Laterality of interhemispheric inhibition depends on handedness

• Published in: Experimental brain research 2007-06, Vol.180 (2), p.195-203
• Main Authors: BÄUMER, T, DAMMANN, E, BOCK, F, KLÖPPEL, S, SIEBNER, H. R, MUNCHAU, A
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Anatomical correlates of behavior; Behavioral psychophysiology; Biological and medical sciences; Brain Mapping; Central nervous system; Central neurotransmission. Neuromudulation. Pathways and receptors; Cerebral hemispheres; Cortex (motor); Cortex (premotor); Electric Stimulation; Evoked Potentials, Motor - physiology; Excitability; Experiments; Female; Functional Laterality - physiology; Fundamental and applied biological sciences. Psychology; Handedness; Hemispheric laterality; Humans; Male; Motor Cortex - physiology; Neural Inhibition - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rest - physiology; Time Factors; Transcranial Magnetic Stimulation; Vertebrates: nervous system and sense organs
• ISSN: 0014-4819; 1432-1106
• DOI: 10.1007/s00221-007-0866-7

There is some evidence that handedness is related to lateralisation of excitability in the motor system. We investigated lateralisation of interhemispheric inhibition (IHI), motor thresholds and short interval intracortical inhibition (SICI) and facilitation (SICF) in relation to handedness in 12 right (RH) and 13 left handed (LH) subjects. Because there is some controversy as to the optimal localisation to produce IHI we also compared IHI induced by conditioning the dorsal premotor cortex (dPM) versus primary motor cortex (M1) in ten RH. IHI was stronger following conditioning the motor dominant as compared to the motor non-dominant hemisphere in RH and LH. Motor thresholds were higher when elicited over the right hemisphere than over the left in both RH and LH, while SICI and SICF showed no differences between hemispheres or dependency from handedness. We hypothesize that IHI is a function of handedness perhaps reflecting predominant usage of the dominant hand, while lateralisation of thresholds and intracortical excitability are determined by other factors.