Evoked Cortical Responses Following Stimulation of the Thalamic VL Nucleus in Man.

Electrophysiological studies on evoked cortical activity following stimulation of the thalamic VL nucleus have been reported in our previous papers^<1),2)>In this paper,some additional data concerning the conduction pathway to the bilateral central dortex and the analysis of AR were presented.The study was performed during thalamotomy for 50 Parkinsonian patients.1)Initial positive wave,which proceeded to the first negative wave,was noted by summating equal numbers of responses with positive and negative stimulations.The positive wave was estimated from the initiation of the evoked response.2)The first deflection time,which meant time from shock artefact to the beginning of the deflection of the initial positive wave ,was ranged from 1.5 to 1.8 msec in the ipsilateral and from 2.2 to 2.7 msec in the contralateral central sites.3)Conduction velocity of the responses was measured from the deflection time and the depth of probe in the ipsilateral side,and the velocities were ranged from 42 to 36 m/sec.4)Difference of the distance of the conduction pathway between the stimulated VL nucleus to the ipsilateral and to the contralateral cortex was estimated from 2.9 to 3.8 cm.5)The implse from the stimulated VL nucleus to the contralateral cortex was thought to be transmitted through the corpus callosum directly.6)AR following suprathreshold stimulation was analized with pulse-selector.The result was that the most pronounced factor of the waxing and waning phenomena was the changes with the growth of the II-PN waves.