experience subjective aswell as objective benefits from ISC-NFT. The results of a comprehensive double-blind study, however, suggest that full-blown insomnia patients are not benefiting from ISC-NFT across 12 sessions.