The subadditive integration of neural responses to passive head rotation and galvanic vestibular stimulation in the vestibular nuclei

초록

Electricalstimulationsareoftenusedtodiagnoseortreatsomedysfunctionalconditionsofthehumanbody.Galvanicvestibularstimulation(GVS)isoneofthemethods,butitsclinicalapplicationshavebeenrestrictedbecauseofunclearstimulatingmechanismsandtargetregionsbyGVS.Ontheotherhand,theanimalexperimentsusingguineapigsandmonkeysshowedthatGVSactivatedtheafferentsneuronsconnectedwiththesemicircularcanalsandotolithicorgansregardlessoftheirhaircells.EventhoughGVShasnospecificdirection,theeffectsontheseperipheralneuronswereclearlyidentifiedandestimated.Also,nomatterwhatGVSconfigurationswereapplied,theireffectsweredirectlytransmittedtotheeighthcranialnervesbypassingtheprocessingmechanismsofhaircells.Here,weinvestigatedhowtheneuralinformationwastransmittedandintegratedinVN,usingacombinedstimulusofapassivekineticstimulusandGVS.WefoundthattheneuralinformationduringtherotationandGVSwaslinearlytransmittedandsub-additivelyintegratedwhentheyweresimultaneouslyapplied.TheintegrationandtransmissionofneuralinformationbetweentheafferentneuronsandVNwereunrelatedwiththedirectionalpreferenceandtheGVSpolarity.However,moreneuralinformationwastransmittedbytheirregularthantheregularneurons. TheneuralinformationbythecombinedstimulusofakineticstimulusandGVSwasinvestigatedtounderstandhowitwastransmittedandintegratedatoneofthefirstcentralvestibularstages.TherotatorystimulationaffectedthechangesoftheamplitudewhileGVSlargelyinfluencedthebaselinesintherespondingfeatures.Inthecomparisonsoftheamplitudesandbaselines,therespondingfeaturesduringthecombinedstimulusreducedtheirsizesoftheamplitudesandbaselines,comparedwiththoseduringtherotationandGVS,respectively.Overall,theneuralinformationwassubadditivelyintegratedaswellastherelationswerelinearlytransmittedinthelateralVN.Inaddition,ourcurrentanalysisimpliedthatthecomparisonsoftherespondingfeaturespossiblyrevealedtheamountsofthetransmittedneuralinformationbymodifyingthesensitivity(slope)oftheneuronalresponsestoanappliedstimulus. RESULT