Sensorimotor rhythm

Description

The Sensory Motor Rhythm (SMR) is also called Mu rhythm fact|date=February 2008 (find a more detailed article there). It is an oscillatory idle rhythm of synchronized electromagnetic brain activity. It appears in spindles in recordings of EEG, MEG, and ECoG over the sensoryimotor cortex. For most individuals, the frequency of the SMR is in the range of 8 to 14 Hz.

Origin

See also mu rhythm.

Meaning

The meaning of SMR is not fully understood. Phenomenologically, a person is producing a stronger SMR amplitude when the corresponding sensory-motor areas are idle, e.g. during states of immobility. SMR typically decrease in amplitude when the corresponding sensory or motor areas are activated, e.g. during motor tasks and even during motor imagery. [Ernst Niedermeyer, Fernando Lopes da Silva Electroencephalography. Basic principles, Clinical Applications and Related Fields. 3rd edition, Williams & Wilkins Baltimore 1993]

Conceptually, SMR is sometimes mixed up with alpha waves of occipital origin, the strongest source of neural signals in the EEG. One reason might be, that without appropriate spatial filtering the SMR is very difficult to detect as it is usually superimposed by the stronger occipital alpha waves.

Relevance in research

Neurofeedback

Neurofeedback training can be used to gain control over the SMR activity. Neurofeedback practitioners believe - and have produced experimental evidence to back up their controversial claims [Tobias Egner and M. Barry Sterman, “Neurofeedback treatment of epilepsy: From basic rationale to practical application,” in press] - that this feedback enables the subject to learn the regulation of the own SMR.People with learning disabilities, [PMID 6542077] ADHD, [cite journal
last = Vernon
first = David
coauthors = Tobias Egner, Nick Cooper, Theresa Compton, Claire Neilands, Amna Sheri and John Gruzelier
title = The effect of training distinct neurofeedback protocols on aspects of cognitive performance
journal = International Journal of Psychophysiology
volume = 47
issue = 1
pages = 75–85
month = January | year = 2003
doi = 10.1016/S0167-8760(02)00091-0] epilepsy, [cite journal
last = Egner
first = Tobias
coauthors = M Barry Sterman
title = Neurofeedback treatment of epilepsy: from basic rationale to practical application
journal = Expert Review of Neurotherapeutics
volume = 6
issue = 2
pages = 247–257
publisher = Future Drugs
month = February | year = 2006
doi = 10.1586/14737175.6.2.247] and autismFact|date=August 2007 may benefit from an increase in SMR activity via neurofeedback. In the field of Brain-Computer Interfaces (BCI), the deliberate modification of the SMR amplitude during motor imagery can be used to control external applications [Andrea Kübler and Klaus-Robert Müller. An introduction to brain computer interfacing. In Guido Dornhege, Jose del R. Millán, Thilo Hinterberger, Dennis McFarland, and Klaus-Robert Müller, editors, Toward Brain-Computer Interfacing, pages 1-25. MIT press, Cambridge, MA, 2007] .

ee also

* Electroencephalography
* Delta wave
* Theta wave
* Alpha wave
* Beta wave
* Gamma wave

References

Further reading

*Cite book|title=A Symphony in the Brain|year=2000|first=Jim|last=Robbins
*M. B. Sterman and W. Wyrwicka, “EEG correlates of sleep: Evidence for separate forebrain substrates,” "Brain Research", vol. 6, 1967, pp. 143–163.
*W. Wyrwicka and M. B. Sterman, “Instrumental conditioning of sensorimotor cortex eeg spindles in the waking cat,” "Physiology and Behavior", vol. 3, 1968, pp. 703–707.
*Cite book|chapter=The SMR|title=The Head Trip: Adventures on the Wheel of Consciousness|year=2007|isbn=978-0679314080|first=Jeff|last=Warren