胡须信息在大鼠双侧初级体感皮层间的传递路径

大鼠的初级体感皮层(primary somatosensory cortex,SⅠ)虽然只接受来自对侧胡须的上行输入,但仍可以被同侧胡须刺激所激活.解剖学研究发现,在两侧SⅠ皮层之间有两条传递胡须信息胼胝体通路:一条是类颗粒区(perigranular zone,PGZ)通路;另一条是异颗粒区(dysgranular zone,DZ)通路.然而,哪一条通路在传递胡须刺激信息的过程中起主要作用还不清楚.本研究使用电压敏感染料(voltage-sensitive dye,VSD)成像技术来观察胡须刺激时整个SⅠ的神经元群体活动的空间分布和时间特性.实验发现,对侧胡须刺激首先激活barrel(颗粒区,granular zone,GZ),然后以兴奋波的形式传播到胡须感觉区(sub-barrel field cortex,BFC)外侧的DZ.而与首先激活BFC的对侧胡须刺激不同,同侧胡须刺激首先激活SⅠ的DZ.所激发的皮层兴奋以波的形式传播并扩散至BFC.失活另一侧皮层可以抑制这种同侧反应.电刺激另一侧半球皮层与刺激同侧胡须类似,也首先激活成像侧DZ.我们的实验结果显示,胡须刺激激活对侧SⅠ,在经过胼胝体传导后,另一侧半球的DZ(同侧于被刺激的胡须)被激活.连接双侧皮层DZ区的胼胝体连接在SⅠ对同侧胡须刺激的反应中起了主导作用.

Transcallosal Pathway of Whisker Information Between Rat Primary Somatosensory Cortices

It has been suggested that rodent primary somatosensory cortex(SⅠ) can be activated by ipsilateral whisker stimulation,while SⅠ only receives the ascending input from contralateral whiskers.Previous anatomical research revealed two transcallosal pathways transferring whisker information between bilateral cortices: perigranular zone(PGZ) pathway and dysgranular zone(DZ) pathway.But which pathway plays more important role in transferring whisker information remains unknown.We used voltage-sensitive dye(VSD) imaging to visualize the SⅠ activation by stimulating whiskers.We found that the contralateral whisker stimulation first activates the barrel(granular zone,GZ),then the activity forms a propagating wave and spread to the DZ outside the sub-barrel field cortex(BFC).In contrast,ipsilateral whisker stimulation first activates the DZ outside the BFC.The evoked activity in the DZ forms a propagating wave and spreads into the BFC in SⅠ.Inactivating opposite cortex blocks this ipsilateral whisker activation.Electrical stimulus to opposite cortex also first evokes DZ in the imaging cortex.Our results suggested that whisker stimulation first activated the barrel and then DZ in the opposite SⅠ.After a delay of transcallosal transfer,the DZ of the other hemisphere(ipsilateral to the whisker being stimulated) was activated.The callosal fibers connecting the DZs on the two hemispheries play a major role in the SⅠ activation by the ipsilateral whisker stimulation.