P 20. Corticobulbar projection and intracortical circuits in the facial motor cortex innervating lower facial muscles in healthy humans

Introduction: Despite the importance of facial muscles in social life and their frequent and disabling involvement in stroke or movement disorders, conclusive data concerning bilaterality, symmetry and hemisphere dominance in the control of lower facial muscles are not available yet. In addition, the role of intracortical circuits in the modulation of resting and active facial muscles is still debated.Objectives: Methods: In nine healthy subjects, left and right hemisphere were tested using single and paired pulse TMS methods to probe hot spot, motor evoked potentials (MEPs) latencies and amplitudes as well as short-interval intracortical inhibition (SICI) and intracortical facilitation (ICF) in the ipsi-and contralateral depressor anguli oris (DAO) muscles both at rest and during activation at 10% of maximal voluntary contraction. Resting and active motor thresholds (RMT and AMT, respectively) were determined following TMS of both hemispheres. Test and conditioning stimuli were 120% and 70% of motor threshold, respectively, and interstimulus intervals (ISIs) were 2ms for SICI and 10ms for ICF. Student’s paired t-test, ANOVA and post hoc t-test have been performed for single paired pulse TMS on the left and right hemispheres.Results: Resting and active MEPs were evoked bilaterally in the relaxed and active DAO following left and right hemisphere stimulations. Student’s paired t test showed no differences between left and right hemisphere as for hot spot, RMT, AMT, MEP amp...
Source: Clinical Neurophysiology - Category: Neuroscience Authors: Tags: Society Proceedings Source Type: research