The magnetic source imaging of pattern reversal stimuli of various visual fields
Jilin Sun · Zhonghua fangshexian yixue zazhi · 2006
Objective To have acknowledgement of characteristics of normal volunteers′ visual evoked fields about full field,vertical half field and quadrant field and their dipole location by magnetoencephalography.Methods The visual evoked fields of full field,vertical half field and quadrant field were detected with 13 subjects.The latency,dipole strength and dipoles′ location on x,y and z axis were analyzed.The exact locations of the dipoles were detected by overlapping on MR images.Results The isocontour map of M100 of full field stimulation demonstrated two separate sources.The two M100 dipoles had same peak latency and different strength.And for vertical half field and quadrant field stimulation,evoked magnetic fields of M100 distributed contralateral to the stimulated side.The M100 dipoles on the(z-axis) to the lower quadrant field stimulation were located significantly higher than those to the upper quadrant field stimulation.The Z value median of left upper quadrant was 49.6(35.1-72.8)mm.The Z value median of left lower quadrant was 53.5(44.8-76.3)mm.The different of two left quadrant medians,3.9 mm,was significant(P0.05).The Z value median of right upper quadrant was 40.0(34.8-44.6)mm.The Z value median of right lower quadrant was 53.8(40.6-61.3)mm.The different of two right quadrant medians,13.8 mm,was also significant(P0.05).Although each of the visual evoked fields waveforms and dipole locations demonstrated large intra-and inter-individual variations,the dipole of M100 was mainly located at area Brodmann 17,which includes superior lingual gyrus,posterior cuneus-lingual gyrus and inferior cuneus gyrus.Conclusion The M100 of visual evoked fields of pattern reversal stimulation is mainly generated by the neurons of striate cortex of contralateral to the stimulated side,which is at the lateral bottom of the calcarine fissure.