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Tue, Sept 14 

Speaker: Inge Zijdewind, PhD (University Medical Center Groningen, The Netherlands)

Title: Associated contralateral activity, what can it tell us?

Abstract: During purposely made unilateral contractions the activity is often not confined to the target muscles but also non-target and even contralateral muscles are activated. This contralateral associated activity is non-intentional and often not noticed by the subject. The amount of this associated activity increases with stronger target contractions and increases further with duration of activity.

We studied the pathways of this contralateral associated activity using transcranial magnetic stimulation and fMRI. The data demonstrated that this activity projects to the spinal motoneurons via the ‘normal’ contralateral primary motor cortex and not via an ipsilateral corticospinal projection. Furthermore, the supplementary premotor area is an important secondary motor area involved in the regulation of this associated behavior.

We used this contralateral activity to study how movement is encoded in the motor cortex. In these experiments we changed the hand-position of contralateral hand between experiments while the subject performed the same task; i.e. a 2-minute maximal force with their in index finger in abduction direction. The data that we obtained suggested that the motor system has a strong preference for an organization coded in an external ‘movement-related’ reference frame and less for an organization coded in an internal ‘muscle-related’ reference frame.

Host: Dr. Zev Rymer