Kohnstamm's phenomenon

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First described by German neurologist Oskar Kohnstamm (1871–1917) in 1915, Kohnstamm's phenomenon is a sustained involuntary contraction of a muscle after a prolonged voluntary contraction. The simplest demonstration, sometimes called "the floating arms experiment", is to have a subject press the arms against a door frame or wall for about thirty seconds, and then step away. The arm will involuntarily rise.

Russian scientists Victor Gurfinkel, Mikhail Lebedev and Yuri Levick used Kohnstamm's phenomenon to activate tonogenic structures in humans and thereby demonstrate postural automatisms, such as neck reflexes.

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  • Kohnstamm, O. Demonstration einer Katatonieartigen Erscheimung beim Gesunden (Katatonusversuch). Neurol. Zentral B1 34S: 290–291, 1915.
  • Gurfinkel, V.S.; Lebedev, M.A.; Levick, Yu.S. (1992). "What about the so-called neck reflexes in humans?". In Vidal, Pierre Paul; Alain Berthoz; Werner Graf (eds.). The Head-neck sensory motor system. Oxford [Oxfordshire]: Oxford University Press. pp. 543–7. ISBN 0-19-506820-3.
  • Gurfinkel' VS; Levik IuS; Lebedev MA (1989). "[Immediate and remote postactivation effects in the human motor system]". Neirofiziologiia (in Russian). 21 (3): 343–51. doi:10.1007/bf01058224. PMID 2770916. S2CID 9327823. Translation into English: Neurophysiology 21: 247–253.
  • Gurfinkel, V. S.; Yu. S. Levik & M. A. Lebedev (1989). "Postural automatisms revealed by enhancement of the tonic background" [Postural automatisms revealed by enhancement of the tonic background]. Doklady Akademii Nauk SSSR (in Russian). 305 (5): 1266–9. PMID 2752900.
  • Duclos C, Roll R, Kavounoudiasa A, Roll JP (January 2007). "Cerebral correlates of the "Kohnstamm phenomenon": An fMRI study". NeuroImage. 34 (2): 774–783. doi:10.1016/j.neuroimage.2006.06.050. PMID 17095251. S2CID 26427706.
  • Ivanenko YP, Wright WG, Gurfinkel VS, Horak F, Cordo P (February 2006). "Interaction of involuntary post-contraction activity with locomotor movements". Exp Brain Res. 169 (2): 255–60. doi:10.1007/s00221-005-0324-3. PMC 1363359. PMID 16369781.
  • Mathis J, Gurfinkel VS, Struppler A (August 1996). "Facilitation of motor evoked potentials by postcontraction response (Kohnstamm phenomenon)". Electroencephalogr Clin Neurophysiol. 101 (4): 289–97. doi:10.1016/0924-980X(96)95599-X. PMID 8761038.