The application of TMS in Sleep Studies
A number of TMS studies have shown that it can affect sleep and the different phases of sleep. This makes TMS useful in investigating the mechanisms behind sleep disorders or in other conditions where sleep problems are seen.
Ongoing research
During much of sleep, cortical neurons undergo near-synchronous slow oscillation cycles in membrane potential. Slow oscillations underlie characteristic features of the sleep EEG, such as slow waves and spindles. A study by Massimini et al. (2007) shows that in sleeping subjects, slow waves and spindles can be triggered noninvasively and reliably by TMS. TMS triggering of slow waves reveals intrinsic bistability in thalamocortical networks during non-rapid eye movement sleep. Moreover, evoked slow waves lead to a deepening of sleep and to an increase in EEG slow-wave activity (0.5–4.5 Hz), which is thought to play a role in brain restoration and memory consolidation.
An example of how TMS can potentially improve quality of sleep can be seen in a study by Van Dijk et al from 2009. Sleep disorders are common in Parkinson's disease (PD) and have negative influences on quality of life. Sleep structure in healthy participants can be changed by rTMS, but this has never been studied systematically in PD. Van Dijk et al characterised sleep in PD patients and examined effects of rTMS using a combination of actigraphy and a pressure sensitive pad. The results indicated that PD patients slept shorter, more fragmented and had a lower sleep efficiency and longer nocturnal awakenings than healthy controls. rTMS over the parietal, but not over the motor cortex improved sleep fragmentation and sleep efficiency and reduced the average duration of nocturnal awakenings. Disturbed sleep in PD patients may partly be reversed by parietal rTMS, without affecting motor symptoms or mood (Van Dijk et al. 2009).
References
- Massimini et al., PNAS, 2007
- Van Dijk et al., Mov Disord, 2009
