1) Researchers used fMRI to study how the human orofacial somatosensory system encodes tactile velocity during saltatory pneumatic stimulation of the lower face. 2) They found that unilateral stimulation produced localized BOLD responses in SI, SII, precentral and PPC that varied spatially depending on stimulus velocity. 3) Bilateral activation of SI, SII and insular cortex occurred for slower velocities, and some subjects showed ipsilateral cerebellar activation at the slowest velocity.

1. ENCODING SALTATORY TACTILE VELOCITY IN THE HUMAN OROFACIAL
SOMATOSENSORY SYSTEM USING fMRI
Rebecca Custead, 1,3, Hyuntaek Oh 2,3, Steven M. Barlow 1-3
1Communication Disorders, 2Biological Systems Engineering, 3Center for Brain, Biology & Behavior, University of Nebraska, Lincoln, NE, USA
Processingdynamic tactileinputsisakeyfunctionofsomatosensorysystems.
Closelytiedtoskilled motoractivity, velocityencoding mechanismsare
importantforfinemotorcontrol(speech,swallow,etc.). Knowledgeof
sensoryprocessing networkscontributetoourunderstanding of
sensorimotorrecoveryfollowing neurologicalinsult.Todate,littleisknown
abouttactilevelocityencoding intrigeminalnetworksthatprocesscutaneous
afferentinformation associated withfacialsensation, proprioception, and
oromotorfeedback.
Background
Objective
Methods Results
Acknowledgements
Conclusions
References
Tousehighresolution fMRItoinvestigatetheneuralsubstratesofvelocity
encodinginthehealthyhuman orofacialsomatosensorysystemduring
saltatory(discontinuous, “jumping”) pneumotactileinputstotheunilateral
orofacialskin.Amultichannel, scalablepneumotactilearraywasusedto
presentstimulusvelocitiesat5cm/s,25cm/sand65cm/s.Thespatiotemporal
organizationofcorticalandsubcorticalBOLDresponseasafunctionofvelocity
wasanalyzedusing generallinearmodeling (GLM)ofsingle-subjectand
collapsedgroupfMRIsignaldata.
Galileo Somatosensory Array
Participants
• 14 R-handed, neurotypicaladults, 19-30years(M=21.2,SD=1.8)
StimulusDelivery
• Galileo Somatosensory array, programmed to generate sequential
saltatory stimuli (60 ms pulse duration, 10ms rise/fall)
• Custom-machined acetyl thermopolymer capsules (TAC-Cells)
arranged along a line (medial-lateral) spanning the right perioral
skin-to-cheek
fMRI Data Acquisition
Stimulus Velocity Control
ThisstudywassupportedbyagrantfromtheBarkleyTrustFoundation.
• Unilateral, sequential saltatory pneumotactile inputs to the lower
face produced localized, predominantly contralateral BOLD
responses in SI, SII, precentral and PPC, whose spatial organization
was dependent on velocity.1, 2
• BilateralSI,SII,andBOLDresponseintheinsularcortexwasnotedduring
slowvelocitypresentations(5cm/s,25cm/s).³
• HalfofthesubjectsshowedanipsilateralcerebellarBOLDresponseforthe
lowestvelocity(5cm/s)inregionsconsistentwiththedentate nucleus.4
• Resultsindicateadaptationviaascalabilityofnetworksprocessingtemporal
cuesassociatedwithvelocitypresentations
1. VenkatesanL,BarlowSM,PopescuM,PopescuA. Integrating approach
forstudying adaptationmechanismsinthehumansomatosensorycortical
network. ExperimentalBrainResearch 2014,232:3545-3554.
2. CusteadR,OhH,BarlowSM. Adaptation ofthecorticalsomatosensory
evokedpotentialfollowing pulsedpneumatic stimulationofthelowerface
inadults. BrainResearch 2015,1622:81-90.
3. AronoffR,MatyasF,MateoC,Ciron,C,SchneiderB,PetersonC. Long-
rangeconnectivityofmouseprimarysomatosensorybarrelcortex.
EuropeanJournalofNeuroscience 2010,31:2221-2233.
4. WardmanD,GandeviaS,ColebatchJ. Cerebral,subcortical, andcerebellar
activationevokedbyselectivestimulation ofmuscleandcutaneous
afferents:anfMRIstudy. PhysiologicalReports 2014,2(4):e00270.
Individual Whole-Brain GLM Analysis:
Main Effect of Velocity Condition
Block Design
ProgrammedtimedelaysbetweenpressurepulsesateachTAC-cellresultedin
5stimulusconditions: 5cm/s,25cm/s,65cm/s,ALL-ONsynchronous
activation, andALL-OFF
5velocityconditionswerepresentedinarandomizedblockdesign(20s
ON/20sOFF), 13.3min=1BOLD, 3BOLDsessions/subject
3TSiemensSkyra,32-channelheadcoil
• Anatomicalscan:(T1-weightedMPRAGE,0.9mmisotropic, TE=3.37ms,
TR=2400ms
• BOLDimages:(T2*-weightedEPI)brainvolume,41interleavedslices(2.5x
2.5x2.5mm³, TE=30ms,TR=2500ms),220mmFOVthatincludedorofacial
sensorimotorcortexandcerebellum
Subcortical Activation:
@ 5 cm/s
Group Whole-Brain Analysis:
Velocity vs. Control (ALL-OFF)
Cortical Response:
Deep Insular Response:
Subcortical - Cerebellar Response:
2015
Subject
Subject
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