The sensorimotor rhythm (SMR) is a

brain wave ''Brain Wave'' is a science fiction novel by American writer Poul Anderson, first published in serial form in ''Space Science Fiction'' in 1953, and then as a novel in 1954. Anderson had said that he could consider it one of his top five books. Th ...

. It is an oscillatory idle rhythm of synchronized electric brain activity. It appears in spindles in recordings of

EEG Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...

, MEG, and

ECoG Electrocorticography (ECoG), or intracranial electroencephalography (iEEG), is a type of electrophysiological monitoring that uses electrodes placed directly on the exposed surface of the brain to record electrical activity from the cerebral cor ...

over the

sensorimotor cortex The motor cortex is the region of the cerebral cortex believed to be involved in the planning, control, and execution of voluntary movements. The motor cortex is an area of the frontal lobe located in the posterior precentral gyrus immediately ...

. For most individuals, the frequency of the SMR is in the range of 13 to 15 Hz.

Meaning

The meaning of SMR is not fully understood. Phenomenologically, a person is producing a stronger SMR amplitude when the corresponding sensorimotor areas are idle, e.g. during states of immobility. SMR typically decreases in amplitude when the corresponding sensory or

motor An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power gen ...

areas are activated, e.g. during motor tasks and even during motor imagery. Conceptually, SMR is sometimes mixed up with

alpha wave Alpha waves, or the alpha rhythm, are neural oscillations in the frequency range of 8–12 Hz likely originating from the synchronous and coherent (in phase or constructive) electrical activity of thalamic pacemaker cells in humans. Historica ...

s 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 because it is usually flooded by the stronger occipital alpha waves. The feline SMR has been noted as being analogous to the human mu rhythm.

Relevance in research

Neurofeedback

Neurofeedback Neurofeedback (NFB), also called neurotherapy, is a type of biofeedback that presents real-time feedback from brain activity in order to reinforce healthy brain function through operant conditioning. Typically, electrical activity from the brain i ...

training can be used to gain control over the SMR activity. Neurofeedback practitioners believe that this feedback enables the subject to learn the regulation of their own SMR. People with learning difficulties,

ADHD Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by excessive amounts of inattention, hyperactivity, and impulsivity that are pervasive, impairing in multiple contexts, and otherwise age-inapp ...

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

, and

autism The autism spectrum, often referred to as just autism or in the context of a professional diagnosis autism spectrum disorder (ASD) or autism spectrum condition (ASC), is a neurodevelopmental condition (or conditions) characterized by difficulti ...

may benefit from an increase in SMR activity via

neurofeedback Neurofeedback (NFB), also called neurotherapy, is a type of biofeedback that presents real-time feedback from brain activity in order to reinforce healthy brain function through operant conditioning. Typically, electrical activity from the brain i ...

. Furthermore, in the sport domain, SMR neurofeedback training has been found to be useful to enhance the golf putting performance. 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

Meaning

Relevance in research

Neurofeedback

See also

Brain waves

References

Further reading